AAFCO
Association of American Feed Control Officials; an organization which sets standards for pet food ingredients and minimum daily requirements.

ACE inhibitor
Angiotensin-converting-enzyme (ACE) inhibitor: Drug which decreases the function of this particular enzyme. The angiotensin-converting-enzyme changes a compound called angiotensin I to angiotensin II. Angiotensin II is a potent blood vessel constrictor. ACE inhibitors, then, have the effect of dilating blood vessels, since less Angiotensin II is produced.

Acid
A fluid containing a high proportion of hydrogen ions, giving the liquid a sour taste. Measured by pH units, with 1 the most acid, and 14 the least acid. Chemical reactions in the body have to take place at or near neutrality, pH 7.

ACTH
Adrenocorticotropic hormone. A hormone, secreted by the pituitary gland, which stimulates the adrenal gland to work.

Activated charcoal
Charcoal which has been treated to increase its adsorptive power (ability to have chemicals adhere to it); used to treat various forms of poisoning. 

Active immunity
Immunity produced when an animal’s own immune system reacts to a stimulus e.g., a virus or bacteria, and produces antibodies and cells which will protect it from the disease caused by the bacteria or virus. Compare with 'passive immunity.'

Acute
Having a sudden and generally severe onset. See also Chronic.

Addisons disease
Addison's disease is also known as hypoadrenocorticism. It is a disease that results from a decrease in corticosteroid secretion from the adrenal gland. See article: Addison's Disease (Hypoadrenocorticism).

Adjuvant
A substance added to killed vaccines to stimulate a better immune response by the body. Common adjuvants contain aluminum compounds.

Adrenal glands
Two small glands near the kidneys that produce many hormones required for life.

Adrenergic
Communication between the nerves and muscles that uses epinephrine as the 'messenger.' Adrenergic stimulation is what is involved in the 'flight or fight' response, which means the body is alerted to a danger of some sort and prepares to basically run or fight. Adrenergic stimulation results in an increased heart rate, sweating, and increased blood pressure.

Adsorbent
Solid substance which attracts other molecules to its surface.

Aerobic
Needing oxygen to live. See also Anaerobic bacteria.

Agglutination
Clumping together.

Albino
An animal that is completely white because it lacks the ability to make pigment. Its eyes are pale blue or pink.

Alkaline
A substance with very few hydrogen ions, and a pH over 7. Lye is strongly alkaline.

Allergen
Substance that causes an allergic reaction, e.g., pollen.

Alopecia
A loss of hair or baldness.

Alveoli
The tiny microscopic areas of the lung where the actual exchange of oxygen and carbon dioxide into and out of the blood occurs. Also called alveolus and alveolar sacs.

Aminoglycoside
A class of antibiotics which act by interfering with bacterial protein synthesis within the bacteria which results in the death of the bacteria. Antibiotics in this class include gentamicin (Gentocin), kanamycin, neomycin, streptomycin, tobramycin, and amikacin. Many of these antibiotics are not well-absorbed from the animal's digestive system, so are often administered as injections, or used topically.

Amylase
Digestive enzyme, produced by the pancreas which breaks down carbohydrates and starches.

Anabolic steroid
A type of steroid (not a corticosteroid like prednisone, cortisone, or dexamethasone) which promotes the building of tissues, like muscle.

Anaerobic bacteria
Bacteria which only live in an environment in which there is no or little oxygen, e.g., Clostridium tetani which causes tetanus.

Analgesia
Pain relief.

Anamnestic response
The faster and greater immune response produced by an animal who has previously encountered that specific antigen. Memory cells are responsible for this more efficient response. Also called 'secondary response.'

Anaphylaxis
Anaphylaxis is a rare, life-threatening, immediate allergic reaction to something ingested or injected. If untreated, it results in shock, respiratory and cardiac failure, and death. See article: Anaphylaxis. May also be referred to as anaphylactic shock or anaphylactoid reaction.

Androgen
A hormone which produces male sexual characteristics, e.g., testosterone.

Anemia
A condition in which the number of red blood cells present in the blood is lower than normal.

Angiotensin-converting-enzyme inhibitor
(ACE inhibitor) Drug which decreases the function of this particular enzyme. The angiotensin-converting-enzyme changes a compound called angiotensin I to angiotensin II. Angiotensin II is a potent blood vessel constrictor. ACE inhibitors, then, have the effect of dilating blood vessels, since less Angiotensin II is produced.

Anisocoria
A condition in which the pupils of the eyes are not of equal size. 

Anorexia
Loss of appetite.

Anthelmintic
Medication which kills certain types of intestinal worms; dewormer.

Antibody
Small disease-fighting proteins produced by certain types of cells called 'B cells.' The proteins are made in response to 'foreign' particles such as bacteria or viruses. These antibodies bind with certain proteins (antigens) on foreign particles like bacteria, to help inactivate them. See also Antigen.

Antibody titer
A measurement of the amount of antibodies in the blood. The test to measure antibodies is usually performed by making a number of dilutions of the blood and then measuring at what dilution there is sufficient antibody to react in the test. For example, a titer of 1:8 (one to eight) means the blood can be diluted to one part blood and seven parts saline and still produce a positive reaction in the test. The higher the titer (1:16 is higher than 1:8), the more antibody is present.

Anticholinergic
Stopping the communications between certain nerves and muscles of the body including those of the gastrointestinal tract and heart. These nerves are called 'parasympathetic' nerves and do such things as constrict the pupils of the eye, stimulate contractions of the muscles in the intestine, and slow the heart rate. Anticholinergic drugs would have the effect, then, of dilating the pupil, slowing contractions of the intestines, and increasing the heart rate.

Anticholinesterase
A drug that blocks the enzyme acetylcholinesterase; this results in stimulation of the parasympathetic nervous system.

Anticoagulation
Stopping the blood clotting process.

Anticonvulsant
A drug used to prevent or decrease the severity of convulsions.

Antiemetic
An agent that decreases or stops vomiting.

Antigen
A molecular structure on surfaces of such particles as bacteria and viruses. This structure is recognized by the body as 'foreign' and stimulates the body to produce special proteins called antibodies to inactivate this foreign invader. See also Antibody.

Antiprotozoal
An agent that kills protozoa, which are one-celled organisms such as Giardia.

Antipruritic
Relieves itching.

Antiseptic
A substance which inhibits the growth of bacteria, but does not kill them.

Antispasmodic
An agent that relieves or decreases spasms in muscle. The muscle could include 'smooth muscle' which is the type of muscle in intestines that causes them to contract and move food through the digestive system.

Antitussive
Cough suppressant.

Anuria
The condition of complete failure in the function of the kidneys such that no urine is produced.

Aplastic anemia
A serious condition in which red blood cells, white blood cells, and platelets are not produced in sufficient quantity.

Aquaculture
The (usually commercial) captive raising of fish, corals, and other aquatic life for aquariums, food, and scientific purposes.

Aqueous humor
The fluid found within the eyeball which provides nourishment to the interior eye structures and keeps the eyeball inflated.

Arrhythmia
A variation from normal heart rhythm.

Articular
Pertaining to a joint.

Ascarid
Roundworm. See article: Roundworms.

Ascites
Fluid accumulation in the abdomen.

Aspirate
Withdraw fluid or cells through the use of suction - usually the suction produced by pulling back on the plunger of a syringe attached to a needle which is inserted into the area to be sampled. Also the breathing in of a fluid or foreign substances.

Asymptomatic
A term used to decide a condition in which no symptoms are present.

Ataxia
A lack of muscle coordination, usually causing an abnormal or staggered gait.

Atoll
A coral island consisting of a reef surrounding a lagoon.

Atopy
An allergy to something that is inhaled such as pollen or house dust. Also called 'inhalant allergy.' See articles in the Allergies section.

ATP
Adenosine triphosphate; a compound used for energy by cells.

Atrial fibrillation
A heart condition in which the atria (chambers of the heart that receive the blood) contract rapidly, irregularly, and independently of the ventricles (the chambers of the heart that pump the blood). This greatly decreases the efficiency of the heart and its ability to move blood.

Atrial flutter
A heart condition in which the atria (chambers of the heart that receive the blood) contract rapidly, irregularly, and independently of the ventricles (the chambers of the heart that pump the blood). This greatly decreases the efficiency of the heart and its ability to move blood.

Atrium
(Plural atria) The two chambers of the heart that receive blood. The right atrium receives blood from the body. The left atrium receives oxygenated blood from the lungs.

Atrophy
An abnormal decrease in size of an organ or tissue.

Attenuated
Weakened. An attenuated virus is one which has been changed such that it will no longer cause disease. An attenuated virus would be used in a modified live vaccine.

Auscultate
To listen for sounds produced within the body, usually with the aid of a stethoscope.

Autoimmune
Condition in which the immune system attacks the body's own tissues. To properly function, the immune system must identify foreign substances such as bacteria, viruses, parasites, slivers, etc., and it must be able to distinguish normal body tissue from these foreign substances. If it fails to distinguish the difference, it attempts to destroy the tissue it wrongly identifies as foreign. For example, in autoimmune hemolytic anemia, the body destroys its own red blood cells. In rheumatoid arthritis it attacks the cells in the joints.

Axilla
Armpit.

B cell
Also called 'B lymphocyte.' The type of lymphocyte which produces antibody. Compare with 'T cells.'

Bacteriocidal
A description of an agent that kills bacteria.

Bacteriostatic
A description of an agent that stops the growth (reproduction) of bacteria, but does NOT kill them.

Benign
A mild illness or non-malignant form of a tumor. Benign tumors usually have well defined edges and tend to grow slowly.

Beta blockers
Heart medications which block certain receptors in the heart called beta receptors. The beta receptors receive signals which generally increase the heart rate. If the heart rate is abnormally fast and uneven, beta blockers will help stabilize the rate and rhythm of contractions.

Beta-carotene
A plant pigment which can be converted to Vitamin A by many animals, but not by cats.

Beta-lactamases
Enzymes produced by some bacteria which inactivate certain types of penicillin, thus making the bacteria resistant to them.

Bilateral
On both sides.

Biopsy
Surgical removal of a small amount of abnormal tissue, usually of tumors, for diagnosis.

Blepharospasm
Spasm of the eyelids often resulting in complete closure of the lids due to eye pain, such as seen with a scratch on the cornea.

Bloat
Filling of the stomach with air.

Blood gases
Gases, such as oxygen or carbon dioxide, that are in the blood. 

Blood glucose
A graph of blood glucose levels over time. At the time of insulin injection, and at regular intervals throughout the day, the level of glucose in the blood is determined through laboratory testing.

Bone marrow suppression
A condition in which the cells of the bone marrow which produce red blood cells, white blood cells, and platelets are inhibited. This may result from the use of certain drugs, such as anti-cancer agents.

Borborygmus
The sound of gas moving through the intestine; bowel sounds.

Bradycardia
An abnormal slowing of the heart rate.

Bronchiole
The small airways in the lung that come off of the larger bronchus; bronchioles are 1 mm or less in diameter.

Bronchodilator
Medication which opens up the main air passages to the lungs.

Bronchospasm
Condition in which the muscles surrounding the air passages to the lungs contract, narrowing the passages. 

BUN
Short for 'blood urea nitrogen,' a blood test that estimates kidney function.

Cachexia
Extreme weight loss.

Calcified
The hardening of tissue through the influx of calcium, usually as a result of chronic inflammation.

Calculus
(Plural calculi) Abnormal stone-like structure(s) usually composed of mineral salts, e.g., a bladder calculus is the same thing as a bladder stone.

Calorie
The unit of measurement of energy derived from digested food. Fat contains about twice as many calories per gram as protein or carbohydrate.

Cancer
Malignant tumor.

Candida
A certain genus of yeast which can cause disease in humans and animals; an infection with Candida is called candidiasis.

Carapace
The upper shell of a turtle or tortoise.

Carbohydrate
Compounds made up of chains of sugar units. Simple carbohydrates include table sugar (sucrose), milk sugar (lactose), and fruit sugar (fructose). Complex carbohydrates are very long chains held together by bonds that may not be digestible in the stomach and intestine of a carnivore. Starch is a digestible complex carbohydrate. Seed hulls such as oat bran are digestible by ruminants and horses, but not carnivores.  

Carcinogen
A substance which causes cancer.

Cardiomyopathy
Diseases of the heart muscle; does not include diseases of the valves of the heart or congenital defects.

Cardiopulmonary
Relating to the heart and lungs. 

Carnivore
An animal whose natural diet includes meat.

Carpus
The wrist (front leg) of dogs and cats. 

Carrier
Animal which harbors an infectious organism, such as a virus, bacteria, or parasite. The animal does not appear ill, but can still transmit the organism to other animals by direct contact or releasing the organisms (bacteria, protozoa, viruses) into the environment in the stool, urine, respiratory secretions, or vaginal discharges.

Cataract
A cloudiness of the lens of the eye, reducing vision and giving the eye a pearly appearance.

Cecum
A blind sac that opens into the colon; found in many animals.

Cell-mediated immunity
The immunity that is the result of either special lymphocytes directly killing the foreign invader, or lymphocytes (T cells) releasing special chemicals which activate macrophages to kill the invader. Compare with 'humoral immunity.'

Cerebral
Relating to the part of the brain known as the cerebrum. 

Chelation
Binding of a substance to a metal, thus helping the body to remove it.

Choana
Plural choanae. An opening between the nasal cavity and oropharynx (mouth) in birds and reptiles.

Chondroitin
Decreases the activity of enzymes which break down cartilage in a joint. 

Chondroprotective agent
A nutritional supplement that protects cartilage.

Chronic
Of a long duration: a chronic illness persists for weeks, months, or even for the life of animal. See also acute.

Chronic superficial keratitis
A chronic condition of the eye in which blood vessels grow across the cornea (the clear surface of the eye). The cornea looks hazy and sometimes reddened; it may eventually take on a dark pigment. This condition is also called pannus.

Class I, II, III, IV medications
Drugs are classified by the Drug Enforcement Administration of the Department of Justice depending upon such criteria as the potential for human abuse.

Cloaca
A common tube-like structure through which feces, urine, and reproductive fluids/eggs pass in birds, turtles, and other lower vertebrates.

Clotting factors
Protein components in the blood which help it to clot. Clotting is a complex mechanism. In addition to platelets, clot formation is the result of a long chain of chemical reactions carried out by individual molecules called 'clotting factors.' Each factor is numbered such that factor I leads to a reaction with factor II forming a new substance. This then reacts with factor III and so on to factor XII. 

CNS
Central nervous system. Includes the brain, spinal cord, and the nerves leading from them.

Coagulation
The process of clotting.

Coagulopathy
A condition affecting the blood's ability to form a clot. 

Coccidia
A one-celled parasite in the category of protozoa. In dogs and cats, coccidia are generally parasites of the intestinal tract. See article: Coccidia.

Cognitive dysfunction
A common medical condition in older dogs that results from abnormal brain function, causing certain behavior changes such as disorientation, housebreaking problems, and changes in sleeping patterns and interactions with others.

Cold-blooded
Having a body temperature that is not regulated internally, but varies with the environmental temperature. Turtles, lizards, and snakes are cold-blooded.

Colitis
An infection or inflammation of the colon.

Colostrum
The antibody-rich first milk produced immediately before and after giving birth.

Coma
Being in a state of unconsciousness.

Comedo
A blackhead, usually the result of a plugged gland within the skin.

Conception
The onset of pregnancy, when the fertilized egg attaches to the uterus.

Congenital
A characteristic of an animal that is present at birth. It may be inherited or induced by events that occur during pregnancy.

Conjunctiva
A thin membrane which lines the inside of the eyelids and covers part of the eyeball. 

Conjunctivitis
An inflammation of the lining of the eyelids; may cause pain, redness, itching, and a discharge.

Core vaccine
Vaccine which should be given to all animals of certain species, example, parvovirus vaccine in dogs or panleukopenia in cats (see noncore vaccine).

Cornea
The clear part of the front of the eye which allows light in. 

Corticosteroid
Hormones produced by the adrenal gland which are important to almost every function of cells and organs. They are divided into two groups: glucocorticoids and mineralocorticoids. Glucocorticoids regulate protein, carbohydrate, and fat metabolism. Mineralocorticoids regulate electrolyte balances.

Coumestan
Estrogen-like substance produced by certain plants such as alfalfa; types of phytoestrogen.

Coumestral
Estrogen-like substances produced by certain plants such as alfalfa; types of phytoestrogen.

Crust
Area of fluid or cells on the skin. The fluid may have been blood, serum, pus, or medication.

Culture
The process in which a sample of fluid or tissue is taken from an animal and placed in special media which allows the bacteria, virus, etc., to grow (reproduce) in the laboratory.

Cushings disease
Cushing's disease is also known as hyperadrenocorticism. It is a disease that results from an increase in corticosteroid secretion from the adrenal gland. See article: Cushing's Disease (Hyperadrenocorticism). 

Cutaneous
Relating to the skin. 

Cyanosis
Bluish or grayish color to the skin and gums which occurs when the animal has insufficient oxygen.

Cyst
An abnormal sac-like structure that is lined with cells which produce a liquid or thick material.

Cytokines
Compounds produced by certain cells, which act as messengers to control the action of lymphocytes and other cells in an immune response.

Cytoplasm
Substances which make up the inside of a cell and surround the nucleus of the cell which contains the genetic material.

DEA
Drug Enforcement Administration. The federal agency which regulates the manufacture, dispensing, storage, and shipment of controlled substances including medications with human abuse potential.

Decontaminate
Remove injurious material. 

Dermal
Relating to the skin. 

Dermatitis
An inflammation of the skin.

Dermatophyte
Fungus that causes ringworm; include Trichophyton, Microsporum, and Epidermophtyon.

Descenting
The removal of the anal sacs of a carnivore to prevent the animal from releasing the very strong-smelling secretion.

Diabetes mellitus
A metabolic disease caused by failure of the pancreas to produce insulin, a hormone that allows blood sugar (glucose) to be taken up by cells that require it for function.

Dialysis
A process which involves removing waste products from the body. 

Diestrus
The stage of the estrus cycle which occurs after the animal goes out of heat (also called Diestrous).

Dietary indiscretion
Eating what one should not. Dogs with dietary indiscretion eat garbage, dead fish on shore, etc.

Digestibility
Expressed as a percent, is a measure of the content of food that is retained in the body after food is eaten. The difference between the weight of food eaten and the weight of stool produced, divided by the weight of the food.

Digitalis glycosides
Class of drugs including digitoxin and digoxin, which are drugs derived from the Digitalis purpurea plant, and used in the treatment of congestive heart failure.

Dilated cardiomyopathy
A heart condition in which the heart enlarges, but the heart muscle becomes thinner.

Dinoflagellate
Single-celled algae, mainly marine and often with a cellulose shell; some species may be luminescent, and some cause the red tides that are extremely toxic to marine life. 

Distemper
Canine distemper is a viral disease that causes a severe and often fatal systemic illness in dogs and their close relatives. Distemper is also fatal in animals such as raccoons, and mustelids including skunks, mink, and ferrets.

Diuresis
Increase in urine production. 

Diuretic
Agent which increases the secretion of urine, ridding the body of excess fluid.

Diurnal
Active during the day, opposite of nocturnal, which means active during the night.

DNA
Deoxyribonucleic acid, the chemical compound that occurs in cells and is the basic structure for genes.

Domestic animal
An animal that has been housed and fed by man for generations and has little fear of man as a result. Some domestic animals learn to depend on human provision so completely that they have little ability to survive if returned to a natural habitat.

Dry Eye
Keratoconjunctivitis sicca (KCS) is the technical term for a condition also known as 'dry eye.' It occurs because of inadequate tear production. Symptoms include a thick, yellowish discharge from the eye.

Duration of immunity
Length of time an animal is protected from a disease. Vaccines for some diseases provide long durations of immunity (years), while vaccines for some other diseases only provide immunity that lasts for 6 months.

Dysecdysis
Abnormal shedding of the skin in reptiles. 

Dysplasia
An abnormal tissue development, common in the bones of the canine.

Dyspnea
Shortness of breath.

Dystocia
Difficult birth.

Dystrophic
Disorder caused by incorrect nutrition.

Ear canal
The tube that connects the external ear with the ear drum.

Ear drum
The membrane that divides the outer ear from the inner ear, where the mechanism of hearing takes place. The membrane prevents infection from reaching the inner ear, as well as vibrating to amplify sounds.

Ear mites
Small parasitic insects that live in the ear canal of an animal, and that are able to survive outside the ear for only very short periods of time.

Ecdysis
Shedding of the external layers of the skin in reptiles. 

ECG
A printout of an analysis of the electrical activity in the heart.

Echocardiogram
The image produced by performing an ultrasound examination of the heart.

Ectoparasite
A parasite that lives on the outside surface or skin of another animal. Ectoparasites include fleas, ticks, lice, and mange mites.

Ectopic
Non-malignant tissue growing in an unusual location (e.g., an ectopic pregnancy is conception of a normal embryo outside the normal location, which is the uterus).

Edema
A condition in which the tissues of the body contain too much body fluid. The fluid accumulation may cause swelling in the affected area.

EKG
A printout of an analysis of the electrical activity in the heart.

Electrocardiogram
A printout of an analysis of the electrical activity in the heart.

Electrocautery
An instrument with a very hot tip, heated by electricity, is applied to a tissue. Electrocautery may be used to make an incision, remove a mass, or to stop bleeding.

Electrolyte
Chemically, an element when dissolved in water, will cause the solution to transmit electricity. In medicine, certain elements in the blood which are critically important to life, including sodium, potassium, chloride, calcium, and phosphorous.

Electroretinography
The recording of electrical changes in the retina of the eye in response to stimulation by light.

Emesis
Vomiting.

Encephalopathy
Any degenerative disease of the brain. Causes include liver disease resulting in the buildup of toxic by-products of metabolism, heavy metal (e.g., lead) poisoning, and loss of blood supply.

Endocrine
Pertaining to the secretion of hormones. The endocrine system consists of various glands which produce hormones.

Endoscope
A long flexible instrument which can be passed into the body to view various structures through the use of fiber optics.

Endotracheal tube
This tube is placed into the animal's trachea (windpipe) to allow the oxygen and gases to be breathed into the lungs. 

Enteral feeding
A method to feed an animal in which a tube is placed through the body wall into the intestine, and a nutritious liquid is forced through the tube into the intestine.

Enteritis
An inflammation of the intestines.

Envenomation
The act of injecting a poisonous material (venom). 

Enzyme
Enzymes are special proteins produced by cells which cause chemical changes in other substances, but which are not themselves changed in the process.

EPA
Environmental Protection Agency. The agency of the federal government which licenses pesticides and herbicides.

Epidermis
The top layer of the skin.

Epiphora
An overflow of tears upon the cheeks due to a blockage or narrowing of the tear ducts.

Erosion
A shallow defect in the skin. When healed, it will not cause a scar.

Erythema
Redness of the skin caused by blood clogging in small blood vessels.

Esophageal reflux
A condition in which stomach contents move backward into the esophagus, i.e., heartburn.

Estrogen
A female hormone produced by the ovaries, which results in the onset of estrus.

Estrus
The time when a female animal is fertile and receptive to the male. Also known as a heat period.

Exophthalmos
The abnormal outward protrusion (bulging) of the eye.

Exotic
An animal not native to the geographical area where it is living.

Extensor rigidity
A condition in which muscles contract and tend to straighten the limb, prevent it from relaxing. 

Extrahepatic
Outside of the liver.

False negative test result
The result of a diagnostic test is negative; but the animal actually does have the condition tested for. 

False positive test result
The result of a diagnostic test is positive; but the animal actually does not have the condition tested for. 

FDA
Food and Drug Administration. The federal agency which approves drugs and medications for use in animals and people.

Fine needle aspirate
Suction is applied to a hollow needle which has been inserted into tissue and a core of the tissue is withdrawn to culture and/or examine microscopically.

First generation
First generation: A description of medications developed from an earlier form of the medication. First generation medications were developed from the original form of the drug; second generation medications are adaptations of first generation drugs; third generation drugs are adaptations of second generation, etc.

Flatulence
Increased stomach or intestinal gas.

Flea dip
A solution made to kill fleas, applied to an animal and not rinsed off, to allow it to have residual action.

Follicle
The group of cells in the skin in which a hair or feather develops.

Foreign body
Any abnormal substance within the body. Examples include wood slivers, ingested cloth or balls, glass in the feet, etc.

Free radical
Atom which carries an unpaired electron; free radicals can potentially injure cells and may be responsible for numerous age-related diseases.

Fungicide
A drug that kills fungi.

Gastric
Relating to the stomach. 

Gastric lavage
To flush out the stomach. 

Gastritis
Inflammation of the stomach.

Gastrointestinal
Also known as GI. Pertaining to the stomach and intestines. The term 'digestive system' includes the mouth, gastrointestinal tract, anus, pancreas, and liver.

Gestation
Pregnancy.

Gingival
Relating to the gums.

Gingivitis
Inflammation of the gums. 

Glipizide
An oral medication that can be used to control blood glucose levels in some diabetic cats who still have some insulin production.

Glucocorticoid
Hormones produced by the adrenal gland which regulate protein, carbohydrate and fat metabolism, and are important to almost every function of cells and organs. They also stabilize cell membranes which is an important part of their function in treating allergic reactions. Also called glucocorticosteroids.

Glucocorticosteroid
Hormones produced by the adrenal gland which regulate protein, carbohydrate and fat metabolism, and are important to almost every function of cells and organs. They also stabilize cell membranes which is an important part of their function in treating allergic reactions. Also called glucocorticoids.

Glucosamine
One of the building blocks the body uses to make new cartilage.

Glucosuria
Glucose in the urine. (Also called glycosuria.)

Glycogen
A storage form of glucose in the body.

Glycosaminoglycans
Compounds which serve as the building blocks of cartilage, which covers the ends of bones within a joint. Glucosamine and chondroitin are necessary for the body to make glycosaminoglycans.

Gram
A measure of weight. 28 grams = 1 oz.; 454 grams = 1 lb.

Gram negative
A classification of bacteria based upon their lack of retention of a certain stain in the laboratory. The staining quality is based on the structure of the cell wall surrounding the bacteria. This structure of the cell wall influences which antibiotics will kill the bacteria. This laboratory staining method was developed by Hans Gram in 1884.

Gram positive
A classification of bacteria based upon their uptake of a certain stain in the laboratory. The staining quality is based on the structure of the cell wall surrounding the bacteria. This structure of the cell wall influences which antibiotics will kill the bacteria. This laboratory staining method was developed by Hans Gram in 1884.

Granuloma
The formation of a nodule as a result of inflammation.

H2 antagonist
A compound which binds (attaches) to the area on a cell at which histamine also binds. By binding at the same site, the antagonist blocks histamine from binding and prevents histamine from producing its effects, which include the production of stomach acid.

Half-life
The time required for the level of a substance in the body (e.g., a drug or toxin) to be reduced by half. 

Head pressing
Pressing the head against a wall or other hard object.

Heart block
A condition in which the electrical impulses of the heart are not properly conducted from the atria (chambers which receive the blood) to the ventricles (chambers which pump the blood).

Heartworm
A species of parasitic worm that lives and reproduces in the chambers of the heart of an animal. Microscopic, immature worms (microfilariae) circulate in the blood and are taken in by mosquitoes that bite the animal. Microfilariae mature in the mouthparts of the mosquito and infect another susceptible animal bitten by the same mosquito.

Heinz body
A condition in which the red blood cells are destroyed and this results in anemia. The specific type of anemia is called 'Heinz body anemia' because the red cells develop an abnormality called a 'Heinz body' which can be seen under the microscope. This anemia can occur as a reaction to certain medications and also in cats who eat onions.

Hematocrit
PCV (Packed Cell Volume), hematocrit: A laboratory test to monitor relative number of red blood cells present in the blood. A blood sample is placed in a tiny glass tube and spun in a centrifuge. The cells are heavier than the plasma and are compacted at one end of the tube. After the tube is spun, it is examined and the packed cell volume is determined as the percentage of the red cellular portion relative to the total amount of blood in the tube (i.e. remainder being the plasma). The normal for dogs is 40-59 and cats is 29-50.

Hematoma
A mass of blood within the tissues. Generally, the result of trauma to the blood vessels or abnormal blood clotting.

Hemodialysis
A process used to remove waste products from the blood. 

Hemolytic
Causing the red blood cells to break open.

Hemorrhage
To bleed excessively; may be the result of injury or blood clotting abnormalities.

Hepatic
Pertaining to the liver.

Hepatitis
An inflammation or infection of the liver.

Herbivore
Animal that eats primarily plants and vegetation.

Hernia
The protrusion of an organ through an abnormal opening.

High titer vaccine
A modified live vaccine that contains a higher number of virus particles than the 'average' vaccine. High titer vaccines can generally elicit an immune system response in young animals who have a maternal antibody level that would prevent them from responding to an 'average' vaccine. 

Histamine H2 receptor antagonist
A compound which binds (attaches) to the area on a cell at which histamine also binds. By binding at the same site, the antagonist blocks histamine from binding and prevents histamine from producing its effects, which include the production of stomach acid.

Hob
A male ferret.

Hormone
Chemical substance produced by one part of the body which serves as a messenger to or regulator of the processes of another part of the body.

Host
The organism in or on which a parasite lives. For example, dogs and cats are hosts for fleas and roundworms.

Humoral immunity
The immunity that is the result of antibody production by B cells. Compare with 'cell-mediated immunity.'

Hybrid
An animal that has parents of two different species, for instance, a mule's mother is a horse and its father is a donkey.

Hypercalcemia
An increased level of calcium in the blood.

Hyperesthesia
Abnormal sensitivity to touch, pain, or other sensory stimuli. 

Hyperglycemia
Higher than normal blood glucose level.

Hyperkalemia
Increased level of potassium in the blood.

Hyperpigmentation
An increased dark color in the skin caused by the pigment 'melanin.'

Hyperplasia
An increase of the number of cells within an organ.

Hyperplastic
Abnormal increase in the amount of tissue, e.g., a hyperplastic ear would have increased numbers of cells in the ear canal, sometimes to the point of closing off the ear canal. In prostatic hyperplasia, the prostate enlarges due to an increased number of normal, not cancerous, cells.

Hyperreactive
Producing an exaggerated, or greater than normal response to a stimulus.

Hypersensitive
A type of allergic condition in which the body overreacts to a certain agent such as a bee sting or medication.

Hypertension
Blood pressure above normal. 

Hyperthermia
An increase in body temperature above normal. 

Hyperthyroidism
A condition, more commonly seen in cats, in which the thyroid gland produces too much thyroid hormone. See article: Hyperthyroidism in Cats.

Hyperventilate
An increase in the rate and/or depth of respiration such that the body loses too much carbon dioxide.

Hypoglycemia
Lower than normal blood glucose level.

Hypokalemia
Lower than normal level of potassium in the blood.

Hypoplasia
Inadequate or defective development of tissue.

Hypotension
Blood pressure below normal. 

Hypothermia
A decrease in body temperature below normal. 

Hypothyroidism
A condition, more common in dogs, in which the thyroid gland does not produce enough thyroid hormone.

Hypovitaminosis A
A condition in which the body suffers from a deficiency in Vitamin A.

Hypoxia
Low oxygen level in blood and tissues.

Icterus
Commonly referred to as jaundice. A yellowing of the tissues, usually as a result of abnormal liver function.

IDDM
Insulin dependent diabetes mellitus (IDDM): A form of diabetes in which so little insulin is produced that supplemental insulin must be given for the animal to live. Also called Type I diabetes mellitus.

Idiopathic
Of unknown cause.

Ileus
A condition in which there is an absence of muscular contractions of the intestine which normally move the food through the system; can result in an intestinal obstruction. 

Immune system
The body's defense system which recognizes infectious agents and other 'foreign' compounds (such as pollen), and works to destroy them.

Immune-mediated
Immune-mediated reaction or disease: A condition or disease caused by abnormal activity of the immune system in which the body's immune system either over-reacts (e.g., immune-mediated contact dermatitis) or starts attacking the body itself (e.g., autoimmune hemolytic anemia). See also autoimmune.

Immunity
A condition in which the animal's immune system has been primed and is able to protect the body from a disease-causing agent such as a certain virus or bacteria. An animal could have immunity to one agent, such as parvovirus, but not have immunity to another agent, such as rabies.

Immunization
The process of rendering an animal protected (immune) against a certain disease. Vaccination is a way to produce immunization. However, just because an animal has been vaccinated (received a vaccine) does not necessarily mean the animal is immune. If the body did not correctly react to the vaccine or if the vaccine was defective, immunity would not occur. No vaccine produces immunity in 100% of the population to which it was given. 'Vaccination' is not the same as 'immunization.'

Immunodeficiency
Reduced function of the immune system of an animal, making it more susceptible to infectious disease. Can be an inherited defect or caused by drugs, radiation, or viruses.

Immunostimulant
A compound which stimulates the immune system to work more effectively to kill bacteria, viruses, or cancer cells.

Immunosuppressive
Something, for instance a drug, hormone, or virus, that reduces the function of the immune system of an animal. An animal with reduced function of its immune system is called 'immunosuppressed.'

Incubation period
The time between the exposure to a disease, causing agent, and the onset of signs of the disease.

Infestation
A term used to describe an invasion of parasites.

Inflammation
A condition in which tissue reacts to injury and undergoes changes during the healing process. As an example, a toe with a sliver of wood in it would be inflamed and show the signs of inflammation which include redness, increased temperature, pain, swelling, and a loss of or disordered function. The toe is swollen, red, hot, painful, and the animal is reluctant to walk on that toe.

Infusoria
Microscopic organisms which are cultured as a food for the fry of freshwater fish.

Inherited
A trait passed from one generation to the next in the genes from each parent.

Innate
A permanent characteristic that is present because of the genetic make-up of the animal.

Insoluble carbohydrate
Also, insoluble fiber. Fiber that resists enzymatic digestion in the small intestine.

Insulin
A hormone produced by the pancreas which is necessary for glucose to be able to enter the cells of the body and be used for energy.

Insulin resistance
A condition in which the blood glucose level remains higher than it should at an insulin dosage of 2 units/pound of body weight per day in cats.

Insulinoma
Insulin-producing tumor of the pancreas; the increased production and blood level of insulin resulting from these tumors can cause low blood sugar (hypoglycemia).

Intermediate Host
In the life cycle of some parasites, the immature form of the parasite must pass through a different type of host (animal, insect, snail, etc.), called the intermediate host, before it can re-enter and infect the type of animal it came from. An example would be heartworms. The adult worm lives in the dog or cat. The immature form, laid by the adult heartworm, is taken up by the mosquito. The immature form develops within the mosquito, and is then reintroduced into another dog or cat where it develops into the mature adult and the cycle repeats itself. The intermediate host for heartworms, then, is the mosquito.

Interstitial
Between parts or within the spaces of tissue.

Intracellular
An action taking place within a cell.

Intramuscular
Into the muscle (IM).

Intranasal
Into the nose.

Intravenous
Into the bloodstream via a vein.

Intussusception
A condition in which one part of the intestine 'telescopes' into another.

Iris
The colored portion of the eye is called the iris. As with humans, dogs' iris colors vary. In the center of the iris is the black opening called the pupil. This opening can be made larger or smaller by muscles called ciliary bodies, that attach to the colored iris, causing it to expand or contract.

Isoflavone
An estrogen-like substance produced by pasture plants; a type of phytoestrogen.

Jaundice
The condition in which there is a buildup of waste products in the body called bilirubin. Bilirubin is yellow in color, therefore, an animal with jaundice will have yellow gums, skin (often seen on the inside flap of the ear), and a yellowish cast to the 'whites' of the eyes. It can occur if a large number of red blood cells are destroyed, the liver is not functioning normally, or the bile ducts are blocked.

Jill
A female ferret.

KCS
Keratoconjunctivitis sicca is the technical term for a condition also known as 'dry eye.' It occurs because of inadequate tear production. Symptoms include a thick, yellowish discharge from the eye.

Keratoconjunctivitis sicca
Keratoconjunctivitis sicca (KCS) is the technical term for a condition also known as 'dry eye'. It occurs because of inadequate tear production. Symptoms include a thick, yellowish discharge from the eye.

Keratolytic
Softens and loosens crusts and scales on the skin. 

Ketoacidosis
A life-threatening condition in which ketones, which result from the breakdown of fat for energy, accumulate in the bloodstream and the pH of the blood decreases.

Killed vaccine
Vaccines which are made by taking the real, disease-causing viruses (or bacteria), killing them, and putting them into a liquid base. Compare with 'modified live vaccine' and 'recombinant vaccine.'

Kinetic skull
Having mobile joints between various parts of the skull, e.g., being able to unhinge the jaws. This allows the mouth of the animal, e.g., snake, to open wider so that it can eat large prey.

Kit
A baby ferret.

Lactating
Producing milk.

Large intestine
The lower part of the intestinal tract, usually made up of the colon, cecum, and rectum. Bacteria that live harmlessly in the large intestine help to digest complex carbohydrates.

Larva
The worm-like offspring of an insect (plural larvae).

Latent
A dormant stage of disease; the patient is infected with an organism, but is not yet ill.

Leukopenia
A condition in which the numbers of white blood cells in the blood are lower than normal.

Lichenification
Thickening and hardening of the skin.

Lipase
Digestive enzyme, produced by the pancreas, which breaks down fat.

Liver
The largest organ in the abdomen, responsible for producing enzymes required for digestion of food, and bile that helps to digest fat. The liver also detoxifies the blood and may be damaged in the process.

Low passage vaccine
A low passage vaccine contains virus particles which have been attenuated, or weakened, less than those in the 'average' vaccine. Low passage vaccines can generally elicit an immune system response in young animals who have a maternal antibody level that would prevent them from responding to an 'average' vaccine.

Lymph nodes
Part of the immune system of an animal. Small masses of tissue that contain white blood cells called lymphocytes. Blood from the nearby area is filtered through the lymph node allowing foreign or infectious material to be recognized and destroyed if possible.

Lymphocytes
The class of cells in the body which are responsible for mounting an immune response. Two main types are B cells and T cells.

Lymphokines
Chemicals produced by T lymphocytes. Some lymphokines signal macrophages and other phagocytes to destroy foreign invaders.

Macrophage
A type of phagocyte (cell in the body which 'eats' damaged cells and foreign substances such as virus and bacteria).

Malabsorption syndrome
Maldigestion syndrome: A condition involving the intestine in which food may not be properly digested or the nutrients not absorbed.

Malignant
A process that does harm to nearby tissues. Usually synonymous with cancer, a tumor that grows quickly and spreads into other tissues.

Malnutrition
Ill health due to dietary deficiency or imbalance.

Mammary
Pertaining to the breast.

Mandible
Lower jaw.

Mange
Any of several skin and ear conditions caused by a variety of mites.

MAOIs
Monoamine oxidase inhibitors. Substances that inactivate the enzyme monoamine oxidase which regulates certain transmitter chemicals between nerves. These compounds include certain types of antidepressants and also insecticides containing amitraz (such as Mitaban and Preventic collars).

Marsupial
An order of mammals including kangaroos, opossums, and sugar gliders in which the female has a pouch on the abdomen which holds the young and has nipples for the young to nurse.

Mast cell tumor
A nodular growth, usually on the skin, which involves cells (mast cells) which contain large amounts of histamine and normally play a role in allergic reactions. All mast cell tumors in dogs should be considered potentially malignant.

Masticate
Chew.

Mastitis
An infection or inflammation of the mammary glands.

Maternal antibody
Antibody in a newborn animal which the newborn acquired through the placenta or colostrum (the first milk).

Meal
When referring to food ingredients, meal means a ground-up preparation. Chicken meal is ground up chicken, which might include bones and feathers. Meat meal means ground up muscle meat.

Median survival time
Time at which 50% of the animals had died.

Megacolon
A condition in which the colon enlarges and dilates, which results in feces accumulating in the colon. Constipation then occurs. This condition is more common in cats than dogs.

Melena
Darkening of the stool due to the presence of digested blood, which indicates bleeding is occurring in the stomach and/or beginning of the small intestine. The feces generally look black and tarry.

Memory
(Immunologic) Memory: When an animal mounts an immune response against a foreign substance, some cells are created to 'remember' the antigens on that substance. If the animal is again exposed to the substance, these cells will help the body respond much faster and to a higher degree.

Metabolic acidosis
A condition in which the pH of the blood is too acidic because of the production of certain types of acids.

Metabolize
To have molecules transformed within the body tissue through chemical processes.

Metabolize energy (ME)
(ME) is the net energy available to an animal from a certain food.

Metacarpus
The front limb between the carpus and the phalanges (toes).

Metastasis
Spread of a tumor from its original location to a remote one, by tumor cells that are carried in the blood.

Metatarsus
The part of the rear limb between the tarsus and the phalanges (toes). 

Methemoglobin
An altered hemoglobin which does not carry oxygen.

Methemoglobinemia
A condition of the blood in which there are large amounts of methemoglobin which is an altered hemoglobin which does not carry oxygen.

Microfilaria
The larval form of some parasitic worms, for example heartworms. These worms do not lay eggs, they produce microfilariae instead.

Microfilaricide
Compound which kills microfilaria, the immature forms of heartworms which circulate in the blood.

Microorganism
A single-celled life form that is invisible to the naked eye and that may cause disease in man or animals.

Mineralization
The process in which minerals are laid down within tissue in an abnormal pattern causing a hardening of the tissue.

Mineralocorticoids
Hormones produced by the adrenal gland which regulate the amounts of sodium, potassium, and chloride in the blood.

Miticide
An agent that kills mites.

Mitochondria
Parts of the cell which are responsible for providing the cell with energy.

mL
Short for milliliter. A liquid measure, the same volume as a cc. 28 mL = 1 liquid oz.

Modified live vaccine
Vaccines which are made by taking the real, disease-causing virus and altering (attenuating) it in a laboratory to a non-disease causing virus. Compare with 'killed vaccine' and 'recombinant vaccine.'

Monoamine oxidase inhibitor
(MAOI): Substances that inactivate the enzyme monoamine oxidase which regulates certain transmitter chemicals between nerves. These compounds include certain types of antidepressants and also insecticides containing amitraz (such as Mitaban and Preventic collars).

Monovalent vaccine
A vaccine that is manufactured to stimulate the body to produce protection against only one disease, e.g., rabies vaccine. Compare with 'multivalent vaccine.'

Motility
Movement, e.g., intestinal motility is the muscular contractions of the intestines which move the food from the stomach to the anus.

Mucolytic
Breaks down mucous.

Mucopolysaccharide
A carbohydrate which also contains a hexosamine molecule and is a component of mucous.

Mucosa
Specialized membrane which covers various passages and cavities exposed to the air such as the mouth, nose, inner portion of the eyelids, vagina. Examination of the mucous membranes can provide important information: if they are dry, the animal is likely dehydrated; pale, and the animal may be anemic or in shock; yellow, and the animal is said to jaundiced due to accumulation of waste products which should be eliminated by the liver. Mucous membranes.

Mucous membranes
Specialized membrane which covers various passages and cavities exposed to the air such as the mouth, nose, inner portion of the eyelids, vagina. Examination of the mucous membranes can provide important information: if they are dry, the animal is likely dehydrated; pale, and the animal may be anemic or in shock; yellow, and the animal is said to jaundiced due to accumulation of waste products which should be eliminated by the liver.

Multivalent vaccine
A vaccine that combines two or more components to stimulate the body to produce protection against all the components. Most 'distemper' vaccines for puppies are of the multivalent type, and commonly include distemper, parvovirus, adenovirus cough, hepatitis, and parainfluenza. Compare with 'monovalent' vaccine.

Musculoskeletal
Pertaining to the muscles and skeleton.

Myasthenia gravis
Myasthenia gravis is a neuromuscular disease in which there is a failure of the nerves' ability to stimulate and control the actions of certain muscles. See article: Myasthenia gravis in Puppies.

Mycosis
Disease caused by a fungus such as blastomycosis, histoplasmosis, and ringworm.

Mydriasis
Small pupil size.

Myelogram
Radiograph (x-ray) of the spinal cord taken after a contrasting dye has been injected into the space around the spinal cord.

Myocardium
The middle layer of heart muscle. 

Nauplii
Newly hatched brine shrimp.

Nebulize
Convert into a fine spray form.

Necropsy
Postmortem examination.

Necrosis
The death and breakdown of cells.

Neoplasia
Abnormal growth and accumulation of cells. Neoplasias may be benign or malignant.

Nephropathy
Any disease or abnormal functioning of the kidney.

Nephrotoxic
Destructive to kidney cells.

Neuropathy
Abnormal functioning of nerves.

Neurotransmitter
Chemical used as a messenger from one nerve cell to another.

Neuter
Sterilization by surgical removal of the testicles of a male animal or ovaries of a female animal.

Neutralize
To change from acidic or alkaline to a neutral pH. 

NIDDM
Non-insulin dependent diabetes mellitus (NIDDM): A type of diabetes mellitus in which although the blood glucose levels are higher than normal, they are not immediately life-threatening, and the animal can survive without supplemental insulin. Also called Type II diabetes.

Nocturnal
Animals that are active during the night and sleep during the day.

Nodule
Solid bump or lump in the skin that is over 1/3 inch in diameter.

Non-steroidal anti-inflammatory
NSAIDS: Agents which reduce inflammation, but are not in the class of drugs known as steroids. Examples include aspirin, Rimadyl, and phenylbutazone.

Noncore vaccine
Vaccine which should only be given to animals at increased risk of exposure to a disease, example, leptospirosis in dogs or feline leukemia in cats (see core vaccine).

Nonpathogenic
Not causing disease. Some bacteria, such as those that normally live in an animal's intestines, are nonpathogenic.

Nonseptic
A condition not caused by an infection. For example, septic arthritis is caused by an infection with bacteria, yeast, or other agent; a case of nonseptic arthritis may be caused by injury or cancer.

Nutraceutical
A very broad term describing certain components in food (plant or animal) or nutritional supplements, which contain substances normally present in the body that aid in the proper functioning of body systems.

Nutrient
Compounds in foods which are essential for life. Nutrients include protein, fats, vitamins, minerals, etc.

Nystagmus
Constant involuntary movement of the eye, often from side to side.

Obligate carnivore
An animal that requires in its diet nutrients that are found in sufficient quantities only in meat or other animal products.

Obsessive compulsive
A behavioral condition in which a pet repeatedly performs an action out of context. It is thought that the behavior is an expression of stress, frustration and/or conflict. Certain breeds are more prone to these behaviors. The behaviors include tail-chasing, some cases of excessive barking, continual licking, and biting the air as if snapping at an invisible fly.

Ocular
Relating to the eye. 

Off label
Term used to describe the use of a medication for a condition for which it was not FDA approved. A large number of medications used in veterinary medicine are used 'off label.' If veterinarians only used FDA approved medications, options for treatments of certain conditions would be severely limited or nonexistent. The safety and efficacy of off-label uses of medications is often determined in university research settings, but the manufacturer of the drug does submit the results or go through the elaborate FDA approval process.

Offal
Animal organs rejected at slaughter as unfit for human consumption, e.g., spleen, intestine, brain, lungs.

Omnivore
Animal that eats both flesh and plants.

Opioid
Narcotic drug which has an activity similar to that of opium.

Oral hypoglycemic
A medication, given by mouth, which lowers the level of glucose in the blood. Example: glipizide.

Osmotic diuretic
A compound that increases the amount of urine formed and rids the body of excess fluid by being filtered through the kidney into the urine in concentrated amounts and carrying water with it.

Osteomyelitis
An inflammation and infection of the bone.

Otic
Pertaining to the ear.

Ototoxic
Destructive to the structures of the ear.

Over the counter
Can be purchased without a prescription, like aspirin and vitamins.

Ovulate
The release of an egg from the ovary of the female.

Oxidize
To combine with oxygen. 

Packed cell volume
(PCV), hematocrit: A laboratory test to monitor the relative number of red blood cells present in the blood. A blood sample is placed in a tiny glass tube and spun in a centrifuge. The cells are heavier than the plasma and are compacted at one end of the tube. After the tube is spun, it is examined and the packed cell volume is determined as the percentage of the red cellular portion relative to the total amount of blood in the tube (i.e., remainder being the plasma). The normal for dogs is 40-59 and cats is 29-50.

Palatable
Tasty; refers to food that is readily accepted.

Palpation
To examine with the hands or fingers.

Pancreatitis
Inflammation of the pancreas, a severe and sometimes life threatening disease often associated with eating fatty foods. Symptoms include vomiting and a painful abdomen.

Pannus
A chronic condition of the eye in which blood vessels grow across the cornea (the clear surface of the eye). The cornea looks hazy and sometimes reddened; it may eventually take on a dark pigment. This condition is also called chronic superficial keratitis.

Papule
Solid bump on the skin, less than 1/3 inch in diameter.

Paralysis
Loss of motor function (movement) in a certain part of the body. Paralysis may be flaccid, in which muscles are weak and have little or no tone; or spastic, in which the muscles are tight.

Parasympathetic
The portion of the nervous system which stimulates the pancreas to produce digestive enzymes and stimulates many of the smooth muscles in the body including those of the stomach and intestine. It also tends to slow the heart rate.

Parenterally
A term used to describe the administration of a drug by means other than by mouth.

Paresis
Slight or incomplete paralysis. 

Parthenogenesis
A form of reproduction in which the egg develops into a new individual without fertilization by sperm. Parthenogenesis has been observed in many lower animals, including some snails and insects.

Parturition
The act of giving birth.

Passive immunity
Immunity produced by providing an animal with antibodies or immunologic cells from another source, such as colostrum. Compare with 'active immunity.'

Pathogenic
Causing disease.

PCV
Packed cell volume. PCV, hematocrit: A laboratory test to monitor the relative number of red blood cells present in the blood. A blood sample is placed in a tiny glass tube and spun in a centrifuge. The cells are heavier than the plasma and are compacted at one end of the tube. After the tube is spun, it is examined and the packed cell volume is determined as the percentage of the red cellular portion relative to the total amount of blood in the tube (i.e., remainder being the plasma). The normal for dogs is 40-59 and cats is 29-50.

Pediculosis
An infestation of lice.

Penicillinase
An enzyme produced by some bacteria which inactivates certain types of penicillin thus making the bacteria resistant to them.

Perianal fistula
A deep infection around the anus which often results in ulcers and deep draining tracts, most commonly seen in German Shepherds.

Perineal
The area between the anus and the genital organs.

Peritoneal dialysis
A process used to remove waste products from the body. Electrolyte fluids are administered into the abdomen, waste products of the body enter the fluids, and then the fluids are removed.

Peritoneum
The membrane lining the wall of the abdominal cavity. 

Peritonitis
Inflammation of the lining of the abdomen.

Phagocyte
Cell in the body which 'eats' damaged cells and foreign substances such as virus and bacteria. A macrophage is a type of phagocyte.

Phalanges
Toes. 

Pheromone
Chemical secreted by an animal and sensed by another animal of the same species, and often causing behavior change in that animal.

Photoperiod
The number of hours of light per 24-hour period.

Photosensitivity
A condition in which the skin reacts abnormally to light, especially ultraviolet light or sunlight. It is usually caused by the interaction of light with certain chemicals in the skin such as antibiotics, other medications, hormones, or toxins.

Phytochemical
Substances in plants which affect a body system and may promote health and decrease the risk of a disease such as cancer.

Phytoestrogen
Substances which have an activity similar to estrogens and are produced by plants.

Placebo
A substance which is given that has no therapeutic value; often called a 'dummy pill' or 'sugar pill.' Often given to half of the patients in a trial of a new drug, to better assess the effectiveness of the new drug.

Plantigrade stance
Standing and walking with the hocks on or almost touching the floor.

Plaque
A build-up of bacteria, saliva, and food on the teeth. See also Tartar.

Plastron
The lower hard shell-like structure which protects the abdomen of a turtle or tortoise.

Platelets
Cellular components found in the blood which help clots to form. In the body, microscopically small vessels often break in the normal course of events. Platelets and a protein called fibrinogen 'plug' the break in the vessel and prevent blood from leaking out.

Polyarthritis
Arthritis which involves two or more joints.

Polydactyl
The presence of extra toes.

Polydipsia
Excessive thirst resulting in excessive drinking.

Polyestrous
During one sexual season, continuing to come into heat if not bred. Cats are polyestrous, dogs are not.

Polyp
A small growth from mucous membranes such as those lining the nasal cavity and intestinal tract.

Polyphagia
Excessive ingestion of food.

Polyuria
Excessive urination.

Posterior
Relating to the area of the body near the tail or the rear half of the animal. 

Postoperative
After surgery.

Proestrus
The stage of the estrus cycle, right before an animal comes into heat.

Progesterone
A hormone produced by the ovaries which is responsible for the continuation of pregnancy.

Prolactin
Hormone secreted by the pituitary gland that stimulates the growth of mammary tissue and the production of milk.

Prolapsed rectum
Because of irritation or injury, the inner part of the rectum is pushed out so that it is visible as a pink mass protruding from the anal opening.

Prostaglandin
Several types of chemicals made by cells which have specific functions such as controlling body temperature, stimulating smooth muscle, and influencing heat cycles.

Protease
Enzyme which breaks down protein.

Protozoans
Single-celled animals invisible to the naked eye. Most are free living and a few are parasites in animals or man.

Pruritus
Itching.

Psittacine
Birds that belong to the order Psittaciformes. Common psittacines include budgies, cockatiels, lories, cockatoos, conures, amazons, African greys, lovebirds, senegals, and jardines.

Pulmonary
Relating to the lungs. 

Pulmonary edema
Fluid accumulation in the lungs.

Pulmonary emboli
Pulmonary embolism: Blood clot that travels to the blood vessels in the lung and obstructs them.

Pupa
A dormant form of an insect (plural pupae). A larva spins a cocoon to protect itself, and becomes a pupa. The pupa does not feed, but gradually changes form and becomes a new adult.

Pustule
Small elevated area on the skin filled with pus.

Pyloroduodenal
An obstruction in the area where the stomach and small intestine meet.

Pyoderma
An infection of the skin; usually the result of a bacterial invasion.

Pyometra
An infection of the uterus.

Queen
A female cat used for breeding.

Queening
In cats, the act of giving birth.

Rabies
A fatal virus disease of warm blooded animals including man, that affects the brain and is spread in the saliva of infected animals. Rabid animals have a temperament change. Wild creatures become bold enough to attack human beings, and docile domestic animals may turn on their owners.

Reagent grade
A compound with the purity and quality that allows it to be used in a laboratory.

Recombinant vaccine
There are certain antigens on viruses and bacteria which are better at stimulating an antibody response by the animal than others. The genes for these antigens can be isolated, and made to produce large quantities of the antigens they code for. A recombinant vaccine contains these antigens, not the whole organism. Compare with 'modified live vaccine' and 'killed vaccine.'

Recumbency
Lying down. 

Reflex ovulator
Only ovulating after being bred. Cats are reflex ovulators, dogs are not.

Regulation
Using insulin to maintain the blood glucose level of an animal within the acceptable range.

Resistance
A term used to describe bacteria which have mutated or changed so they are not affected by an antibiotic that previously killed them or slowed their growth. As more bacteria become resistant to various antibiotics, there are fewer antibiotics which will have an effect on them, thus newer and stronger antibiotics will need to be developed. Inappropriate use of antibiotics (using them too often, for too short a duration or in insufficient dose) may promote the development of resistance.

Resorption
In pregnancy, a condition in which the fetus dies, and instead of being aborted, the fetal tissue dissolves within the uterus and is absorbed by the mother. The mother will show no outward signs of a fetal resorption.

Respiratory
Relating to breathing or the lungs. 

Respiratory depression
Decrease in the rate or depth of respiration.

Retina
The rear interior surface of the eyeball is called the retina. The retina contains nerve cells referred to as rods and cones. The rods are sensitive to light and the cones to color. The retina receives the light and color and converts them into nerve impulses which go to the brain.

Scale
Accumulation of loose fragments of the top layer of the skin.

Schiff-Scherrington posture
A condition, caused by a lesion in the spinal cord, in which the front legs are held rigid and straight, and the rear legs are weak or paralyzed. Sometimes, the neck may be hyperextended, with the head held up and over the back.

Sclerosis
A hardening of tissue, usually the result of chronic inflammation.

Scute
In turtles and tortoises, the plates which cover the bony portion of the shell. In snakes, the larger, thicker scales on the underside of the body which provide support, protection, and traction.

Sebaceous adenitis
Inflammation of a sebaceous (oil-producing) gland. In dogs, sebaceous glands are found on the top of the tail near its base, and at the junction of mucous membranes with skin. In cats, these glands are found on the chin, lip margins, and the top of the tail.

Sebaceous gland
A gland in the skin which produces an oily substance.

Second generation
A description of medications developed from an earlier form of the medication. First generation medications were developed from the original form of the drug; second generation medications are adaptations of first generation drugs; third generation drugs are adaptations of second generation, etc.

Secondary infection
Infection which occurs because the tissue and its natural defenses have been damaged by another condition.

Secondary response
The faster and greater immune response produced by an animal who has previously encountered that specific antigen. Memory cells are responsible for this more efficient response. Also called 'anamnestic response.'

Seizure threshold
The level of stimulation at which a seizure is produced. Raising the seizure threshold makes it less likely a seizure will occur.

Selective serotonin reuptake inhibitor
(SSRIs), Selective serotonin reuptake inhibitors: Medications which slow down the ability of nerve cells to absorb serotonin, a neurotransmitter (chemical that serves as a messenger between nerves). Example: Prozac.

Separation anxiety
A behavioral condition in which the pet becomes anxious when separated from the owner. Dogs with separation anxiety tend to 'shadow' their owners, greet them exuberantly when they return after being gone, and sometimes vocalize, chew destructively, and urinate or defecate when separated from their owners.

Sepsis
The presence of toxins in the blood or other tissues; the toxins are produced by bacteria or other microorganisms. 

Septic
A condition caused by an infection e.g., with bacteria or fungi, or toxins they produce.

Septicemia
A disease affecting many organ systems due to toxins in the blood which are released by bacteria or other microorganisms. Signs include fever, pinpoint bruises on mucous membranes, and lesions in the joints, heart valves, eyes, or other organs.

Serology
Laboratory testing for antibody-antigen reactions and antibody levels. 

Serotype
A subdivision of a species of microorganism, e.g., a bacteria, based upon its particular antigens.

Serous
Thin and watery.

Serum
The fluid portion of the blood after it has clotted and the cells have been removed. 

Shedding
Shedding (of organisms): A term used to describe the release of organisms (bacteria, protozoa, viruses) into the environment from an infected animal. The organisms may be in the stool, urine, respiratory secretions, or vaginal discharges. The 'shedding' animal may or may not be showing symptoms of disease.

Skin scraping
Scraping some material from the surface of the skin and looking at it under a microscope, e.g., to check for skin mites.

Smooth muscle
The type of muscle found in the internal organs such as stomach and intestines (not the heart).

Soluble carbohydrate
Also, soluble fiber. Easily digested carbohydrates like starch.

Somnolence
Sleepiness, a condition of semiconsciousness approaching coma. 

Somogyi effect
A condition in which the blood glucose level increases if too much insulin is given. It occurs when insulin causes the blood glucose level to go so low it stimulates the production of other hormones in the body such as epinephrine, which promote the breakdown of glycogen (the chemical compound which the body uses to store glucose) and increases the blood glucose level above normal. It is also called rebound hyperglycemia or insulin-induced hyperglycemia.

Spay
Sterilization by surgical removal of the ovaries and uterus of a female animal.

Sphincter
A ring-like band of muscle that constricts a passage or closes an opening, e.g., the anal sphincter constricts to close the anus and relaxes when the animal is passing stool. The urethral sphincter closes the urinary bladder.

Spirochete
A type of bacteria which is long, slender, and assumes a spiral shape. Leptospira species and the bacteria that causes Lyme disease (Borrelia burgdorferi) are spirochetes.

Spleen
Part of the immune system of an animal. A large, tongue-shaped organ in the abdomen containing many lymphocytes. The spleen filters blood and removes damaged cells. It can also manufacture new blood cells if the animal's bone marrow is damaged.

Squamate
Scaly-bodied reptile including lizards and snakes.

SSRI
Selective serotonin reuptake inhibitors: Medications which slow down the ability of nerve cells to absorb serotonin, a neurotransmitter (chemical that serves as a messenger between nerves). Example: Prozac.

Stasis
In the gastrointestinal tract, a condition in which the food does not move through normally, but remains in one section, e.g., food does not pass from the stomach into the intestine.

Status epilepticus
A condition in which the animal exhibits one severe (Grand Mal) seizure right after another, with no time to recover in-between.

Stenosis
The narrowing of an organ of passage such as a blood vessel or intestine.

Stress-induced hyperglycemia
A condition in cats in which the blood glucose level becomes abnormally high when the animal is stressed, e.g., in the veterinarian's office.

Stricture
The narrowing of an organ of passage such as a blood vessel or intestine.

Struvite
A chemical compound, magnesium ammonium phosphate, which is made by the body and can form crystals and stones in the urinary bladder.

Subcutaneous
Under the skin; often called 'sub Q.'

Subluxation
A partial dislocation of a joint in which the bones become out of alignment, but the joint itself is still intact.

Substrate
Relative to the husbandry of reptiles, amphibians, and small mammals, the substrate is the material that lines the bottom of a cage.

Sulfonamides
A class of antibiotics which contain sulfur. They are bacteriostatic (they stop the growth (reproduction) of bacteria, but do NOT kill them).

Superfecundation
Having a litter with more than one father (or breeding).

Supraventricular tachycardia
A condition in which the heart beats very rapidly because of signals coming from the atria (chambers of the heart that receive the blood) or near the junction of the atria with the ventricles (the chambers of the heart that pump the blood to the body or lungs).

Sympathomimetic
Producing effects similar to the 'flight or fight' response, which means the body is alerted to a danger of some sort and prepares to basically run or fight. Sympathomimetic effects include increased heart rate, sweating, and increased blood pressure.

Synergist
An agent that enhances the action of another.

Synovial
Pertaining to a joint made up of bone ends covered with cartilage, ligaments, a cavity filled with synovial fluid (joint fluid) and an outside fibrous capsule, e.g., hip joint, elbow joint.

Systemic
Throughout the body.

T cell
Also called 'T lymphocytes.' The type of lymphocyte which is responsible for cell-mediated immunity. T cells may directly kill a cell or produce chemicals called lymphokines that activate macrophages which will kill the cell. Compare with 'B cell.'

Tachycardia
An abnormally high heart rate.

Tarsus
The ankle (rear leg) of dogs and cats; also called the hock. 

Tartar
A build-up of bacteria, saliva, and food on the teeth which becomes mineralized, forming a hard coating and eventually causing gum disease and tooth loss. See also 'Plaque.'

Temporomandibular joint
The joint between the lower jaw and the skull.

Third generation
A description of medications developed from an earlier form of the medication. First generation medications were developed from the original form of the drug; second generation medications are adaptations of first generation drugs; third generation drugs are adaptations of second generation, etc.

Thrombocytopenia
A lower than normal number of platelets in the blood. Platelets, which are actually fragments of specific types of cells, are necessary for blood to clot. Signs of thrombocytopenia include bruising and bleeding from the nose, into the gastrointestinal tract, etc.

Thyrotropin releasing hormone
Hormone produced by the hypothalamus that stimulates the pituitary gland to produce thyrotropin (thyroid stimulating hormone-TSH), which in turn stimulates the thyroid gland to produce thyroid hormone. Also called TSH releasing factor or TSH releasing hormone.

Tissue
A group of specialized cells that together perform a particular function, e.g., muscle tissue, nerve tissue, bone.

Titer
A measurement of the amount of antibodies in the blood. The test to measure antibodies is usually performed by making a number of dilutions of the blood and then measuring at what dilution there is sufficient antibody to react in the test. For example, a titer of 1:8 (one to eight) means the blood can be diluted to one part blood and seven parts saline and still produce a positive reaction in the test. The higher the titer (1:16 is higher than 1:8), the more antibody is present. (NOTE: The word 'titer' may also be used when discussing the amount of antigen present, e.g., a high titer vaccine has a large number of virus particles.)

Topical
To be used on the skin.

Torsion
The twisting of an organ.

Toxemia
A condition in which toxins move into the bloodstream.

Tracheobronchitis
Inflammation of the trachea and bronchi.

Transient
Temporary. 

Transport host
An animal or insect which carries an immature parasite from one mammalian host to another.  

Tricyclic antidepressant
A class of antidepressants which work by decreasing the amount of certain chemical transmitters taken up by specific nerve cells. The tricyclic antidepressants include clomipramine, amitriptyline, and nortryptyline and are often used to treat behavioral problems in small animals.

Tumor
Abnormal growth or swelling; term often used to designate cancer.

Type I diabetes
A form of diabetes in which so little insulin is produced that supplemental insulin must be given for the animal to live. Also called insulin dependent diabetes mellitus (IDDM).

Type II diabetes
A type of diabetes mellitus in which although the blood glucose levels are higher than normal, they are not immediately life-threatening, and the animal can survive without supplemental insulin. Also called non-insulin dependent diabetes mellitus (NIDDM).

Ulcer
A lesion in which the tissue surface is eroded away.

Ultrasound
Ultrasound/ultrasonography: A technique used to get the image of a deep structure within the body by directing ultrasound waves at it and recording the reflections (echoes) from it.

Umbilicus
The area of the body where the umbilical cord is attached; the belly button.

Urate
A chemical compound which contains uric acid and is made by the body, and can form crystals and stones in the urinary bladder. Uric acid is a waste product from the breakdown of certain proteins.

Urea
Wasteproduct of protein metabolism that is removed from the body by the kidneys.

Urease
An enzyme that breaks down urea. Urea is a wasteproduct of protein metabolism that is removed from the body by the kidneys.

Urinary incontinence
A phrase used to describe the inability to control urination.

Urinary obstruction
A blockage in the urinary system, most often occurring in the urethra, the tube that leads from the urinary bladder to the outside of the body.

Urinary retention
A condition in which the urinary bladder does not rid itself of all urine it contains during the process of urination.

Urticaria
Hives; development of small swellings which may itch; usually caused by an allergic reaction. 

USP
United States Pharmacopeia - a drug regulating agency.

Uveitis
Inflammation of the eye.

Vaccination
The act of giving a vaccine. See also 'immunization,' since the two words have different meanings and are often confused.

Vaccine failure
A term often used to describe a condition in which an animal who was vaccinated against a disease still gets the disease. In truth, there is usually nothing wrong with the vaccine, but for some reason, the animal's immune system did not adequately react to it.

Vasculitis
Inflammation of blood vessels.

Vasoconstriction
A decrease in the diameter of blood vessels. 

Vasodilator
Agent which dilates, or increases the diameter of blood vessels.

Ventricle
The chambers of the heart that pump the blood to the body or lungs.

Ventricular arrhythmia
A heart condition in which the heart beats irregularly and/or at an abnormal rate because of signals coming from the ventricles (chambers of the heart that pump the blood).

Vertebrate
Animal with a vertebral column (spine); includes such animals as fish, birds, turtles, reptiles, amphibians, and mammals.

Vesicle
Small elevated area on the skin filled with a clear fluid.

Vestibular system
Portions of the inner ear, nerves, and brain which help the body maintain balance.

Villi
Microscopic projections which cover the intestine, greatly increasing the surface area and therefore, increasing the ability to absorb nutrients. Singular: Villus.

Virus
The smallest form of life, invisible with an ordinary microscope. An infectious unit that enters and uses cells of plants or animals for replication. Some viruses cause disease in animals or plants.

Viscerocutaneous
Pertaining to the internal organs and skin. 

Viscosity
Thickness of a fluid, e.g., molasses is more viscous than water. 

Vital signs
The signs of life which are pulse, respiration, and temperature.

Volvulus
Twisting of the stomach or intestine, which often has the effect of cutting off the blood supply to it. 

Vomeronasal organ
Sensory organ also called 'Jacobson's organ,' which detects pheromones.

Warm-blooded
Having a relatively high body temperature that is regulated internally and is independent of the environmental temperature. Mammals and birds are warm-blooded.

Wart
Benign growth caused by a virus.

Wasting
Loss of muscle mass due to decreased food intake or increased metabolic rate.

Whelping
In dogs, the act of giving birth.

White blood cells
Cells in the blood whose major role is to defend the body against invading organisms such as bacteria, viruses, and fungi. There are different types of leukocytes: lymphocytes are part of the immune system; monocytes, eosinophils, and neutrophils eat or engulf organisms; basophils contain histamine and are involved in inflammatory reactions.

Window of susceptibility
A time period in the life of a young animal in which the maternal antibodies are too low to provide protection against a certain disease, but too high to allow a vaccine to work and produce immunity.