"A" Vocab for 'Anatomy and Physiology of Companion Animals'
Terms
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- A bands
- Large, dark bands in a skeletal muscle fiber that aleternate with lighter I bands to give a striped appearance to skeletal muscle fibers under a microscope. The A bands are composed of thick filaments of the contractile protein myosin.
- abduction
- The joint movement whereby an extremity is moved away from the median plane
- abomasum
- The "true stomach" of the ruminant; secretes acids, mixes and contracts ingesta, and moves liquid chyme into the small intestine.
- aboral direction
- Away from the mouth.
- absorptive cell
- A cell commonly found in the small intestine that can absorb nutrients from the luminal surface cia phagocytosis and pinocytosis. Absorptive cells have large surface areas as a result of the presence of microvilli. The expanded surface area increases the absorptive capability of the cell.
- accommodation
- The focusing of the lens of the eye to allow close-up and faraway vision. It is accomplished by the muscles of the ciliary body that apply or relieve tension on the suspensory ligaments that attach it to the lens.
- acetabulum
- The socket portion of the ball-and-socket hip joint. It is formed at the junction of the ilium, ischium, and pubis bones of the pelvis.
- acetylcholine
- Neurotransmitter; associated with parasympathetic nervous system effects even though it is the neurotransmitter used in the preganglionic ceuron in both the sympethetic and parasympathetic nervous system; has a stimulatory effect on the gastrointestinal tract; increases secretions and muscle contractions in the esophagus, stomach, ruminant forestomachs, intestine, and colon.
- acetylcholinesterase
- The enzyme that breaks down acetylcholine.
- acinar gland
- The secretory units of exocrine glands that contain one or more saclike structures.
- acromegaly
- A form of giantism that results from an excess of growth hormone.
- acromsome
- The caplike structure that partially covers the heads of spermatozoa. It contains digestive enzymes that are activated when the cells enter the female reproductive tract. They help the cell penetate through the layers areound the ovum to fertalize it.
- ACTH
- Adrenocorticotropic hormone
- actin
- A protein that composes microfilaments. It is found in teh cytoskeleton, in myofibrils of muscle fibers, and in spindle fibers during cell division.
- actin filaments
- One of the two contractile proteins of muscle (myosin is the other one) that slide over each other to produce the shortening of the muscle cell that we refer to as muscle contraction.
- action potential
- The change in electrical charges that occurs during nerve depolarization; also called the nerve impulse; the changes in cellular polarity that define the electrical activity of cardiac tissue.
- active immunity
- Activation of the imune system by either administration of a vaccine that contains a modified antigen or exposure to the antigen (e.g., by disease)
- active site
- The specific area on an enzyme that connects with a substrate to cause a chemical reaction.
- active transport
- The process that moves ions or molecules across the cell membrane and against the concentration gradient, requiring energy or ATP to be accomplished.
- adduction
- The joint movement whereby an extremity is moved toward the median plane.
- adenine (A)
- One of the nucleotides present in both DNA and RNA. It is a purine base that corresponds to RNA's uracil and DNA's thymine.
- adenosine diphosphate
- The "discharged" form of adenosine triphosphate. It is a nucleotide that contains two phosphoric acid groups. When a phosphate group is split off an ATP molecule to produce ADP, energy is released that, in muscle, powers the sliding of the actin and myosin filaments over each other. When the phosphate group is reattached (which requires another energy source), ADP is converted back to ATP and the molecule is ready to provide energy again.
- adenosine triphosphate
- A high-energy molecule produced in the mitochondria of cells. It is a nucleotide that contains three phosphoric acid groups. When a phosphate group is split off an ATP molecule to produce ADP, energy is released that, in muscle, powers the sliging of the actin and myosin filaments over each other. When the phosphate group is reattached (requires another energy source), ADP is converted back to ATP and the molecule is ready to provide energy again. The more active a cell or body part is, the more ATP it will have produced and stored. For instance, muscles have a great deal of stored ATP, whereas fat has very little.
- ADH
- Antidiuretic hormone
- adipocyte/adipose cells
- A type of ficed cell in the connective tissue that stores fat (lipids) in its cytoplasm. The nucleus and other organelles are pushed to the periphery of the cell.
- adipose connective tissue
- A subclass of connective tissue proper, adipose connective tissue is a vascularized type of connective tissue whose general functions are to protect, insulate, and provide a major source of energy to the body. Adipose conncetive tissue can ovvur as either brown or white adipose tissue. White adipose tissue, found commonly throughout the body, is a storage area for lipids. These lipids may be used for the production of energy or ATP. Brown adopose tissue, found in neonate and hibernating specias, has its lipids converterd to heat.
- adipose
- Fat.
- adrenal cortex
- The outer portion of the adrenal gland that produces glucocorticaid, mineralocorticoid, and sex hormones.
- adrenal glands
- Two endocrine glands loxated near the cranial poles of the kidneys. Each consists of an outer cortex and an inner medulla.
- adrenal medulla
- The inner portion of the adrenal gland that produces the hormones epinephrine and norepinephrine.
- adrenergic neurons
- Neurons that secrete catecholamines as their neurotransmitter.
- adrenocorticotropic hormone (ACTH)
- A hormone secreted by the anterior portion of the pituitary gland, which in turn activates the adrenal gland. The adrenal gland then releases its own hormones. ACTH is vital to the normal function and decelopment of the adrenal gland.
- adult hemoglobin
- The primary type of hemoglobin founjd in the red blood cells of animals beginning a couple of weeks to a couple of months after birth.
- aerobic metabolism
- Ocygen-consuming metabolism. The type of metabolism in muscle in which the supply of acailable ocygen is sufficient to keep up with the energy needs of the muscle fibers. Aerobic metabolism extracts the maximum amount of energy from glucose molecules.
- aerobic respiration
- The cell function that produces chemical energy with the use of oxygen.
- afferent glomerular arterioles
- The smallest arteriole branches that carry blood into the glomerulus for filtration.
- afferent nerve
- Nerve that carries impulses toward the central nervous system.
- afterbirth
- The name given to the placenta at parturition becuase it is delivered 'after' the newborn.
- afterload
- The sum of the forces that the heart must overcome during ventricular contractions.
- agglutination
- Precipitation of clumping of anigen-antibboy complexes; one of the methods by which the immune system nuetralizes antigens.
- agranulocytes
- White blood cells without vytoplasmic granules. The agranulocutes are the momocytes and the lumphocytes; also known as nongranulocytes.
- air sacs
- Nine thin, transparent membranses that are connected to the primary and secondary bronchi and act as reservoirs for air entering and leaving the lungs.
- albumin
- Protein manufactured by the liver that plays an importnat role in maintaining the osmotic fluid balance between capillaries (blood) and tissues; a lack of albumin reulsts in movement of fluid from the capillaries into the tissues, producing edema and fluid accumulation in body cavities.
- aldosterone
- A mineralocorticoid hormone secreted by the cortex of the adrenal gland. It stimulates the kidney to conserve sodium ions and water and to eliminate potassium and hydrogen ions.
- alimentary canal
- Also called the digestive tract, this encompasses all of the parts of the digestive system that transport frood from teh mouth to the anus; mouth, esophagus, stomach, small and large intestines, and anus.
- alkaline
- The adjective that describes substances with a pH above 7 (basic). Basic or alkaline solutions have fewer hydrogen ions or more hydroxide ions than pure water.
- allantoic sac
- Part of the placenta. It is a fluid-filled sac formed by the allantois that surrounds the amniotic sac.
- allantois
- Part of the placenta. It is the membrance that forms the allantoic sac.
- all-or-none principle
- Refers to the way in which a neuron depolarizes completely or not at all in response to stimulation.
- all-or-nothing principle
- The principle that an individual muscle fiver either contracts completely or does not contract at all.
- alopecia
- Loss of hair.
- alpha1-adrenergic receptors
- Receptors associated with teh sympathetic nercous system response; these receptors, when stimulated by catecholamines, tend to cause vasoconstriction (constriciton of blood cells).
- alpha cells
- Cells in the pancreas that produce glucagon
- alpha helix
- The coiled structure in a complex protein composed of gyderogen bonds and amino acids.
- altricial
- Chicks that are hatched with their eyes closed and their skins bare and that are immobile.
- alula
- Bone in birds that originates from the wrist and is comparable with a first finger; carries feathers that aid in steering.
- alveolar ducts
- The smallest air passageways in the lungs. The alveolar ducts carry air to the alveolar sacs.
- alveolar gland
- Secretory units of exocrine glands that are saclike in form; also called acinar gland.
- alveolar sacs
- Clusters of alveoli at the ends of the alveolar ducts. The alveoli are arranged like bunches of grapes.
- alveoli (alveolus)
- Microscopic, thin-walled sacs surrounded by networks of capillaries. The interface between the wall of the alveoli and the wall of the capillary is where the actual exchange of gases takes place in the lungs.
- amino acid
- The basic building block of peptides and proteins; those organic compounds, numbering around 80, that are made up of amino group (NH2) and a carboxyl group (COOH). Amino acids make up proteins when joined together in peptide bonds. They are naturally occuring in all plants and animals.
- aminopeptidase
- Protease secreted in an inactive form from the pancreas and activated by trypsin.
- amnion
- Part of the placenta. It is teh membrance that forms the fluid-filled amniotic sac.
- amniotic sac
- Part of the placenta. It is the fluid-filled sac that immediately surrounds the deceloping fetus.
- amoeboid motion
- Amoeba-like movement accomplished by the extension of pseudopodia to create a streaming movement of cytoplasm.
- amorphous
- Having no defined shape
- amphiarthrosis
- A slightly movable cartilaginous joint, such as the pelvic symphysis.
- ampulla
- An enlargement in each semicirculat canal that conatains the receptor structure (the crisa).
- ampulla of the cas deferens
- An enlargement of the vas deferens just before it enters the urethra. It is present in some species and absent in others.
- amylase
- Enzyme produced by the pancreas and, in some species, the saliva; attacks starch and breaks it into disaccharides (two sugar molecules)
- amyloid
- An excessive amount of a waxlike, proteinaceous substance in the body's tissue.
- anabolism
- The form of metabolism by which cells build complex compounds from simpler ones; the opposite of catabolism. The process by which the cell uses energy to manufacture large molecules form smaller ones; these molecules are used to matintain the cell and carry out metabolic processes.
- anaerobic
- A biochemical pathway that can function without oxygen. The term also may be used to describe microbes that can live in the absence of oxygen.
- anaerobic glycolysis
- An alternative expression for glycolysis referring to the fact that the reaction does not require oxygen.
- anaerobic metabolism
- Nonoxygen-dependent metabolism. The type of metabolism in muscle that occurs when the need for energy to produce muscular activity exceeds the available oxygen supply. Anaerobic metabolism is not as efficient as aerobic metabolism and results in the formation of lactic acid as a byproduct. Lactic acid can cause discomfort in muscle tissue and requires oxygen to be converted back to glucose.
- anaerobic respiration
- The cell function that produces energy chemically with the use of free oxygen.
- anagen phase
- The active phase of hair growth.
- anal sacs
- Perianal sacs, containing apocrine and sebaceous glands, that are located at teh 5 o'clock and 7 o'clock positions relative to the anus. The sacs reside between the internal and external sphincter of carnivores and prduce a strong smelling fluid when expressed. They are important for fecal territorial marking and are expressed during fearful episodes.
- analgesia
- Decreased perception of pain.
- anaphase
- The phase of mitosis when the daughter chromosomes begin to migrate to their respective centrioles, away from the center of the dividing cell.
- anaphylaxis
- A sever, potentially life-threatening, allergic response.
- anatomy
- The study of the form and structure of an animal body and its parts. Through anatomy we can describe where things are located in or on the animal body and what they look like.
- anconeal process
- A beak-shaped process at the proximal end of the trochlear notch of the ulna. When it fails to unite with the ulna, an ununited anconeal process can cuase the elbow joint to become unstable, leading to lameness.
- androgens
- Hormones that promote the development of male characteristics; make sex hormones. The principal androgen is testosterone.
- anemia
- Decreased oxygen-carrying capacity of the blood cuased by insufficient numbers of red blood cells, decreased hemoglobin concentration, or a combination of bothe these conditions.
- anesthesia
- Complete loss of sensation.
- anestrus
- The period when the ovary "shuts-down" between the estrous cycles or bredding seasons of some animal species.
- angle
- The angle of the hoof wall as viewed from a lateral aspect when the foot is flat on teh ground.
- anions
- A negatively charged atom or molecule; a negatively charged ion.
- anisodactyly
- Toe position in which three toes face forward and one faces the rear.
- antagonist
- Something that opposes that action of something else. An antagonist muscle or muscle group directly opposes the action of a "prime mover" muscle or muscle group that is directly producing a desired movement.
- antebrachium
- The "forearm" region of the thoracic limb.
- anterior chamber
- The portion of the aqueous compartment of the eye in front of (rostral to) the iris.
- anterior pituitary gland
- The adenohypophysis; the rostral portion of the pituitary gland that produces seven hormones, many of which influence other endocrine glands.
- antibodies
- Proteinds produced by plasma cells (transformed B lymphocytes) in response to the presence of an antigen. A specific serum antibody is generated for a specific antigen.
- anticlinal vertebra
- The thoracic vertebra whose spinous process projects straight up dorsally in contrast to the caudally inclined spinous processes cranial to it and the cranially inclined spinous processes caudal to it. It acts as a landmark on radiographs of the thoracolumbar region, particulatly in dogs, in which it is the eleventh thoracic vertebra.
- anticoagulant
- A substance that prevents blood from clotting when it is added to the blood.
- anticodon
- The triplet pair of nucleotides in tRNA that correspond to the triplet bases or codons of mRNA.
- antidiuretic hormone (ADH)
- A hormone released by the posterior pituitary. It facilitates water conservation in the body by promoting water reabsorption from urine in the collecting ducts. Low levels of ADH cause diabetes insipidus, a condition that results in excessive water loss from the body though increased urine volume.
- antigens
- Cells or organisms that are "not self". An antigen also can be a structure on a cell membrane that the body recognizes as foreign. The presence of an antigen initiates an immune response in a healthy animal.
- antineoplasticic drugs
- Drugs that inhibit the growth and spread of malignant cells and tumors; also known as chemotherapeutic drugs.
- antiport system
- When two separate materials are moved acress the plasma membrane in opposite directions at the same time.
- antrum
-
1) The fluid-filled space within an ovarian follicle.
2) The muscular part of the stomach that is responsible for grinding of food; located between the body of the stomach and the pylorus. - anucleated
- Having no nuclei.
- anuria
- Condition in which no urine is being passed from the body.
- aorta
- Major artery of the systemic circulation that receives blood from the left ventricle.
- aortic valve
- A semilunar valve; it separates the left ventricle and the aorta during diastole.
- apex (tooth)
- The tip of the tooth root where the blood and nerce supply enter the tooth; the uppermost point of a structure.
- apical surface
- The side of an epithelial cell that faces in toward the body cavity.
- apocrine gland
- A gland whose secretions contain some of its cellular material. Part of the secretory vell is destroyed and must regenerate before the cell can secrete again. Examples of these glands are mammary glands and some sweat glands.
- apocrine sweat glands
- Exocrine glands that secrete substances into the hair follicle rather than directly to the skin surface.
- aponeurosis
- A broad sheet of fibrous connective tissue that attaches cetain muscles to bones or to other muscles.
- appendicular skeleton
- The bones of the limbs (appendages)
- apteryla
- Bare areas of skin of birds where feathers do not originate.
- aqueous compartment
- The compartment of the eye in front of (rostral to) the lens and ciliary body. It contains a watery fluid, called aqueous humor, and is subdivided by the iris into the anterior chamber and the posterior chamber.
- aqueous humor
- The watery fluid that fills the aqueous compartment of the eye. It is produced in the posterior chamber and drained from the anterior chamber by the canal of Schlemm.
- arachnoid
- The delicate, weblike layer of the meninges between the dura mater and the pia mater.
- areolar connective tissue
- A soft, spongy connective tissue, also known as loose connective tissue. It is located throughout the body and is composed of a soft ground substance, numerous cell types (white blood cells, fibroblasts, macrophages), and all three types of fibers (elastic, reticular, and collagenous).
- arrector pili muscles
- Smooth muscle that is attached to the base of the hair follicle. It is responsible for the involuntary "hair raising" response to cold and fear or aggression.
- arthrodial joint
- A gliding joint in which two flat articular surfaces rock on each other. This type of joint usually allows only the movements of flexion and extension.
- articular cartilage
- The thin layer of hyaline cartilage that covers the articular surfaces of long bones in synovial joints. It forms a smooth layer over the joint surfaces of teh bones, which drecreases friction and allows free joint movement.
- articualr process
- The process of a vertebra that forms a synovial joint with an adjacent vertebra.
- articular surface
- The smooth joint surface of a bone that contacts another bone in a synovial joint.
- arytenoid cartilages
- Two of the cartilages of teh larynx. The coval cords atach to the arytenoid cartilages. The arytenoid cartilages and the coval cords form the boundaries of th glottis (opening to larynx).
- ascites
- An abnormal condition in which an excessive amount of fluid accumulation is present in the abdominal cavity. Abdominal distention or a petbellied appearance can be clinically evident.
- asternal rib
- A rib whose costal cartilage joins the costal cartilage of the rib ahead of it instead of directly joining the sternum.
- ataxia
- Incoordination/drunken behavior.
- atlas
- The first cervical vertebra. It forms the atlantooccipital joint with the occipital bone of teh skull and and the atlantoaxial joint with the axis (the second cervical vertebra).
- ATP synthase
- The enzyme in the mitochondria of body cell that functions as a tiny 'molecular machine" to regenerate ATP from ADP and detached phosphate groups. It is powered by the proton gradient present across interior mitochondrial membranes.
- atrial septal defect
- Abnormal formation of teh interatrial septum resulting in a communiction (a hole) between the left and right atria.
- atrophy
- Shrinkage.
- auriculars
- Small contour feathers located around the external ear openings in birds.
- auroimmune disease
- An abnormal condition in which the body starts recognizing some of its own cells as "not self" and initiates an immune response to destry the cells.
- autolysis
- The self-digestion of tissues or cells by enzymes that are released by their own lysosomes.
- autonomic nervous system
- The part of teh nercous system that controls smooth muscle, cardiac muscle, and endocrine glands automatically without conscious control; has motor and sensory branches.
- autonomic reflex
- A reflex that results in stimulation or inhibition of smooth or cardiac muscle or endocrine gland funciton; mechanisms of homeostasis are autonomic reflexes.
- avascular
- Without a vascular or blood supply.
- axial skeleton
- The bones along the central axis of the body; made up of the skull, the hyoid bone, the spinal column, the ribs, and the sternum.
- axis
- The second cervical vertebra. It forms the atlantoaxial joint with the first cervical vertebra (the atlas).
- axon
- Extension of the neuron that conduvts the nerve impulse away from the cell body to the terminal bouton (synaptic bulb) at the end of the neuron.