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abdomen - the area between the diaphragm and the pelvis
abdominal cavity - superior portion of the abdominopelvic cavity that contains the stomach, spleen, liver, gallbladder, pancreas, small intestine, and most of the large intestine
abdominopelvic - inferior component of the ventral body cavity that is subdivided into an upper abdominal cavity and a lower pelvic cavity
abduction - movement away from the axis or midline of the body or one of its parts
abortion - premature loss (spontaneous) or removal (induced) of an embryo or non-viable fetus; any failure in the normal process of developing or maturing
abrasion - a portion of skin that has been scraped away
abscess - a localized collection of pus and liquefied tissue in a cavity
absorption - the taking up of liquids by solids or of gases by solids or liquids; intake of fluids or other substances by cells of the skin or mucous membranes; the passage of digested foods from the gastrointestinal tract into blood or lymph
accommodation - a change in the curvature of the eye lens to adjust for vision at various distances; focusing
accretion - a mass of material that has accumulated in a space or cavity; the adhesion of parts
acetabulum - the rounded cavity on the external surface of the coxal (hip) bone that receives the head of the femur
acetylcholine - a neurotransmitter, liberated at synapses in the central and peripheral nervous systems and at neuromuscular junctions to stimulate muscle contraction
achlorhydria - absence of hydrochloric acid in the gastric juice
acidosis - a condition in which blood pH ranges from 7.35 to 6.80 or lower
acinar - flasklike
acini - masses of cells in the pancreas that secrete digestive enzymes
acoustic - pertaining to sound or the sense of hearing
acromegaly - condition caused by hyper-secretion of human growth hormone (hGH) during adulthood; characterized by thickened bones & enlargement of other tissues
acrosome - a dense granule in the head of the spermatozoon; contains enzymes that facilitate the penetration of a spermatozoon into a secondary oocyte
actin - the contractile protein that is located in the thin myofilaments of a muscle fiber (cell)
acuity - clearness or sharpness, usually of vision
acupuncture - the insertion of a needle into a tissue for the purpose of drawing fluid or relieving pain; also an ancient Chinese practice employed to cure illnesses by inserting needles into specific locations of the skin
adaptation - adjustment of the pupil of the eye to light variations; the property by which a neuron relays a decreased frequency of action potentials from a stimulus of constant size; decrease in perception of sensation with continued stimulation
adduction - movement toward the axis or midline of the body or one of its parts
adenohypophysis - the anterior portion of the pituitary gland
adenoids - the pharyngeal tonsils
adenosine triphosphate - universal energy-carrying molecule manufactured in all living cells as a means of capturing and storing energy; it consists of the purine base adenine, the sugar ribose & 3 linearly-arrayed phosphate groups
adenylate cyclase - the enzyme that converts ATP into cyclic AMP; it is located in cell membranes and is activated when messenger molecules (e.g., neurotransmitters or hormones) bind to specific molecular receptors on the cell surface
adherence - firm contact between the plasma membrane of a phagocyte and an antigen or other foreign substance
adhesion - abnormal joining of parts to each other
adipocyte - fat cell; derived from a fibroblast
adrenal cortex - the outer portion of an adrenal gland; divided into three zones, each of which has a different cellular arrangement and secretes different hormones
adrenal medulla - inner portion of an adrenal gland; consists of cells that secrete epinephrine and norepinephrine in response to stimulation of preganglionic sympathetic neurons
adrenergic fiber - a nerve fiber that when stimulated releases norepinephrine (noradrenaline) at a synapse
adrenocorticotropic hormone - hormone produced by the adenohypophysis (anterior lobe) of the pituitary gland; influences the production & secretion of certain hormones of the adrenal cortex
adventitia - the outermost covering of a structure or organ
afferent arteriole - blood vessel of a kidney (nephron) that subdivides into a capillary network called the glomerulus; there is one afferent arteriole for each glomerulus
agglutination - clumping of microorganisms or blood corpuscles; typically an antigen-antibody reaction
agglutinin - a specific principle or antibody in blood serum; capable of causing the clumping of bacteria, blood corpuscles or particles; also called an isoantibody
agglutinogen - a genetically-determined antigen located on the surface of erythrocytes; basis for ABO grouping and Rh system of blood classification; also called an isoantigen
agnosia - loss of the ability to recognize the meaning of stimuli from the various senses (visual, auditory, tactile)
agraphia - an inability to write
albinism - abnormal, nonpathological, partial or total absence of pigment in skin, hair and eyes
albumin - the most abundant (60%) & smallest plasma protein; functions primarily to regulate osmotic pressure of plasma
albuminuria - presence of albumin in the urine
aldosterone - mineralocorticoid produced by the adrenal cortex; brings about sodium and water reabsorption and potassium secretion
alimentary - pertaining to nutrition
alkaline - containing more hydroxyl ions (OH-) than hydrogen ions (H+) to produce a pH of more than 7
alkalosis - a condition in which blood pH ranges from 7.45 to 8.00 or higher
allantois - a small, vascularized membrane between the chorion and amnion of the fetus; serves as an early site for blood formation
alleles - genes that control the same inherited trait (such as height or eye color); they are located at the same position (locus) on homologous chromosomes
allergen - an antigen that evokes a hypersensitivity reaction
allergic - pertaining to or sensitive to an allergen
alveolus - a small hollow or cavity; an air sac in the lungs; milk-secreting portion of a mammary gland
Alzheimer's disease - disabling neurological disorder characterized by dysfunction and death of specific cerebral neurons; this results in widespread intellectual impairment, personality changes, and fluctuations in alertness
ambulatory - capable of walking
amenorrhea - absence of menstruation
amnesia - a lack or loss of memory
amniocentesis - removal of amniotic fluid by inserting a needle transabdominally into the amniotic cavity
amnion - innermost fetal membrane; a thin transparent sac that holds the fetus suspended in amniotic fluid; also called the bag of waters
amniotic fluid - fluid in the amniotic cavity, the space between the developing embryo (or fetus) and amnion; the fluid is produced initially as a filtrate from maternal blood and later, from fetal urine
amorphous - without definite shape or structural differentiation; pertains to solids without crystalline structure
amphiarthrosis - articulation in which the articulating bony surfaces are separated by an elastic substance to which both are attached; the mobility is slight, midway between a synarthrosis and a diarthrosis
ampulla - saclike dilation of a canal
amyotrophic - amyotrophic lateral sclerosis (ALS) - progressive neuromuscular disease characterized by spinal cord motor neuron degeneration that leads to muscular weakness; also called Lou Gehrig's disease
anabolism - synthetic energy-requiring reactions whereby small molecules are assembled into larger ones
anaerobic - not requiring molecular oxygen
analgesia - pain relief
anaphase - the third stage of mitosis in which the chromatids that have separated at the centromeres move to opposite poles of the cell
anaphylaxis - against protection; a hypersensitivity (allergic) reaction in which IgE antibodies attach to mast cells & basophils, causing them to produce mediators (e.g., histamine) leading to greater capillary permeability, smooth muscle contraction & mucus secretion
anastomosis - an end-to-end union or joining together of blood vessels, lymphatics or nerves
anatomical position - a position of the body universally used in anatomical descriptions in which the body is erect, facing the observer, the upper extremities are at the sides, the palms of the hands are facing forward, and the feet are on the floor
anatomy - the structure or study of structure of the body and the relation of its parts to each other
androgen - substance producing or stimulating male sex characteristics, e.g., the male hormone testosterone
anemia - condition of the blood in which the number of functional red blood cells or their hemoglobin content is below normal
anesthesia - total or partial loss of feeling or sensation, usually defined with respect to loss of pain sensation; may be general or local
aneuploid - a cell that has one or more chromosomes of a set added or deleted
aneurysm - a saclike enlargment of a blood vessel caused by a weakening of its wall
angina pectoris - pain in the chest related to reduced coronary circulation; it may or may not involve heart or artery disease
angiography - X-ray examination of blood vessels after injection of a radiopaque substance
angiotensin - either of two forms of a protein associated with regulation of blood pressure; angiotensin I, produced by action of renin on angiotensinogen, is converted by a plasma enzyme into angiotensin II which releases aldosterone
anion - a negatively charged ion; e.g., the chloride ion (Cl-)
ankyloglossia - tongue-tied; restriction of tongue movements by a short lingual frenulum
ankylosis - severe or complete loss of movement at a joint
anomaly - abnormality that may be a developmental (congenital) defect; a variant from the usual standard
anopsia - a defect in vision
anorexia nervosa - a chronic disorder characterized by severe self-induced weight loss, body-image and other perceptual disturbances, & physiological changes resulting from nutritional depletion
anosmia - loss of the sense of smell
antagonist - a muscle that has an action opposite that of the prime mover (agonist) and yields to the movement of the prime mover; a substance which blocks a receptor site where a specific molecule (agonist) binds
antepartum - before delivery of the child; occurring (to the mother) before childbirth
anterior - nearer to or at the front of the body; also called ventral
anti-oncogene - a gene that can cause cancer when inactivated inappropriately
antibiotic - literally, antilife; a chemical produced by a microorganism that is able to inhibit the growth of or kill other microorganisms
antibody - a protein produced by certain cells in the body in the presence of a specific antigen; the antibody combines with that antigen to neutralize, inhibit, or destroy it
anticoagulant - a substance that is able to delay, suppress, or prevent the clotting of blood
antidiuretic - substance that inhibits urine formation
antigen - any substance that when introduced into the tissues or blood induces the formation of antibodies and reacts only with its specific antibodies
antrum - any nearly closed cavity or chamber, especially one within a bone, such as a sinus
anulus fibrosus - a ring of fibrous tissue & fibrocartilage; encircles the pulpy substance (nucleus pulposus) of an intervertebral disc
anuria - a daily urine output of less than 50 ml
anus - the distal end and outlet of the rectum
aorta - the main systemic trunk of the arterial sustem of the body; emerges from the left ventricle
aperture - an opening or orifice
apex - the pointed end of a conical structure, such as the apex of the heart
apgar score - a method for assessing the overall status of an infant soon after birth; based on evaluation of heart rate, respiratory effort, muscle tone, reflex irritability, and color
aphasia - loss of ability to express oneself properly through speech, or loss of verbal communication
apnea - temporary cessation of breathing
apneustic area - portion of the respiratory center in the pons; sends stimulatory nerve impulses to the inspiratory area to activate and prolong inspiration and to inhibit expiration
apocrine gland - a type of gland in which the secretory products gather at the free end of the secreting cell and are pinched off, along with some of the cytoplasm, to become the secretion, as in the mammary glands
aponeurosis - a sheetlike tendon joining one muscle with another or with bone
appendage - a structure attached to the body
appendicitis - inflammation of the vermiform appendix
appositional growth - growth due to surface deposition of material, as in the growth in diameter of cartilage and bone; also called exogenous growth
aqueduct - a canal or passage, especially for the conduction of a liquid
aqueous humor - the watery fluid, similar in composition to cerebro-spinal fluid, that fills the anterior cavity of the eye
arachnoid - the middle of the three coverings (meninges) of the brain or spinal cord
arbor vitae - the treelike appearance of the white matter tracts of the cerebellum when seen in midsagittal secion; a series of branching ridges within the cervix of the uterus
areflexia - absence of reflexes
areola - any tiny space in a tissue; the pigmented ring around the nipple of the breast
arrector pili - smooth muscles attached to hairs; contraction pulls the hairs into a more vertical position, resulting in goose bumps
arrhythmia - irregular heart rhythm; also called dysrhythmia
arteriogram - roentgenogram of an artery after injection of a radi-opaque substance into the blood
arteriole - small, almost microscopic, artery that delivers blood to a capillary
artery - a blood vessel that carries blood away from the heart
arthritis - inflammation of a joint
arthrocentesis - insertion of a needle into a synovial (joint) cavity to remove a sample of synovial fluid, to relieve pressure, or to inject anesthetic or medication
arthrology - the study or description of joints
arthroscopy - a procedure for examining the interior of a joint, e.g., the knee, by inserting an arthroscope into a small incision; used to determine extent of damage, to remove torn cartilage, to repair cruciate ligaments, or to obtain samples for analysis
arthrosis - a joint or articulation
articular capsule - sleevelike structure around a synovial joint; composed of a fibrous capsule and a synovial membrane
articulate - to join together as a joint to permit motion between parts
articulation - a joint; a point of contact between bones, cartilage and bones, or teeth and bones
arytenoid - ladle-shaped
ascites - accumulation of serous fluid in the peritoneal cavity
aseptic - free from any infectious or septic material
asphyxia - unconsciousness due to interference with the oxygen supply of the blood
aspiration - inhalation of a foreign substance (water, food or foreign body) into the bronchial tree; drainage of a substance in or out by suction
astereognosis - inability to recognize objects or forms by touch
asthenia - lack or loss of strength; debility
astigmatism - irregularity of the lens or cornea of the eye causing an image to be out of focus and producing faulty vision
astrocyte - a neuroglial cell having a star shape; supports neurons in the brain and spinal cord and attaches neurons to blood vessels
ataxia - lack of muscular coordination; lack of precision
atelectasis - collapsed or airless state of all or part of the lung; may be acute or chronic
atherosclerosis - a process in which fatty substances are deposited in arterial walls in response to stimuli such as hypertension; following endothelial damage, white cells adhering to the walls take up cholesterol, etc., ultimately forming plaque that occludes the lumen
atresia - abnormal closure of a passage; abnormal absence of a normal body opening
atrial fibrillation - asynchronous contraction of the atria; results in the cessation of atrial pumping
atrial natriuretic factor - peptide hormone produced by the atria of the heart in response to stretching; it inhibits production of aldosterone and, thus, lowers blood pressure
atrioventricular bundle - portion of the heart's conduction system beginning at the AV node, passing through the cardiac skeleton between the atria and ventricles and into the interventricular septum where it splits into right and left bundle branches; also called bundle of His
atrium - a superior chamber of the heart