Medical Terminology
Glossary
h.c. somatomammotropin - hCS; a hormone produced by the chorion of the placenta that may stimulate breast tissue for lactation
h. chorionic gonadotropin - hCG; a hormone produced by the chorion of the placenta; it maintains the corpus luteum
Haldane effect - decreased carbon dioxide binding in the blood as a result of increased oxygen-hemoglobin binding; oxyhemoglobin is more acidic than unbound hemoglobin and, therefore, combines with less carbon dioxide
hallucination - the sensory perception of something that does not really exist in the world; a sensory experience created from within the brain
haploid - having half the number of chromosomes normally found in the somatic cells of an organism; characteristic of mature gametes
haustra - the sacculated elevations of the colon
Haversian system - the basic structural LETTER in adult compact bone, consisting of a central (Haversian) canal with concentrically arranged lamellae, lacunae, osteocytes, and canaliculi; also called an osteon
heart murmur - one of a number of abnormal heart sounds; consists of a flow noise that is heard before the normal lubb-dupp or that may mask normal heart sounds
hematocrit (Hct) - percentage of blood made up of red blood cells; usually calculated by centrifuging a blood sample in a graduated tube & reading off the volume of red blood cells and total blood
hematology - the study of blood
hematopoiesis - blood cell production occurring in the red bone marrow; also called hemopoiesis
hematuria - blood in the urine
hemiballismus - violent muscular restlessness of half of the body, especially of the upper extremity
hemiplegia - a paralysis of the upper extremity, trunk, and lower extremity on one side of the body
hemocytoblast - immature stem cell in bone marrow; it develops along different lines into all the types of mature blood cells
hemodialysis - filtering blood while it is circulated outside the body by means of an artificial device; substances are removed as a result of their different rates of diffusion through a selectively permeable membrane
hemodynamics - study of factors and forces that govern the flow of blood through blood vessels
hemoglobin - molecule in red blood cells consisting of the protein globin and the iron-containing red pigment heme and constituting about 33% of the cells' volume; it is involved in the transport of oxygen and carbon dioxide
hemolysis - escape of hemoglobin from the interior of red blood cells into the surrounding medium; results from disruption of the integrity of the cell membrane by toxins or drugs, by freezing or thawing, or by hypotonic solutions
hemolytic disease - a hemolytic anemia of a newborn child; it results from the destruction of the infant's red blood cells by antibodies produced by the mother; usually involves antibodies due to Rh blood type incompatibility; also called erythroblastosis fetalis
hemophilia - a hereditary blood disorder where there is a deficient production of certain factors involved in blood clotting, resulting in excessive bleeding into joints, deep tissues, and elsewhere
hemopoiesis - blood cell production occurring in the red marrow of bones; also called hematopoiesis
hemoptysis - spitting of blood from the respiratory tract
hemorrhage - bleeding; escape of blood from blood vessels, especially when it is profuse
hemorrhoids - dilated or varicosed blood vessels (usually veins) in the anal region; also called piles
hemostasis - the stoppage of bleeding
hepatic - referring to the liver
hepatitis - inflammation of the liver due to an infectious agent, drugs, or chemicals
hepatopancreatic ampulla - a small, raised area in the duodenum where the combined common bile duct and main pancreatic duct empty into the duodenum; also called the ampulla of Vater
hernia - protrusion or projection of an organ or part of an organ through a membrane or a cavity wall, usually the abdominal cavity
herniated disc - rupture of intervertebral disc so that the nucleus pulposus protrudes into the vertebral cavity; also called a slipped disc
heterocrine gland - any gland, such as the pancreas, which is both endocrine and exocrine
heterozygous - possessing a pair of different genes on homologous chromosomes for a particular hereditary characteristic
hiatus - an opening; a foramen
hilus - an area, depression, or pit where blood vessels and nerves enter or leave an organ; also called a hilum
hirsutism - excessive growth of hair in females and children, due to the conversion of vellus hairs into large terminal hairs; occurs in response to higher-than-normal levels of androgens; the distribution is similar to that in adult males
histamine - a substance found in many cells, particularly mast cells, basophils, and platelets, and released when the cells are injured; results in vasodilation, increased permeability of blood vessels,and bronchiole constriction
histocompatibility testing - comparison of human leucocyte associated (HLA) antigens between donor and recipient to determine the degree of compatibility between the two; also called HLA antigen typing or tissue typing
histology - microscopic study of the structure of tissues
hives - skin condition marked by reddened elevated patches that are often itchy; may be caused by infections, trauma, medications, emotional stress, certain foods or food additives
holocrine gland - type of gland in which the entire secreting cell, containing its accumulated secretions, is included in the secretory product of the gland, as in the sebaceous or oil glands
homeostasis - the condition in which the body's internal environment remains relatively constant, within physiological limits
homologous - a correspondence of two organs in structure, position, and origin
hormone - a secretion of an endocrine gland; it alters the physiological activity of target cells in the body
humoral immunity - the component of immunity in which lymphocytes (B cells) develop into plasma cells that produce antibodies to destroy antigens; also called antibody-mediated immunity
hyaline membrane disease - a disease of newborn infants, especially those who are premature, in which insufficient amounts of surfactant are produced and breathing is labored; also called respiratory distress syndrome (RDS) of the newborn
hyaluronic acid - viscous, amorphous extra-cellular material; it binds cells together, lubricates joints, and maintains the shape of the eyeballs
hyaluronidase - enzyme that breaks down hyaluronic acid, increasing the permeability of connective tissues by dissolving the substances that hold body cells together
hydrocele - a fluid-containing sac or tumor; specifically, a collection of fluid formed in the space along the spermatic cord and in the scrotum
hydrocephalus - abnormal accumulation of cerebrospinal fluid on the brain
hydrophobia - rabies; a condition characterized by severe muscle spasms when attempting to drink water; also, an abnormal fear of water
hymen - a thin fold of vascularized mucous membrane at the vaginal orifice
hyperbaric oxygenation - using a hyperbaric chamber to raise oxygen levels in blood to treat anaerobic (tetanus and gangrene) bacterial infections; also used to treat carbon monoxide poisoning
hypercalcemia - an excess of calcium in the blood
hypercapnia - an abnormal increase in the amount of carbon dioxide in the blood
hyperemia - an excess of blood in an area or part of the body
hyperextension - continuation of extension beyond the anatomical position, as in bending the head backward
hyperglycemia - elevated blood sugar level
hypermetropia - condition in which visual images are focused behind the retina with resulting defective vision of near objects; farsightedness
hyperphosphatemia - an abnormally high level of phosphate in the blood
hyperplasia - an abnormal increase in the numer of normal cells in a tissue or organ, increasing its size
hyperpolarization - increase in the internal negativity across a cell membrane, thus increasing the voltage and moving it farther away from the threshold value
hypersecretion - overactivity of glands resulting in excessive secretion
hypersensitivity - overreaction to an allergen, leading to pathological changes in tissues; also called allergy
hypertension - high blood pressure
hyperthermia - elevated body temperature
hypertonia - increased muscle tone that is expressed as spasticity or rigidity
hypertonic - having an osmotic pressure greater than that of the solution with which it is compared
hypertrophy - excessive enlargement or overgrowth of tissue without cell division
hyperventilation - a rate of respiration higher than that required to maintain normal level of plasma PCO2
hypervitaminosis - an excess of one or more vitamins
hypocalcemia - lower than normal levels of calcium in the blood
hypochloremia - deficiency of chloride in the blood
hypoglycemia - abnormally low concentration of blood glucose; can result from excess insulin (injected or secreted)
hypokalemia - deficiency of potassium in the blood
hypomagnesemia - deficiency of magnesium in the blood
hyponatremia - deficiency of sodium in the blood
hyponychium - the epithelium of the nail bed, particularly the posterior part
hypophosphatemia - an abnormally low level of phosphate in the blood
hypophyseal pouch - a fold of ectoderm in the stomodeal (mouth) roof, from which the adenohypophysis (anterior lobe) of the pituitary gland develops embryologically
hypophysis - pituitary gland
hypoplasia - defective (decreased) tissue development
hyposecretion - underactivity of glands resulting in decreased secretion
hypospadias - displaced urethral opening; in the male, it may be on the underside of the penis, at the penoscrotal junction, between the scrotal folds, or in the perineum; in the female, the urethra opens into the vagina
hypothalamic-hypophyseal tract - a bundle of nerve processes made up of fibers that have cell bodies in the hypothalamus but release neurosecretions in the posterior pituitary gland or neurohypophysis
hypothalamus - portion of the diencephalon that lies beneath the thalamus and forms the floor and part of the wall of the third ventricle
hypothermia - lowering body temperature below 35 C (95 F) degrees; in surgical procedures, it refers to deliberate cooling of the body to slow metabolism and reduce tissue oxygen needs
hypotonia - state of decreased or lost muscle tone in which muscles appear flaccid
hypotonic - having an osmotic pressure lower than that of another solution with which it is compared
hypoventilation - a rate of respiration lower than that required to maintain the normal level of plasma PCO2
hypovolemic shock - shock characterized by decreased intravascular volume resulting from blood loss; may occur because of acute hemorrhage or other excessive fluid loss
hypoxia - lack of adequate oxygen at the tissue level
hysterectomy - the surgical removal of the uterus
