Review Glossary


A band

a region containing the full length of the myosin filaments and also parts of actin filaments; located in the sarcomere of skeletal muscle; see also H band


absorptive cell

Cell that is efficient in absorbing substances from the lumen via apical cytoplasmic processes (microvilli or stereocilia)


acidophil

cell of the adenohypophysis which stains pink red; i.e. somatotropes and mammatropes


acinar cell

a cell of an acinus unit


acinus

cells arranged into a circular secretory unit (i.e. pancreatic acinus and mucous acinus)


acrosome

dense structure of the anterior portion of a sperm cell; contains enzymes that allow it to penetrate the egg during fertilization


actin

thin filament protein which allows contractility and confers support in cells


adenocarcinoma

malignant cancer with cells arranged in a gland-like pattern; i.e. prostate and breast adenocarcinoma


adenohypophysis

anterior lobe of the pituitary; composed of glandular secretory tissue


adipocyte

large cell (up to 200 um in diameter) with only a thin rim of cytoplasm due to the presence of a large flat droplet; TEM shows an external lamina; stores large lipid vacuoles


adipose tissue

a grouping of adipocytes

adrenocorticolipotrope

cell of the adenohypophysis which produces ACTH and LPH


adventitia

connective tissue with high content of adipose, nerves, and blood vessels


afferent arteriole

vessel that branches from an interlobular artery and supplies the glomerulus


afferent lymphatic vessel

a vessel involved in bringing lymph to the lymph node


alpha-actinin

protein that anchors actin to the Z-disk


alveolar duct

long airway lined only with alveolar cells and some smooth muscle


alveolar macrophage

macrophage located in the alveolar space and its surrounding connective tissue; serves to remove inhaled particles; also referred to as "dust cell"


alveolar sac

alveoli cluster surrounding an air space; found at the end of alveolar ducts


alveolar wall

the site where alveoli exchange gas with the blood; composed of:


alveolus

1) the basic unit of gas exchange; small air-filled chamber lined by squamous cells
2) mammary gland secretory structure; lined by cuboidal cells and myoepithelial cells


amnion

innermost membrane surrounding the embryo


ampulla of uterine tube

see oviduct


anal apocrine gland

gland of the anus associated with hair follicles


anal gland

branched, straight tubular mucus gland extending into the submucosa


anal transitional zone (ATZ)

area where the simple columnar epithelium of the rectal mucosa meets an area of stratified squamous epithelium


anchoring villi

see basal plate


anterior chamber of eye

space between the cornea and the iris; filled with aqueous humor


anterior lobe

see adenohypophysis


anthracoid pigment

black debris found in the alveolar macrophages of those individuals chronically exposed to smoke


antigen-presenting cell

a cell that processes and presents antigens to lymphocytes; this category includes:


antrum

cavity inside the secondary and Graafian follicles


apical surface

that side of the cell facing the lumen; typically the site of secretion and reception of substances (i.e. hormones, antibodies, and nutrients)


apocrine sweat gland

large sweat gland associated with hair follicles in the eyelid, axilla, areola, anal region, and genitalia


apoptosis

controlled cellular death in which the organelles are packaged in membranes for eventual phagocytosis; apparent as a shrinkage in cell size and a pyknotic nucleus


appositional growth

bone growth due to addition of new matrix by osteoblasts in bone or chondroblasts in cartilage


APUD cell

endocrine cell of the digestive tract; activated by nervous stimulation


aqueous humor

watery fluid of the anterior chamber and posterior chamber of eye


arcuate artery

branch of the interlobar artery; traces a course along the base of the renal pyramid


arcuate vein

vessel carrying blood away from the kidney medulla; traces a course along the pyramid base


arrector pili muscle

small muscle attached to the base of a hair follicle


arteriole

vessel with 1-2 layers of smooth muscle; leads to a capillary


artery

vessel which takes oxygen-rich blood from the heart to tissues


ascites

fluid found in the peritoneal cavity; consists of mesothelial cells, red blood cells, leukocytes and may contain cancer cells


atherosclerotic plaque

necrotic mass of lipid and cells (macrophages, smooth muscle cells, and fibroblasts) resulting from endothelial damage


atretic follicle

disintegrating follicle within the ovary; has not undergone ovulation


atrophy

a wasting away of muscle due to denervation or disuse


Auerbach's plexus

ganglion cell group between the two muscle layers of the muscularis externa in the digestive tract; controls motility of the digestive tract


axon

extension of neurons which transmits signals to other neurons or effector cells


axon hillock

the point from which the axon emerges from the neuron body


azurophilic granule

the lysosome of leukocytes


BALT

Bronchus Associated Lymphatic Tissue; lymphatic aggregations of the respiratory system


band cell (neutrophilic)

precursor to the neutrophil with an "S" shaped nucleus


band form

juvenile/immature forms of granulocytes with "U" or "S" shaped nuclei; immediate precursors to the mature forms


basal body

structure derived from the centriole which organizes the microtubules of cilia


basal cell

a cell type that comprises the bottom layer of epithelia; serves as precursor/replacement for the cells above it


basal lamina

noncellular, protein-polysaccharide layer which anchors an epithelium to the connective tissue beneath; also known as 'lamina densa' known in light microscopy as basement membrane


basal plate

maternal side of the placenta; many blood vessels traverse here to supply the intervillous space; contains numerous anchoring villi which attach it to the chorionic plate


basal surface

that side of the cell that is anchored to the basal lamina or to other cells; faces away from the lumen


basement membrane

Light microscopic term for basal lamina


basilar membrane

membrane within the cochlea; its vibrations allow for frequency determination, with high frequency sounds discriminated at the base, and low frequency sounds at the apex


basophil

1) least in number of all leukocytes; possesses vasoactive and immunoreactive substances similar to those of mast cells which are released after IgE binding; nucleus often obscured by coarse cytoplasmic blue (H&E) granules in cytoplasm.

2) cell of the adenohypophysis which stains blue-purple; includes: adrenocorticolipotropes, gonadotropes, and thyrotropes


basophilic erythroblast

erythrocyte precursor slightly smaller than the proerythroblast; has deeply basophilic cytoplasm; EM reveals considerable numbers of polyribosomes present (beginning of hemoglobin synthesis at this stage); division of basophilic erythroblast gives rise to polychromatophilic erythroblast


bile

product of the liver stored in the gallbladder and released into the duodenum; allows for solubilization and uptake of lipids


bile canaliculus

"canal" between two adjacent hepatocytes; site of bile release from the hepatocyte


bile duct

ducts which carry bile from the liver parenchyma; bile ducts fuse to form the hepatic duct


blast cell

the earlier precursor of blood cells


blood vessel

structure that carries blood and blood-borne substances; lined by smooth muscle; types include:


blood-testis barrier

the junctional complex between adjacent Sertoli cells; keeps developing germ cells isolated from potentially harmful antibodies of the circulation


blood-thymus barrier

a barrier between lymphocytes and the lumen of vessels in the thymus; consists of:


B-lymphocyte

see lymphocyte


bone

specialized connective tissue with a mineralized (hydroxyapatite) matrix


bone marrow

blood-rich material in the center of bone; involved in hemopoiesis


bone-lining cell

flat cell that aligns bone surfaces; is an inactive osteoprogenitor cell


bony callus

stage in bone repair; replaces the fibrocartilaginous callus after mineralization


Bowman's capsule

site of plasma filtration; a double-layered cup-shaped structure that surrounds the glomerulus


Bowman's gland

"olfactory gland"; the secretion of this serous glands traps and dissolves odor-producing particles in the nasal cavity to allow for new smells to be detected


Bowman's membrane

basal lamina of the corneal epithelium


bronchial artery

branches of this vessel supply all lung tissue except for the alveoli


bronchial vein

this vessel drains the connective tissue of the lung hilus


bronchiolar cell

also known as "Clara cell"; nonciliated cell lining bronchioles that secretes a lipoprotein to prevent adhesion of the airway walls


bronchiole

structure extending from the bronchi to the alveoli


bronchus

see trachea


Brunner's gland

submucosal mucous glands of the duodenum


brush border

the appearance of the numerous microvilli of an absorptive epithelium


brush cell

a columnar epithelial cell of the respiratory system with numerous microvilli; serves as a sensory receptor; basal surface is in contact with a nerve ending


calcified cartilage

a stage of endochondral bone formation in which cartilage previously laid down is mineralized


canal of Schlemm

opening at the corneal-scleral junction which drains the aqueous humor


canaliculus

"tunnel" which allows osteocytes housed in separate lacunae to communicate via cytoplasmic processes


cancer cell

cell that exhibits uncontrolled growth; may spread throughout the organism affected


capillary

a small blood vessel which receives from arteries and delivers to veins; thin endothelium is ideal for exchange of substances


capillary space

the side opposite the urinary pole in the glomerulus; contains blood


capsular matrix

material of the capsule consisting of sulfated proteoglycans


capsule

1)a covering layer of connective tissue of the lymph node, spleen, testis, prostate and other organs

2)secreted matrix surrounding the lacunae of chondrocytes


carcinoma in situ (CIS)

a condition in which cancer cells are limited (at least temporarily) by the basement membrane from spreading to other areas


cardiac gland

gland located within the stomach at its junction with the esophagus; similar in property to the esophageal cardiac gland


cardiac muscle

involuntary, striated muscle that makes up the mass of the heart and lines some large vessels (i.e. large branches of the pulmonary vein)


cardiac myocyte

the elongate cell whose contractile and electric communication properties allow the heart to beat


cartilage

tissue consisting of chondrocytes and a surrounding matrix; types include:


cartilage plate

supporting structure found in good number in the bronchi; becomes smaller and less numerous in smaller bronchial branches


cartilage ring

C-shaped hyaline cartilage which maintains the tubular shape of the trachea and the main bronchi


cell body

the main mass of the cell, from which various processes may extend


cell lineage

the full developmental stages of a given cell


central artery

name for the splenic artery within the white pulp


central vein

large vessel which drains the hepatic sinusoids


centriole

cellular stucture involved in organizing the microtubular apparatus and also the mitotic spindle which is needed for faithful division of genetic material in cellular division


centroacinar cell

a cell of the proximal intercalated duct within the pancreatic acinus


cervical gland

mucous gland of the cervical mucosa; secretes less viscous mucous during mid-menstrual cycle


cervical mucosa

lining of the head of the uterus (cervix); contains large branched glands; does not undergo sloughing


cervical myometrium

see myometrium


cervical stroma

see stroma


Chief cell

basophilic cell of the stomach fundic gland that secretes pepsinogen and a weak lipase


chondroblast

a cell that secretes cartilage matrix; referred to as chondrocyte when surrounded by matrix


chondrocyte

see chondroblast


chondrogenic layer

a region of cartilage formation


chorionic plate

fetal part of the placenta from which chorionic villi project


chorionic villus

finger-like extension of the chorionic plate which allows for maternal-fetal blood exchange; lined on the outer surface by the syncytiotrophoblast and cytotrophoblast and contains a core of fetal blood vessels; the intervillous spaces contain maternal blood; this arrangment allows for maternal-fetal exchange


choroid

vascular layer which provides nutrition to the retina


chromaffin cell

cell of the adrenal medulla which secretes epinephrine and norepinephrine


chromatin

a tightly packed complex of DNA and histones (proteins) located in the nucleus


chromophobe

cell of the adenohypophysis which does not stain


chromosome

paired chromatids joined by a centromere; the chromatids consist of chromatin; humans possess 23 paired chromosomes


ciliary body

tissue located between iris and choroid; produces the aqueous humor and houses muscles which control lens shape


ciliary muscle

smooth muscle of the ciliary body that controls the shape of the lens


ciliated columnar epithelium

the typical epithelium of the respiratory system; the cilia serve to move mucus and inhaled particles


ciliated epithelial cell

cell equipped with cilia; primarily in the respiratory system and the oviduct


cilium

projection of certain cells containing microtubules which allows for cellular movement or the propulsion of other particles (i.e. mucus, an oocyte, etc.)


circular fiber of ciliary muscle

allows lens to become more spherical


circumvallate papillae

large, dome-shaped structures anterior to the sulcus terminalis of the tongue which contain taste buds


Clara cell

see bronchiolar cell


classical lobule

hexagonal model of liver organization with six portal triads surrounding a central vein


cleft of Schmidt-Lantermann

spaces within the myelin sheath containing Schwann cell cytoplasm


closed circulation theory

a model for splenic circulation in which blood empties from splenic arterioles into the sinuses of the red pulp


cochlea

the coiled structure located in the inner ear that houses the auditory apparatus


cochlear canal

space divided into the scala vestibuli superiorly and scala tympani inferiorly and the scala media in the center


cochlear duct

A triangular space bordered by the basilar membrane, Reissner's membrane, and the lateral cochlear wall


cochlear nerve

the auditory portion of the vestibulocochlear nerve (CN VIII)


collagen bundle

a large grouping of collagen fibers


collagen fiber

see collagen


collagen fibril

the basic functional and structural unit of collagen fibers consisting of a repeating pattern of collagen molecules in a banded array


collagen

a triple helix protein which allows for great tensile strength; types include:


collecting duct

duct of the kidney cortex and medulla that drains the tubule network into the larger ducts of Bellini; lined by squamous cells, cuboidal cells, and columnar epithelial cells, in that order as the duct increases in size


collecting tubule

tubule that emerges in the cortical labyrinth; a number of these merge to form a collecting duct within a medullary ray


collecting vein

same as central vein


colloid

gel-like material of the follicles; site of thyroglobulin storage


columnar epithelial cell

a cell which is taller than it is wide; lines large glands and ducts; ideal for absorptive epithelia


common bile duct

structure which drains the cystic and hepatic duct into the duodenum


compact bone

bone characterized by heavy matrix deposition; confers great tensile strength; also known as 'cortical' bone


conducting portion

structures of the respiratory system which bring air to the sites of gas exchange; include:


cone

photoreceptor cell responsible for color vision


conjunctiva

mucus membrane lining the space between inner eyelids and surface lateral to the cornea


connective tissue

supportive tissue; includes:


continuous capillary

capillaries with a continuous endothelium; present in muscle, lung, and the CNS


cornea

chief refractive element and anterior window of the eye


coronary artery

a vessel that brings blood to heart tissue


coronary vein

a vessel that takes deoxygenated blood away from heart tissue


corpus albicans

a degenerated corpus luteum; filled with lipid and hyaline


corpus cavernosum

see erectile tissue


corpus luteum

after ovulation, the collapsed Graafian follicle gives rise to this endocrine structure; produces progesterone and estrogen


corpus spongiosum

see erectile tissue


cortex

1) the outer layer of the lymph node and thymus; contains high concentration of lymphocytes

2) the outer portion of a given organ

3) the outer portion of the adrenal gland; comprised of the (outer to inner):


cortical labyrinth

the combination of the renal corpuscle, the proximal and distal tubules


cortical sinus

also known as "subcapsular sinus"; area under the capsule where the afferent lymphatic vessels drain; lined by myoepithelial cells


corticotrope

cell of the pituitary which stimulates release of hormones by the adrenal cortex


crypt

area of the tonsil that contains large amounts of lymphocytes


crypt of Lieberkuhn

mucous gland of the intestinal mucosa


cuboidal cell

a cell with even dimensions on all sides; serves for absorption, barrier, and especially duct-lining


cytotrophoblast

derivative of the trophoblast (a segment of the blastocyst which gives rise to the supportive structures of the embryo) that is mitotically active and fuses with the syncytiotrophoblast


decidual cell

cells of the endometrial stroma which, under the influence of estrogen and progesterone, store large amounts of glycogen; this creates a favorable environment for implantation of the blastocyst; appears as large, pale cell


deep cortex

area of the lymph node cortex which is adjacent to the medulla; T-lymphocytes are abundant here


dendrite

the signal receiving appendage of neurons


dense irregular connective tissue

connective tissue with randomized arrangement of abundant collagen fibers and sparse cellular content (i.e. submucosa)


dense regular connective tissue

connective tissue with ordered and densely packed fibers (i.e. collagen) and cells; provides significant strength; see also tendon


dermal papillae

connective tissue evaginations from the dermis into the epidermis


dermis

the inner layer of the skin; composed of dense irregular connective tissue


Descemet's membrane

basal lamina of the corneal endothelium


desmosome

a strong adhesion on the lateral surfaces of cells; the strength is imparted by intermediate filament; also known as 'macula adherens'


diapedesis

process of lymphocyte migration through the blood vessel lining


diaphysis

the shaft of a long bone


dilator pupillae muscle

increases the iris (pupil) opening


distal convoluted tubule

a tortuous tubule of the cortex lined by cuboidal cells; exchanges sodium for potassium, reabsorbs bicarbonate, and converts ammonia to ammonium; houses the macula densa


distal straight tubule

tubule of the medullary ray lined by cuboidal cells


dome-shaped cell

cell of the bladder which changes shape according to the state of distension


dorsal surface of the tongue

the top surface of the tongue which is covered with papillae


duct

conduit that delivers substances from site of production to target site; sweat ducts are typically simple cuboidal epithelium or stratified cuboidal epithelium


ductuli efferentes

structure that connects the rete testis to the ductus epididymis; lined by pseudostratified columnar epithelium


ductus deferens

same as vas deferens; leads from the ductus epididymis to the prostatic urethra; lined by pseudostratified columnar epithelium


ductus epididymis

highly coiled tube lined with pseudostratified columnar epithelium; the principal cells of this epithelium possess stereocilia which move maturing spermatozoa through the channel


duodenal gland

see Brunner's gland


duodenum

the initial portion of the intestine; receives contents of the stomach


dust cell

see alveolar macrophage


early spermatid

one of the more mature spermatozoan precursors; it is a round cell that is attached to the apical membrane of a Sertoli cell


eccrine sweat gland

sweat gland found all over the body except the lips and external genitalia


efferent arteriole

drainage vessel of the glomerulus


efferent lymph vessel

a vessel that takes lymph away from the lymph node


ejaculatory duct

the ductus deferens and the duct of the seminal vesicle form this structure in the body of the prostate gland; empties into the urethra


elastic artery

vessel with dense concentration of elastic laminae in the tunica media; i.e. aorta


elastic cartilage

see cartilage


elastic cartilage matrix

consists primarily of elastic fibers


elastic fiber

connective tissue fiber that allows for flexibility; composed of the protein elastin


elastic laminae

elastic fibers arranged in concentric layers:


elastin

polypeptide component of elastic fibers


endocardium

the heart wall layer which contacts blood; consists of outer endothelial layer and inner subendothelial layer of connective tissue


endocervix

the part of the cervix facing inward toward the uterus; see also squamocolumnar junction


endochondral bone formation

a process of bone formation involving a cartilaginous precursor which is later mineralized and replaced with bone; occurs in all long bones


endolymph

fluid of the membranous labyrinth of the inner ear


endometrium

lining of the uterus and cervix consisting of two layers:

the uterine lining undergoes changes during the menstrual cycle:

  1. proliferative phase- estrogen regulated; thickening of uterine glands, proliferation of stroma, growth of spiral artery
  2. secretory phase- progesterone regulated; very thick endometrium; uterine glands and spiral arteries coil
  3. menstrual phase- rupture of vessels; sloughing of the endometrium; overall loss in endometrial mass


endomysium

connective tissue layer of reticular fibers surrounding muscle fibers


endoneurium

connective tissue which surrounds individual nerve fibers


endosome

membrane-enclosed compartment surrounding a particle/cell that was phagocytosed


endosteum

lining of the bone surface facing the marrow and also of trabeculae; consists of osteoprogenitor cells that are referred to as "endosteal cells"


endotendineum

connective tissue which surrounds a fasicle (the subunit of a tendon); contains vessels and nerves


endothelial cell

squamous cell that lines blood and lymphatic vessels


endothelium

1)layer of endothelial cells and their underlying basement membrane; lines all but the smallest vessels
2)the deepest layer of the cornea


entero-endocrine cell

see APUD cell


eosinophil

leukocyte with bilobed nuclei; engages in phagocytosis of antigen-antibody complex; possesses histaminase and other enzymes which neutralize the substances released by mast cells and basophils to prevent hyperinflammation; bilobed nucleus (humans); rodent eosinophils have annular shaped nucleus and monkeys eosinophils contain multilobed nuclei; have red granules (H&E) in cytoplasm


epicardium

see pericardium


epidermis

outer layer of skin; the keratinized stratified squamous epithelium that comprises the upper skin layer; extensive keratin deposition allows for effective barrier function; has five strata (from inner to outer):


epimysium

dense connective tissue that surrounds a group of muscle fiber fascicles (bundles)


epinephrine

also known as "adrenaline"; hormone of the adrenal medulla; involved in the sympathetic response


epineurium

connective tissue that binds bundles of nerve fibers


epiphyseal plate

cartilaginous layer at the epiphysis of long bones which is the site of longitudinal bone growth


epiphysis

the ends of long bones


epitendineum

connective tissue layer that surrounds a tendon


epithelioreticular cell

stellate-shaped cell that serves a supportive role in the thymus


erectile tissue

the corpus cavernosum and the corpus spongiosum which when engorged with blood, allow for erection


ergastoplasm

another name for the rough endoplasmic reticulum


erythrocyte

see red blood cell


erythropoiesis

the process of red blood cell formation, occurs in the bone marrow


erythropoietin

a kidney protein which stimulates erythropoeisis in times of reduced tissue oxygen


esophageal cardiac gland

gland of the terminal esophagus; located in the lamina propria; secretes a neutral mucus to protect the esophagus from gastric regurgitation


esophageal gland

occurs throughout the esophageal submucosa; secretes a slightly acid secretion which lubricates the esophageal lumen


estrogen

steroid hormone which maintains/develops female sex characteristics


euchromatin

light-staining matter of the nucleus; represents less condensed, more actively transcribed DNA regions


excretory duct

see duct; in esophagus: lined by stratified squamous epithelium as it emerges from the esophageal gland


exocervix

the segment of the cervix facing the vaginal space; see also squamocolumnar junction


external anal sphincter muscle

voluntary sphincter of the anus


external elastic lamina

see elastic laminae


external elastic membrane

same as external elastic lamina


external root sheath

outer layer of the hair follicle; derived from a downgrowth of the epidermis


exudate

debris material containing dead leukocytes and foreign cells found at sites of infection


eyelash

a hair of the eyelid


eyelid

protects the eye from foreign objects and desiccation


F-actin

filamentous actin composed of two G-actin (globular actin) strands


fascia adherens

plates on the transverse intercalated disc that allow muscle cells to anchor to each other; analogous to the zonula adherens of epithelial cells


fenestrated capillary

capillary with a discontinuous basal lamina as well as gaps (covered by diaphragms) between the endothelial cells


fenestrated cortical sinusoidal capillary

see sinusoidal capillary


fenestration membrane

a discontinuous basal lamina of a fenestrated capillary covered by a diaphragm


fibroblast

Fusiform cell with cytoplasm that is usually indistinguishable from the surrounding matrix; tapering processes are present but are difficult to visualize in most sections; some very active cells have basophilic cytoplasm; has elliptical nucleus, sometimes slightly folded, with sparse chromatin that presents a "speckled" appearance (may be mistaken for plasma cell); has one to two nucleoli; makes fibers and ground substance


fibrocartilage

see cartilage


fibrocartilaginous callus

a stage of bone repair in which fibrocartilage is deposited to stabilize the ends of the fractured bones; later replaced by the bony callus


fibromuscular stroma

dense irregular connective tissue and smooth muscle of the prostate gland


filiform papillae

appendages on the dorsal surface of the tongue; covered with keratinized stratified squamous epithelium


fimbriae

finger-like extensions of the infundibulum which catch the oocyte after its departure from the ovary


fixed cell

a cell that is a resident of connective tissue; i.e mast cell


foam cell

a macrophage containing large lipid stores; located within an atherosclerotic plaque


foliate papillae

appendages of the dorsolateral surface of the tongue; contain many taste bud


follicle

1) the spherical structure responsible for hormone production in the thyroid gland

2) see hair follicle


follicle stimulating hormone (FSH)

pituitary hormone which stimulates the maturation of the ovarian follicle


follicular cell

the cuboidal cell of the thyroid follicle or the developing follicle


folliculogenesis

the process of follicular development; includes several stages (in the following order):


fundic gland

simple, branched tubular gland of the stomach fundus that produces the substances necessary for digestion; contains Chief cells, mucous neck cells, parietal cells, APUD cells, and stem cells


fungiform papillae

mushroom-shaped appendages of the dorsal tongue; contain numerous taste buds


G-actin

"globular" actin, appears bead-like in structure


GALT

Gut Associated Lymphatic Tissue; lymphatic aggregates located throughout the digestive tract


ganglion

a group of neuronal cell bodies


ganglion cell

1) a cell of a ganglion 2) postganlionic cell of the adrenal medulla; causes release of norepinephrine and epinephrine upon nervous stimulation


ganglion cell layer

layer of the neural retina which houses neurons involved in transmitting the signals of photoreception


gap junction

channel that allows electrical, electrolyte, and fluid communication between adjacent cells; also known as nexus


gastric gland

another name for fundic glands


gastric pit

depression of the stomach lining that opens into the gastric gland


germinal center

area of lymphatic tissue containing rapidly developing/differentiating lymphocytes


germinal epithelium

cuboidal cells that line the surface of the ovary; does NOT give rise to germ cells


gland

structure involved in producing substances to be secreted; sweat glands tend to be lined by either stratified cuboidal epithelium or stratified columnar_epithelium


glomerular basement membrane

GBM; basal lamina between the podocytes and endothelium; allows selective permeability by size and charge (positive, small particles filter easier


glomerulus

capillary meshwork of the kidney nephron


glucocorticoid

see zona fasciculata


glycogen

primary energy storage form of animal cells; appear as empty vacuoles in LM


goblet cell

special mucus-secreting columnar epithelial cell located in the respiratory system and intestines; large vacuoles can be seen in light microscopy


Golgi complex

cellular structure involved in modifying, packaging, sorting, and secreting proteins; has cis face for receiving and trans face for releasing products


gonadocorticoid

LH and FSH; released by the gonadotropes


gonadotrope

cell of the adenohypophysis which releases LH and FSH


Graafian follicle

see folliculogenesis


granulocyte

neutrophils, eosinophils, and basophils, all of which possess certain immunoreactive substances contained in granules


granulopoiesis

the developmental process of granulocytes


granulosa cell

cell which comprises a layer which surrounds the antrum of the mature follicle; catalyzes the conversion of androgens to estrogen


granulosa lutein cell

cell of the corpus luteum derived from the granulosa cell


ground substance

viscous substance that occupies the space between fibroblasts and connective tissue


H band

a region of the sarcomere with only myosin filaments; shortens with contraction


hair

appendage of the skin composed of keratinized cells


hair cell

the cell of audioreception protruding from the basilar membrane; registers vibration, which is then converted to electrical signals transmitted along the cochlear nerve


hair follicle

skin structure from which hairs arise


Hassall's corpuscle

concentric arrangement of epithelioreticular cells; more prominent in adults


Haversian canal

see Haversian system


Haversian system

concentric lamellae arranged around a central (Haversian) canal which conatins blood vessels and nerve supply


heart failure cell

alveolar macrophage filled with hemosiderin; indicative of congestive heart failure


helper T-lymphocyte

a cell that stimulates B-lymphocytes and T-lymphocytes to carry out their respective functions


hematopoiesis

same as hemopoiesis


hemidesmosome

structure on the basal surface of an epithelial cell that anchors it to connective tissue elements


hemocytoblast

large cell with basophilic cytoplasm and large nucleus which was at one time considered to be the precursor to all blood cell types


hemopoiesis

process of blood cell formation from a common stem cell; occurs in bone marrow in the adult


hemosiderin

debris found in heart failure cells


hepatic acinus

see liver acinus


hepatic artery

vessel carrying oxygen rich blood to the liver


hepatic duct

duct which delivers bile from the liver to the cystic and common bile ducts


hepatic sinusoid

sinusoids of the liver

hepatic vein

drains deoxygenated blood from the liver to the inferior vena cava


hepatocyte

the basic functional cell of the liver


Herring body

axonal dilation within the neurons of the pars nervosa; contains either oxytocin or vasopressin


heterochromatin

dark staining regions of chromatin in the nucleus; signifies DNA regions of little transcripitional activity


hilus

the area of a lymph node where vessels enter and exit


Hofbauer cell

macrophage-like cell of the chorionic villus; unknown function; contains stores of lipids and glycoproteins


holocrine

mode of secretion in which part of the secretory cell is exuded in the product; i.e. sebaceous gland


Howship's lacuna

the space underneath an osteoclast where bone matrix is being resorped


hyaline cartilage

see cartilage


hypertrophy

overgrowth of cells due to: overstimulation of the tissue/organ which they comprise, a cancer, or a benign condition such as BPH (benign prostratic hypertrophy)


hypodermis

a layer of connective tissue beneath the dermis; contains ample adipose


hypophyseal portal system

capillary network carrying neuroendocrine secretions from the median eminence and infundibular stem to the pars anterior


hypothalamohypophyseal tract

nerve tract leading from the hypothalamus to the pituitary


I band

a region of the sarcomere whose span includes only actin filaments


ileum

terminal portion of small intestine; opens into cecum of the large intestine


immunoglobulin

antibody secreted by the plasma cells; types include:


inactive mammary gland

mammary gland with much dense irregular connective tissue and no secretory activity


inflammation

bodily response to injury characterized by pain, swelling, redness, and loss of function; triggered by heavy infiltration of leukocytes, particularly neutrophils


infundibulum

1)attachment between the hypothalamus and pituitary
2)see oviduct


inner circumferential lamellae

concentric rings of bone matrix closer to the bone center


inner elastic membrane

same as internal elastic lamina


inner limiting membrane

layer of the neural retina composed of the basal lamina of Muller cells


inner nuclear layer

layer of neural retina housing horizontal, amacrine, bipolar and Muller cells


inner plexiform layer

contains processes of the cells of the inner nuclear layer


intercalated disc

structure which connects adjacent muscle fibers at their ends; also allows for communication via gap junctions which span it


intercalated duct

located between an acinus and larger ducts in salivary glands; secrete bicarbonate and absorb chloride; most prominent in salivary glands that produce watery secretions


intercellular bridge

the actin filament bundles interposed between adjacent Sertoli cells


intercellular space

a space between adjacent cells


interlobar artery

branch of the renal artery; travels between adjacent renal pyramids


interlobular artery

vessel that branches from an interlobar artery and descends into a kidney lobule; a lobule is a segment of a lobe, which in turn consists of a pyramid and surrounding tissue on its base and sides


interlobular duct

duct of the mammary gland; located at a distance from lobules


interlobular vein

vessel that carries deoxygenated blood in the same region as the interlobular artery, but in reverse course


intermediate filament

cytoskeletal element which serves a general supportive and structural function


intermediate lobe

see pars intermedia


internal anal sphincter muscle

the involuntary, inner anal sphincter; composed of smooth muscle


internal elastic lamina

see elastic laminae


internal elastic membrane

same as internal elastic lamina


interstitial growth

process of bone/cartilage growth due to cell division rather than matrix deposition


interstitial lamellae

rows of bony matrix in the area between Haversian systems


interterritorial matrix

in cartilage, material at a distance from cells; proteoglycans are in sparse concentration here; see also territorial matrix


intervillous space

see chorionic villus


intestinal gland

same as crypt of Lieberkuhn


intracellular canaliculus

invagination of the parietal cell membrane with numerous microvilli; this system enhances the surface area available for HCL release


intralobular duct

1) the equivalent of the striated duct; lined by cuboidal cells; functions in reabsorption of sodium and secretion of potassium; found in salivary glands and the pancreas

2) duct leading from the mammary lobules to the interlobular duct


intramembranous bone formation

process in which bone is laid down by osteoblasts without a prior cartilaginous precursor; primary mode of flat bone formation


intrinsic striated muscles of tongue

visceral striated muscle; allow for voluntary tongue movement


iridocorneal angle

the space between where the iris and cornea are anchored


iris

diaphragm extending over the lens surface; controls pupil diameter


islet cell

see islet of Langerhans


islet of Langerhans

functional unit of the endocrine pancreas; composed of three cell types:


isogenous group

group of contiguous chondrocytes that results from the division of a single precursor


isthmus

see oviduct


Ito cell

see lipocyte


jejunum

middle portion of the small intestine


junctional complex

the combination of desmosomes, zonula adherens, and zonula occludens


juxtaglomerular apparatus

structure adjacent to the afferent and efferent arterioles; it is involved in the release of renin, and hence the control of blood pressure; consists of:


juxtaglomerular cell

see juxtaglomerular apparatus


keratinized stratified squamous epithelium

see epidermis


keratinocyte

cell of the epidermis which produces keratin


keratohyalin

protein produced by the keratinocyte which becomes keratin when combined with tonofilaments (intermediate filaments)


killer T-lymphocyte

a cell of the immune system that directly attacks foreign cells, causing lysis


Kupffer cell

cell of the mononuclear phagocytic system which resides in the space of Disse; degrades damaged erythrocytes


labial mucosa

lining of the oral surface of the lip; consists of stratified squamous non-keratinized epithelium


lacteal

a small lymphatic vessel located at the intestinal villus tip


lacuna

the housing compartment of chondrocytes and osteocytes within their respective matrices


lamina propria

the loose connective tissue of mucous membranes


Langerhans cell

antigen-presenting cell of the stratum spinosum; has clear cytoplasm and dark-staining nucleus


larynx

air passage between the oropharynx and the trachea


late spermatid

elongate spermatozoan precursor bordering the seminiferous tubule lumen, yet still attached to a Sertoli cell


lateral surface of epithelial cell

that side of the cell in contact with other cells; usually anchored by various filament complexes


layer of rods and cones

layer of neural retina housing the photoreceptors


lens

transparent, elliptical structure which along with the cornea, is a refractive element of the eye


lens capsule

thick basal lamina covering the lens


leukemia

a cancer in which the numbers of leukocytes in the blood increase dramatically; immature blood cells are also found in circulation in this condition


leukocyte

a cell of the immune system; also known as a white blood cell


leutinizing hormone

pituitary hormone which stimulates theca interna cells to secrete androgens


Leydig cell

cell of the stroma surrounding the seminiferous tubule which produces testosterone; this hormone is important in the male for:


limbus

a transitional area between cornea and sclera


lipid

fatty acids, cholesterol, etc. housed in cells as vacuoles


lipid droplet

lipid vacuoles inside cells; usually lost in preparation for microscopy


lipocyte

also known as "Ito cell"; cell of the liver which stores large amounts of lipid as well as vitamin A


lipofuscin

vacuole containing debris; the older a cell, the more lipofuscin it will contain; also known as tertiary lysosome and residual body


liver acinus

elliptical model of liver organization with central veins on the ends of the long axis, and portal triads on the ends of the short longitudinal axis


lobe

subdivision of the lung; the left lung is divided into an upper and lower lobe, the right lung is divided into an upper, middle, and lower lobe


lobule

1)a group of ducts and surrounding connective tissue within the mammary gland
2)the functional unit of liver organization; defined variously as: the classical lobule, the liver acinus, and the portal lobule
3)an area of the lung supplied by a bronchiole


longitudinal (meridional) fiber

part of the ciliary muscle; causes tension of the lens


loop of Henle

a U-shaped structure of the nephron consisting of the descending proximal straight tubule, the thin segment, and the ascending distal straight tubule


loose connective tissue

connective tissue with an abundance of cells and sparse fibers


lymph nodule

aggregates of lymphocytes in the cortex of the lymph node


lymphatic channel

same as lymphatic vessel


lymphatic vessel

a vessel that carries lymph, which consists of interstitial fluid, cells of the immune system, foreign cells, and other substances


lymphocyte

Small round cell with dark nucleus and only a thin rim of cytoplasm:


lymphopoiesis

the process of development of lymphocytes in lymph nodes


lysosome

digestive organelles containing various hydrolytic enzymes;


M band

located in the sarcomere, a region at the center of the H band which signifies the attachment sites of myosin filaments to each other


macrophage

massive cell involved in phagocytosis of foreign material or defective host cells, and in antigen presentation; usually irregular in shape with vacuolated cytoplasm; the macrophage is difficult to distinguish from a fibroblast without the presence of phagocytosed material


macula adherens

see desmosome


macula densa

specialized cell group of the distal convoluted tubule that is part of the juxtaglomerular apparatus


malignant acinus

in prostate cancer, the presence of glandular hypertrophy


Mallory body

eosinophilic inclusion found in the hepatocyte of alcoholics


MALT

mucosa associated lymphatic tissue; lymphatic aggregates of the cervical mucosa


mammatrope

acidophilic cell of the adenohypophysis which releases luteotropic hormone (LTH)


marginal zone

area between the red pulp and white pulp of the spleen


marrow

see bone marrow


mast cell

large fixed cell that has large granules containing immunoreactive and vasoactive substances: histamine, slow-reacting substance of anaphylaxis, eosinophilic chemotactic factor of anaphylaxis, and heparin; found near blood vessels; round small nucleus (as compared to cell size); numerous granules show metachromasia with some stains


mature cell

a cell after it has fully developed from its precursors; if applied to granulocytes, refers to the cell form of the circulation, which usually contains a multilobed segmented nucleus


median eminence

continuous with the infundibulum; carries neurosecretory nerves


mediastinum testis

connective tissue that projects into the parenchyma of the testis, carrying with it blood and lymph vessels


medulla

the inner portion of an organ; in the thymus and lymph node, area of relatively sparse lymphocyte concentration


medulla of lymph node

inner portion which contains a lesser concentration of lymphocytes


medullary cord

tissue of the medulla in lymph organs containing reticular cells, lymphocytes, macrophages, and plasma cells


medullary ray

aggregate of the proximal, distal straight and collecting tubules


medullary sinus

space between adjacent medullary cord; drains lymph into the efferent lymph vessel


medullary vein

also known as "central vein"; large, muscular vein of the adrenal medulla; its strong contractility facilitates quick release of the medullary hormones


megakaryocyte

a massive precursor of platelets within the bone marrow; possesses a multilobed nucleus


meiosis

a process which produces daughter cells with half the DNA content of the parent; results in germ cell production


Meissner's corpuscle

receptors of low frequency tactile stimuli; located on hairless skin


Meissner's plexus

a ganglion of the submucosa which controls secretion in the digestive tract


melanocyte

a cell of the epidermis which produces melanin, the substance responsible for pigmentation


melanotrope

cell of the pars intermedia which stimulates melanin production; found in some non-human species


membrane coating granule

found within the keratinocytes of the stratum spinosum; contains a glycolipid that forms a water barrier on the skin surface


menstrual phase of the endometrium

see endometrium


Merkel cell

cell of stratum basale which functions in cutaneous sensation


mesangial cell

cell of the juxtaglomerular apparatus and renal corpuscle; involved in phagocytosis of debris


mesaxon

slit left exposed on outer myelin sheath after myelin wrapping is complete


mesothelial cell

squamous cell comprising the cellular part of the mesothelium


mesothelium

epithelial lining of the body cavities (i.e. thoracic, pericardial, abdominal)


metachromasia

phenomenon in which a basic dye changes color from blue to red/purple due to the dense presence of polyanionic groups (i.e. phosphates, sulfates)


metamyelocyte

precursor of granulocytes which shows varying degrees of indentation, and elongation of the nucleus indicative of differentiation into the more mature juvenile or band forms.


metaphysis

the curve between the ends of the bone (epiphysis) and the shaft of the bone (diaphysis)


metastasis

the spread of a cancer to areas away from where it originated


metastatic cancer cell

cell involved in metastasis


microbiological flora

bacteria; found in certain body cavities; see Pap smear


microfilament

cytoskeletal element involved in cell anchorage, contraction, exocytosis/endocytosis, structure of microvilli, and locomotion; actin and myosin are examples


microtubule

cytoskeletal element found in cilia, flagella, basal bodies, the mitotic spindle, centrioles, cytoplasm, and elongating cell processes (i.e. axon)


microvilli

processes of the apical plasma membrane of absorptive cells; increase surface area for absorption


mineralocorticoids

see zona glomerulosa


minor calyx

the point where the collecting ducts of a pyramid drain; several of these structures drain into a major calyx


mitochondria

oxidative organelle of the cell; believed to be derived from a prokaryotic symbiote


mitochondrial cristae

involutions of the inner mitochondrial membrane protruding into the matrix; contain enzymes of oxidative phosphorylation


mitosis

process which produces two daughter cells, each with genetic material equal in amount to the parent


mitotic cell

cell in the process of dividing into two daughter cells which will contain the same amount of genetic material as the parent


mixed spicule

newly forming bone atop calcified cartilage; seen in endochondral bone formation


modiolus

bony core around which the cochlea turns 2 and 3/4 times


monoblast

precursor of the promonocyte


monocyte

the large blood-borne precursor of mononuclear phagocytic system cells; has some vacuoles and indented nucleus frequently lacking nucleoli


mononuclear phagocytic system

cells capable of vigorous phagocytosis; arise from monocytes; this system includes:


mucocutaneous junction

the border between the epidermis of the outer lip and the labial mucosa


mucosa

the combination of an epithelial lining, the lamina propria, and muscularis muscosae


mucous acinus

a mucous secretory unit with a circular arrangement of mucous cells


mucous cell

a cell that produces and releases mucous; vacuoles are usually visible within the eosiniphilic cytoplasm


mucous gland cell

a cell of a mucous gland located in the digestive tract, respiratory system, etc


mucous gland

a gland that release mucous, a glycoprotein


mucous neck cell

located at the neck of the fundic gland; secretes a soluble mucous


mucous-secreting cell

see mucous cell


mucous surface cell

cell lining the gastric pit; secretes an insoluble mucous


muscle fiber

see myofiber


muscular artery

most numerous of artery types; notable for thick, muscular tunica media; example is brachial artery


muscularis

see muscularis externa


muscularis e