Histology Flashcards
4 basic tissue types
epithelial tissue (epithelium
connective tissue
muscle tissue
nervous tissue
epithelial tissue characteristics
large sheets of cells covering all surfaces of body (exposed to outside) lining organs, internal cavities and passageways
highly cellular
cell junctions: adjoining cells form specialized intercellular connection between their cell membrane
avascular
capable of rapidly replacing damaged and dead cells,
function of epithelial tissue
provides protection from physical chemical and biological wear and tare, many have barriers with selective transportation of molecules, capable of secretion and release mucous
in small intestine, repiratory tract, etc.
tight junction
in epithelial tissue, separates the cells into apical and basal compartments, tight junctions seal cells together (material can’t get through)
anchoring junction
stabilize epithelial tissues, in lateral and basal surfaces of cells provide strong / flexible connections
desmosomes
patches on membrane of cells made of structural proteins on the inner surface of the cell’s membrane, hold cells together
hemidesmosomes
link cells to the extracellular matrix ex: basal lamina
adheren junctions
connect isolated patches or form belt like structure inside cell, influence shape and folding of epithelial tissue, characterized by presence of contractile protein actin on cytoplasm
gap junction
forms an intercellular passageway between membranes of adjacent cells, facilitates movement of small molecules and ions between cytoplasm and cells, allow electrical and metabolic coupling of adjacent cells which coordinates function in large groups of cells
shapes of epithelial tissue
squamous, cuboidal, columnar
simple epithelium
one cell layer, every cell rests on basement membrane
stratified epithelium
more than one layer, only basal layer of cells rests on basement membrane
pseudo-stratified
describes tissue with a single layer of irregularly shaped cells that give the appearance of more than one layer
transitional
describes a form of specialized stratified epithelium in which shape of the cells can vary
Simple squamous
Structure: appearance of thin scales. Squamous cell nuclei tend to be flat, horizontal, and elliptical, mirroring the form of the cell
Function: diffusion, filtration, provide a smooth and protective surface. secrete a fluid that lubricates the mesothelium,
Location: air sacs and alveoli, lining of blood vessels, serous membranes lines vessels of the lymphatic and cardiovascular system, is present where rapid passage of chemical compounds is observed, alveoli of lungs where gases diffuse and the lining of capillaries, mesothelium is a simple squamous epithelium that forms the surface layer of the serous membrane that lines body cavities and internal organs
simple cuboidal
Structure: the nucleus of the box-like cells appears round
Function: absorption and secretion active in the secretion and absorption of molecules
Location: kidney tubules, glands near the center of the cell, lining of the kidney tubules and in the ducts of glands
Simple columnar
Structure: the nucleus of the tall column-like cells tends to be elongated and located in the basal end of the cells, composed of simple columnar epithelial cells with cilia on their apical surfaces
Function: absorption, secretion, movement (if ciliated)
Location: forms the lining of some sections of the digestive system, namely the stomach, small intestine, and large intestine, lining of the uterine tubes, where the beating of the cilia helps remove particulate matter
pseudo-stratified columnar
Structure: appears to be stratified but instead consists of a single layer of irregularly shaped and differently sized columnar cells, nuclei of neighboring cells appear at different levels rather than clustered in the basal end, all the cells are in contact with the basement membrane, although some do not reach the apical surface
Function: protection, movement
Location: lines respiratory tract
stratified squamous
Structure: several stacked layers of cells
Function: protection
Location: epidermis of skin, lining of the oral cavity, pharynx, esophagus, anus, and vagina
transitional
Structure: appears thicker and more multi-layered when the bladder is empty, and more stretched out and less stratified when the bladder is full and distended
Function: distention and relaxation of urinary structures
Location: lining of uterus, bladder, and urethra
Endocrine gland
hormones, released into interstitial fluid, to blood stream to cell receptors, regulatory system coordinates the regulation and integration of body responses
ex: anterior pituitary, thymus, adrenal cortex, gonads
Exocrine glands
release contents through a duct that goes to epithelial surface
ex: mucous sweat saliva, breast milk, secretion of gastrointestinal tract