Epithelial Tissue Flashcards
Body parts and relationship hierarchy
- chemical
- cellular
- tissue
- organ
- system
Histology Definition
Study of microscopic structures of tissues
Types of Tissues
- nervous
- epithelial
- muscle
- connective
Nervous Tissue
Brain, Spinal Cord, Nerves
Epithelial Tissue
Lining of GI tract organs & hollow organs
Skin surface
Muscle Tissue
Cardiac Muscle
Smooth Muscle
Skeletal Muscle
Connective Tissue
Fat
Bone
Tendon
H&E Stains
Hematoxylin – behaves like a base & stains blue
Eosin – behaves like an acid & stains pink
Parenchyma
cells responsible for the organ’s specialized function
Stroma
supporting cells, usually connective tissue
Epithelial Tissue
composed of sheets of cells that cover body surfaces, line body cavities, & form glands
Epithelia Function
physical protection
controls permeability - filtration, absorption, excretion
provides sensation
produces secretions
Epithelia Characteristics
- densely packed cells bound by specialized cell junctions
- polarity
- attachment via basement membrane to underlying CT
- avascular
- innervated
- regenerates
Basement Membrane
Function
acellular, consists of molecules secreted by basal epithelial cells & cells of CT
- supports overlying epithelium
- anchors epithelial tissue to underlying CT
- semipermeable
- scaffold for repair and regeneration
Microvilli
finger like extensions on apical surface
abundant on epithelial surface where absorption & secretion occur
function - increase absorptive surface area
Cilia
long, motile processes on apical surface; microtubules & associated proteins form their core
respiratory tract, uterine tube
function - beat in a coordinated fashion to move substances over the epithelial surface
Tight (Occluding) Junctions
zonula occludens
binds plasma membrane of adjacent cells together
seal created by tight interactions between transmembrane proteins: claudin & occludin
fn - acts as a permeability barrier, prevents passive flow between cells, limits movement of membrane proteins from surfaces
Anchoring Junctions
attach cytoskeletons of adjacent epithelial cells together
- adherens junction
- desmosomes
- hemidesmosomes
Adherens Junction
zonula adherens
actin microfilament of adjacent cells are linked by transmembrane proteins: cadherins
fn - firmly anchors neighboring cells & provides stength & distributes shear forces
band - goes all around
Desmosomes
macula adherens
disc shaped
links intermediate filaments of adjacent cells by transmembrane proteins: cadherins
fn - creates strong connections between cells & distriubutes shear forces
Hemidesmosomes
links intermediate filament network of the cytoskeleton across the basal surface to the BM by transmembrane proteins: integrins
fn - resist separation from underlying tissue
Gap Junctions
Complex of 6 transmembrane proteins (connexins) form channels (connexons)
multiple connexons from 2 adjacent cells align to form the gap junction
fn - mediates intercellular communication
Simple Squamous
lines vessels & serous lining of cavities
fn - regulate passage of substances into underlying tissue
Simple Cuboidal
surface of ovary, kidney tubules, some glands
fn - line surfaces involved in secretion & absorption
Simple Columnar
lines small intestine, colon, stomach, gall bladder, uterine tube
fn - secretion & absorption; larger cells thus more organelles than cuboidal
Pseudostratified Columnar
appears stratified but all cells are anchored to BM & nuclei appear at different levels
usually has cilia
lines respiratory tract, ductus deferens, & epididymis
fn - secretion & conduit
Stratified Squamous Keratinized Epithelium
develops a tough layer of keratin (no nuclei) & found in skin
fn - protection against abrasion, water loss, UV, foreign particles
Stratified Squamous Non - Keratinized Epithelium
lines wet surfaces - mouth, esophagus, pharynx, vagina
fn - protection against abrasion, water loss, UV, foreign particles
Transitional
stratified epithelium
lines bladder, ureters, urethra; surfaces that change in response to stretching & relaxing
in relaxed state looks like stratified cuboidal, except apical cells are found and large
fn - allows for stretch and recoil
Glandular Epithelia
exocrine glands: secretions travel through ducts to the epithelial surface
endocrine glands: ductless glands that exist within some covering epithelia
Exocrine Glands
serous glands: watery fluid with enzymes
mucous glands: secrete glycoproteins called mucins
mixed exocrine glands: contains both serous and mucus secretions
Unicellular Glands
goblet cells
secrete mucus onto exposed surface of epithelial sheet & functions to protect apical surface
Structural Classification of Exocrine Glands
Duct:
simple - unbranched
compound - branched
Secretory portion:
tubular or branched tubular
acinar or alveolar
Modes of Secretion - Exocrine
merocrine glands - secretions released by exocytosis
holocrine glands - entire vesicle shed into lumen
apocrine glands - pinched off portion of cell is secreted
Endocrine Glands
ductless gland that exist within some covering epithelia
secrete cell product (hormones) directly into intersititial fluids or blood
hormones enter systemic circulation by diffusion
