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Histology: Epithelial Tissue (Tissue Types (Glandular epithelia: …
Histology: Epithelial Tissue
Tissue Types
Covering epithelia:
Lines all surfaces
of body, body cavity or
organ
E.T cells
( Layers &
shape of cells)
Stratified
(two or more
layer of cells)
Cuboidal
sweat glands, developing ovarian follicles
Columnar
Conjuctive
Squamous
(non-ketanized)
Mouth, vagina, larynx,
esophagus, anal canal
Transitional
(stretching)
Bladder, renal calyces, ureter
Squamous
Kertinized
Epidermis
Pseudostratified
Lining of Trachea, bronchi, Nasal cavity
Simple (One Layer of cell)
cuboidal
(secretion mostly,
some absorptive)
Kidney tubules, ovaries, thyroid follicles
secretory portions of small glands
columnar
(absorption mostly)
Lining of intestine & gallbladder
small bronchi, uterine tube, uterus
Squamous
(diffusion & filtation
mostly)
Vessels (blood & lymph), Alveoli
lining of heart, Renal corpuscles, serosa
Special type: Endothelium ( inner covering
of hollow organs), Mesothelium ( middle covering, lines peritoneal, pleural, & pericardial cavities)
Glandular epithelia:
secretory glands
Exocrine: (Ducts carry
products to epithelial surface)
Unicellular
Digestive & respiratory track
Goblet cells producesmucin
protects internal body surface
Multicellular
Merocrine
secretion
Serous, water w/ some
non-glycosylated protein
parotid glands, pancreas
Mixed: Serous & mucus,
submandibular gland
Mucous: mucus (heavily
glycosylated
sublingual glands, goblet cells
Holocrine
secretion
Whole cell disintegrates
(sebaceous gland)
Apocrine
secretion
Endocrine
Ductless, hormones into tissue fluid, not all epithelia, may occur in small groups or singly
Overview of E.T
Function: Absorption, Secretion, covering, lining & protection
Tightly packed cells w/ little ECM, innervated, avascular
Associated w/connective tissue through Basement Membrane
Has a basal, apical, and lateral side (polarity)
E.T ECM
(very little)
Apical to basal
layer intercellular adhesion & junctions organization (Tightly packed cells through
intercellular adhesion & junctions)
Tight junction
(occluding,
Zonula Occludens)
Most apical location, prevents paracellular
transport (transport through intercellular space)
Transcellular transport ( transport s of solutes by a cell through a cell
C. Perfringens binds to claudin ( claudin and occludin transmembrane protein interactons help form tight junctions), poke a hole and kills cell
Adherens junction
(anchoring)
Below tight junctions, mechanical
attachment b/w cells
Allows cells to move as a unit,
Cadherins attach to catenins, that link to actin
Gap junction
(communicating junction)
Channel b/w two adjacent cells
allows small (cAMP) ions to move
Cells connected by hollow
cylinders of connexins
Desmosomes
(macula adherens,
anchoring)
Coupling b/w adjacent cells,
gives mechanical strength to tissues
Stress & stretch resistance
Hemidesmosomes
(anchors cells to basal
lamina)
Anchors epithelia basal cell
to lamina Lucida of basal lamina
Disruption can lead to bullous phemphigoid (blisters)