There are fo ur primary t is sue s: epithe lial, c onnective, ne r vo us, and muscular tissue . •
These differ f rom each other in the t yp es and f unct ions of t he ir c el ls, t he character is tics of the mat rix •
(extrace llular mater ial) t hat surro unds th em , and the relative amount of space occupie d by ce lls vers us
mat rix.
A tissue is compo se d of cells an d matr ix , and the mat rix if composed o f fibe rs & gro und substanc e. •
Cha rac terist ics of Epi thelial Tissues:
Epitheli al t is sue a re also called e pi thelium. It forms lini ngs, membranes, and glands. •
The ce ll s and the extrace llula r mater ia l ca n be loos el y compared to brick s and mortar o f a wall. •
Cells a re tightly packed together wit h sma ll amoun t of i ntersti tial fluid in be twee n the ce lls. •
Epitheli a are avascular : me aning there is no room b etwee n the cells for blood ve ssels. •
Epitheli a is always supporte d by co nnecti ve tiss ue. •
Between an epithelium and the under lying connect ive tissue is a layer c al led the basement membrane . •
The su rf ace o f an epithelial cell that f aces t he basemen t membrane its basa l surface, the one t hat faces •
away from the basement membrane toward the inte rnal cav ity (lume n) of an org an is the apical sur face.
In simple ter ms: t he basal surf ace (laye r) is closer t o the membrane and the apic al s urface (layer) is fu rther •
from the membrane.
Lume n: is a space •
The apica l surf ace is clo se to lume n •
Epitheli a are clas sifie d in to t wo broad c ate gories :
1. Simple epithelia: h as one laye r of e pi th elium cel ls.
2. Stratified epithelia: h as t wo or more laye rs of epi
theli um cells.
EEpithelial tissue
membrane
BM Basement
Ct ConnectiveTissue
1
2
