Basic Tissue Types: Epithelium Flashcards
Endothelium
lining of the blood or lymphatic vessels
mesothelium
lining of serous body cavities
main functions of epithelia
absorption, protections, secretion
single layer of epithelium that provides all 3 functions
small intestine
basement membrane
support for epithelial tissue
separate epithelia from support tissue beneath
Never penetrated by blood vessels
external laminae
structure for muscle and nervous tissue similar to that of the basement membrane for epithelial tissue
basal surface
side of epi facing the basement membrane
apical surface
side of epi which faces outwards (away from basement membrane)
3 types of junctions
anchoring
occluding
communication
anchoring junction
provides mechanical strength
occluding junction
link cells to form an impermeable barrier
communication junction
allow direct communication between cells
Classification of epis is based on
number of layers
cell shape
presence of surface specializations
layers of cells
simple: 1 layer
stratified: at least 2 layers
pseudostratified: only 1 layer thick, but gives appearance of being stratified
cell shapes
squamous: flattened
Cuboidal: cube shaped
columnar: hight is at least 2x the width
examples of surface specializations
they are features on cell surface that enhance function of the epi
keratin found on skin surface (increases protective nature of the skin surface)
cilia, microvilli, stereocilia
Simple epi
1 layer of cells
absorption, secretion, selective diffusion
little protection against abrasion
Simple squamous epi
Appearance: flattened, irregularly-shaped cells, “fried egg”
Location: Lungs, walls of blood capillaries, lining of pleura, pericardial and peritoneal cavities
Function: Passive transport of gases and fluids
simple cuboidal epi
Appearance: square or cube shaped, section perpendicular to basement membrane
Location: lining of small ducts or tubules, collecting ducts of kidneys, salivary glands, pancreas
Function: excretory, secretory and absorptive
Simple columnar epi
Appearance: cells are tall (“columns”) from the basement membrane; height may vary depending on site/function
Location: mucosal lining or small intestine, stomach, gall bladder
Function: absorption, secretion
simple columnar ciliated epi
columnar cells with cilia
cilia propel a fluid or minute particle over the surface by beating in synchonic rhythm with adjacent cells
Ex. egg moving through fallopian tube
pseudostratified columnar ciliated epi
Appearance: appear to have more than one layer of cells but all cells are touching the basement membrane (actually only one layer); nuclei at different levels; cilia on apical surface
Location: large airways of respiratory system
Function: cilia collect material; propel a fluid or minute particle
Stratified epi
more than one layer of cells
primarily protective functions
degree of stratification depends on amount of physical stress the surface must endure
Stratified squamous epi
Appearance: multiple layers of cells (transition from cuboidal basal layer to flattened outer layer)
Location: Oral cavity, pharynx, vagina, areas with minimal abrasion that are kept moist by glandular secretion
Function: Protection
