EPITHELIAL TISSUE Flashcards
what are the 3 primitive (germ cell) layers?
Mesoderm / Ectoderm / Endoderm
what is connective tissue derived from?
mesoderm
what is muscular tissue derived from?
mesoderm
what is nervous tissue derived from?
ectoderm
what is epithelium tissue derived from?
meso, ecto and endoderm
what is epithelia?
tissues that serve as protective layers and/or secretory components of body organs and systems
what is the characteristics of epithelia?
Formed into tightly cohesive cellular sheets
what is the function of epithelia?
Function is to cover/line body surfaces
e.g. Alimentary canal, Exocrine ducts
what does epithelia form?
functional unit of secretory glands e.g. Salivary, Mammary, Sweat
what are common attributes of epithelia?
Limited intercellular space Single/multiple layers of cells Free apical surfaces Basement membrane Mitotic capability
why does epithelia have limited intracellular space?
Specialised intercellular junctions hold cell memb close together - effective barrier - blocks infiltration of fluids between cells
why does epithelia have single/multiple layers?
Form linings/coverings. where diffusion/filtration is important, epithelia is single layer
where protection e.g. abrasion is needed - multiple layers
what is the free apical surface?
formed during development or at maturity. The apical surface is where cells of an epithelium face internal lumens
what is the basement memb?
opposite to the apical surface. Basal surface attaches to underlying tissues via basement memb derived from underlying CT.
why does epithelia have mitotic capability?
Epithelia covering/lining tissues are constantly subjected to wear and tear. This enables repair and regeneration.
what are epithelia’s distinguishing features?
All the vital traffic of the body passes through epithelial layer. e.g. digested food, oxygen, secretions
High capacity for regeneration.e.g. wound healing, intestinal abrasion
what are the different arrangements of cells in epithelia?
Simple, Pseudostratified, Stratified
what are the different cell shapes in epithelia?
Squamous , Cuboidal, Columnar, Transitional
what is simple epithelia?
one cell thick
what is stratified epithelia?
many cells thick but only bottom layer in contact with basement memb
what is pseudostratified epithelia?
appear more than one cell thick but all cells rest on basement memb
what do squamous cell look like?
flattened cells like paving stones
what do columnar cells look like?
cells are taller than they are wide
what do cuboidal cells look like?
cells are of similar height depth and width
what do transitional cells look like?
cells in layers which change their shape when they are stretched
where is simple squamous found?
alveoli & capillaries of lungs
where is simple cubical found?
kidney tubule
where is simple columnar found?
small intestine
where is transitional epithelia found?
only in urinary tract
stretches to accommodate fluid changes
where is stratified squamous found?
oesophagus