Flashcards in Epithelia I Deck (16):
Face the spaces (outside world, ducts, internal spaces, and form insides of organs, glands).
Shared properties of epithelia
-Are adherent to one another
-Are arranged in layers or sheets
-Are polarized (apical and basolateral) (inside cytoplasm too)
-Basal lamina (sheet of extracell material) lines and is attached to underlying connective tissue
-Undergo turn-over/renewal. Stem cells.
-Avascular (nutrients, O2 must diffuse through connective tissue and basal lamina)
-Highly diverse. Even w/in an epithelium can be several diff types.
-Barrier that protects internal itssues
-Selective absorption/transport of mlcs from enviro
-Selective secretion of various mlcs/fluids
-Movement of particles/mucous through passageways
-Biochemical modification of mlcs (liver)
-Communication to/from other tissues/organs
-Reception of sensory stimuli (smell etc.).
2 types of epithelia are diff from others...
1.) Face internal fluids (blood and lymph... ENDOTHELIUM). Face internal spaces of enclosed body cavities (MESOTHELIUM). Still have adherent cells, free surface facing blood/lymph, rest on basal lamina usually.
2.) Special fx/structural relationship to other epithelia connective tissue etc.
Moist linings of internal passages?
Mouth nose GI reproductive etc.
Called mucosa. Surface layer of all mucosa is epithelium.
Organs composed of mainly epithelial cells
Liver, pancreas, kidney.
Origin of epithelia?
All 3 germ layers (Ecto, meso, endo).
Epithelial to mesenchymal transition
Embryonic epithelia disassemble and move to mesenchymal (connective) tissues.. from there migrate to make new epithelia or transform in distinct cell linages that give rise to other tissues.
This should stop after development. Except cancer.
Basal side attached to basal lamina, this is attached to connective tissue
Blood vessels run through CT (how get nutrients and O2). Capillaries are closer to epithelia, big blood vessels are depper. Muscles are also deep.
Muscle, blood vessels, nerves and CT
They are surrounded by their OWN basil laminae that attach to their own neighboring connective tissues.
Epithelia directly attach to connective tissue so are linked but separate from blood vessels etc.
Sensory nerves can however make direct contact (taste buds in tongue) or specialized immune cells that infiltrate epithelia.
1.) Outer epithelium
2.) CT directly underneath (called lamina propria)
have lots of immune system cells, small blood vessels. They survey and extract foreign or ingested materials and mlcs from enviro.
Transport and monitor.
Deeper layer of CT, continuous with lamina propria. BIgger vessels, muscles, nerve bundles etc.
Layers of skin
Epidermis (= epithelium)
Hypodermis (like submucosa, superficial fascia)
Epithelial classification, 2 general forms
1.) Simple (single layers)
Pseudostratified (some do not reach free surface, but all directly contact basal lamina).
2.) Stratified (multiple layers). Outer layers do not directly contact basal lamina. Polarity of whole tissue.