Epithelia I

Question 1

Epithelia

Answer 1

Face the spaces (outside world, ducts, internal spaces, and form insides of organs, glands).

Question 2

Shared properties of epithelia

Answer 2

• 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.

Question 3

Epithelia fx.

Answer 3

• 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.).

Question 4

2 types of epithelia are diff from others…

Answer 4

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.

Question 5

Moist linings of internal passages?

Answer 5

Mouth nose GI reproductive etc.

Called mucosa. Surface layer of all mucosa is epithelium.

Question 6

Organs composed of mainly epithelial cells

Answer 6

Liver, pancreas, kidney.

Question 7

Origin of epithelia?

Answer 7

All 3 germ layers (Ecto, meso, endo).

Question 8

Epithelial to mesenchymal transition

Answer 8

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.

Question 9

Basal side

Answer 9

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.

Question 10

Muscle, blood vessels, nerves and CT

Answer 10

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.

Question 11

Mucosa layers

Answer 11

1. ) Outer epithelium

2. ) CT directly underneath (called lamina propria)

Question 12

Lamina propria

Answer 12

have lots of immune system cells, small blood vessels. They survey and extract foreign or ingested materials and mlcs from enviro.
Transport and monitor.

Question 13

Submucosa

Answer 13

Deeper layer of CT, continuous with lamina propria. BIgger vessels, muscles, nerve bundles etc.

Question 14

Layers of skin

Answer 14

Epidermis (= epithelium)
Dermis (CT)
Hypodermis (like submucosa, superficial fascia)

Question 15

Epithelial classification, 2 general forms

Answer 15

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.

Question 16

Shape classification

Answer 16

Squamos (flat)
Cuboidal
Columnar (taller than wide)
Stratified epithelia are named by outermost layer
Transitional… special case. found around bladder. stratified but when stretched go from cuboidal to squamos.