Epithelia

Front 1

Describe simple squamous epithelial cells.
- Shape
- Location
- Functions

Back 1

Shape: flat, irregular shape

Location: Blood vessels, organ mesothelium

Functions: transport of nutrients, adhesion, permeability barrier, organ mesothelium

Front 2

Describe stratified squamous epithelial cells.
- Shape
- Location
- Functions

Back 2

Shape: flat, irregular shape

Location: skin, esophagus

Functions: protection, permeability barrier

Front 3

Describe simple cuboidal epithelial cells.
- Shape
- Location
- Functions

Back 3

Shape: Cell height = width

Locaiton: kidney tubules, thyroid gland

Functions: secretion, ion transport

Front 4

Describe stratified cuboidal epithelial cells.
- Shape
- Location
- Functions

Back 4

Shape: cell height = width

Location: sweat glands

Functions: protection, secretion

Front 5

Describe simple columnar epithelial cells.
- Shape
- Location
- Functions

Back 5

Shape: cell height > width

Location: intestinal lining, goblet cell

Functions: absorption, secretion

Front 6

Describe psuedostratified columnar epithelial cells.
- Shape
- Location
- Functions

Back 6

Shape: cell height > width

Location: trachea airways

Functions: protection, cilia move mucus

Front 7

2. Explain the concept of a polarized cell and its key features.

Back 7

Polarized cell = apical surface is molecularly & functionally different than basal surface (i.e. different proteins on each side)

Front 8

Name specialized structures of the apical, basal, and lateral surfaces (functions and features)

Back 8

Apical
Functions: secretion, absorption, protection, pump
Features: microvilli, cilia endocytosis

Basal
Functions: ion pump, synthesis of basement membrane, transport of absorbed substanes
Features: rests on basement membrane and faces connective tissue, infolding of basement membrane

Lateral:
Functions: contact & form structures with nearby cells (ie: form seals, structural support)
Feature: cell junctions

Front 9

Describe tight junctions.
- Formal Name
- Location
- Function
- Proteins involved
- Appearance

Back 9

Formal Name: occluding zonule

Location:
1. uppermost component of junctional complex
2. at the apex of the cell
3. joins two neighboring membranes tightly together

Function:
1. prevent diffusion between the apical and basolateral surfaces of the epithelial cell
2. prevent paracellular leakage of EC substances between the cells or across the epithelium
- therefore: can block passage of ions, water, and molecules of all sizes from passing between the cells

Proteins inolved: claudins, ,occludins

Appearance: cells appear fused together, eliminating the intracellular space

Front 10

Describe Adherens Junction.
- Formal Name
- Location
- Function
- Proteins involved
- Appearance

Back 10

Formal Name: adhering zonule

Location:
1. continuous ring around the apex of the cell
2. generally below tight junctions

Function:
1. cadherin domain on one cell binds to identical cadherin domain of another cell, producing a strong bond
2. sorting function, useful in the organization of organs

Proteins inolved: cadherin (binding to other cells), catenin (link to actin cytoskeleton within cell)

Appearance: ?

Front 11

Describe Desmosomes.
- Formal Name
- Location
- Function
- Proteins involved
- Appearance

Back 11

Formal Name: desmosomes

Location:
1. NOT a continuous ring around the cell
2. can be scattered in different locations

Function:
1. provide mechanical strength to epithelial sheets
2. resist shearing force

Proteins inolved:cadherin (form the bond between desmosomes in adjoining cells), connect to intermediate filament cytoskeleton

Appearance: spot welds

Front 12

Describe Gap Junction.
- Formal Name
- Location
- Function
- Proteins involved
- Appearance

Back 12

Formal Name: gap junctions

Location: not limited to epithelial tissues. Na+ transport between cardiac muscle cells take place via gap junctions

Function:
1. allow small molecules to pass between cytoplasm of two cells
2. synchronization

Proteins inolved: connexins (6 protein subunits that surround a central aqueous canal)

Appearance:Plasma membranes of 2 cells are adjacent, but not fused.

Front 13

4. Explain the molecular and cellular mechanisms of directional transport of glucose across a polarized cell in the intestinal epithelium

Back 13

Apical surface
1. Na+ / glu symport couples Na+'s movement down its electrochemical gradient to transport glucose INTO cell (secondary active transport)

Basolateral surface
2. Na+ / K+ ATPase uses ATP hydrolysis to pump 3 Na+ out of the cell and 2 K+ into cell
(primary active transport) - serves to maintain secondary active transport on apical surface
3. glucose passively diffuses out of cell and into bloodstream through a passive glucose transporter found only on the basolateral surface

Front 14

5. Describe the polarized release of mucus from a goblet cell in the intestinal epithelium.

Back 14

mucus = slippery, viscous material made up of heavily glycosylated glycoprotein. secreted by GOBLET CELLS

Goblet cells: well developed RER - for protein synthesis, large golgi complex, abundant secretory vesicle @ apex

Release of mucus: mucus is stored in vesicles of goblet cells and release is stimulated by an increase in intracellular Ca2+

Front 15

6. Explain the function of adult epithelial stem cells.

Back 15

adult epithelial stem cells = undifferentiated epithelial cells that give rise to new epithelial cells

ł during mitosis, one daughter cell continues undergoes mitosis while the other becomes differentiated
ł stem cells are needed to keep the # of epithelial cells CONSTANT
ł they give rise to new epithelial cells in response to distress