Systems Lec 3 and 4: Epithelium

Function of epithelia

line or cover a surface

Epithelia have a basement membrane. What is that?

Fibrous sheet on the basal side that separates epithelia from underlying tissue.

What are the two layers of the basement membrane?

Basal lamina (closest to epithelial cells)

Reticular lamina

What is the basal lamina made of?

Lamina lucida- integrins and laminins

lamina dense- type IV collagen

What is the reticular lamina made of?

Anchoring plaques/fibers (collagen) along with reticular fibers.

Tight Junctions (zona occludens)

Forms a seal between apical and basolateral compartments to prevent free flowing materials between cells. Also allow cellular polarity.

Adhesion belts

firmly attach cells to each other near the apical surface and allow integration of the microfilament network and cooperative membrane organization. forms a mechically strong link between adjacent epithelial cells through microfilaments

Desmosomes

Spot welds that from a mechanically strong link between adjacent epithelial cells through an intermediate filament network. without them the cells could easily slough off

Hemidesmosomes

spot welds that from link between cells and basement membrane using microfilaments and intermediate filaments. could easily slough off if not there

Gap junctions

creates a connection between adjacent cells that allow small molecules to pass through

Infoldings/Invaginations

Type of basolateral specialization for specialized fluid and ion transport. Increases surface area for more transport.

Microvili

form of apical specialization. made of actin and microfilaments. increases surface area for absorption. can be seen like a brush border.

stereocilia

form of apical specialization. very long specialized microvilli made of actin that increases surface area for transport and absorption. Seen as wispy hairs

Cilia

form of apical specialization. Very long motile structures. Much larger than microvilli. made of tubulin and microtubules. Have basal bodies at insertion points. K

Keratinization

Form of apical specialization. It is a fibrous structural protein. Creates friction resistance surface.

Naming formula

Layers, shape, specializations

What are glands?

structures that secrete a product that can be exocrine or endocrine and are made of epithelia

Exocrine Glands

Secrete a product out of the body using ducts. Examples include sweat, salivary, intestinal, etc. Can be simple or compound.

Endocrine glands

Secrete products into blood. Examples include pituitary gland, adrenal, thyroid, etc. Do not have ducts and are usually surrounded by capillaries.