EPITHELIUM AND GLANDS Flashcards
EPITHELIUM TISSUE
- Avascular - without blood vessels. Oxygen and nutrients via diffusion from underlying connective tissue
- Covers the exterior body surfaces
- Lines internal close cavities
- Lines body tubes
- Forms secretory portion and ducts of glands
- Specialized cells function as receptors for special senses ( hearing, vision, smell, taste)
THREE PRINCIPAL X-TICS OF EPITHELIAL CELLS
*Cells closely attached or a-posed to each other (cell to cell junctions)
- three surface domains;
- Apical
- Lateral
- Basal
*Basal surface attached to underlying basement membrane ( cell to matrix junctions)
JUNCTIONAL COMPLEXES IN THE LATERAL SURFACE/DOMAIN
- Occluding junctions:
* Tight junctions ( zonula occludens)
* Transmembrane proteins: Claudins (paracellular diffusion) and Occludins ( present in most occluding junctions); maintains barrier between apical and lateral cell surface
* Paracellular pathway ( across the Zonula occludens between two cells)-Claudins
* Transcellular pathway ( across the plasma membrane of the epithelial cell) - Anchoring junctions;
* Adhering junctions (zonula adherens)—interaction with actin filaments
- Desmosomes ( macula adherens)—-interaction with intermediate filaments of the cytoskeleton
- TRANSMEMBRANE PROTEIN: E-cadherin (Calcium dependent)
- Communicating junctions; gap junctions- communication. Present in a variety of tissues; epithelium, smooth and cardiac muscle, nerve
-Transmembrane protein subunits: Connexin
* CONNEXON-Half channel formed by 6 connexins.
Connexonx align to form a communicating channel connecting the cytoplasm of adjacent cells
What two layers make up the basement membrane?
- Basal lamina- called external lamina in non-epithelial cells.
Composition: Laminins, Type IV collagen, proteoglycans and Glycoproteins - Reticular membrane
FOCAL ADHESION
- Anchoring junctional complex
- Cell to ECM junctions
- Helps to anchor epithelial cells to basement membrane
- Transmembrane proteins = Integrins
- Link between actin microfilaments of cytoskeleton and ECM
- Important in cell migration
HEMIDESMOSOME
*Anchoring junctional complex
- Cell to EM junctions
-Helps to anchor epithelial cells to basement membrane
* Transmembrane proteins=Integrins
Interactions with intermediate filaments of the cytoskeleton
**BULLOUS PEMPHIGOID-HEMIDESMOSOMES- disease characterized by blister formation at epithelium attachment to basement membrane
Two major groups of glands
- Exocrine
- Excrete to the surface directly or through ducts that are connected to the surface
- THREE RELEASE MECHANISMS;
- H-Holocrine-apoptosis releases secretory products and cell debris ex. Sebaceous glands of skin
- A-Apocrine-product released at apical surface;bleb, ex.lactating mammary gland
- M-Merocrine-exocytosis of membrane-bound vesicles. This is the most common.
- Endocrine
- S-Secrete hormones into the blood stream and then enter blood stream
- A-Autocrine=same cell
- P-Paracrine =nearby cells
Unicellular glands
Goblet cells
-mucus-secreting cells
-PAS- Periodic Acid Shift
Multicellular glands
- Shape of secretory cells
- Tubular=tubes
- Alveolar (acinar) =flask
- Tubuloalveolar= tube ends in a dilation
- Presence or absence of branching duct
Simple-unbranded duct
-Compound=branched duct
Simple tubular-large intestine
Simple coiled tubular- eccrine skin glands
Simple branched tubular-mucus-secreting glands; stomach, uterus
Simple acinar-urethra
Branched acinar-stomach, skin
Compound tubular-duodenum
Compound acinar-pancreas;exocrine portion
Compound tubuloacinar-submandibular salivary gland
EXOCRINE GLANDS
Based on type of section produced
- Serous glands
- watery
- Nuclei rounded or oval
- ex. Exocrine pancreas and Parotid salivary glands
-Mucous glands- appear-empty in H&E staining
* viscous/slimy
*Nuclei within cells flattened
PAS positive d/t anionic oligosachharides
Submandibular gland
-Mixed glands; contains both mucous and serous secretory components
- Serous>Mucous
* Compound tubuloacinar gland
Sublingual gland
-Mixed gland
Mucous> Serous
