5. Epithelia Flashcards
What is the embryological origin of epithelium?
= Ectoderm
What is the histological criteria for classifying epithelia?
- Do all cells in a pseudostratified epithelium actually contact the basal lamina?
- What type of epithelium lines the trachea?
Trachea = Pseudostratified
What is Transitional epithelium and where is it found?
What type of epithelium is this?
= Simple Squamous (fried eye)
What type of epithelium is this?
= Simple cuboidal
What type of epithelium is this?
= Simple columnar
What are 3 types of specialised epithelium?
Specialised epithelia
Endothelium
- Lines blood vessels.
- Simple squamous.
Mesothelium
- Lines body cavities and surfaces of organs in those cavities (secretes a mucus-like material to prevent friction between organs and cavity).
- Simple squamous
Transitional epithelium
- Lines renal pelvis, ureter, urinary bladder and upper urethra.
- Specialised function and properties.
- Stratified
What kind of specialised epithelium lines blood and lymphatic vessels?
Which epithelium is labeled here?
Label this - what kind of skin is it?
- Epidermis
- Sweat gland
- Sebaceous gland
- Shaft sheath
- Hair = Thin hairy skin
Label this.
What are the Epithelial Gland Forms?
- Glands are epithelial tissue (secretory function)
- Myoepithelial cells are very important in glands to contract and propel substance out.
What is the histology of a compound salivary gland?
Why is Epithelia described as having Polarity?
Epithelia
Cells have POLARITY- reflects function
-
Apical domain
- Exposed to a lumen or external environment
-
Lateral domain
- Facing neighbouring epithelial cells linkedby adhesion molecules and junctional complexes
-
Basal domain
- Associated with the epithelial basal lamina
- Basal lamina separates the epithelium from the connective tissue
- Basal lamina reinforced by connective tissue components (lamina reticularis) forms the basement membrane
What happens at the apical domain of epithelium?
Function? (SPAT EGGS)
What are the 5 types of junctions?
Five types of junctions:
- Tight or Occluding - Zonulae occludentes
- Adhering (belt desmosome) - Zonulae adherentes
- Anchoring or Desmosomes (spot) - Maculae densae
- Gap Communicating
- Hemidesmosomes
What 3 things does the baso-lateral domain of epithelium provide?
Baso-lateral domain provides:
- Gap Junctions cell to cell communication
- Adhesion molecules – intercellular communication
- Junctional complexes – anchorage
What is the function of the Junctional complexes of the Baso-lateral domain of epithelium?
3 types?
Which are associated with the cytoskeleton?
What are Tight/Occluding Junctinos?
Occluding or Tight Junctions
- Also known as a Zonulae occuldens
- Adhesion belt encircles cells completely and bind to neighbouring cells.
- Apical surface: keep enzymes, acids and wastes of GIT damaging underlying tissues.
What are Gap Junctions? Function?
Role in cardiac muscle?
Gap Junctions
- Adjacent plasma membranes communication between excitable cells though cylindrical proteinaceous connexions.
- Cell to cell communication through pores between cells.
- Passage of ions and simple sugars in heart muscle.
- Electrically couples cells together.
What are Desmosomes/Anchoring Junctions?
Desmosomes or Anchoring Junctions
- Bind cells together.
- Anchoring done by cytoplasmic plaques and intermediate filaments = through the cytoskeleton, distribute tension to the whole cellular sheet.
What are Adhering Junctions? Function?
Especially important in what?
Zonula Adherens = Adhering Junctions
- Link with the cytoskeletal actin filament network.
- Penetrate the plasma membrane of adjacent cells.
- Especially important where mechanical stress occurs e.g. skin, gut.
What are Hemidesmosomes?
Where are they found? Function?
What is the Structure & Function of the Basement Membrane?
Basement Membrane (Epithelial Basal Lamina)
- At the basal surface of ALL epithelia
- Flexible & firm support
- Acts as molecular filter
- Basement Membrane (BM) is the limit all CT’s
- Electron Microscopy (EM) shows three zones
- Lamina rara (lamina lucida of laminin)
- Lamina densa (of type IV collagen coated with perlacan
- Lamina reticularis (fibroreticular lamina) which composes the reticulin anchoring (bound with fibronectin)
