Tissue, Organs And Systems Flashcards
Define tissue
Collection of cells that are adapted to perform a specific function
Define organ
2+ tissues combined to create a structured unit with a particular function that are a sum of its parts
What holds cells together?
- cell-cell adhesion molecules
- extracellular matrix proteins (fibres)
- internal-external scaffolding
- close proximity (compression/pressure)
List the lateral surface epithelial cell adherence systems
’Tightrope Acts Demand Great Coordination’
- tight junctions
- adherens junctions
- desmosomes
- gap junctions
- cell adhesion molecules
List the basal surface epithelial cell adherence systems
- hemi-desmosomes
- focal adhesions
- integrins
- proteoglycans
- cell adhesion molecules
How are cells held together in a tissue?
Their attachments to each other laterally
e.g. tight junctions, desmosomes + gap junctions
Role and location of tight junctions
- Seal neighbouring cells together in an epithelial sheet to prevent leakage of molecules between them
- at the top, nearest to the apical surface
- lateral surface
Role and location of adherens junction
- tissue stabilising + transport barrier
- 1/3 from the apical surface
- lateral surface
- only in epidermal and endothelial cells
Role and location of desmosomes
- mechanical strength + prevent tissue destruction
- 1/2 between top and bottom
- lateral surface
- random distribution
- in tissues that experience intense mechanical stress e.g. cardiac muscle, bladder tissue..
Role and location of hemi-desmosomes
-anchor epithelial cells to basal lamina + prevent loss to external surface
- cytokeratin attach to laminin via integrins
- basal surface
Role and location of focal adhesions
- allows passage of small water soluble ions and molecules
- actin filaments bind to fibronectin using integrins
- basal surface
Compare focal adhesions and hemi-desmosomes
- both use integrins
- both on basal surface
- focal adhesions use actin filaments attached to fibronectin
- hemi-desmosomes use cytokeratin attached to laminin
What are integrins?
Transmembrane proteins that function:
- mechanically - attaching cytoskeleton to extracellular matrix
- biochemically - sensing whether adhesion has occurs
Functions of integrins
- attachment of cell to extracellular matrix
- signal transduction from ECM to cell
Name and describe each layer of the GI tract
- mucosa - mucus membrane
- muscularis mucosae - thin discontinuous smooth muscle
- submucosa - connective tissue layer containing arteries and veins
- musclaris externa - smooth muscle layer with fibres running in 2 directions (circular + longitudinal)
- *serosa - connective tissue layer containing collagen, elastic, smaller arteries + veins
