Characteristics of Tissues Flashcards
What does histogenesis involve?
Cell differentiation and specialisation.
What does organogenesis involve?
Interactions of specialised cells to form organs.
What is a fibroblast?
Flat cell that is found in mesenchyme, responsible for the formation of epithelial tissue.
What is a basal lamina?
Membrane found beneath all epithelial tissues.
Give 5 characteristics of epithelia.
1) Predominantly made of cells, all cells bound by cell junctions.
2) Polarity (apical and basal surfaces)
3) Attached to a basal lamina
4) Avascular (lacks blood vessels)
5) Regenerate via stem cells
How does epithelial tissue provide a protective barrier?
Prevents mechanical abrasion and biological contamination (skin/pathogens). Also prevents dehydration - skin disruption leads to water loss.
Name three types of cell junction.
Tight junctions, gap junctions and desmosomes.
Describe a TIGHT JUNCTION.
Between 2 cell membranes, adhesion belt (made of actin filaments) attaches to terminal web. NO PASSAGE OF WATER/SOLUTES.
Describe a GAP JUNCTION.
Made from connexin, little holes formed by connexons. Big enough for passage of SMALL MOLECULES. Cytoplasmic connection, electrical unison.
Describe a DESMOSOME.
Formed from CAMs (cell adhesion molecules), dense areas and intercellular cement. Button desmosomes are supported internally by INTERMEDIATE FILAMENTS which allow bending/twisting. Tie cells to BASAL LAMINA.
What is a hemidesmosome?
Half a desmosome.
Name the two fundamental types of cell interaction.
Humoral and solid state factors.
What does humoral cell interaction involve?
Soluble growth factors.
Give an example of humoral cell interaction.
Endocrine system - hormones (soluble factors) travel long distance via circulation.
Give an example of a solid state factor.
Cell adhesion molecules (anchored in membrane).
What are the two families of CAM?
Cadherins and Ig Superfamily
Which family of CAM is calcium dependent?
Cadherins
Which family of CAM is calcium independent?
Ig Superfamily
What are the 3 main roles of membrane surface proteins?
- Dissociate tissues with proteins.
- Allow cells to synthesise new proteins.
- Allow cells to re-aggregate.
Cadherins only bind to the same type of cadherin as themselves, this makes them…
Homophilic
What is the function of cadherins?
Bind to the extracellular tail of a transmembrane protein, whilst catenin binds to the cytoplasmic tail. Catenins link cadherins to the actin cytoskeleton. Signals to nucleus to regulate gene expression.
What is the function of beta-catenin?
Links cadherins to the cytoskeleton. Also functions as a transcription faxtors when it enters nucleus. Competition between cell adhesion/regulation of gene expression.
Give two properties of Ig CAM Superfamily
Calcium independent, adhesion is weaker than in cadherins.
Name the cell membrane receptors for ECM molecules.
Integrins.
Name two ECM proteins.
Fibronectin and Laminin
Where is fibronectin mainly found?
In the interstitial extra-cellular matrix.
What is the function of fibronectin?
Enables cells to adhere to extracellular membranes.
What is the function of Laminin?
Used by epithelial cells to adhere to ECM basement membranes (exclusive to BASAL LAMINA).
