Characteristics of Tissues

Question 1

What does histogenesis involve?

Answer 1

Cell differentiation and specialisation.

Question 2

What does organogenesis involve?

Answer 2

Interactions of specialised cells to form organs.

Question 3

What is a fibroblast?

Answer 3

Flat cell that is found in mesenchyme, responsible for the formation of epithelial tissue.

Question 4

What is a basal lamina?

Answer 4

Membrane found beneath all epithelial tissues.

Question 5

Give 5 characteristics of epithelia.

Answer 5

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

Question 6

How does epithelial tissue provide a protective barrier?

Answer 6

Prevents mechanical abrasion and biological contamination (skin/pathogens). Also prevents dehydration - skin disruption leads to water loss.

Question 7

Name three types of cell junction.

Answer 7

Tight junctions, gap junctions and desmosomes.

Question 8

Describe a TIGHT JUNCTION.

Answer 8

Between 2 cell membranes, adhesion belt (made of actin filaments) attaches to terminal web. NO PASSAGE OF WATER/SOLUTES.

Question 9

Describe a GAP JUNCTION.

Answer 9

Made from connexin, little holes formed by connexons. Big enough for passage of SMALL MOLECULES. Cytoplasmic connection, electrical unison.

Question 10

Describe a DESMOSOME.

Answer 10

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.

Question 11

What is a hemidesmosome?

Answer 11

Half a desmosome.

Question 12

Name the two fundamental types of cell interaction.

Answer 12

Humoral and solid state factors.

Question 13

What does humoral cell interaction involve?

Answer 13

Soluble growth factors.

Question 14

Give an example of humoral cell interaction.

Answer 14

Endocrine system - hormones (soluble factors) travel long distance via circulation.

Question 15

Give an example of a solid state factor.

Answer 15

Cell adhesion molecules (anchored in membrane).

Question 16

What are the two families of CAM?

Answer 16

Cadherins and Ig Superfamily

Question 17

Which family of CAM is calcium dependent?

Answer 17

Cadherins

Question 18

Which family of CAM is calcium independent?

Answer 18

Ig Superfamily

Question 19

What are the 3 main roles of membrane surface proteins?

Answer 19

• Dissociate tissues with proteins.
• Allow cells to synthesise new proteins.
• Allow cells to re-aggregate.

Question 20

Cadherins only bind to the same type of cadherin as themselves, this makes them…

Answer 20

Homophilic

Question 21

What is the function of cadherins?

Answer 21

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.

Question 22

What is the function of beta-catenin?

Answer 22

Links cadherins to the cytoskeleton. Also functions as a transcription faxtors when it enters nucleus. Competition between cell adhesion/regulation of gene expression.

Question 23

Give two properties of Ig CAM Superfamily

Answer 23

Calcium independent, adhesion is weaker than in cadherins.

Question 24

Name the cell membrane receptors for ECM molecules.

Answer 24

Integrins.

Question 25

Name two ECM proteins.

Answer 25

Fibronectin and Laminin

Question 26

Where is fibronectin mainly found?

Answer 26

In the interstitial extra-cellular matrix.

Question 27

What is the function of fibronectin?

Answer 27

Enables cells to adhere to extracellular membranes.

Question 28

What is the function of Laminin?

Answer 28

Used by epithelial cells to adhere to ECM basement membranes (exclusive to BASAL LAMINA).