Lecture 16: Contiss 1

Question 1

Complex organisms do not only consist only of cells, but are a collection of:
?

Answer 1

Cells
Extra cellular matrix
Extra cellular fluid

Cells of similar structure and function, along with their associated matrix form tissues
A collection of functionally associated tissues form organs

Question 2

Connective tissues are designed to resist forces.

What are the 3 main types of forces experienced by body tissues?

Answer 2

1. Compression (pushing)
2. Tension (pulling)
3. Shear (twisting)

Question 3

In connective tissues it is the extra cellular matrix not the cells that dictates tissue function.
ECM must be produced and maintained by local cell types. What are these 3 cell types?
ECM is continually turned over by?

Answer 3

Fibrocyte/blast- fibrous tissue
Chondrocyte/blast- cartilage
Osteocyte/blast- bone
ECM is continually turned over by?
-Mostly digested by specific enzymes (collagenase, etc)
-specialised resorptive cells in bone (osteoclasts)

Question 4

What are the 3 principle components of ECM?

Answer 4

1. Fibres
   - collagen, elastin, reticular
2. Ground substance
   - proteoglycans
3. Interstitial fluid
   - partially bound with proteoglycan

Bone has an additional component which is inorganic mineral

Question 5

ECM: 1. Fibres
What is collagen, how is it assembled, what does it consist of etc
What is elastin

Answer 5

Collagen is the most abundant protein in the body

• has a glistening white appearance, refractile on microscopy
• provides tensile strength (it dominates in tension baring parts of the body eg ligaments, tendons, dermis (leather)

Elastin has long branching fibres or sheets
-gives natural elasticity to tissues eg arteries
Refer to slides for pictures

Question 6

ECM: 2. Ground substance

What is it?

Answer 6

A semi fluid, amorphous gel
Composed of mainly glycosaminoglycans
-hyaluric acid
-sulphate-rich proteoglycans
-huge aggrecans

Proteoglycans

• highly-charged polysaccharides side chains form bottle brush like structure on a protein core
• highly hydrophilic (attract and trap large volumes of water and extra cellular ions)

Question 7

Fibrous connective tissue
What generates the connective tissue?
What are its mechanical properties?
What is it categorised into?

Answer 7

Matrix generators are fibroblasts (elongated and have condensed nucleus)
-elongated, condensed nucleus with little visible cytoplasm
mechanical properties depend on the fibre type:
-Tendon-linear arrays of collagen
-Skin: irregular meshwork- much more stretchy

Loosely categorised into:
Dense regular connective tissue
Dense irregular connective tissue
Loose (areolar) connective tissue

Question 8

How does cartilage have its resistance to compression?

Answer 8

Provided by the water attracting aggrecans complexes which swell up like a sponge and stiffen the restricting type 2 collagen network