Question

6) Answer the following briefly:

a) How is collagen made and where do the different steps of synthesis take place. What purposes do the hydroxylysine and the hydroxyproline serve? Why does collagen appear striated?

b) Know the classifications of connective tissues and where they might be found. Be able to identify a slide of each type and their histological properties.

c) What are the cell types found in connective tissues? What is the difference between a transient and fixed cell type? Know their functions and histological hallmarks used to identify them.

d) What is the difference between brown fat and white fat?

e) How is a mast cell activated and degranulated ? What is the difference between a primary and secondary mediator, and examples of each?

Answer 1

Ans a-) Collagen is a protein which is synthesised in the cells of connective tissue. Collagen is found in the extracellular matrix.
The steps of synthesis of collagen occur in the fibroblast cells which are specialised for synthesis of protein collagen. Extracellularly and intracellularly there is synthesis of collagen.
Hyrdoxylysine have two hydroxyl groups which functions as they provide the sites for adhesion for carbohydrates such as sugars and they are involved in stabilizing the cross links which are intramolecular and intermolecular.
Hydroxyproline are involved in the stability of collagen. When the residues of proline are modified the triple helix colllagen stability is increased.
When molecules of collagen are packed and thus forms collagen fibrils. When the terminal ends of collagen molecules are replaced by one other which then observed under electron micrographs give the appearance of collagen molecules as striated.

Ans b-) Connective tissues are involved in joining and binding of tissues together, which forms packaging material and a protective sheath around various organs so that different activities do not interfere with each other.
Classification of connective tissue:
1. Loose connective tissue is found around the blood vessels. Also, they are found near the organs. Loose connective tissue like adipose tissue is flexible, tough and is comprised of the membranes
2. Dense regular connective tissue: They are mainly found around tendons and ligaments. Areas which require high tensile strength.
3. Skeletol tissue: is found in between the bones and is a voluntary muscle thus its functions are under control.
4. Adipose tissue: it is found under the skin in the heart covering. Also, in kidney and blood vessels
5. Vascular tissue: plant vascular tissues are found in all parts of plants that it stem, root and leaves.

Ans c-) the different types of cells present in connective tissue are :
1. Plasma cells.
2. Leucocytes.
3. Adipocytes.
4. Most cells.
5. Macrophages.
6. Fibroblast.
Out of these , fibroblast is very common which secretes amophous ground substance as well as fibre also.
Adipocytes : they are well known as far strong tissue.
Macrophage , most cell and plasma cells are called as cells for immune.
Difference between fixed cells and transient cells :
Fixed cells : These are also known as white blood cells that reaches the site of immune response by circulating through the stream of blood. It has eosinophils , basophils , monocytes , lymphocytes and neubophils.
Neutrophils : Responsible for digesting and helping bacteria.
Monocytes : Bacteria is break down with the help of monocytes.
Lymphocytes : Produces antibodies for killing bacteria and harmful other Invaders.

Ans d-) Brown fat are mostly found in newborns mammals and hibernating animals.
It helps in thermoregulation.
Brown adipose fat have a number of smaller droplets of adipocytes and huge number of mitochondria.
They contain more capillaries.

White fat are mostly present in adults.
It also helps in thermoregulation by shivering thermogenesis.
White fat have a single droplet of adipocytes and less no of mitochondria.
They have less no of capillaries.

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