Lecture 11 - Connective & Adipose Tissue (Part 1)

Question 1

What is connective tissue?

Answer 1

Tissue that supports, protects, and gives structure to other tissues and organs in the body

Question 2

What are the 6 main kinds of connective tissue?

Answer 2

Fibrous (dense), Loose, Blood, Bone, Cartilage, Adipose

Question 3

What are the 3 main components of connective tissue and what different kinds do you get?

Answer 3

1) Cells - fibroblasts, chondrocytes, osteocytes, stem cells
2) Fibres - collagen, elastin, reticulin
3) Ground substance - proteoglycans

Question 4

What are the 6 main functions of connective - give an example of a connective tissue that does each.

Answer 4

1) Binding and support (e.g.: holding skin, lungs together)
2) Protection (e.g.: bones and fat)
3) Insulation (e.g.: fat and bone marrow)
4) Storage/Fuel reserve (e.g.: fat and bone marrow)
5) Transporting substances (e.g.: blood)
6) Separation of tissues (e.g.: fascia, cartilage, tendons)

Question 5

What is loose and dense connective tissue also known as? What are the 2 types of dense?

Answer 5

Loose = areolar
Dense = fibrous
Irregular dense (fibres run in different directions) and regular dense (fibres run parallel to each other)

Question 6

What cell and fibre types do loose connective tissue have?

Answer 6

Cells = fibroblasts, macrophages, WBC's, mast cells, adipocytes
Fibres = Collagen & Elastin

Question 7

What is the function of loose connective tissue?

Where is it found?

Answer 7

• Holds vessels together that supply fluid, e.g.: capillaries
• Involved inflammation pathways
• Holds things in place and stabilises organs
• Found under epithelial cell layers, around glands, capillaries etc

Question 8

What are the 4 main cell types in connective tissue?

Answer 8

1) Fibroblasts
2) Macrophages
3) Mast cells
4) Adipocytes (unilocular/white + multilocular/brown)

Question 9

What is the role of fibroblasts in connective tissue?

Answer 9

• Synthesise and secrete fibres that lie in ground substance
• Important in wound healing and formation of scar tissue
• Can change phenotype into myofibroblasts which contain actin + myosin which are responsible for wound contraction

Question 10

What is the role of macrophages in connective tissue?

Answer 10

Phagocytose foreign organisms and cell debris & present antigens to T+B lymphocytes

Question 11

What is the role of mast cells in connective tissue?

Answer 11

They are coated with IgE which bind allergens. These causes contents of their granules (which contain histamine, heparin and cytokines) to be rapidly released from the cell - therefore involved in the inflammatory response.

Question 12

What is the role of white/unilocular adipocytes?

How many lipid droplets does it contain and where is the nucleus?

Answer 12

• Padding, shock absorber, insulation & energy reserve
• Single large lipid droplet, nucleus and other organelles sequeezed to side of cell
  NB - appear white on H&E staining (see slide)

Question 13

What is the role of brown/multilocular adipocytes?

How many lipid droplets does it contain and where is the nucleus?

Answer 13

• Provides insulation and energy reserves.
• Uncoupling of oxidative phosphorylation which generates heat
• Multiple small lipid droplets, nucleus squeezed into centre of cell

Question 14

Is there more brown adipose tissue in neonates or adults?

Answer 14

Neonates.

Question 15

What are the main fibres found in connective tissue?

Answer 15

1) Collagen
2) Reticulin
3) Elastin
4) Fibrillin

Question 16

What is the main type of collagen fibre?

Answer 16

Type 1 - consisting of 90% of all collagen - fibrils aggregate into fibres and fibre bundles.

Question 17

What is the role of collagen, elastin and reticulin fibres in connective tissue?

Answer 17

Collagen = flexible to provide high tensile strength 
Elastin = Allows tissues to recoil after stretch/distention
Reticulin = Provide a supporting framework

Question 18

What makes up ECM?

Answer 18

Ground substance AND fibres

Question 19

What is ground substance? What is it composed of?

Answer 19

• Viscous, clear substance with high water content

- Composed of proteoglycans to which glycosaminoglycans are attached (GAG’s attract water), such as hyaluronic acid.