Structure and composition of connective tissue

Question 1

What is the function of connective tissue?

Answer 1

Provide mechanical support & allow movement

Arena for fighting infection

Regulates cell behaviours

Question 2

Give examples of different types of connective tissue

Answer 2

Bone
Muscles
Fat
Tendons
Ligaments
Skin
Cartilage
Blood vessels
Nerves
Fascia
Lymph nodes

Question 3

What do connective tissues contain?

Answer 3

Contain blood vessels & nerves
- except cartilage

All connective tissues are composed of the same basic molecules even though there is huge diversity of connective tissue structure & function
- e.g. Cornea vs tendons

Consists of specialised cells embedded in the extracellular matrix

Question 4

What are the components of connective tissue?

Answer 4

3 types of fibres
- Collagen fibres
- Retinacular fibres
- Elastic fibres

Other components
- Glycosaminoglycans (GACS)- Form proteoglycans to make up the ground substance
- Glycoproteins
- Water

Cells
- Fibroblasts
- Chondroblasts and chondrocytes
- Myofibrilblasts
- Transient immune cells

Question 5

Describe the structure of collagen fibres.

Answer 5

Main structural component of connective tissue

Structure
- 3 alpha chains arranged in triple helix
- Stacking & overlapping of molecules gives banding appearance
- Coil structure
- Hydrogen bonds & disulphide bonds

Unique amino acid composition
- Glycine gorms hydrogen bond w/ proline to provide stability & rigidity
- Smallest amino acid
- X - proline
- Y - hydroxyproline

28 collagens, 43 genes - many roles & function
- Homotrimer = made up of 3 identical alpha chains
- Heterotrimer = made up of 2 or more different alpha chains
- Each alpha chain is a single gene product

Type III collagen allows a high degree of elasticity

Question 6

What is the role of elastic fibres? Structure? Where in the body is it found?

Answer 6

Role:
- Structural
- Regulatory e.g. growth factor signalling

Structure:
- Lots of cross links

Found in
- Tendons contain elastin, fibrillin-1, fibrillin-2 & long microfibrils between collagen fibre bundles

Question 7

What are ground substances? What are they made up of? What is their function?

Answer 7

Ground substance = everything other than collagen
- Are variable in size
- Form glycosaminoglycan (GAG) side chains

Made up of:
- Aggrecan
- Versican
- Decorin
- + more

Aggrecan:
- Commonly found in cartilage
- Sucks in a lot of water
- Form huge multimeric aggregates in cartilage
- Huge complex
- highly hydrophobic
- High turgor pressure in tissue to resist compression
- Link protein stabilises binding to hyaluronan

Function:
1. Hold water in tissues due to hydrophilic nature
- Are hydrophilic due to negative sulphate/ carboxyl group which attracts polar water molecules
2. Interact w/ cells, cytokines & collagen
3. Have viscoelastic properties
- Means that the level of stretchiness depends on speed of force
- E.g. less stretchy when you stretch quickly, more stretchy when you pull slowly

Question 8

What are the functions of the cells present in connective tissue?

Answer 8

Fibroblasts:
- synthesis of extracellular matrix
- Spindle shaped cells arranged in a branching patter
- Fibroocytes- Fibroblasts w/ low metabolic activity

Chondrocytes
- synthesis & organisation of extracellular matrix

Osteocytes
- Osteoblasts-build bone
- Osteoclasts: resorb bone

Myofibroblasts
- Assist w/ wound contraction & therefore abundant in wound healing areas
- hybrid cells w/ features of both fibroblasts & smooth muscle cells

Immune cells e.g. macrophages, plasma cells, lymphocytes