Connective Tissue

Question 1

What are the functions of connective tissue?

Answer 1

1) Binding and supporting (such as holding skin, gut, lungs)
2) Protecting (such as bone protecting vital organs, eg. fat acting as shock absorber)
3) Insulating
4) Storing reserve fuels and cells (bone marrow and fat tissue)
5) Transporting substances within the body (blood and interstitium)
6) Separation of tissues (fascia and tendons/cartilage)

Question 2

What is interstitium?

Answer 2

Space between tissues and organs of the body

Question 3

What are the two types of connective tissue proper?

Answer 3

• Loose connective tissue

- Dense connective tissue

Question 4

What is loose connective tissue also known as?

Answer 4

Also known as areolar tissue

Question 5

What is dense connective tissue also known as?

Answer 5

Also known as ‘fibrous’ or collagenous tissue

Question 6

What are the two types of dense connective tissue?

Answer 6

Irregular
- Fibres running in different directions
Regular
- Fibres running in parallel to each other

Question 7

What are the types of adipocytes?

Answer 7

• Unilocular

- Multilocular

Question 8

What adipocytes are found in loose connective tissue?

Answer 8

White adipocytes (unilocular)

• Single lipid droplet, with nucleus cytoplasm and organelles all squeezed to one side of the cell
• Acts as padding and shock absorber, insulation and energy reserve

Question 9

What are multilocular adipocytes?

Answer 9

Brown adipocytes

• Few of these in an adult
• Multiple small lipid droplets with the nucleus, cytoplasm and organelles squeezed to the centre of the cell.
• Provide insulation and energy reserve

Question 10

What are the differences between white and brown fat tissue?

Answer 10

White adipose tissue:

• Single lipid droplet
• Normal number of mitochondria
• Single peripheral nucleus
• In adults, lipid breakdown is slow and heat is only generated after shivering reflex

Brown adipose tissue:

• Multiple lipid droplets
• Increased number of mitachondria
• Single central nucleus
• In neonates and young children, lipid breakdown is accelerated, oxidative phosphorylation is uncoupled to generate heat

Question 11

What is collagen

Answer 11

The most common protein in the body

Question 12

How many types of collagen are there?

Answer 12

4

• Type I
• Type II
• Type III
• Type IV

Question 13

What is Type I Collagen?

Answer 13

• The most widely distributed type (90%)
• Fibrils aggregate into fibres and fibre bundles

eg. tendons, capsules of organs and skin dermis

Question 14

What is Type II Collagen?

Answer 14

Fibrils do not form fibres

eg. present in hyaline and elastic cartilage

Question 15

What is Type III collagen?

Answer 15

Fibrils form fibres around muscle and nerve cells and within lymphatic tissues and lymphatic organs (eg. spleen) and in tendons
- Called reticulin

Question 16

What is Type IV collagen?

Answer 16

Unique form present in basement membranes

Question 17

What is extracellular matrix?

Answer 17

A term used to describe a complex extracellular structural network that consists of ground substances and fibres

Question 18

What fibres are found in connective tissue?

Answer 18

Collagen
- Flexible with high tensile strength
Reticular (absent in areolar tissue)/reticulin
- Provide a supporting framework/sponge
Elastin
- Allows tissues to recoil after stretch or distension

Question 19

How is collagen produced?

Answer 19

• Fibroblasts secrete procollagen that is converted to collagen molecules outside the cell
• The collagen molecules are then aggregated to form collagen fibrils
• In some tissues, fibrils group together to form collagen fibres to give strength (bone, tendons, ligaments)

Question 20

What is required for procollagen production?

Answer 20

Vitamin C

- Required for intracellular production of procollagen, where it hydroxylates proline and lysine

Question 21

What happens with a vitamin C deficiency?

Answer 21

-Disrupts collagen formation leading to scurvy

Question 22

What happens in scurvy?

Answer 22

• The thin collagen fibrils aggregate in some areas to form thicker collagen fibres

Question 23

What are the symptoms and signs of scurvy?

Answer 23

• Gum disease and tooth loss
• Bruising of the skin and hair loss
• Bleeding
• Poor wound healing
• Weakness and fatigue
• Impaired bone development in the young

Question 24

What is Marfan’s syndrome?

Answer 24

• Autosomal dominant disorder

- Expression of the fibrillin 1 gene is affected so elastic tissue is abnormal

Question 25

What are signs and symptoms of Marfan’s syndrome?

Answer 25

• Abnormally tall and large wingspan
• Arachnodactyly (long fingers and toes)
• Frequent joint dislocation
• At risk of catastrophic aortic rupture

Question 26

What is the primary component of elastic fibres?

Answer 26

Elastin

- Elastin infolds and is surrounded by microfibrils of fibrillin

Question 27

Where are elastin fibres found in the body?

Answer 27

• Dermis
• Artery walls
• Lungs
• Sites bearing elastic cartilage

Question 28

What is Osteogenesis Imperfecta?

Answer 28

‘Brittle Bone Disease’

Question 29

What causes Osteogenesis Imperfecta?

Answer 29

• Mostly autosomal dominant

- Due to mutated collagen fibres that do not ‘knit together’