S2) Connective and Adipose Tissues

Question 1

Describe 4 functions of connective tissue

Answer 1

• Connects cells to form tissues, connects tissues to form organs and connects organs to form the body

- Defence against infection (blood, lymph, fixed and wandering cells)

- Wound healing (macrophages, fibroblasts, myofibroblasts)

- Storage (adipose tissue)

Question 2

What are the 3 components of Connective Tissue Proper?

Answer 2

• Cells
• Fibres
• Ground Substance

Question 3

Identify and describe the 3 types of fibre in connective tissue

Answer 3

• Collagen – flexible with high tensile strength
• Reticular – provide a supporting framework/sponge
• Elastin – allows tissues to recoil after stretch or distension

Question 4

Describe the properties of ground substance in connective tissue

Answer 4

• Viscous, clear substance with a high water content
• It is composed of proteoglycans

Question 5

What is a proteoglycan?

Answer 5

A proteoglycan is a large macromolecule consisting of a core protein to which glycosaminoglycans (GAGs) are covalently bound

Question 6

What is an extracellular matrix?

Answer 6

The extracellular matrix is the complex extracellular structural network that consists of ground substance and fibres

Question 7

Distinguish between the structure of loose and dense connective tissue

Answer 7

• Loose:

I. Many cells

II. Sparse collagen fibres

III. Abundant ground substance

• Dense:

I. Few cells, nearly all fibroblasts

II. Many collagen fibres

III. Little ground substance

Question 8

Where can loose connective tissue be found?

Answer 8

• Located beneath epithelia (to facilitate diffusion)
• Associated with epithelium of glands
• Located around small blood vessels

Question 9

Describe the strategic location of the connective tissue

Answer 9

It is located at the sites where pathogens that have breached an epithelial surface and can be challenged and destroyed by the cells of the immune system

Question 10

Identify two examples of loose connective tissue in the body

Answer 10

• Superficial layer of the dermis in the skin
• Submucosa of the colon

Question 11

Describe the structure and function of dense regular connective tissue

Answer 11

• Structure:

I. Collagen fibres are arranged in parallel bundles and are densely packed

II. Fibroblasts are between the bundles

• Function: designed to withstand stress in a single direction

Question 12

Where is dense regular connective tissue found?

Answer 12

• Tendons
• Ligaments
• Aponeuroses

Question 13

Describe the structure and function of dense irregular connective tissue

Answer 13

• Structure:

I. Collagen fibres are arranged in bundles orientated in various directions

II. Fibroblasts are between the bundles

• Function: designed to withstand stress in multiple directions

Question 14

Where is dense irregular connective tissue found?

Answer 14

• Submucosa of intestine
• Deep layers of dermis

Question 15

What do tendons do?

Answer 15

Tendons connect muscles to bones

Question 16

Describe the arrangement of connective tissue in a tendon

Answer 16

The collagen bundles lie in a parallel, densely packed formation in line with the tensile force exerted by the muscle

Question 17

What do ligaments do?

Answer 17

Ligaments connect bone to bone

Question 18

Describe the arrangement of connective tissue in ligaments

Answer 18

The collagen bundles are densely packed in parallel arrangement, but undulate and are arranged in fascicles, separated by loose connective tissue

Question 19

Describe how the structure of dense irregular connective tissue in the dermis is adapted to its function

Answer 19

• Bundles of collagen are densely packed but irregularly arranged, so the skin can resist forces in multiple directions to prevent tearing
• The elastic fibres allow a degree of stretch and a restoration to the original shape after the skin is bent or folded

Question 20

What are the fixed cells in connective tissue?

Answer 20

• Fibroblasts (and myofibroblasts)
• Melanocytes
• Mast cells
• Macrophages
• Adipocytes
• Mesenchymal ‘stem cells’

Question 21

What are the wandering immune cells in connective tissue?

Answer 21

• Leucocytes
• Plasma cells
• Monocytes
• Eosinophils
• Basophils

Question 22

What is the role of fibroblasts?

Answer 22

• Fibroblasts synthesise and secrete both ground substance and the fibres that lie within the ground substance
• Important in wound healing and are the cells primarily responsible for the formation of scar tissue

Question 23

What is the role of myofibroblasts?

Answer 23

• Myofibroblasts are modified fibroblasts that contain actin
• They are responsible for wound contraction when tissue loss has occurred.

Question 24

What are macrophages and what do they do?

Answer 24

• Macrophages are derived from blood monocytes which move into loose connective tissue (especially during local inflammation)
• They are phagocytic and are professional antigen presenting cells

Question 25

What are mast cells and what do they contain?

Answer 25

- Mast cells look like blood basophils but are not derived from them - Mast cell cytoplasm contains abundant granules, containing: I. Histamine II. Heparin III. Substances that attracted eosinophils and neutrophils

Question 26

Describe the role of mast cells

Answer 26

- Mast cells become coated with IgE moleules which specifically bind to allergens and release the contents of its granules - These secretions result in immediate hypersensitivity reactions, allergy and anaphylaxis

Question 27

Differentiate between Collagen Type I - IV

Answer 27

- **Type I:** widely distributed type, fibrils aggregate into fibres and fibre bundles **- Type II:** fibrils do not form fibres (hyaline and elastic cartilage) **- Type III:** fibrils form fibres around muscle and nerve cells and within lymphatic tissues and organs (**reticulin)** **- Type IV:** present in basal lamina of basement membrane

Question 28

How is collagen linked to diseases such as scurvy?

Answer 28

- Fibroblasts secrete procollagen that is converted to collagen - Vitamin C is required for the intracellular production of procollagen - Vitamin C deficiency, as seen in **scurvy**, leads to poor wound healing and impaired bone formation

Question 29

How is collagen linked to diseases such as osteogenesis imperfecta?

Answer 29

- **Osteogenesis imperfecta** is due to abnormal type 1 collagen - It manifests as blue sclera and bone malformation

Question 30

Describe the structure, location and function of elastic fibres

Answer 30

- **Structure:** primary component of elastic fibres, surrounded by microfibrils called fibrillin - **Location**: occurs in most connective tissues to varying degrees - **Function**: allows for distension in the dermis, artery walls & lungs

Question 31

What is Marfan's Syndrome?

Answer 31

- **Marfan's syndrome** is an autosomal dominant disorder in which expression of the fibrillin gene is abnormal such that elastic tissue is abnormal - Sufferers are abnormally tall, exhibit arachnodactyly, have frequent joint dislocation and are at risk of aortic rupture

Question 32

Most adipose tissue in the body is white fat. Describe the structure and function of white adipose tissue

Answer 32

- **Structure**: unilocular, cytoplasm & nucleus displaced to periphery - **Function**: a fuel reserve, thermal insulation & shock absorption

Question 33

Describe the structure, function and location of brown adipose tissue

Answer 33

- **Structure**: multilocular, central nucleus, rich vascular supply, abundant mitochondria - **Location**: found close to the scapula, sternum and axillae - **Function**: high respiratory capacity for heat generation

Question 34

Brown adipose tissue allow for non-shivering thermogenesis. This is important for which groups of organisms?

Answer 34

- Babies - Hibernating animals