S2) Connective and Adipose Tissues Flashcards

1
Q

Describe 4 functions of connective tissue

A
  • 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)

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2
Q

What are the 3 components of Connective Tissue Proper?

A
  • Cells
  • Fibres
  • Ground Substance
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3
Q

Identify and describe the 3 types of fibre in connective tissue

A
  • Collagen – flexible with high tensile strength
  • Reticular – provide a supporting framework/sponge
  • Elastin – allows tissues to recoil after stretch or distension
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4
Q

Describe the properties of ground substance in connective tissue

A
  • Viscous, clear substance with a high water content
  • It is composed of proteoglycans
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5
Q

What is a proteoglycan?

A

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

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6
Q

What is an extracellular matrix?

A

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

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7
Q

Distinguish between the structure of loose and dense connective tissue

A
  • 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

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8
Q

Where can loose connective tissue be found?

A
  • Located beneath epithelia (to facilitate diffusion)
  • Associated with epithelium of glands
  • Located around small blood vessels
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9
Q

Describe the strategic location of the connective tissue

A

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

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10
Q

Identify two examples of loose connective tissue in the body

A
  • Superficial layer of the dermis in the skin
  • Submucosa of the colon
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11
Q

Describe the structure and function of dense regular connective tissue

A
  • 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
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12
Q

Where is dense regular connective tissue found?

A
  • Tendons
  • Ligaments
  • Aponeuroses
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13
Q

Describe the structure and function of dense irregular connective tissue

A
  • 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
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14
Q

Where is dense irregular connective tissue found?

A
  • Submucosa of intestine
  • Deep layers of dermis
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15
Q

What do tendons do?

A

Tendons connect muscles to bones

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16
Q

Describe the arrangement of connective tissue in a tendon

A

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

17
Q

What do ligaments do?

A

Ligaments connect bone to bone

18
Q

Describe the arrangement of connective tissue in ligaments

A

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

19
Q

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

A
  • 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
20
Q

What are the fixed cells in connective tissue?

A
  • Fibroblasts (and myofibroblasts)
  • Melanocytes
  • Mast cells
  • Macrophages
  • Adipocytes
  • Mesenchymal ‘stem cells’
21
Q

What are the wandering immune cells in connective tissue?

A
  • Leucocytes
  • Plasma cells
  • Monocytes
  • Eosinophils
  • Basophils
22
Q

What is the role of fibroblasts?

A
  • 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
23
Q

What is the role of myofibroblasts?

A
  • Myofibroblasts are modified fibroblasts that contain actin
  • They are responsible for wound contraction when tissue loss has occurred.
24
Q

What are macrophages and what do they do?

A
  • 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
25
Q

What are mast cells and what do they contain?

A
  • 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

26
Q

Describe the role of mast cells

A
  • 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
27
Q

Differentiate between Collagen Type I - IV

A
  • 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

28
Q

How is collagen linked to diseases such as scurvy?

A
  • 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
29
Q

How is collagen linked to diseases such as osteogenesis imperfecta?

A
  • Osteogenesis imperfecta is due to abnormal type 1 collagen
  • It manifests as blue sclera and bone malformation
30
Q

Describe the structure, location and function of elastic fibres

A
  • 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
31
Q

What is Marfan’s Syndrome?

A
  • 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
32
Q

Most adipose tissue in the body is white fat.

Describe the structure and function of white adipose tissue

A
  • Structure: unilocular, cytoplasm & nucleus displaced to periphery
  • Function: a fuel reserve, thermal insulation & shock absorption
33
Q

Describe the structure, function and location of brown adipose tissue

A
  • 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
34
Q

Brown adipose tissue allow for non-shivering thermogenesis.

This is important for which groups of organisms?

A
  • Babies
  • Hibernating animals