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Tissues > Tissues 3 > Flashcards

Tissues 3 Flashcards

1
Q

What does extracellular matrix surround?

A

Connective tissue

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2
Q

What is extracellular matrix.

A

Complex network of proteins and carbohydrates

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3
Q

What are the functions of the ECM?

A
  1. Physical Support
  2. Determines mechanical and physiochemical properties
  3. Influences growth, adhesion and differentiation status
  4. Essential for development, tissue function and organogenesis.
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4
Q

What are the components of connective tissues?

A
  1. Collagens
  2. Glycoproteins
  3. Proteoglycans

(cellular component)

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5
Q

Types I-III collagen are?

A

Fibrillar

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6
Q

Type 4 collagen is present where?

A

In the basement membrane (basal lamina)

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7
Q

Give examples of glycoproteins.

A
  1. Fibronectin
  2. Fibrinogen
  3. Laminins (in basement membrane)
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8
Q

Give examples of proteoglycans.

A
  1. Aggrecan
  2. Versican
  3. Decorin
  4. Perlecan (in basement membrane)
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9
Q

How can matrix proteins be affected?

A

Gene mutations

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10
Q

Name 5 diseases arising from matrix proteins being affected.

A
  1. Osteogenesis imperfecta - Type 1 Collagen
  2. Marfan’s Syndrome - Fibrillin 1
  3. Alport’s syndrome - Type IV collagen (a5)
  4. Epidermolysis bulls - Laminin 5
  5. Congenital Muscular Dystrophy - Laminan 2 (a2)
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11
Q

Diseases arising from ECM metabolism being affected?

A

Hurler’s Syndrome - L-a-iduronidase

Other micopolysaccharidioses

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12
Q

What causes fibrotic disorders?

A

Excess ECM deposition

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13
Q

Name some fibrotic disorders.

A

Liver fibrosis - cirrhosis
Kidney fibrosis - diabetic nephropathy
Lung fibrosis - silicosis

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14
Q

Disorders due to excessive loss of ECM?

A

Osteoarthritis

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15
Q

What are collagens?

A

Family of fibrous proteins - found in all multicellular organisms

Major proteins of bone, tendon and skin

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16
Q

What is the most abundant protein in mammals?

A

Collagen

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17
Q

How are collagen fibrils arranges in skin?

Why?

A

Successive layers are perpendicular to each other (same as in bone and cornea).

Resists force in all directions. Gives tissues tensile stress.

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18
Q

How many known types of collagen are there?

A

28

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19
Q

How many alpha chains comprise a collagen?

A
  1. Forms a triple helix
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20
Q

How many genes form Type 1 Collagen?

A

2 genes

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21
Q

Which types of collagen are homotrimeric?

A

Type 2 and 3

They have the same a chain

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22
Q

How many genes code for collagen?

A

42.

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23
Q

Every 3rd amino acid residue in the a chain is?

A

A glycine.

24
Q

Why does the glycine face the interior of the polypeptide chain?

A

It is hydrophobic.

Smallest amino acid so can fit in the gap

25
Q

Collegen is a stiff triple helical structure?

A

True

26
Q

What is the characteristic of the collagen a-chain?

A

Consists of a repetitive pattern.

X, Y, Glycine.

X is often proline

Y is often hydroxyproline

27
Q

In fibrillar collagens, how many amino acid residues long are the a-chains?

A

1000.

28
Q

How do collagen molecules form a collagen fibril?

A

By associating laterally.

29
Q

What do collagen fibrils form to make?

A

Collagen fibres, visible to naked eye

30
Q

Where are the non-collagenous domains located in newly synthesised collagen chains?

A

At the N and C terminals

31
Q

What happens to the non-collagenous domains after secretion?

A

They are removed.

32
Q

What do the N and C terminals of the pro collagen have?

A

Globular proteins associated

33
Q

How are the globular proteins associated to procollagen cleaved?

A

Peptidase cleaves them off

Some collagen types retain globular ends

34
Q

How are the hydrogen bonds formed between collagen fibrils?

A

Cross links are formed between adjacent collagen fibres

35
Q

Explain the biosynthesis of collagen.

A
  1. Procollagen synthesised.
  2. Hydroxylation (selected Prolines and Lysines)
  3. Glycolysation of certain hydroxylysines.
  4. Self assembly of 3 pro -a-chains
  5. Procollagen triple helix formation
  6. Secretion
  7. Cleavage of pro-peptides
  8. Self assembly into fibril
  9. Aggregation of fibrils to form fibre.
36
Q

Why hydroxylate lysine and proline in collagen biosynthesis?

A

Hydroxylation contributes to hydrogen bond cross link formation

37
Q

How are proline and lysine hydroxylated?

A

Hydroxylated by prolyl and Lysyl hydroxylases

38
Q

What do prolyl/lysyl hydroxylases require?

A
  1. Vitamin C

2. Fe(2+) (Post translational modification)

39
Q

How is scurvy caused?

A
  1. Underhydroxylated collagens.
  2. Lack cross links, less stable collagen
  3. Tissues less stable
40
Q

What happens to hydroxylysine and hydroxyproline after secretion?

A

Undergoes further modification - forms covalent cross links.

41
Q

Why do tendons have tensile strength in one direction?

A

They have parallel collagen fibres?

42
Q

How are collagen fibres arranged?

A

In a staggered array.

43
Q

Do all collagens form fibrils?

A

NO

44
Q

What do types 9 and 12 collagens do?

A

Associate with fibrillar collagens and regulate their organisation.

45
Q

Which collagen is a network forming collagen and is present in all basal laminae (by assembling into a sheet-like network)?

A

Type 4

46
Q

What do elastic fibres do?

A

They give structures elasticity.

47
Q

How is the extent of stretching limited?

A

Collagen and elastic fibres are interwoven

48
Q

What are elastic fibre cores made up of?

A

Microfibrils and proteins

Microfibrils rich in protein fibrillin

49
Q

How is Marfan syndrome caused?

A

Fibrillin I mutations.

50
Q

What does elastic fibre integrity depend on?

A

Depends on microfibrils containing fibrillin,

51
Q

What happens in patients with Marfan’s?

A

Elastic fibres lack integrity - overly stretched

52
Q

What are Marfan’s patients more susceptible to?

A

CVS problems.

They are tall and slender.

53
Q

What are the 2 segments that make up elastin?

A
  1. Hydrophobic regions
  2. a-helical chains (rich in alanine and lysine)

Many lysine side chains are cross linked

54
Q

What are basement membranes/basal laminae?

A

Flexible, thin mats of ECM that underlie Epithelial sheets and tubes

Highly specialised

55
Q

What do basal laminae surround?

A

Muscle, peripheral nerve and fat cells

56
Q

Give a use of ECM.

A

Filter for macromolecules, acting as a highly selective filter

57
Q

What is diabetic nephropathy?

A
  1. ECM accumulation
  2. Causes thick kidney glomerulus
  3. Thicker basement membrane
  4. Causes restricted renal filtration as capillaries are impinged.

Tissues (11 decks)

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