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Med 2024-2028 > TOB L5 > Flashcards

TOB L5 Flashcards

1
Q

State functions of connective tissue

A
  1. Provide sturctural form to the body and organs
  2. Provide a medium for diffusion of nutrients and wastes
  3. Attach muscle to bone and bone to bone
  4. Provide a cushion between tissues and organs
  5. Defend against infection
  6. Aid in tissue repair (stem cells)
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2
Q

State two components making up connective tissue

A
  1. Cells
  2. ECM (extracellular matrix)
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3
Q

State the components of the ECM

A
  1. Ground substance
    (hyaluronate proteoglycan aggregates)
  2. Fibrillar proteins
    (collagen fibres, elastin, fibronectin, fibrillin)
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4
Q

Describe the composition of ground substance / how hyaluronate

A

Gel-like like substance
Consists of highly glycosylated proteins (proetoglycans) attached to high molecule weight hyaluronic acid (HA) backbone
Forming long unbranched polysaccharides - glycosaminoglycans
Polysccharides form hyaluronate proteoglycan aggregates

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5
Q

Describe the characteristics of hyaluronate proteoglycan aggregates

A
  1. Inflexible
  2. Highly polar, hence attract water (90% of ECM is water)
  3. Resistant to compression
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6
Q

Describe how connective tissue is derived

A

From multipotent embryonic mesenchymal cells:

  1. Cells of mesoderm (middle embryonic germ layer) proliferate + migrate to form mesenchyme in early embryo (with ectodermal cells that form some of bones + muscles in head + neck)
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7
Q

How is mesenchyme found in adults?

A

Mescenchyme persists in adults as stromal stem cells

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8
Q

Diagram showing lineages derived from mesenchymal cells

A

This diagram is showing what mesenchymal cells can specialise into

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9
Q

Describe mesenchymal tissue in the developing fetus

A

Mesenchymal cells morphologically similar but give rise to cells that differentiate into different cell types

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10
Q

Describe the role of mesenchymal cells in adults

A

Mesenchymal cells persist in the adult

FACILITATE HEALING + RENWEAL

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11
Q

Describe the classification of connective tissue

A

Embryonic connective tissue:
- mesenchyme
-mucous connective tissue (foetal umbilical cord)

Connective tissue proper:
- loose (or areolar, meaning space) connective tissue
- dense connective tissue (irregular or regular)

Specialised connective tissue
- adipose tissue
- blood + lymphatic tissue
- cartilage (type II collagen), bone (type I collagen)

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12
Q

What is the most abundant human protein ?

A

Collagen
30% of whole body (90% of this is collagen type I)
28 types of collagen

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13
Q

Diagram showing triple helix structure of tropocollagen

A
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14
Q

Describe the process of collagen synthesis

A

RER:
1. Synthesis of pre-procollagen alpha chains (glycine every third residue allows helical conformation)
2. Vitamin C dependent hydroxylation of prolyl and lysyl residues - stabilises and strengthens collagen cross links
3. Assembly of triple helix to form procollagen

Golgi:
Packaging into secretory vesicles

Cell membrane
Constituitive exocytosis

Extracellular environment:
1. Non-helical terminal peptides cleaved
2. Collagen molecules assemle into fibrils

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15
Q

Describe type I collagen assembly

A
  1. We have collagen subunits
  2. Each fibril is composed of staggered collegen molecules with a periodic banding which repeats every 67 nm
  3. Fibrils assemble into fibres (visible under light microscopy), fibres assemble into larger bundles
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16
Q

Describe the types of collagen

A

Type I: 90% of all collagen. Fibrils aggregate into fibres, which assemble into large bundles (e.g. tendons , capsules of organs, dermis, organic component of bone)

Type II: Fibrils do not form fibres, so form a very fine mesh (e,g. in hyaline cartilage)

Type III: fibrils form branching fibres but not bundles. (e.g. around muscle, nerve cells) (e.g. within lymphatic tissues + organs, here it is called reticulin) (e.g. in skin, particularly papillary dermis)

Type IV: Unique (sheet) form present in basal lamina of basement membrane

Type VIII: Anchors basal lamina to underlying reticular lamina

17
Q

Describe disorders related to collagen synthesis

A

Ehlers-Danlos (ED)
-can occur due to failures in various stages in collagen synthesis
-Faiulre in Type IV ED (vascular type),
-Failure Type III - aortic rputure

Scurvy
-lack of vit c reduces prolyl hydroxylase activity, leading to gum ulcerations + haemorrhage

Osetogenesis imperfecta (OI, brittle bone disease)
-loss of function of COL1A1, collagen 1A gene
-results in spontaneous bone fracture

18
Q

Describe the structure, location and function of Elastic Fibres

A
  1. Composites of elastin deposited on a fibrillin microfibril sacffold
  2. Elastic fibres found in connective tissue
  3. Allow tissue to distend + return to original shape e.g. in dermis, artery walls, elastic cartilage
19
Q

TEM of elastic fibre

A

Pay att

Med 2024-2028 (56 decks)

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