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Body Logistics > L10) Connective tissue (proper) ✔ > Flashcards

L10) Connective tissue (proper) ✔ Flashcards

1
Q

Define connective tissue

A

A tissue that connects, supports, binds, or separates
other tissues or organs, typically having relatively few cells embedded in an amorphous matrix, often with collagen or other fibres.

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2
Q

What 3 components of connective tissue ?

A

Cells – mainly mature fibroblasts/fibrocytes, fixed adipocytes, reticular cells (found in all lymphatic tissues)
Fibres – collagens, elastin, reticular fibres
Ground substance – proteoglycans, (glucosaminoglycans, e.g. hyaluronic acid)

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3
Q

What makes up extracellular matrix ?

A

Ground substance + fibres

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4
Q

Define interstitium

A

Space between tissues and organs of the body

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5
Q

What are the 2 types of proper connective tissue ?

A

Loose (areolar tissue and adipose tissue)
Dense (fibrous & collagenous tissue)

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6
Q

Where is loose connective tissue found ?

A
  • In the lamina propria beneath mucosal membranes
  • Abounds the basal lamina
  • Least specialised connective tissue in the adult
  • Widely distributed: under epithelial cell layers (e.g. lamina propria) & around glands, surrounds capillaries, nerves and sinusoids
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7
Q

What are the 2 types of dense connective tissue ?

A

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

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8
Q

What is the structure of loose connective tissue ( areolar tissue )?

A

Contains multiple cell types - Fibroblast, macrophages, other white blood cells & mast cells adipocytes

Contains two main fibres - Collagenous & elastic

Gel-like ground substance - Proteoglycans, hyaluronic acid, etc.

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9
Q

What are the functions of loose connective tissue ( areolar tissue) ?

A

Holds vessels that supply fluids
Permits cell migration
Involved in inflammation pathways
Acts as packaging around organs
Generally hold everything in place
Cushions and stabilises organs

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10
Q

What is the function of Fibroblasts ?

A

Synthesise and secrete the fibres that lie within the ground substance(extracellular matrix).

Very important in the wound healing process & are the cells primarily responsible for the formation of scar
tissue.

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11
Q

What are myofibroblasts ?

A

Modified fibroblasts that contain actin & myosin.
They are responsible for wound contraction when
tissue loss has occurred.

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12
Q

Where are macrophages derived from ?

A

From blood monocytes - move into loose connective tissue, especially when there is local inflammation

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13
Q

What is the functions of macrophage ?

A

Phagocytic - can degrade foreign organisms and cell debris.

Are ‘professional antigen presenting cells’ (i.e. they can present foreign material to the T lymphocytes of the immune system)

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14
Q

What are the abundant granules in the mast cells cytoplasm ?

A

Histamine (increases blood vessel wall permeability)
Heparin (an anticoagulant)
Cytokines that attract eosinophils and neutrophils

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15
Q

Where are mast cells found ?

A

Found in areolar connective tissue near blood vessels
Absent from CNS - avoid damaging effects of oedema

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16
Q

What are mast cells coated with ?

A

IgE ( immunoglobulin) - molecules which specifically bind allergens - when an allergen cross-links these surface-bound IgE molecules, the contents of the granules are all rapidly released from the cell

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17
Q

What is the structure of adipocytes (unilocular) ?

A

A single enormous lipid droplet, with the nucleus, cytoplasm & organelles all squeezed to one side of the cell

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18
Q

What type of adipocytes (unilocular) are present in loose connective tissue ?

A

Mostly white to yellow = white adipocytes

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19
Q

What is the function of adipocytes ( unilocular ) ?

A

Padding and shock absorber, insulation and energy reserve.

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20
Q

What is the structure of adipocytes (multilocular) ?

A

Brown adipocytes
Very few of these in the adult
Multiple small lipid droplets, with the nucleus, cytoplasm & organelles all squeezed to the centre of the cell

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21
Q

What is the function of adipocytes (multilocular) ?

A

Provides insulation and energy reserve

In neonates: main method of generating heat (non-shivering thermogenesis)

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22
Q

What are fat tissues mainly made of ?

A

white adipose cells trapped in a fine mesh of reticulin fibres

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23
Q

What are the 2 types of fat tissue ?

A

White adipose tissue - single lipid droplet
Brown adipose tissue - many lipid droplet

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24
Q

What are the differences in fat tissue structures ?

A

White adipose tissue :
Normal number of mitochondria
Single peripheral nucleus

Brown adipose tissue :
Increased number of mitochondria
Single central nucleus

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25
Q

How is heat generated in the fat tissues ?

A

White adipose tissue - In adults, lipid breakdown is
slow and heat only generated after shivering reflex.

Brown adipose tissue - In neonates and young children,
lipid breakdown is accelerated, oxidative phosphorylation is uncoupled to generate heat - Calories generated can double

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26
Q

What are adipose cells generated from ?

A

Immature fibroblasts or mesenchymal stem cells

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27
Q

Define collagen

A

The commonest protein in our body and may constitute between ¼ & ⅓ of our whole-body protein content; with the ground substance it constitutes the extracellular matrix

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28
Q

What are the 4 types of collagen ?

A

Type I
Type II
Type III
Type IV

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29
Q

Describe Type I collagen

A

The most widely distributed type (90% of all collagen).
Fibrils aggregate into fibres and fibre bundles (e.g. in tendons, capsules of organs and skin dermis)

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30
Q

Describe Type II collagen

A

Fibrils do not form fibres (present in hyaline and elastic cartilage)

31
Q

Describe Type III collagen

A

Fibrils form fibres around muscle & nerve cells & within lymphatic tissues & lymphatic organs (e.g. spleen) and in tendons - It is called reticulin

32
Q

Describe Type IV collagen

A

Unique form present in basement membrane (considered of epithelial tissues)

33
Q

What are the features of fibres in connective tissue?

A

Collagen – Flexible with high tensile strength
Reticular/reticulin – Provide a supporting framework/sponge
Elastin – Allows tissues to recoil after stretch or
distension.

(Absent in areolar tissue )

34
Q

What is a ground substance ?

A

A viscous, clear substance with a slippery feel- it has a high water content.
Composed of proteoglycans (large macromolecules consisting of a core protein to which GAGs are covalently bound)

35
Q

What are Glycosaminoglycans(GAGs) ?

A

Long-chained polysaccharides
GAGs attract water to form a hydrated gel - permits rapid diffusion but also resists compression

36
Q

What is present in the ground substance cartilage ?

A

A unique GAG is hyaluronic acid that is bound to proteoglycans by a
link protein to form giant hydrophilic macromolecules.

37
Q

What type of cell is present in mucoid connective tissue?

A

Immature fibroblast (undifferentiated mesenchymal cells)

38
Q

What type of fibre is present in mucoid connective tissue ?

A

Thin collagen III fibres

39
Q

Where are mucoid connective tissues found ?

A

Umbilical cord (Wharton’s Jelly)
Vitreous humor of the eye

40
Q

What are the 2 types of connective tissue?

A

Regular
Irregular

41
Q

What is the function of tendons ?

A

Connect muscle to bone

42
Q

What is the structure of regular dense connective tissue in tendons ?

A

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

43
Q

What is the myotendinous junction ?

A

Skeletal muscle fibres connecting with tendon collagen bundles at myotendinous junctions - provides physiological strength

44
Q

How is the myotendinous junction formed ?

A

Collagen passes from the tendon to the muscle fibres - interacts with the collagen fibres coating the muscle fibres
Cross-links between these fibres results in mechanical strength

45
Q

How are forces transmitted in tendon ?

A

Along collagen bundles because they can glide over each other

46
Q

What makes up tendon ?

A

30% collagen
2% elastin
68% water

47
Q

What types of collagen make up tendons ?

A

70% Collagen I
30% Collagen III (reticulin)

48
Q

What is the function of ligament ?

A

Connecting bone to bone

49
Q

What is the structure of regular dense connective tissue in ligaments ?

A

Parallel collagen fibres
Not straight, but undulate
Wrapped in loose connective tissue - fascicles

50
Q

What is the structure of irregular dense connective tissue in the superficial layer of the dermis in the skin?

A

Densely packed but irregularly orientated collagen bundles - skin can resist forces in multiple directions to prevent tearing.
The elastic fibres allow a degree of stretch & a restoration to the original shape after skin is bent or folded

51
Q

What are the 3 types of fascia ?

A

Superficial
Deep
Visceral or parietal

52
Q

What is fascia made up of ?

A

fibrous connective tissue containing closely packed bundles of collagen fibres oriented in a wavy pattern parallel to the direction of pull

53
Q

What are the properties of fascia ?

A

flexible & able to resist great unidirectional tension forces until the wavy pattern of fibres has been straightened out by the pulling force

54
Q

What produces the collagen fibres in the fascia ?

A

Fibroblasts located within the fascia

55
Q

Name some locations that have dense irregular tissue ?

A

Deep layer of the dermis
Submucosa of intestine

56
Q

Name some locations that have dense regular tissue ?

A

Tendons
Ligaments
Aponeuroses

57
Q

Summarise the structure of dense irregular connective tissue ?

A

Contains fibroblasts
Collagen I fibres in all directions
Resists stresses in all directions

58
Q

Summarise the structure of dense regular connective tissue ?

A

Contains fibroblasts
Collagen I fibres in parallel
Resists stress in only one direction

59
Q

How is collagen fibril produced ?

A

Fibroblasts secrete procollagen that is converted to collagen molecules outside the cell.
The collagen molecules are then aggregated to form the final collagen fibrils

60
Q

What is vitamin C required for ?

A

Intracellular production of procollagen, where
it hydroxylates proline and lysine

61
Q

What is the importance of Vitamin C in collagen ?

A

Without vitamin c - collagen formation is disrupted

62
Q

Which disease is caused by vitamin C deficiency?

A

Scurvy

63
Q

What is scurvy ?

A

A condition that includes poor wound healing & impaired bone formation

64
Q

What are the symptoms/signs of scurvy ?

A

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

65
Q

What is Marfan’s syndrome ?

A

Autosomal dominant disorder in which expression of the fibrillin 1 gene is affected such that elastic tissue is abnormal

66
Q

What are the signs/symptoms of Marfan’s syndrome ?

A

Abnormally tall,
Arachnodactyly,
Have frequent joint dislocation

67
Q

What are those with Marfan’s syndrome at risk of ?

A

Catastrophic aortic rupture

68
Q

Define Elastin

A

Primary component of elastic fibres

69
Q

How are elastin fibres formed ?

A

Enfolds itself and is surrounded by microfibrils called fibrillin

70
Q

What are Desmosine & Isodesmosine

A

Amino acids that hold fibrillin to elastin

71
Q

Name the sites at which elastic fibres have an
important role

A

Dermis
Artery walls
Lungs
Sites bearing elastic cartilage

72
Q

What is Osteogenesis imperfecta

A

“Brittle bone disease” - congenital defect of bone formation resulting in weak bone

73
Q

What causes Osteogenesis imperfecta ?

A

Mutated collagen fibres that do not ‘knit together’ or not enough produced or both

74
Q

What are the signs/symptoms of Osteogenesis imperfecta ?

A

Weakened bones (fractures are common)
Short stature (depends on type)
Presence of blue sclera
Hearing loss
Hypermobility (loose joints) & flat or arched feet
Poor teeth development

Body Logistics (15 decks)

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