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ESA1 - Tissues Of The Body > Connective Tissue > Flashcards

Connective Tissue Flashcards

1
Q

Define ‘connective tissue’

A
  • Links muscles, nerves and epithelial tissues in a structural way
  • Provides support in metabolic and physiological ways
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2
Q

Name 5 types of specialised connective tissue in the body

A
  • Lymphatic tissue
  • Blood
  • Cartilage
  • Adipose tissue
  • Bone
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3
Q

Describe the composition of the extracellular matrix of connective tissue

A
  • GROUND SUBSTANCE containing hyaluronic proteoglycan aggregates
  • FIBRES consisting of collagen, reticular and elastin
  • CELLS such as fibroblasts, mast cells, leukocytes, mesenchymal and plasma cells
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4
Q

What cell types may be present in connective tissue?

A
  • Fibroblasts
  • Mesenchymal cells
  • Mast cells
  • Leukocytes
  • Plasma cells
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5
Q

How might connective tissues differ from eachother?

A
  • Types of cells which they contain
  • Abundance/density of certain cell types
  • Constitution of extracellular matrix (e.g. fibre content/arrangement, ground substance composition)
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6
Q

Describe the classification of connective tissues

A
  • EMBRYONIC > mesenchymal, mucous (umbilical cord)

- PROPER > loose, dense irregular, dense regular

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7
Q

What is meant by connective tissue being ‘mesenchymally derived’?

A
  • Mesenchymal cells are MULTIPOTENT PROGENITOR CELLS derived from the middle germ layer, the MESODERM
  • Mesenchymal cells are undifferentiated and have the potential to become a range of cells; cell type depends on the type of connective tissue
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8
Q

Describe the structure of mesenchymal cells

A
  • SPINDLE SHAPED
  • Cytoplasmic projections give tapered appearance
  • Abundant viscous (almost gelatin-like) extracellular matrix
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9
Q

Explain the structure of the ground substance in connective tissue

A
  • Hyaluronic proteoglycan aggregates
  • Hyaluronic acid molecules form linear aggregates each with many proteoglycan monomers (interwoven within a network of collagen fibres)
  • High density of -ve charge attracts water molecules forming a hydrated gel
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10
Q

What is RETICULIN?

A
  • Type III collagen

- Fibrils form fibres around muscle and nerves and within lymphatic tissues and organs

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11
Q

Describe the structure of type I collagen

A
  • Periodic banding repeated every 68nm
  • Triple helix of α chains with repeating GLY-X-Y amino acid sequence
  • Each fibre is 300nm long, 1.5nm wide
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12
Q

Explain why fibroblasts contain an abundance of RER

A
  • Fibroblasts secrete PROCOLLAGEN which form collagen fibrils in the extracellular matrix
  • Lots of RER needed for protein synthesis of procollagen
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13
Q

List 3 locations in the body where you would find LOOSE connective tissue

A
  • Submucosa of gut wall
  • Mammary gland
  • Adipose tissue
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14
Q

How could you distinguish reticular fibres in connective tissue?

A
  • Irregular anastomosing network

- Stain dark blue/brown

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15
Q

Explain the signs and symptoms of Marfan’s Syndrome

A
  • Autosomal dominant
  • Abnormal expression of fibrillin gene so results in abnormal elastin tissue
  • Sufferers are abnormally tall, exhibit arachnodactyly and frequent joint dislocation
  • Can be at risk of catastrophic aortic rupture
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16
Q

Describe the structure and staining of elastic fibres

A
  • Composed of elastin, surrounded by microfibrils called FIBRILLIN
  • Amorphous appearance (low electron density)
  • Fibrillin fibres are more electron dense so stain darker and lie at the periphery and within elastic fibres
  • Elastic fibres stain BLACK
17
Q

Where in the body would you find elastic fibres?

A
  • Tunica media of arterial walls
  • Dermis
  • Sites containing elastic cartilage
18
Q

What are the features of loose connective tissue?

A
  • Loosely arranged fibres
  • Large matrix:fibre ratio
  • Allows elasticity and movement
19
Q

Describe the composition of loose connective tissue

A
  • Non branching collagen fibres (type I and type III/reticular)
  • Branching elastic fibres
  • Small blood vessels
  • Mast cells
  • Fibroblasts
20
Q

Explain the arrangement of dense irregular connective tissue in the dermis and how this relates to function

A
  • Bundles of collagen are densely packed and irregularly arranged (orientated in multiple directions)
  • Skin can RESIST FORCES in multiple directions to prevent tearing
  • Elastic fibres allow a degree of stretch and RESTORATION of shape after skin is bent or folded
21
Q

Describe the arrangement and composition of DENSE REGULAR connective tissue

A
  • Mainly type I collagen
  • Collagen bundles lie parallel in one direction (in line with direction of tensile force)
  • Elongated flattened fibroblasts arranged in rows between fibres
22
Q

What is the role of fibroblasts?

A
  • Synthesise and secret extracellular matrix composed of ground substance and fibres
  • Important in wound healing and the formation of scar tissue
23
Q

Describe the structure of a macrophage

A
  • Kidney shaped nucleus
  • Cytoplasmic extensions on surface
  • Abundant dark staining LYSOSOMES
  • Contain phagocytic vesicles
24
Q

Explain the role and function of macrophages in the immune response

A
  • Move into loose connective tissue where there is local inflammation
  • PHAGOCYTIC so can degrade foreign organisms and cell debris
  • Contain many lysosomes (digestive enzymes) for breakdown of engulfed material
  • Professional antigen presenting cells so can present foreign antigens to T lymphocytes in immune response
25
Q

Describe the action of mast cells during an allergic reaction

A
  • IgE bound to specific cell surface receptors are cross-linked by allergens
  • Granules containing HISTAMINE, heparin or substances that attract neutrophils are rapidly released from cell
  • Causes immediate hypersensitivity and possibly anaphylaxis
26
Q

Explain the action of histamine and why it is not normally present around the CNS

A
  • Increases permeability of capillary walls causing local inflammation
  • Absent from CNS to prevent damaging effects of oedema (swelling) on brain and spinal cord
27
Q

Why do adipocytes appear empty in H&E wax embedded preparations?

A

Toluene and xylene used in tissue preparation dissolve away the lipid contents

28
Q

Describe the appearance of white adipocytes

A
  • Completely filled with single fat droplet
  • Cell contents and cytoplasm displaced to periphery
  • Nucleus displaced to one side on edge of cell
29
Q

How does the appearance of brown adipose tissue differ to that of white adipose tissue?

A
  • Contains multiple lipid droplets
  • CENTRAL NUCLEUS
  • Abundant mitochondria and rich vascular supply giving a brown colouring
30
Q

Explain the role of brown adipose tissue in non-shivering thermogenesis

A
  • UNCOUPLING in oxidative phosphorylation by increased permeability of inner mitochondrial membrane (dissipates PMF)
  • More heat is generated and less ATP produced
  • Important in babies and hibernating animals
31
Q

How could you distinguish a neutrophil from a macrophage histologically?

A
  • Macrophages have kidney shaped nucleus and are abundant in dark staining lysosomes
  • Neutrophils have 5-lobed nucleus (irregular shaped so very distinguishable)

ESA1 - Tissues Of The Body (19 decks)

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