CAL: connective tissue histology

Question 1

Name the key cell of fibrous connective tissue. What is its function? Appearance under the light microscope? Where is it found?

Answer 1

• Fibroblasts
• Synthesise and maintain the ECM
• Appearance -
• Found in all connective tissues

Question 2

Name the 3 fibre systems in human connective tissue and describe their respective functions.

Answer 2

1. Collagen type I (collagen fibres) - the most abundant collagen, present in tendons, ligaments, the organic part of bone and forms scar tissue.
2. Collagen type III (reticular fibres) - composed of type III collagen secreted by reticular cells. Reticular fibres form a delicate supporting network for soft tissues e.g. liver, bone marrow and lymphatic system.
3. Elastin - highly elastic protein which allows distensibility of tissues e.g. the skin. Also found in load-bearing tissues.

Question 3

Describe the appearance of the 3 main fibre systems under the light and electron microscope.

Answer 3

LM:

• Collagen fibres - fibrous bundles with few cells.
• Reticular fibres -
• Elastin - long, thin fibres appearing black on iron haematoxylin. Thinner elastin fibres found alongside delicate collagen fibres closer to the epithelium. Thicker fibres found deeper.

EM:

• Collagen fibres - fine banded
• Reticular fibres -
• Elastin -

Question 4

Name the major type of molecule in the amorphous component of the ECM and explain its function.

Answer 4

The amorphous “ground substance” of ECM is a gelatinous material which fills the spaces between cells and the various fibres. The major molecular consituent is glycosoaminoglycans (GAGs), which link together to form proteoglycans. These absorb a large amount of water, allowing the ECM to resist compressive forces.

Question 5

Annotated diagram of basal lamina and its attachment to lipid bilayer.

Question 6

Name the major types of connective tissue and their subdivisions, providing examples.

Answer 6

Connective tissue proper

• Loose connective tissue
• Dense connective tissue
  
  • Dense regular - tendons and ligaments
  • Dense irregular
• Special connective tissue
  
  • Reticular connective tissue
  • Adipose tissue
  • Cartilage
  • Bone
  • Blood

Question 7

Which 3 cell types, other than fibroblasts and adipocytes, are commonly found in connective tissue? What are their respective functions?

Answer 7

1. Macrophages
2. Mast cells
3. Leukocytes