L29: Connective tissue

Question 1

3 types of connective tissue

Answer 1

1. CT proper
   - Loose
   - Dense
2. Specialised CT
   - Cartilage, Bone
   - Haemopoietic tissue (Blood, Lymphatic)
   - Adipose
3. Embryonic CT
   - Mesenchyme
   - Mucous CT

Question 2

Properties of CT

Answer 2

1. Derived from mesenchyme (mesodermal germ layer)

2. Abundant ECM

Question 3

Functions of CT

Answer 3

1. Support epithelium
2. Connect tissues: ligaments
3. Protection
4. Tissue repair
5. Regulate behaviour of cells (ECM)

Question 4

Origin of CT

Answer 4

Stem cell

1. Undifferentiated mesenchymal cell
   - mesothelial
   - endothelial
   - fibroblast
   - adipocytes
   - osteoblasts
2. Haematopoietic stem cell
   - RBC
   - WBC

Question 5

Components of CT

Answer 5

1. Extracellular matrix (ECM): Regulate behaviour of cells, PAS stain due to sugar
   - Ground substance (Proteoglycan, Glycoproteins)
   - Fibrous components (Collagen, Elastic, Reticular (type III collagen))
2. Cellular components
   - Fibroblasts
   - Macrophage
   - Plasma cells
   - Mast cells
   - Adipocytes (unilocular/white vs multilocular/brown)

Question 6

Describe proteoglycan

Answer 6

Core protein + GAG (glycosaminoglycan, repeating dissaccharide)

Examples of GAG:
Chondroitin
Hyaluronan
Dermatan

Question 7

Features of GAG

Answer 7

• Repeating Dissaccharide units

- Osmotically active (absorbs water to form hydrated gel)

Question 8

Examples of glycoprotein

Answer 8

Fibronectin, laminin

Question 9

Describe Collagen fibre

Answer 9

• Present in all CT
• Acidophilic (Eosinophilic)
• Type I most abundant
• single collage fibre (protocollagen: triple helix)
• hydroxyproline + hydroxylysine

Question 10

Types of collagen

Answer 10

I: fibroblasts, osteoblasts
II: chondroblasts
III: fibroblasts
*IV: epithelial cells (Basal Lamina)
V: mesenchymal cells
*VII: keratinocytes (Basement anchoring)

Question 11

Describe Reticular fibre

Answer 11

• Collagen type III
• extensive network
• Argyrophilic (silver stain)
• PAS stain (large amount of glycoprotein)

Question 12

Describe Elastic fibre

Answer 12

• Elastin (Cross-linking desmosine & isodesmosine)+ Fibrillin (Marfan’s syndrome)
• Stretchable
• Loose network
• Yellow
• e.g. ligamentum flavum

Question 13

Classification of connective tissue

Answer 13

1. Loose / Dense
2. Regular / Irregular
3. Collagen (white) / Elastic (yellow)

Question 14

Examples of loose CT

Answer 14

Mesentery, Wharton’s jelly, lamina propria (CT of mucous membrane)

Question 15

Examples of dense CT

Answer 15

Dense irregular: Dermis

Dense regular: Ligament, tendon

Question 16

2 types of adipose tissue

Answer 16

1. Unilocular (white)
   - one large fat vacuole
   - adult main energy source
2. Multilocular (brown)
   - several fat vacuoles
   - large amount of mitochondria and blood capillaries
   - transform into heat efficiently —> chemical thermogenesis
   - children / hibernating animal

Question 17

Describe mast cells

Answer 17

IgE surface receptor (similar to basophils)
Mast cell granules are metachromatic
Metachromasia
Content of granules: histamine, leukotriene