Connective Tissue

Question 0

The ground substance of CT is made up of what?

Answer 0

Glycosaminoglycans (GAG): repeating disaccharides
-Sulfated (keratan, chondroitin, and dermatan sulfate)
-Attract water, resist compression
-Unsulfated (hyaluronic acid)
Proteoglycans (PG): protein core bound to sulfated GAGs
-Bind and activate growth factors
Glycoproteins: fibronectin, laminin, entactin
-Bind components of ECM and integrins
Collagen

Question 1

Connective tissue proper includes dense regular and dense irregular CT. Where are they located?

Answer 1

Regular: tendons, ligaments

Irregular: dermis, nerve sheaths, spleen capsules,
kidney, lymph nodes, testes, ovaries
• Fills spaces just deep to skin: mosothelial lining of body cavity, blood vessel adventitia, surrounds parenchyma of glands, lamina propria of gastrointestinal tract

Question 2

___ is the major fibrous protein of CT. What is its characteristic amino acid sequence?

Answer 2

Collagen, triple alpha helix, every third aa is glycine, others are mainly proline, hydroxyproline, and hydroxylysine

Question 3

What are the step of collagen synthesis?

Answer 3

1. Transcription, mRNA signaled to ER…
2. Translation (preprocollagen): α-chains with N- and C-terminus propeptides
3. Hydroxylation
4. Glycosylation
5. Formation of triple helix
6. Secretion via TGN
7. Cleavage of propeptides by procollagen peptidase –> tropocollagen
8. Self-assembly of tropocollagen into collagen fibril

Question 4

Scurvy is caused by…

Answer 4

Vitamin C deficiency, which is a cofactor for proline hydroxylase, a necessary enzyme of collagen ?synthesis?

Question 5

Ehlers-Danlos syndrome is caused by…

Answer 5

Type III collagen defect (reticulin – skin, blood vessels, uterus, fetal tissue, granulation tissue)

Question 6

Marfan’s syndrome is caused by a defect in ____.

Answer 6

fibrillin

Question 7

What is the principal cell of CT? What are two subtypes?

Answer 7

Fibroblasts; myofibroblasts (wound healing), pericytes (undifferentiated mesenchymal cells of capillaries)

Question 8

What are the two types of adipocytes in CT?

Answer 8

Unilocular (yellow fat, lipid storage)

Multilocular (brown fat, cytochromes in mitochondria, rich capillary bed, does thermogenesis under sympathetic control)

Question 9

With respect to adipocytes, childhood obesity is marked by ____ whereas adult onset obesity is marked by ____.

Answer 9

increase in adipocyte count (hypercellular obesity); increase in adipocyte size (hypertrophic)

Question 10

What is the principal phagocytic cell of CT?

Answer 10

histiocyte/macrophage (come from monocytes in bone marrow, part of MPS)

Question 11

What are the characteristics of plasma cells?

Answer 11

1. Originate from B lymphocytes
2. “Cartwheel” nucleus, basophilic cytoplasm (blue)
3. Abundant at sites of chronic inflammation
4. Synthesize and secrete IGs

Question 12

How do mast cells mediate the inflammation response?

Answer 12

Secretion of primary mediators (heparin, histamine, chemotactic factors for eosinophils and neutrophils)
Secretion of secondary mediators (leukotrienes, thromboxanes, prostaglandins)