Connective Tissue DLA

Question 1

Where do connective tissue derive from?

Answer 1

Mesoderm

Question 2

What are the common cell types for connective tissue?

Answer 2

Permanent residents of CT

a) fibroblasts
b) adipose cells
c) macrophages/monocytes
d) mast cells
e) mesenchymal stem cells

Transient/ wandering cell population

a) lymphocytes
b) plasma cells
c) eosinophils
d) basophils
e) neutrophils

Question 3

What is the most common cell in connective tissue?

Answer 3

Fibroblasts

Question 4

What is the structure-function of fibroblasts

Answer 4

Synthesize fibers and ground substance

Spindle-shaped, May be active (fibroblasts) or inactive (fibrocysts)

Myofibroblasts - wound healing. Presence of contractile filaments

Question 5

Summarize Adipocytes

Answer 5

Unicellular vs multicellular

Uniocular adipocytes- one large fat droplet- “white fat”

1. Typical fat cell - signet ring cell
2. Large fat inclusion; organelles/ nucleus pushed to periphery of the cell
3. Major energy source- triglycerides
4. Rich blood supply

Question 6

What are the characterizations of brown fat?

Answer 6

• Many lipid droplets
• central nucleus
• rich in mitichondria
• Highly vascular
• Rich in innervation
• Lipochrome pigments
• Main function- heat production
• Speciaalized locations in the body neck, abdomen of neonates

Question 7

Describe macrophages

Answer 7

1. Derived from monocytes- migrate to connective tissue, differentiate to macrophages
2. In connective tissues- macrophages
   
   • liver= kupfer cells
   • brain= microglia
   • bone= osteoclasts
3. Irregular cell membrane/ cytoplasmic extensions (pseudopodia)
4. Phagocytic; produce cytokines
5. Antigen presenting cells; multicellular giant cells

Question 8

Describe mast cells

Answer 8

• Originate in the bone marrow from precursor cells lacking cytoplasmic granules
• When they migrate to connective tissue or lamina propria of mucosae, they proliferate and accumulate cytoplasmic granules
• Mast cells and basophils circulating in the blood are derived from the same progenitor in the bone marrow

Question 9

What is metachromasia?

Answer 9

After staining with a metachromatic dye like toluidine blue, the mast cell granules stain with a color that is different from the color of the dye (purple red instead of blue)

-Thus phenomenon is determined by a change in the electronic structure of the dye molecule after binding to the granular material. In addition mast cell granules are PAS positive because of their glycoprotein nature

Question 10

Describe lymphocytes

Answer 10

1. Small, spherical cell- scant cytoplasm
2. Condensed, basophilic nucleus
3. Immune cells- B and T cells
4. B-lymphocytes develop into plasma cells

Question 11

Explain What are plasma cells

Answer 11

• plasma cells are derived from the dfferentustion of B lymphocytes
• Synthesis and secretes single class of immunoglobulin
• Immunoglobulins are glycoproteins
• Basophilic cytoplasm
• “clockface” nucleus-peculiar distribution of chromatin
• negative Golgi- slightly acidophilic area close to the nucleus

Question 12

Describe eosinophils

Answer 12

1. Eosinophilia (red) granules in the cytoplasm
2. Condensed, bilobed nucleus
3. Phagocytosis of antibody-antigen complexes
4. Kill parasitic worms

Question 13

What are the components of extracellular matrix?

Answer 13

Fibers:

• collagen fibers
• reticular fibers
• elastic fibers

Ground substance

Question 14

Outline the structure of collagen

Answer 14

1. Long protein polymer-most abundant protein( about 30% of total)(unbranched)
2. Many different types of collagen (type 1 most abundant)
3. Fibril-forming, fibril-associated, network-forming and anchoring types
4. Acidophilic (eosinophilic)
5. Collagen type 1 structure and formation is well described
6. Glycine (about 30%), proline, hydroxyproline, hydroxylysine
7. Procollagen formation intracellular, collagen assembled extracellular

Question 15

Describe reticular fibers

Answer 15

1. Type 3 collagen primarily
2. They are short, thin and branching in nature
3. Found in organs with large volume chaanges( spleen, arteries, intestine, testes, etc)
4. Argyrophilic(silver staining) and PAS positive (due to carbohydrate content
5. First type of collagen Synthesized during wound healing

Question 16

Describe elastic fibers

Answer 16

1. Three developmental stages: oxytalan (1st), elaunin (2nd), elastic (3rd)
2. Fibrillin(glycoprotein) and elastin (protein)
3. Elastin-glycine, proline, desmosine and isodesmosine (lysine-like)
4. Extremely elastic- 5x more than rubber (150% their resting length)
5. Found in large arteries, elastic cartilage, vocal ligament, bronchi, etc
6. Special staining required- Orcein,resorcin, Verhoeff’s

Question 17

What are the functions of ground substance?

Answer 17

1. “Glue” - binds cells to fibers
2. “Lubricant”- allows ease of motion (pathway for cell migration)
3. “Barriers”- physical prevention of bacteria and microorganisms
4. Tissue tensile strength

Question 18

What are the components of ground substance ?

Answer 18

1. Glycoaminoglycans (GAGs)
   - hyalauronic acid (hyalauronan)
   - Dermatan sulfate, chondroitin sulfate, keratin sulfate, heparan sulfate
   - “bottle brush “ structure
2. Proteoglycans (GAGs covalently bound to the core protein)
   - Aggrecan, syndecan, versican, decorin
3. Glycoproteins
   - Fibromectin, laminin (yes spelled correctly), chondronectin-adhesion molecules
   - integrins (RGD sequence)- cell surface receptors that bind cells to matrix

Question 19

What are the main proteoglycans?

Answer 19

Aggrecan, decorin, versican, syndecan

Question 20

What are the main examples of glyosaminoglycans?

Answer 20

Hyaluronan, Chondroitin-4- sulphate, Chondroitin-6-sulphate, heparan sulphate, keratin sulphate

Question 21

What is interstitial fluid composed of?

Answer 21

Small quantity if water- for solvation. And diffusion

Excessive edema