Origins and types of connective tissue cells

Question 1

a. Fibroblasts:

Answer 1

most abundant type of CT cell; derived from mesenchymal cells
i. Role- synthesis of components of the ECM (collagen, elastic fibers, GAGs, proteoglycans, multi-adhesive glycoproteins)
ii. Two forms- fibroblast (active form) and fibrocyte (quiescent form- less evidence of protein machinery)

Question 2

b. Myofibroblasts:

Answer 2

intermediate between fibroblast and smooth muscle cell, with features of both cell types
i. Abundant in wound repair- cause wound contraction
ii. Found in PDL- might be responsible for tooth eruption

Question 3

c. Adipocytes:

Answer 3

specialized for storage of energy in the form and neutral fats
i. Role: synthesis and storage of TAGs, production of estrogen and leptin
ii. White cells:
1. Unilocular; cell filled with large lipid droplet, cytoplasm and nucleus pushed to periphery; highly vascular
iii. Brown fat cells:
1. Multilocular; numerous mitochondria; richly vascularized, main function is heat production; central nucleus

Question 4

d. Macrophages:

Answer 4

derive from hematopoietic precursors  monocytes (circulate in blood)  leaves blood + matures  macrophages (also known as histiocytes)
i. Role- phagocytosis of senescent, damaged and dead cells and cellular debris, foreign substances and microorganisms, also acting as antigen-presenting cells

Question 5

ii. Mononuclear phagocytic system (MPS)

(macrophages)

Answer 5

1. Kupffer cells- liver
2. Microglial cells- CNS
3. Langerhans cells- skin
4. Dust cells/alveolar macrophages- lungs
5. Osteoclasts- bone
6. Microglia- brain

Question 6

e. Pericytes:

Answer 6

derived from mesenchymal cells; partially surround endothelial cells of capillaries and small venules
i. Multipotent/pluripotent: can differentiate into other cell types- vascular smooth muscle cells, fibroblasts, adipocytes, endothelial cells
ii. Have contractile properties- facilitate blood flow

Question 7

f. Mast cells

Answer 7

derived from hematopoietic cells; granules contain bioactive compounds such as heparin, histamine, and leukotrienes
i. Activated by IgE, released by plasma cells in response to antigens
ii. Binding of IgE to receptors on mast cells causes degranulation- release of granule contents producing an allergic reaction

Question 8

g. Plasma cells

Answer 8

: activated B lymphocytes; peripheral clumps of chromatin  clock-face appearance
i. Role- respond to antigen and produce antibodies

Question 9

h. Leukocytes

Answer 9

: all non-erythrocyte cells originating from hematopoietic tissue; escape from the bloodstream by migrating between endothelial cells (diapedesis)
i. Neutrophils: phagocytose bacteria
ii. Eosinophils: combat parasites, moderate allergic reaction
iii. Basophils: initiate, maintain and control inflammation processes
iv. Lymphocytes: found at site of chronic inflammation
v. Monocyte/ macrophages/ dendritic cells