Most connective tissues are subject to _____.
dynamic regulation, and also dynamically control development and repair of other tissues (epithelia, muscle, blood vessels)
example: wound healing
____ is key to CT dynamic-ness
CT cell communication
CT cells communicate with _____
each other, with epithelial cells, with muscle and nerve cells, with endothelial cells, and with blood cells using a complex network of secreted ligands, cell receptors, and intracellular signaling systems.
When a wound occurs, a general, overlapping sequence of events typically occurs:
- inflammation and blood clotting
- new tissue formation
- tissue remodeling
Inflammation and blood clotting:
Rupture of tissue and blood vessels releases blood platelets into CT and activates them to produce blood clots that temporarily seal the wound (discussed in a later course on Blood system).
CT fibroblasts, mast cells, and other blood cell derivatives like macrophages release a plethora of signaling compounds that function to:
- increase water permeability of capillary endothelia leading to swelling
- increase cellular permeability of endothelia, to promote migration of monocytes, lymphcytes and other blood cells into the C.T.
- attract migration of white cells to the site of the wound (chemotaxis)
- stimulate proliferation of fibroblasts and differentiation of monocytes into macrophages.
Histamine secreted by mast cells promotes:
endothelial permeabilization
numerous cytokines secreted by white blood cell derivatives and by fibroblasts can signal ____
long distance to hematopoietic tissue to stimulate productions of more white blood cells.
New tissue formation:
- Fibroblasts are stimulated to divide and secrete ECM components.
- other specific signals trigger division and differentiation of epithelial stem cells and other stem cells of muscle.
- Cytokines and other protein growth factors are important in this phase.
- signals from multiple cell types, particularly macrophages, trigger new blood vessel growth (angiogenesis), repair, and remodeling
Tissue remodeling:
- The ECM, cellular composition, and overall structure of the CT, epithelium, and other tissues is altered to different extents, depending on wound location and severity.
- the cellularity (density of cells) is reduced, and ECM becomes thinner and altered in organization.
- If tissue damage is extensive, remodeled tissue is imperfect leading to formation of scar tissues (essentially disorganized epithelial/CT tissues lacking differentiated structural features of original tissue)
Several important diseases are tied to this inflammation process:
- crohns
- rhematoid arthritis
- stomach ulcers
4.
_____ is a hallmark of diseases such as ulcerative colitis or Crohn’s disease (inflammatory bowel diseases), rheumatoid arthritis, stomach ulcers, and several skin disorders.
Chronic inflammation
Convincing new evidence has linked chronic inflammation under some epithelia to development and/or promotion of ______.
malignant carcinomas, including colon cancer and other GI cancers
malignant metastatic tumors are believed to co-opt _____
inflammatory processes to promote their continued growth and vascularization
