Connective tissue Flashcards
What are the functions of connective tissue?
- provide multiple attachments linking tissues and organs together
- defend against infectious agents
- control nutrient/metabolite exchange with blood and signaling ligands that communicate with different organ cell types
- directly control the behavior and functions of cells that contact the connective tissue matrix (control inflammation and repair due to injury, cell proliferation, guidance and regulation of cell migration through the matrix)
What are mesenchymal stem cells (MSCs)?
- precursors to all connective tissue family members
- prominent in embryogenesis
- small number persist through adulthood to function as stem cells for new connective tissue
What are myofibroblasts?
- derivatives of fibroblasts
- capable of smooth muscle like function
- found in connective tissue that require a contractile function
- often found in wound sites and contribute to retraction of scar tissue
What do lymphocytes become in the connective tissue?
lymphocytes (B cells, T cells, plasma cells)
What do basophils become in the connective tissue?
mast cells
What are the functions of lymphocytes?
immunity/defense against diverse foreign agents
What are the functions of neutrophils?
fight bacterial and parasite infections
What are the functions of eosinophils?
fight bacterial and parasite infections
What are the functions of mast cells?
inflammation control
What do monocytes become in the connective tissue?
macrophages
What are the functions of macrophages?
- microbe defense;
- tissue morphogenesis, angiogenesis (blood vessel development), and repair
- removal of damaged tissue
- remodeling of normal tissue
What are the functions of osteoclasts?
- phagocytic cells that are derived from blood monocytes
- function in bone resorption and remodeling
What is the ground substance?
gelatinous fluid that fibrous proteins are embedded in the connective tissue
What is the structure of each collagen molecular unit?
trimer of three intertwined polypeptide chains that forma fairly rigid rope like triple helix
What is fibrillar collagen?
- form fibrils (large bundles)
What are fibril-associated collagen?
- very thin fibers
- assemble into interlaced tissue networks that form porous sheets (can connect fibrils)
What are network forming collagen?
- thin fibers that form sheets, interlaced networks that form porous sheets
- part of the basal lamina
What is the central CT cell type that makes the components of the ECM of most connective tissues?
fibroblasts
Where are collagens translated?
ER
How are collagens transferred out of the cell?
- after being modified in the Golgi, in a vesicle
- assembled into a triple helix
How are collagens modified extracellularly?
- N- and C- termini of collagen are cleaved by specific proteases
- N- termini fragments are called N-telo peptides
Why are N-telo peptides clinically important?
- N-terminal fragments
- their levels in urine and blood are used to diagnose important connective tissue and bone diseases
What proteins do elastic fibers contain?
elastin and fibrillin
How do elastic fibers function?
- stretchable and resilient fibers and sheets
- predominantly random coil conformation that can be stretched upon exertion of force
What does the ground substance contain?
- proteoglycans
- variety of other secreted proteins and glycoproteins (e.g. proteases)
- many other small and large organic compounds
- water and inorganic solutes
- membrane vesicles (pinched off from cells)
What are proteoglycans made of?
- glycosaminoglycans (GAGs) and protein core