Blood Vessels Flashcards
What is the function and makeup of the adventia?
connective tissue: collagen
structural support
What are the layers of a blood vessel?
aventia, media, and intima
as you move through the bv system, A and M decrease and M becomes mostly smooth muscle til you get to the capillaries and then no M or A, just I
what is the function and makeup of the media?
smooth muscle, collagen, elastin: mix varies depending on size of vessels and location
controls size of vessels
What is the function and make up of the intima?
endothelial layer
permeability (regulates what goes in and out), immune response (recruits WBCs to the sites of infection), angiogenesis, modulates vascular resistance (increased flow, tells bv to relax)
How does the intima act as a selective barrier to proteins?
needs proteins to stay in the blood to maintain oncotic pressure, but also needs proteins (antibodies) and other bigger molecules (immune cells to mediate infection) to be able to travel in and out to mediate immune responses;
What is the intima permeable and not permeable to?
very permeable to sugars and other small molecules like ATP, amino acids,
not permeable to small or large proteins
What regulates permeability?
- endothilium structure
- basement membrane
- glycocalyx
- intercellular junctions
What are the endothelial structures?
1) continuous
2) fenestrated : small pores that are technically large enough for proteins to pass but don’t diffuse bc slit diaphragm cross the window and basement membrane
3) discontinuous : in liver and spleen; highly permeable
What is the structure of the basement membrane and how does it regulate permeability?
negatively charged barriers made of glycoproteins and proteoglycans, negative so repels neg charged proteins, thickness depends on location, on cytoplasmic side of cell
What is the glycocalyx?
on lumenal side of cell, layer made with glycoproteins and proteoglycans and negative charge also keeps proteins from getting out (determined experimentally)
What intercellular junctions are present in endothelial cells?
Tight junctions (clauddins and occuldins) ; and adhering junctions (VE - vascular endothelia -cadherin) (on continuous cells the only place where diffusion can occur) tight junctions less important in endothelium (as opposed to epithelium) except in the brain
What is the role of transcytosis in the endothelial cells?
transports large proteins across the cell
receptor mediated: receptors identify albumin that is a bound to other substance (i.e. a transporter) and endocytoses it and the receptor with the membrane shape change driven by calveolin (similar in fn to clathrin); then vessel acidifies, releases molecule on the the side of the cell
What is the structure of adhering junctions in endothelial cells?
actin in the cytoplasm attaches to alpha and beta catenin complex which is bound to endocytotic domain (endocytotic domain bounds to p120) and then the endocyt. domain is bounds to VE cadherin outside the cell
How does the cell loosen adhering junctions to allow fluids and larger cells to pass during infection?
1) signal from immune response activates kinases that phosphorylate beta catenin and cause the b catenin/ a catenin to release the cadherin complex from actin; also phosphorylate endocytotic domains that release p120, attract beta arrestin and cause endocytosis of the cadherin
2) signal molecule activates myosin that contracts and pulls junction apart (thrombin acts to increase tension)
How do leukocytes transmigrate across endothelium
1) rolling phase: selectin proteins on endo cells and WBCs slow down movement of WBCs ( bind and release with high off rate)
2) Adhesion phase: integrins cause tight associate with WBCs (immune response up regulates integrins)
3) Emigration phase: WBCs squeeze through gap between adjacent endothelium (after junctions have been loosened)
