Blood Vessels II Flashcards
1
Q
capillaries
A
- smallest vascular channels
- diameter of 5-10 microns
- length of 0.05-1 mm depending on organ
2
Q
endothelial cell
A
- cytoplasm has golgi complex
- few mito
- rough ER
- free ribosomes
- some structural support from intermediate filaments desmin and vimentin
- pinocytotic vesicles associated with PM
- endothelial cells secrete a basal lamina
- joined by tight and gap junctions
- life span of 150-180 days
- non thrombogenic if in tact and synthesizes types I, III, IV, V collagens, fibronectin, laminin, coagulants, anticoags
- weibel-palade body- has vonWillibrand factor which binds to factor VIII, and secretes selectins
3
Q
pericytes
A
- stellate cells that surround capillaries and some post capillary venules
- extensive branching processes and posses large nuclei rich in heterochromatin, small golgi, mito, rough ER, and filaments extending into the processes
- pericytes share basal lamina of endo cell
- some capable of contraction to regulate blood flow
- can serve as stem cells for endo and smooth muscle cells after injury
4
Q
continuous capillaries
A
- most common of the 3 types
- muscle, nervous, CT, exocrine pancreas
- endothelial lining and BL are complete
- endo cells sealed by tight junctions that permit passage of small molecules
- cytoplasm has many vesicles that transport large molecules
5
Q
fenestrated capillaries
A
- pancreas, intestines, endocrine glands
- special type with no diaphragms in the renal glomerulus
- continuous but thin endo and BL
- small pores or fenestrae in their walls 60-80 nm in diameter covered by a diaphragm except renal glomerulus
- specialized for rapid interchange of substances between blood and tissue
6
Q
sinusoids
A
- sinusoidal cap found in endocrine glands
- discontinuous sinusoids in liver and bone marrow
- venous sinusoids in spleen
- 30-40 microns in diameter as opposed to 5-10
- irregular blood channels that conform to the shape of the structure they line
- continuous BL and fenestrae with diaphragms that are much larger than in fenestrated capillaries
- discontinuous sinusoids have discontinuous or absent BL and have large gaps between endo cells that permits enhanced exchange
7
Q
capillary permeability
A
-two distinct pore systems
small 9-11nm and large 50-70 nm
-small pores are believed to be pores in the tight junctions
-large pores correspond to transcytosis by vesicles
8
Q
veins vs. arteries
A
- veins show greater variation in size and structure than arteries
- veins are of larger caliber and more numerous in the body
- veins have more extensive vasa vasorum and lymphatics
- veins contain more collagen and less elastic substance and smooth muscle
- veins owe most of their thickness to adventitia
- small and medium veins have valves that are formed from an infolding of the intima with an elastic CT core
9
Q
large veins
A
- intima with continuous endo and BL, no IEL
- media is frequently incomplete or absent
- adventitia is largest, best developed tunic and forms 95% of the thickness of the vessel wall
- contains thick bundles of longitudinally oriented smooth muscle and collagen and elastic fibers
- well developed vasa vasorum and lymphatics
- SVC, IVC, portal vein
10
Q
small and medium veins
A
- intima has continuous endo and BL, complete IEL usually only in veins of leg
- some valves
- media-poorly developed except for limbs, smooth muscle is circumferential
- adventitia is thickest and usually has no smooth muscle
- contains collagen and elastic fibers, fibroblasts, lymphatics, vasa vasorum
11
Q
venules
A
- pericytic and muscular
- functions are to continue the exchange of materials that was started in the cap
- preferred location for leukocyte emigration
- leaky in response to histamine and serotonin
12
Q
pericytic venules
A
- post cap venules that are 10-50 microns in diameter and resemble large caps
- have a pericyte
13
Q
muscular venules
A
- receive blood from pericytic venules and accompany arterioles
- media has 1 or 2 circular layers of smooth muscle cells
- thin adventitia of loose CT
14
Q
portal systems
A
- carry blood from one cap bed to another
- hepatic portal vein
- hypophyseal portal veins of pituitary
- efferent arterioles of the renal cortex
15
Q
arteriovenous anastomoses
A
- direct cross connections between arterioles and venules
- smooth muscle cells form a sphincter that regulates blood flow and allows bypass of capillary bed
