Blood Vessel Histology Flashcards
How are the walls of blood vessels innervated in general terms?
by postanglionic, unmyelinated sympathetic nerve fibers which cause vsoconstriction
What are the examples of elastic (conducting) arteries?
aorta, common carotid, sublcavian, common iliac, pulmonary trunk
Why do the elastic conducting arteries appear yellowish in fresh state?
because they have an abdunance of yellow elastin
In the elastic conducting arteries, which way are the endothelial nuclei oriented? smooth muscle nuclei?
endothelium - longitudinally
smooth muscle - circumferentially
What are the membrane-bound inclusions contained in arterial endothelial cells?
weibel-palade bodies
What do the weibel-palade bodies contain?
von willebrand factor, which facilitates coagulation of platelets during clot formation
What is the tunica medial comprised of in elastic conducting arteries?
many fenestrated lamellae of elastin - like swiss cheese lasagna
What is the dominant component of the tunica medial in elastig conducting arteries?
elastin
What’s special about the ECM in the elastic conducting arteries?
it’s secreted by smooth muscle cells, not fibriblasts
What blood vessle is contained int he tunica dventitia in the elastic conducting arteries?
vasa vasorum - blood vessel to the vlood vessles
Most of the named arteries fall into what cateogy of artery?
muscular distributing arteries
What is the chief characteristic of the musculuar distributing arteries?
thick tunica media comprised primarily of smooth muscle cells
Although the tunica intima is htinner than that observe in elastic arteries, what layer of it is more prominent?
the internal elastic lamina - it’s the boundary between the intima and media
What do the outermost endothelial cells of the intima made gap junctions with?
the outermost smooth muscles cells of the tunica media - via gap jucnitons
What is the range in # of smooth muscle cell layers in the musclar arteries?
small ones - only 3-4 layers
large ones - up to 40 layers
What is the boundary between the media and adventitia in muscular arteries?
external elastic lamina
What is the typical diameter of the arterioles?
less than 0.1 mm
What controls blood flow into the capillary bed by encircling the vessel where a capillary springs from?
metarterioles - smooth muscle cells that act as sphincters
what do the carotid sinuses sense?
blood pressure changes - they’re barorectpros
Where are the carotid sinuses?
in the wlalls of the internal carotid artery (just above the bifurcation of the common carotid arteries)
What nerve endings are involved in the carotid sinuses?
glossopharygneal
What are the carotid bodies and aortic bodies?
chemoreceptors that sense changes in oxygen, carbon dioxide and protons in the blood and send the signal via the glossopharyngeal and vagus nerves
What is the typically diameter of capillaries?
8-10 micrometers
What type of vesicles are associated with eh ppasmalemma of capillaries? what are they for?
pinocytic vesicles used to transport substance across the membrane
What cells are found outside the capillaries and small venules with primary and secondary processes which run longitudinally and circumferentally along and around the capillary
pericytes
What is the likely function of pericytes
they’re probably contractile and help regulate blood flow through the capillaries
upon damage they probably give rise to smooth muscle and endothelial cells
What are the three types of capillaries?
conitnuous capillaries
fenestrated capillaries
sinusoidal capillaries
Where are continuous capillaries found?
muscle, nervous and CT
What makes fenestrated capillaries different from continuous capillaries?
fenestrated have pores in the wall while continuous don’t
What are the pores covered by ?
a thun diaphragm probably made with glycocalyx
Where in the body are fenestrated capillaries found/
pancreas, intestine and endocrine glands
Of the three types of capillaries, which have small diameters and which have bigger diamaters?
continuous and fenestrated are small
sinusoidal is large
What makes the fenetrates of the sinusoidal capillaries different from the fenestrated capillaries found?
they’re larger and don’t have diaphragms
What organs are the sinusoidal capillaries found/
bone marrow liver spleen lmphoic organs some endocrine organs
What are the two ways we regulate blood flow into a capillary bed?
- ateriovenous anastomoses
2. central channels
What is an arteriovenous anastomosis? How does it work?
it’s where an artery joins a venous channel
if the shunt is open, blood will bypass the capilary bed through the anastomosis
If the shunt is closed, the blood passes into the capillary bed
What is the important role of the arteriovenous anastomoses?
temperature regulation on the skin
What is the central channel?
It’s the straight shot from arteriole to venule composed of a metarteriole on the arteriole side and a thoroughfar channel on the venous side
blood will pass thorugh the central channel if the sphincters are closed
What molecules are expressed on the luminal side of capillaries to bind leukocytes and help them pass through
- selectins (P and E) help the leukocytes to stop roling
2. Integrins bind them even more strongly and help them diapedese
What are some of the general functions that endothelial cells can do?
- produce prostacyclin, plasminogen activator, IL-1, growth factors, etc.
- have enzymes that convert angiotensin I to II (and other activating enzymes)
- adipose tissue endothelium have enzymes on the luminal surface of capillaries to break down lipoprotiens into fatty acids and triglycerides for storage
Which are greater in number - veins or arteries?
veins - they hold almost 70% of th total blood volume
What sort of capillary are the postcapullary venules potentially mistaken for if you don’t know what tissue you’re in?
sinusoidal
What replaces the pericytes in larger venules?
smooth muscle cells
Which is the preferred site for leukocytes migration - capillaries or post capillary venules? why?
postcapillary venules because the walls are more permeable than those of capillaries
What are high endothelial venules and how are they different from regular venules?
they ser specialized venules in lymphatic organs where the endothelium is cuboidal rather than squamous
Which is the thickest layer in medium veins?
the adventitia. NOT the media!
What are examples of alrge veins?
venae cavae, pulmonary veins, portal, renal, internal jugular, iliac, azygous
Describe the tunica media in large veins
not well developed - often not apparent at all
What is unique about the tunica adventitia in large veins?
the smooth muscle cells are located here instead of in the meda and they’re oriented longitudinally, no circumferentially
What are vericose veins?
abnormally large and tortuous veins- usually the superficial leg veins of older people due to loss of muscle tone, wall degeneration and valvular incompetence
What veins have valves -
many small and medium-sized veins, but only some large veins
most in the limbs, some in the throax and abdomne, none in the brain and spinal cord
What are the valves composed of?
folds of intima endothelium with connective tissue core rich in elastic fibers
How do lymph capillaries differ from blood capillaries?
- larger diameter
- end blindly in tissue
- have scanty basement membrane
- endothelial cells are separated by substantial spaces and held together by few tight junctions
How do lymph collecting vessels differ from veins?
walls are thinner
valves ar emore closely spaced because of the passive nature of lymph flow
