Microcirculation Flashcards
describe the normal circulatory pattern
- start in the heart
- high pressure to large arteries, need elastic arteries to accommodate for this
- as arteries get smaller, need resistance, so need muscular arteries
- then reach capillaries, gas exchange
- into venules and veins, where pressure is low
- back to the heart (pre-load) - I think this relates to how venous filling of the heart affects the pressure with which blood is pumped into the arteries
what is the pathway of blood vessels that a red blood cell would travel through?
left ventricle –> elastic artery –> muscular artery –> arteriole –> capillary –> small venule –> large venule –> vein –> right atrium
- this is a continuous circuit!!
what happens to elastic and muscle tissue as you go from large to small arteries?
going from large to small arteries, amount of elastic tissue decreases and amount of smooth muscle increases
what happens to the intima, media, and adventitia as you go from arteries to veins?
intima: stays the same
media: decreases (so veins can have thinner walls and therefore better compliance, and arteries can have thicker/more muscular walls for resistance)
- adventitia: increases (sort of a “wall” so veins don’t collapse due to low pressure)
where do all functions of the circulatory system occur?
capillary beds! (the rest of the system consists of two pumps (the heart) and associated plumbing)
define microcirculation
network of small blood vessels, the smallest of which are capillaries
what are the three routes that blood can take when traveling from arterioles to venules?
- true capillaries: normal capillaries where gas exchange occurs (can be continuous, fenestrated, or discontinuous)
- metarterioles: direct blood to thoroughfare channels and play a role in thermoregulation
- thoroughfare vessels: shunts that allow blood to bypass the capillary system, so no gas exchange will occur
where are thoroughfare channels commonly found?
- skin of nose, lips, and external ear
- submucosa of nose and alimentary canal
- erectile tissue of sexual organs
describe the role of precapillary sphincters
- precapillary sphincters are bands of smooth muscle before capillaries
- when they are dilated, blood will flow into true capillaries. heat can be lost during this process
- when they are constricted, blood will instead flow into metarterioles and then through thoroughfare channels. heat can be conserved during this process
are all capillary beds supplied at all times?
blood is supplied to all parts of the body at all times, but all capillary beds do not contain blood at all times!
describe continuous capillaries
- endothelial cells have a continuous cytoplasm and basal lamina
- calveolae (invaginations in membranes) and vesicles transport substances across the cytoplasm in a bidirectional pathway
- this means we have transcytosis and pinocytosis (there are no gaps between cells that molecules can be transported through, so have to go through endothelial cells themselves).
define transcytosis
things to through cells: endocytosis, transport across cell, exocytosis on the other side
define pinocytosis
cell takes in fluid that has nutrients in it via vesicles
describe fenestrated capillaries
- have pores (fenestrae) in the cytoplasm with or without diaphragms
- this basically means there are gaps between the endothelial cells and there is not a continuous cytoplasm
- this allows for substantial fluid transport
- the basal lamina however is continuous
what are diaphragms in fenestrated capillaries?
- membranes between the endothelial cells that basically open and close for the transport of certain substances
- fenestrated capillaries without a diaphragm are characteristic of the renal glomerulus, so the continuous basal lamina constitutes an important permeability layer in this case