Microcirculation Flashcards
Blood volume (%CO) increases blood flow to what 4 places?
brain. kidneys, liver, and muscle
Blood volume/tissue weight increases relative blood flow for what 6 places?
brain, kidneys, liver, heart, thyroid gland, and adrenal gland
When precapillary sphincters are open, blood flows to _____.
capillaries
When precapillary sphincters are closed, blood flows to ____.
metarterioles
When arteriovenous anastomosis (AVA) is open, blood passes through ______.
AVA
When arteriovenous anastomosis (AVA) is closed, blood passes through ______.
capillary bed
_____ is the intermittent blood flow through the capillaries, turning on/off every few seconds or minutes.
Vasomotion
_____ originated from altering periods of vasoconstriction and vasodilation of metarterioles and precapillary sphincters.
Vasomotion
What types of endothelial junctions do capillaries have?
only a few tight junctions
Capillary exchange is mediated by what three thing?
intercellular clefts
fenestrations
caveolae (plasmalemmal vesicles)
____ are curving channels between endothelial cells.
intercellular clefts
____ are pores within the plasma membrane.
fenestrations
True or False? Fenestrations have larger diameter than intercellular clefts
True
____ are invaginations of the plasma membrane that may coalesce to form vesicular channels all the way through the endothelial cell.
Caveolae
______ and _____ has a role in diffusion of water-soluble ions and small solutes.
Intercellular clefts and Fenestrations
_____ has a role in transcytosis of macromolecules, mainly plasma proteins, through the endothelium.
Caveolae
What can’t pass through the blood-brain barrier (BBB)?
most neurotransmitters and toxins and bacteria
Width of pores and fenestrations are smaller than albumin. Any molecule/cell larger than albumin will only pass through _____ capillaries.
sinusoid
Continuous capillaries contain _____.
intercellular clefts
Fenestrated capillaries contain _____.
fenestrations
The _____ are the Hydrostatic and Colloid Osmotic Forces that Determine whether fluid will move out of the blood into he IF or in the opposite direction.
four Starling forces
Name the 4 Starling forces.
Hydrostatic: - capillary pressure - interstitial fluid pressure Osmotic: - plasma colloid osmotic pressure - interstitial fluid colloid osmotic pressure
____ states that the fluid movement across the wall of a capillary is dependent on the balance between the hydrostatic pressure gradient and the oncotic pressure gradient across the capillary.
Starling’s hypothesis
The change in _____ is the major factor responsible for the filtration-absorption along the capillary
hydrostatic pressure
True or False? The change in hydrostatic pressure helps in the blood flow along the capillary.
True
Filtration on the arterial side is slightly ____ than the absorption on the venous side.
larger
______: the amount of fluid filtering from the arterial ends equals almost exactly the fluid by absorption.
Starling equilibrium
Excess of filtration (Net fluid filtration) is the fluid that must be returned through the ______.
lymphatics
What is the normal rate of net filtration in the entire body, not including the kidneys?
about 2 ml/min (2 L/day)
True or False? Blood flow is regulated at the minimal level that will supply each tissue’s requirements — heart workload is kept at a minimum.
True
What is the most important of the endothelial-derived relaxing factors?
Nitric Oxide
____ is a lipophilic gas continually released from endothelial cells in response to a variety of chemical, physical, and mechanical stimuli (shear forces).
Nitric Oxide
Endothelial-derived nitric oxide synthase (eNOS) enzymes synthesize NO from ____ and _____ (in the presence of Ca2+), in endothelial cells.
arginine and oxygen
____ acts locally in tissues around due to 6 second half life.
NO
NO diffuses into the vascular smooth muscle cells where it activates _____.
soluble guanylate cyclases
What are the five actions of NO?
- direct vasodilation
- indirect vasodilation by inhibiting vasoconstriction
- anti-thrombotic effect (inhibits platelet activation and vasospasm)
- anti-inflammatory effect (inhibits leukocyte adhesion to endothelium)
- anti-proliferative effect (inhibits smooth muscle hyperplasia)
What happens when NO reacts with the iron-containing heme groups of oxyhemoglobin in the erythrocytes?
NO is rapidly destroyed
___ plays a role in the control of blood flow in the heart, blood vessels, brain and muscle.
Adenosine
How does adenosine regulate cardiac blood flow and function?
- it regulates coronary blood flow (binding to AR2): vasodilation of coronary arterioles
- it regulates heart rate, contractility (binding to AR1): action through SA and AV nodes
____ has a role in vasodilation and capillary leakage of fluids during inflammation.
Bradykinin
____ causes both powerful arteriolar dilation and increased capillary permeability.
Bradykinin
____ has a powerful role in vasodilation and leakage of fluids in capillaries and arterioles.
Histamine
____ is released upon tissue damage, inflammation, or an allergic reaction.
Histamine
_____ is derived from mast cells in the damaged tissues and from basophils in the blood.
Histamine
___ is an important vasodilator during hemostasis.
Prostacyclin
___ is produced by endothelial cells.
Prostacycin
_____ is a powerful vasoconstrictor, present in endothelial cells, but greatly released upon damage to the endothelium.
Endothelin
_____ has an important role in hemostasis: helps prevent extensive bleeding from arteries as large as 5 mm in diameter.
Endothelin
___ has a role in damage to the endothelium by hypertension.
Endothelin
As little as one millionth of a gram of ___ can increase the arterial pressure of a human being 50 mm Hg or more.
Angiotensin II
____ normally acts on many of the arterioles of the body at the same time to increase the total peripheral resistance and to decrease sodium and water excretion by the kidneys, thereby increasing the arterial pressure.
Angiotensin II
_____ is the intrinsic ability of tissue to maintain a relatively constant blood flow despite large fluctuations in blood pressure.
Autoregulation
