Vessel Anatomy and Pressures Flashcards
Describe arteries grossly
Thick, hold their shape; 3 tunics of the wall
Describe veins grossly
Thin walls, collapsible, large lumen; low pressure; contain valves; 3 tunics but thinner
Describe capillaries grossly
Thinnest vessel, site of gas exchange; just 1 tunic
Describe blood flow from arteries to veins
Blood flows down artery, into arteriole, into capillary bed; drains into venule, flows into vein
Which vessels contain valves?
Veins
What is the purpose of valves in veins?
Low pressure vessels prone to backflow; valves prevent this
What are the tunics of arteries and veins?
Tunica interna (endothelia, basement membrane); tunica media (smooth muscle); tunica externa
Where is the external elastic lamina found?
Tunica interna and tunica media of arteries
What are the tunics of capillaries?
Just tunica interna; endothelium and basement membrane
Describe the tunica interna/intima
lines lumen, in contact with blood; smooth simple squamous endothelia. Beneath endothelia is the basement membrane; loose CT that contains collagen
What is the function of the subendothelial layer/basement membrane?
Aids in clotting; collagen of the connective tissues draws platelets
Describe the tunica media
Middle layer made of smooth muscle; contains elastin (elastic fibers) in arteries. Innervated by SNS fibers that control vasodilation/constriction; controls blood pressure
Describe the tunica externa/adventitia
Loose collagen fibers & elastin; contains nerve, lymph and blood vessels that serve the vessel itself; anchors and protects the vessel
What is the vasa vesorum?
The system of blood vessels that serve other blood vessels
What is blood pressure?
Force per unit area exerted on the wall of a vessel by the blood; mmHg
What is generally being referred to when talking about BP measures clinically?
systemic arterial BP in the largest arteries near the heart, like the radial artery
What are the different types of arteries?
Elastic arteries, arterioles, muscular arteries
What are elastic arteries?
Largest type of arteries; conducting vessels. Include aorta, pulmonary trunk, common carotid, etc. Thick walled, low resistance high in elastic tissue
What are muscular arteries?
Distributing vessels; lots of smooth muscle and more fibrous tissue. Active in vasoconstriction
What are arterioles?
Smallest arteries; resistance vessels. Control blood flow into capillaries
What affects arterial blood pressure?
Stretch: how much can elastic arteries stretch?
Volume: how much blood is forced into the arteries?
What is atherosclerosis?
Hardening of the elastic arteries due to plaque build up; increases blood pressure by greater resistance to blood flow through arteries
What is the systolic BP measuring?
Pressure in artery resulting from ventricular ejection phase (higher number on top)
What is a diastolic BP measuring?
Pressure in artery resulting from the non-ejection phase (lower number on bottom)
What is pulse pressure?
The difference between systolic and diastolic blood pressure (sys-di)
What is the mean arterial pressure?
Average pressure propelling blood to the tissues of the body; diastolic + 1/3 pulse pressure
What are the 3 types of capillaries?
Continuous, fenestrated, and sinusoidal
What are continuous capillaries?
Most common, fewest holes; intercellular clefts that allow for a little leakage. Found in brain and muscles & allow substances like glucose, H2O, O2, hormones, etc to exit the blood stream
What are fenestrated capillaries?
have fenestrations/pores, not as common; found in places like the kidneys where the blood is filtered
What are sinusoidal capillaries?
Contain large holes called sinusoids. Found in liver, red bone marrow and allow for passage of large molecules like RBCs
What is the pressure in the different vessels?
Highest in the arteries, much lower in capillaries but slightly lower than that in the veins. Needs to be like this to allow for blood flow (high -> low pressure)
Why is low pressure preferable in the capillaries?
They’re very fragile; high pressure will cause rupture. They’re highly permeable, and high pressure can cause edema
What are venules?
Very small veins that carry blood intermediate to capillaries and veins; extremely porous
What is the “volume sink” of vasculature?
Veins, because they carry ~65% of blood volume at any given time
Compare veins to arteries.
Veins have larger lumen and thinner tunics, much lower pressure. Veins contain valves to prevent backflow from low pressure
If veins are low pressure, how is blood flow back to the heart against gravity facilitated?
Muscular pump & respiratory pump. Backflow prevented by valves
Describe a simple circulatory pathway
Flows from artery into one capillary bed, then to vein
What is a portal system?
Blood flows through 2 consecutive capillary networks before returning to the heart. Found in places like the intestines, liver, kidneys, hypothalamus/pituitary (hypophyseal portal)
What is an anastomoses?
System of blood vessels that allows blood to take alternate routes. Merging of multiple paths from artery to capillary; examples include the circle of willis and vasculature of the cardiac muscle
