Blood Vessels and Circulation Flashcards
Arteries
Carry blood away from the heart. They do not have valves. The inner layer consists of perforated sheets of elastic tissue, alternating with thin layers of smooth muscle, collagen, and elastic fibers. They expand during systole, recoil during diastole. They lessen the fluctuation of blood pressure
Veins
Carry blood too heart. They have valves and sinuses. They have low blood pressure with little fluctuation. They have thinner walls, less muscular and elastic tissue, expand easily. Since veins are elastic, blood pools in them easily. We have to move to keep our blood moving.
Capillaries
Where delivery of nutrients or oxygen happens
What are the largest arteries?
Conducting (elastic) arteries
Conducting (elastic) arteries
The inner layer consists of perforated sheets of elastic tissue, alternating with thin layers of smooth muscle, collagen, and elastic fibers. They expand during systole, recoil during diastole. They lessen the fluctuation of blood pressure
Resistance (small) arteries / Arterioles?
Arterioles control amount of blood to various organs
Metarterioles
Short vessels that connect arterioles to capillarties. Muscle cells form a precapillary sphincter about entrance to capillary.
Throughfare channel
Metarteriole continues through capillary bed to venule.
Precapillary sphincters
Muscles that control which beds are well perfused (that get the blood). Only 25% of capillaries are open at a given time
Venules
Proximal venule is quite porous, exchanges fluid with tissues, like a capillary, at this point only.
Venous sinuses
Veins with thin walls, large lumens, no smooth muscle
Where is blood pressure measured?
The brachial artery of the arm
What is the normal blood pressure for a young adult?
120/80
Mean arterial pressure
The average between the two BP numbers (120/80)
Pulse pressure
Difference between the two BP numbers (120/80)
Hypertension
140/90. Can weaken small arteries and cause aneurysms (when a vessel bulges and can burst).
Hypotension
Abnormally low BP. 90/60
Why is it important that arteries are elastic?
Expansion and recoil maintains steady flow of blood throughout the cardiac cycle, smooths out pressure fluctuation and lowers stress on small arteries.
Why does BP rise with age?
Because the arteries are less distensible (stretchy)
Blood viscosity
It’s determined by the RBC’s and albumin. (the thickness and stickiness of blood. It is a direct measure of the ability of blood to flow through the vessels.)
Vessel radius
It has a very powerful influence over the flow. It is the most adjustable variable, controls resistance quickly. (The vessels can change their size because of the muscles in them)
Vasoconstriction
Shrinks vessels
Vasodilation
Opens the vessels up bigger
Local control of BP
It opens more capillary beds to decrease BP, close more to increase BP
