Blood Vessels Flashcards
What are the 3 different layers of tissues within blood vessels?
Tunica Adventitia: (outer layer of fibrous tissue)
Tunica Media: (middle layer of smooth muscle and elastic tissue)
Tunica intima: (inner lining of squamous epithelium aka endothelium)
Which vessels contain more elastic tissue and less smooth muscle?
Aorta and large arteries (otherwise known as elastic arteries)
Systemic blood pressure can be described as being mainly determined by what?
Resistance vessels.
What are anastomoses?
Arteries that form a link between main arteries supplying an area. e.g to palms of the hand.
If there is arterial occlusion (blockage) what is the response?
Anastomotic arteries provide collateral circulation. This is more likely to happen if the occlusion occurs gradually, as anastomotic arteries need time to dilate.
What is an end artery?
An artery which is the sole source of blood to a tissue.
If an end artery is blocked, the tissues it supplies will die.
What is the width of a capillary?
Roughly the same as that of an erythrocyte, about 7 nanometers.
What is a capillary bed?
The site of exchange between substances in the blood and tissue fluid. It bathes almost all body cells except skin surface cells and in the cornea of the eye.
What guards capillary beds?
Rings of smooth muscle called pre-capillary sphincters (which direct blood flow). They dilate in hypoxic conditions or high levels of tissue waste in order to increase blood flow to an area.
What are sinusoids?
Wider and more leaky than average capillaries found in the liver and bone marrow. The walls are incomplete and lumen is much larger.
Why do we need sinusoids?
The larger lumen and incomplete walls allow reduced pressure of blood, so cells come directly into contact with the sinusoid wall. This allows faster exchange of substances between blood and tissues.
What is another name for a vein?
Capacitance vessels, because they have the capacity to hold a large proportion of the body’s blood.
The outer layers of tissue of thick walled blood vessels receive their blood supply via what network?
A system of blood vessels called the vasa vasorum.
What is peripheral resistance?
The way in which the diameter of the blood vessels determines blood flow/pressure.
What factors contribute to blood flow?
Length of vessels, viscosity and peripheral resistance (diameter)
How is blood vessel diameter regulated?
By the smooth muscle of the tunica media.
What connection do most blood vessels lack?
There is no parasympathetic nerve supply to most blood vessels.
What is autoregulation?
The ability of an organ to control it’s own blood flow
What is the role of nitric oxide?
It is an important short-term vasodilator.
Name the different methods in which blood transports CO2 to the lungs.
7% dissolved in water of blood plasma.
70 % in chemical combination with sodium
23% combination with haemoglobin.
What is hydro-static pressure and osmotic pressure?
Hydro-static is pressure that pushes fluid out of the bloodstream.
Osmotic pulls fluid back into the bloodstream (mainly due to albumin)
What is normal hydrostatic and osmotic pressure at the arterial end?
hydrostatic: 5kPA or 35mmHg
osmotic: 3kPa or 25mmHg
What is the normal hydrostatic and osmotic pressure at the venous end?
hydrostatic: 2kPa or 15mmHg
Osmotic: 3kPa or 25mmHg (unchanged)
