WEEK 3: Structure & Function of Blood Vessels Flashcards
How much blood do we have in a human body?
5 Litres- 7-8% of the body weight of a normal healthy person
What is the order of systemic circulation
Aorta -> Muscular arteries -> Small arteries -> Arterioles 1st- 4th order -> Capillaries -> Venules 4th-1st order -> Small veins -> Larger veins -> Inferior Vena Cava
What is the innermost layer of a blood vessel called?
Tunica Intima
- Composed of the endothelium
-Is in direct contact with the blood
What is the purpose of the endothelium?
It is a single layer of squamous epithelial cells that reduce friction and facilitate smooth blood flow
What is the middle layer of blood vessel called?
Tunica media
What is the function of the tunica media
it is made of smooth muscle cells and elastic fibres that allow vasoconstriction and vasodilation
what is the outer layer of blood vessels called?
tunica adventitia - made of connective tissue collagen fibres - providing strength and preventing over-expansion by controlling diameter
From which direction does blood flow?
From large vessels like the aorta and large arteries into smaller vessels (like capillaries) and back to larger vessels
Why does blood flow
Because the human body has areas of high pressure and blood travels from these areas into areas of low pressure (eg. pressure in the aorta is much higher than the pressure in capillaries, venules and veins)
Arteries direct blood towards the heart: T or F?
F
What is the purpose of capillaries
Places of exchange: exchange of gases, nutrients and waste between blood and tissues
Veins direct blood to the heart: T or F?
T
delta P is known as?
pressure difference.
What is driving pressure?
pressure diff between two points in a blood vessel that drives blood flow
blood flows from high to low pressure because of this gradient
eg. aorta pushes blood to veins
What is transmural pressure?
difference between pressure inside a blood vessel and pressure outside it (pressure gradient across a vessel wall). the stiffer the wall is- the higher the transmural pressure
What is hydrostatic pressure?
pressure exerted by weight/density of blood due to gravity
What are the two types of large arteries?
Elastic (more elastic fibres) - aorta, pulmonary arteries
Muscular (More smooth muscle) - femoral artery, radial & brachial arteries
T or F: Blood flow is constant, it never stops.
T
What is the windkessel effect?
during systole, the aorta expands and stores some ejected blood which is released during diastole when no blood is ejected from the heart
What are arterioles
Small blood vessels with 1-4 layers of smooth muscle
They can change the diameter and increase resistance to blood flow- hence it has the ability to regulate blood flow
How is velocity affected during blood flow?
Velocity remains high in arteries and aorta, and decreases its level at arterioles (higher resistance in arterioles)
equation to calculate blood flow?
F (blood flow) = delta P (pressure difference) / R (resistance)
What are different types of capillaries?
- Brain capillary (continuous capillary)
-Kidney capillary (fenestrated capillary)
-Liver capillary (sinusoidal capillary)
What are the different types of venules?
HEV
Normal venule
What is a venule
The smallest type of vein -> collects blood from capillaries and transports it into veins
Why do veins have valves?
valves prevent backflow of blood and ensure a one-way flow toward the heart
what are lymphatic vessels?
thin walled tubes that transport lymphs, a clear fluid containing immune cells, proteins and waste from tissues back into the bloodstream. they also contain valves to limit backflow.
