Session 8: Cardiovascular System Flashcards
What is the function of the CVS?
To circulate and transport nutrients, oxygen, carbon dioxide, hormones and blood cells to and from the cells of the body
What are the three essential components of the CVS?
Heart
Blood
Blood vessels
What is the pulmonary circulation?
The portion of the CVS which carries deoxygenated blood away from the heart, to the lungs, and returns oxygenated blood back to the heart
What is the systemic circulation?
The part of the CVS which carries oxygenated blood away from the heart to the body, and returns deoxygenated blood back to the heart
What is the meaning of a “closed” CVS?
Blood never leaves the network of arteries, veins and capillaries
Red blood cells are also known as what?
Erythrocytes
What is the structure of RBCs?
How is this beneficial?
Concave
It means they can pass through the capillaries and remain largely unharmed
How much circulating blood does an average adult have?
5 litres
Of the 5 litres of circulating blood, how much is RBCs?
2 litres
How much of the 5 litres of circulating blood is plasma?
3 litres
Where does the majority of our blood lie?
In our peripheral veins (65%)
What percentage of our circulating blood is found in our capillaries?
5%
Even though capillaries contain the smallest percentage of circulating blood, what makes them ideal for substance exchange?
Their massive surface area
What are the three layers of the walls of arteries and veins?
Tunica intima (next to the lumen) Tunica media (intermediate) Tunica adventitia (outer layer)
The tunica intima (the inner most layer) of arteries, consists of what three layers?
Endothelium
Subendothelial layer
Thick internal elastic lamina
The tunica media (the intermediate layer) of arteries, consists of what main feature? Which are connected by what?
40 layers of smooth muscle cells
Connected by gap junctions
They also have a prominent external elastic lamina
Why are the smooth muscle cells in the tunica media of arteries connected by gap junctions?
So that they can coordinate their contraction
What is the tunica adventitia (the outer layer) of muscular arteries, made up of?
Thin layer of fibroelastic connective tissue containing vasa vasorum (network of small blood vessels), lymphatic vessels and nerve fibres
What are vasa vasorum?
A network of small blood vessels that supply the walls of large blood vessels
What are arterioles?
Arteries with a diameter of less than 0.1mm
What is the difference in the tunica media of arteries compared to arterioles?
Arteries have 40 layers of smooth muscle in their tunica media, arterioles have 1-3 layers of smooth muscle in their tunica media
The tunica intima of arterioles is made up of what layers?
Endothelial cells
Very thin layer of subendothelial connective tissue
The tunica media of arterioles is made up of what?
A single layer of smooth muscle
The tunica adventita of arterioles is made up of what?
Layers of fibroblasts
What are metarterioles?
What is their function?
A blood vessel that links arterioles and capillaries
Supply blood to the capillary bed
What do metarterioles have instead of a continuous tunica media?
Individual smooth muscle cells that are spaced apart and form individual precapillary sphincters
What is the function of the precapillary sphincters of metarterioles?
To control blood flow through arterioles and metarterioles into the capillary bed
Is it possible to by-pass the capillary bed?
Yes, from metarteriole through a thoroughfare channel to the postcapillary venule
What is the function of the lymphatic capillaries at the capillary bed?
Drain away excess extracellular fluid and return it to the blood
At what junctions do the lymphatic capillaries drain excess extracellular fluid into the blood?
The internal jugular vein (Left lymphatics)
The subclavian vein (Right lymphatics)
What happens when precapillary sphincters are closed?
This is known as what?
The blood flow through capillaries is greatly reduced
Peripheral vasoconstriction
Most arterioles can dilate to ____% - ____% of their resting diameter
60-100%
Most arterioles can maintain up to a ___% constriction for a long time
40%
The ability of arterioles to constrict and dilate allows what?
Blood to be directed to where it may be most needed
During strenuous physical exertion, blood flow to skeletal muscles will be increased or reduced? How?
Increased
Through dilation of arterioles
During strenuous physical exertion, blood flow to the intestines will be reduced or increased? How?
Reduced
Through constriction of arterioles