Flashcards in Cardiovascular System Deck (39):
Which two 'loops' of the circulatory system exist?
What is meant by a closed cardiovascular system?
Blood never leaves vessels
The average adult has how much how much circulating blood? What does this consist of?
3 litres of plasma
2 litres of red blood cells
Where does most of our blood lie in our blood vessels at any one time?
In peripheral veins (65%)
What is the valve between the right atrium and right ventricle called?
What is the valve between the left atrium and left ventricle called? How many cusps does this have?
What is the valve between the pulmonary artery and the right ventricle called?
What is the valve between the aorta and left ventricle called?
Why are the structures of the right side of the heart generally more fragile?
Deals with blood which is at lower pressures
What are the two main arteries supplying the heart? Where do they stem from?
Left and right coronary arteries
Stem from the aorta
What are end arteries? What occurs in blockage of end arteries?
Terminal artery supplying all or most of the blood to a part of the body
So blockage ---> insufficient blood supply to tissue
Give two examples of end arteries? What is the only example of an absolute end artery in the body?
Central artery to the retina
What is stenosis?
Narrowing of an artery
What is meant by collateral circulation?
More than 1 artery supplies blood to a particular part of the body
What happens at the SA node?
Wave of excitation results in atrial systole
What happens at the AV node?
Wave of excitation down the left and right bundle branches to the Purkinje fibres ----> ventricular systole
Why is the wave of excitation paused at the AV node?
To avoid simultaneous contraction, allows all the blood to enter the ventricle
The elasticity of arteries allows them to respond to changes in blood _____ to keep blood flowing
What is the systolic pressure?
Typically 120mmHg - the blood pressure in the aorta during systole
What is the diastolic pressure?
What are the 3 layers present in the walls of most blood vessels?
Tunica Intima - endothelium next to lumen
What is the difference between the tunic media found in arteries and veins?
Much thicker in arteries
What is an aneurysm?
Dilation of a blood vessel
What is the tunica adventitia?
A thin layer of fibroelastic connective tissue on the outer layer of blood vessels
What is the thickness of the tunic media in arteries? How are the smooth muscle cells in this layer connected?
40 layers of smooth muscle
By gap junctions
What are arterioles? What is the structure of its tunica media?
Arteries with a diameter of less than 0.1mm
Only 1-3 layers of smooth muscle in the tunica media
What is the wall structure of capillaries?
A single layer of endothelium and a basement membrane
Is there a high or low blood velocity through capillaries? Why?
Low - around 0.3 mm/s
Allows gas/nutrient exchange to take place
Where are pericytes found?
In capillaries and venules - form a branching network on outer surface of endothelium
What is the structure of the wall of postcapillary venules?
Same as capillaries (endothelium + pericytes)
What is the wall structure of venules?
Endothelium + pericytes OR thin smooth muscle cells
What do veins and venules contain to prevent the back flow of blood?
What is the largest diameter blood vessel?
What is the structure of the wall of a vein?
More connective tissue
Less muscle fibres
Tunica media = 2-3 smooth muscle cell layers
What is the meaning of capacitance vessels?
Can stretch to hold more blood (or recoil to hold less) with no pressure changes
Blood flows in which order through vessels starting with muscular arteries?
Post capillary venules
How does blood flow in veins? (2)
With the help of contraction of skeletal muscle
Thoracic pump when breathing
What is the major vein of the heart?