Overview Of The CVS
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Main function of the CVS
Transport from external to internal environment, between cells and materials leaving the body
Arrangement of the CVS
Pulmonary exchange leaves the pulmonary vein into the left atrium then ventricle then pumped out of the aorta into the arterial system. Blood flows through the systemic circulation through the venous system into the right atrium then ventricle out of the pulmonary artery into the pulmonary circulation.
Why are vascular beds arranged in parallel?
So all the beds get the same level of oxygenation and prevents changes in blood flow in one organ affecting flow in other organs.
Systole?
Phase of ventricular contraction and ejection
Diastole?
Phase of ventricular relaxation and filling
Blood pressure entering the heart?
0mmHg. It is said to be atmospheric pressure
Blood pressure out of the heart to the lungs?
25 mmHg
Blood leaving the aorta?
90mHg
Cardiac output?
Volume of blood pumper / min. = 5L/min
What is CO determined by?
Stroke volume (volume ejected per contraction. Heart rate (HR)
Diastole is what % of the cardiac cycle?
60%
Pulse pressure?
Systolic pressure - diastolic pressure
Ambulatory blood pressure equation
SP - DP / 3 + DP
Why does pressure drop as it moves through the system?
There is resistance to the flow
What determines pressure in the arterial system?
Resistance to blood flow and blood volume in the arterial system
Pressure equation (Ohms law)
Flow x resistance
ABP equation
CO x TRP (total peripheral resistance)
How is blood flow altered in arterioles
Vasodilation and vasoconstriction
How are veins suited to their function
Thin walls Carry blood at low pressure Muscle under control of ANS Wide lumen to accommodate large volumes Reservoirs used to adjust ventricular filling
How are arteries suited to their function?
Carry blood at high pressure Thick, muscular walls Elastic layers Relatively small lumen High pressure conduits
How are venues suited to their function?
Low pressure Resemble capillaries Low pressure conduits
How are smaller arteries, arterioles suited to their function?
Carry blood at modest pressure Thick, muscular walls Muscle under influence of local factors and ANS Function to control flow to tissues
How are capillaries suited to their function?
Carry blood at low pressure Single endothelial cell wall Gets blood to the call via diffusion Maximise exchange between blood and tissue
What % of body weight is blood?
Around 7%