biology the heart and immunity

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  • Created by: julie
  • Created on: 28-12-13 17:42

Mass flow is the bulk movement of substances from one area to another due to differences in pressure. The differences in pressure depend mainly on the pumping action of the heart. 

Blood goes from a high to a low pressure. However the heart produces the main pressure gradient. Contractions of skeketal muscles also squeeze the blood along the veins and when we breathe in the pressure inside the thoracic cavity is reduced and helps to draw blood back to the heart. Valves in the heart and veins prevent backflow to ensure blood flows in one direction only. 

The hearts pumping action ensures fresh supplies of oxygen and nutrients are continuously delivered to all the luving cells of the body. The heart is covered in a double layer of tough elastic membranes whuch form the pericardium. The pericardium fluid is secreted between the membranes. Thus allows them to move easily over each other. The pericardium protects the heart from over expansion. Caused by elastic recoil when its beating very fast. The walls of the heart consist mainly of cardiac muscle, this is a special type of muscle found only in the heart. Unlike any other muscle it will never fatigue. However it doesnt tolerate a lack of blood due to a lack of nutrients or oxygen (it would soon die) the septum becomes rigid just before the heart contracts so that it functions as a fulcrum for the action of the heart muscle.


Tricuspid valve between ra and rv has 3 flaps. The bicuspid valve has 2.

The tendinous chords on the papillary muscles prevent valves turning insude out. They increase the tension so valves can resist powerful back pressure of blood.  

The rythm is made faster or slowerby nervous impulses and hormones. 

The pace maker deterermines the rate of contraction of the…


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