The Heart - Internal Structure
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The Heart - External Structure
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Simple Heart Functions
The right side of the heart pumps
... [Show More] deoxygenated blood to the lungs and the left side pumps oxygenated blood to the rest of the body
The Valves
The atrioventricular valves link the atria to the ventricles, and the semi - lunar valves link the ventricles to the pulmonary artery and aorta. They all stop blood flowing the wrong way.
How the Valves Work
1) The valves only open one way, whether they're open or closed depends on relative pressure of the heart chambers
2) If theres higher pressure behind a valve, its forced open
3) If theres higher pressure in front of a valve, its forced shut
The Cardiac Cycle
- The cardiac cycle is an ongoing process of contraction and relaxation of the atria and ventricles that keeps blood continuously circulating around the body.
- The volumes of the atria and ventricles change as they contract and relax, altering pressure in each chamber. - This causes valves to open and close, which directs the blood flow through the heart
The Cardiac Cycle - Ventricles Relax and Atria Contract
Stage 1
- The ventricles are relaxed
- The atria contract, which decreases their volume and increases their pressure
- This pushes the blood into the ventricles through the atrioventricular valves
- Theres a slight increase in ventricular pressure and volume as the ventricles receive the ejected blood from the contracting atria
The Cardiac Cycle - Ventricles Contract and Atria Relax
Stage 2
- The atria relax
- The ventricles contract (decreasing their volume), increasing their pressure
- The pressure becomes higher in the ventricles than the atria, which forces the atrioventricular valves shut to prevent back flow
- The high pressure in the ventricles opens the semi lunar valves so blood is forced out into the pulmonary artery and aorta
The Cardiac Cycle - Ventricles Relax and Atria Relax
Stage 3
- The ventricles and the atria both relax
- The higher pressure in the pulmonary artery and aorta causes the semi - lunar valves to close, preventing back flow
- The atria fill with blood (increasing their pressure) due to this higher pressure the vena cava and pulmonary vein
- As the ventricles continue to relax, their pressure falls below the pressure of the atria
- This causes the atrioventricular valves to open and blood flows passively (without being pushed by arterial contraction) into ventricles from the atria
- The atria contract, and the whole process begins again
Cause of the 'lub-dub' Sound
- The first 'lub' sound is caused by the atrioventricular valves closing (stage 2)
- The second 'dub' sound is caused by the semi-lunar valves closing (stage 3)
Heart Dissection - Equipment
- Pig or cow heart
- Dissecting Tray
- Scalpel
- Apron
- Lab Gloves [Show Less]