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William harvey, Parts of Heart, Blood vessels, Control of heart rate,…
William harvey
the heart has a double pump - left and right side. The left side has oxygenated blood and pumps blood via the aorta whereas the right side is deoxygenated blood that goes to the lungs via pulmonary veins
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discovery on the circulation of blood after the discovery of Galen in the 17th century who thought blood was produced in the liver and then pumped out of heart.
William harvey opposed Galen's theories and refined them and published his results all the way in Europe and thus as a result his findings are widely accepted.
William discovered the blood flow throughvessels is unidirectional and thus valves are needed to avoid backflow of the blood.
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He showed that blood passes through arteries to the body and returns using a veins.He also predicted that veins and arteries are connected by smaller vessels but due to the absence of microscope his theory was not proven until in 1660 when a microscope proved his predicition
Harvey discovered double circulation in humans -
- Pulmonary circulation(lungs to heart)
- Systematic circulation (heart to body)
Parts of Heart
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Two valves also separate the ventricles from the large blood vessels that carry blood leaving the heart:
The pulmonic valve is between the right ventricle
and the pulmonary artery, which carries blood to the lungs.
The aortic valve is between the left ventricle and the aorta, which carries blood to the body.
It is also made up of four valves: the tricuspid, pulmonary, mitral and aortic valves.
The right atrium receives non-oxygenated blood from the body’s largest veins — superior vena cava and inferior vena cava — and pumps it through the tricuspid valve to the right ventricle.
CARDIAC MUSCLES
Cardiac muscles contract on their own without being stimulated by a nerve(myogenic contraction). There are many capillaries in muscular wall of heart where the blood is supplied through coronary arteries from aorta near to semilunar valve. it brings oxygen for cell respiration for muscle contraction. Valves prevent backflow of blood. atria are collecting chambers while ventricle are pumping chambers.
The right ventricle pumps the blood through the pulmonary valve to the lungs, where it becomes oxygenated.
The left atrium receives oxygenated blood from the lungs and pumps it through the mitral valve to the left ventricle.
The left ventricle pumps oxygen-rich blood through the aortic valve to the aorta and the rest of the body.
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Blood vessels
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The thick smooth muscle layer in the arteries can be used to help regulate blood pressure by changing the diameter of the arteries.
Elastin fibres store energy when they are stretched by the flow of blood. As they recoil the blood is further propelled through the artery
The function of arteries is to convey blood at high pressure from the heart ventricles to the tissues of the body and lungs. Because large volumes of blood are flowing directly out of the heart, arteries must be able to withstand the high pressure and high blood volume created when the ventricles contract.
They have a narrow lumen (relative to wall thickness) to maintain a high blood pressure (~ 80 – 120 mmHg)
They have a thick wall containing an outer layer of collagen to prevent the artery from rupturing under the high pressure
Very thick wall of smooth muscle tissue surrounding arteries makes them strong
and elastic in nature with a narrow lumen (area where the blood flows).
Veins :
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Very low blood pressure and therefore the walls can be thin.. As the muscles contract, the veins are squeezed, pushing the blood back towards the heart
Large lumen allows large amounts of blood to slowly return
to the heart because the blood has to slow down as it passes through the capillary beds.
Valves are flaps of tissue that form pockets to prevent blood from flowing backwards in the wrong direction
If the blood starts to flow backwards, it gets caught in the pocket valves causing that section of the vein to fill.
The walls have pores, making them very permeable allowing plasma to leak out and form tissue fluid, which contains
oxygen, glucose and all other substances contained
in the blood plasma, except proteins (too large to fit through the pores in the capillary wall)
Highly branched networks of capillaries increase the surface area, maximizing the amount of nutrients and gases that can move in and out of the capillaries.
Because they are highly branched, the blood slows down to allow efficient
transfer of O2 and CO2 into and out of the capillaries.
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Capillaries : carry blood through tissues.They have very thin permeable walls which leads to easier diffusion of substances between tissue cells and blood in capillary
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Control of heart rate
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Sinoatrial node sends out electrical signal that causes contraction as its propagated first through atria and then through ventricle.
messages can be carried to SA node through hormones and nerves. Impulse from the brain given out by two nerves to sinoatrial ; one nerve for increasing the pace , other for decreasing.
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CARDIAC CYCLE
As blood exits the ventricle and travels down the aorta, ventricular pressure falls
When ventricular pressure drops below aortic pressure,
the aortic valve closes to prevent back flow (second heart sound)
When the ventricular pressure drops below the atrial pressure,
the AV valve opens and blood can flow from atria to ventricle
Throughout the cycle, aortic pressure remains quite high as
muscle and elastic fibres in the artery wall maintain blood pressure
As ventricles contract, ventricular pressure exceeds 'atrial pressure and AV valves close to prevent back flow (first heart sound)
With both sets of heart valves closed, pressure
rapidly builds in the contracting ventricles (isovolumetric contraction)
When ventricular pressure exceeds blood pressure
in the aorta, the aortic valve opens and blood is released into the aorta
The beating of heart consists of a cycle of actions -
The walls of atria contract , pushing blood from atria to ventricles trhough the atrio ventricular valves which open and thus ventricles fill with blood.
Coronary heart disease
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this causes blow flow to be restricted and thus leads to chest pain . minerals make it often rough and hard.
Casues of it : high blood cholestrol level 2. smoking 3. high blood pressure 4. high blood sugar 5. genetic factors
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