Download Heart and Blood Vessels

Heart and Blood Vessels
Open and closed blood systems
Open Circulatory System:
Blood flows into open ended vessels
Blood leaves these vessels and around the cells
Not very efficient at getting blood quickly to parts of body it’s needed
Examples of organisms that have an open system = insects, spiders, snails
Closed Circulatory System:Blood remains in a continuous system of blood vessels
Much more efficient than open system
Allows for a much faster metabolism
Allows for blood flow to be increased to certain organs
Example = Human
Blood Vessels
Arteries + Veins + Capillaries
Artery
 Carries blood to heart
 Usually carries blood rich in oxygen (Excretion = Pulmonary artery)
 Outer layer = Collagen. An inelastic Protein that prevents walls from
over expanding
 Middle layer = Thick layer of Muscle and Elastic fibres. Has ability to
expand and relax
 Inner layer = Endothelium. Lining of Artery
Vein
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Carries blood to the heart
Usually carries blood low in oxygen (Exception = Pulmonary Vein)
Outer layer = Collagen. An inelastic Protein that prevents walls from
over expanding
Middle layer = Thin layer of Muscle and Elastic fibres. Has ability to
expand and relax
Inner layer = Endothelium. Lining of Vein
Veins have valves = to prevent backflow of blood
Capillary
 One Cell thick = Endothelium
 Allows for materials to easily pass in and out of capillary
Venule and Arteriole
 Venule = smaller branched veins
 Arteriole = smaller branched arteries
The Heart.
Structure….
 4 Chambers
Right atrium
Right Ventricle
Left Atrium
Left Ventricle
Septum
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Dividing Wall =
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Major Vessels =
Vena Cava – Carries blood lacking in oxygen into the heart
Pulmonary Artery – Carries blood to the lungs
Pulmonary Vein – Carries blood back from lungs to heart
Aorta – Carries blood rich in oxygen out of heart
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Valves =
Tricuspid Valve = Between RA and RV
Bicuspid Valve = Between LA and LV
Semilunar Valves = prevents backflow of blood into the RV and LV
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Pacemaker =
Controls heartbeat
LHS of heart thicker than RHS. This is because the LHS of heart has to pump blood strong enough to
travel all round the body
How blood flows around the heart….
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Blood lacking in oxygen enters the heart via the vena cava.
It flows into the right atrium
Walls of the right atrium contract and blood is forced through the tricuspid valve into the right ventricle
Walls of the right ventricle contracts, the tricuspid valves shut and blood if forced up through the
semilunar valves through the pulmonary artery to the lungs.
At the lungs it picks up oxygen
It returns to the heart via the pulmonary vein and fills into the left atrium.
Walls of the left atrium contract and blood is forced through the bicuspid valve into the left ventricle.
Walls of the left ventricle contracts, the bicuspid valves shut and blood if forced up through the semilunar
valves through the Aorta and all around the body.
Control of heartbeat
Pacemaker (SA Node) in the wall of the top of the right atrium.
Pacemaker sends out regular electrical impulses which cause the atria to contract
The impulse from the Pacemaker stimulates the AV node further down in the right atrium (septum)
to send an impulse via special fibres
This impulse causes the ventricles to contract
Blood supply to heart….
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Just like every other muscle in the body the heart muscle needs a supply of blood (with its food and
oxygen and to remove waste)
This blood if supplied to heart via the Coronary Artery
Blockage of Coronary Artery = cause of heart attack
Stages of a Heartbeat
Key words
Systole = contracting
Diastole = relaxing
1. Blood enters the heart
All valves closed
All chambers in diastole
Blood enters the atria
2. Blood goes from Atria to Ventricles
Pacemaker sends impulse to atria
Atria contract – Systole
Tri and bicuspid valves open
Blood pumps into ventricles
Pulmonary vein & vena cava close
3. Blood leaves the heart
Impulse from AV node causes Ventricles to contract – systole
Blood is forced out of the heart & to pulmonary artery and aorta
Semi lunar valves open and bi and tricuspid valves close
Ventricles then relax again.
Cycle begins again
Dietary factors
1. Saturated Fats – block arteries
2. Salt – raised blood pressure
3. Overweight – raises blood pressure, causes heart attack