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Copy of Copy of The circulatory system

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Kandace Woodford

on 1 March 2013

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Transcript of Copy of Copy of The circulatory system

The Pumping Mechanism - The Heart What is the purpose of the heart? The heart is a hollow muscle that pumps blood throughout the blood vessels by repeated, rhythmic contractions. Facts about the Human Heart The human heart pumps around 70 times per minute, every minute of every day until we die!
It must pump fluid through 160 000 km of vessels.
It must pump in two directions at once, without mixing the fluid travelling in the two directions. It must adapt and adjust pumping.
All of this happens under unconscious control! The Mammalian Heart The heart of a mammal is divided into four chambers.
The right atrium
The right ventricle
The left atrium
The left ventricle Blood enters the heart through the atria.
Blood leaves the heart though the ventricles. The Basic Pathway of Blood throughout the Heart Tissues to right heart.
Right heart to lungs to left heart.
Left heart to tissues. Blood Vessels Directly Associated with the Heart Vena Cava
Pulmonary Arteries
Pulmonary Veins
Aorta What is the Vena Cava? The largest vein in the human body.
Collects deoxygenated blood from the body (except the lungs) and carries it to the right atrium.
Has two sections. The Superior Vena Cava collects blood from the upper body The Inferior Vena Cava Collects blood from the lower body Carry deoxygenated blood from the right ventricle to each of the lungs, in order to pick up oxygen (and remove carbon dioxide). Pulmonary Arteries Pulmonary Veins These veins carry oxygenated blood from the lungs to the left atrium. What is the Aorta? •The largest artery in the human body.
•Blood enters the aorta from the left ventricle.
•The aorta branches into smaller arteries that will carry oxygenated blood throughout the entire body. The two atria contract simultaneously and the two ventricles contract simultaneously shortly afterward.
This double pump action forces blood through the cardiac cycle. How does blood flow in the proper direction in the heart? A series of valves - prevent blood from flowing backward in the heart. The Atrioventricular Valves
The Semilunar Valves Where are the Atrioventricular Valves? On both sides of the heart, the atrium and ventricle are separated from one another by a set of valves called the atrioventricular valves.There are two of them. The Bicuspid Valve Located between the left atrium and the left ventricle.
It has two parts called cusps. The Tricuspid Valve Located between the right atrium and the right ventricle.
It has three cusps. What are the Semilunar Valves? These are valves that prevent blood from being sucked back into the heart when the ventricles relax after forcing blood out of the heart
There are two of them. The Pulmonary Semilunar Valve Located between the right ventricle and the pulmonary arteries The Aortic Semilunar Valve Located between the left ventricle and the aorta. What causes the sound of a heartbeat? When you listen to a heartbeat through a stethoscope, the “lub-dup” sound you hear is caused by the opening and closing of the valves of the heart. “Lub” – The softer sound you hear that results from the closing of the atrioventricular valves. “Dup” – The louder sound you hear that results from the closing of the semilunar valves. What causes the heartbeat to happen? Sinoatrial Node (S-A node) - A bundle of specialized muscle tissue located in the wall of the right atrium that stimulates the muscle fibers to contract and relax rhythmically producing a regular heartbeat.
The S-A node is more commonly referred to as the pacemaker.
The S-A node generates an electrical impulse that spreads over the two atria and makes them contract simultaneously. As the atria contract, the impulse reaches another node called the atrioventricular node or A-V node.
The A-V node is located near the atria on the partition between the two ventricles and it transmits the electrical impulse over the wall of the ventricles which in turn causes them to contract. Cardiac output - The amount of blood pumped by the heart.
It is a measure of blood pumped from each ventricle per unit of time.
It is also a measure of the level of oxygen delivery to the body and an indicator of the total level of work that the muscles can perform.
Cardiac output = stroke volume X heart rate (beats/min) Stroke volume is the amount of blood forced out of the heart with each heartbeat.
The average person has a stroke volume of 70 mL and a resting heart rate of 70 beats/min.
This results in a cardiac output of 4900 mL/min A low resting heart rate is considered an indicator of physical fitness because it means that the stroke volume is high.
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