the cardio vascular system

8/3/2019 the cardio vascular system

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Describe the structure and function of the cardiovascular system

The cardiovascular system includes the heart and the blood vessels. The heartpumps blood and the blood vessels channel and deliver it throughout the body.Arteries carry blood filled with nutrients away from the heart to all parts of thebody. The blood is sometimes compared to a river, but the arteries are more like ariver in reverse. Arteries are thick-walled tubes with a circular covering of yellow,elastic fibres, which contain a filling of muscle that absorbs the high pressure waveof a heartbeat and slows the blood down. This pressure can be felt in the arm andwrist - it is the pulse. Eventually arteries divide into smaller arterioles and then intoeven smaller capillaries, the smallest of all blood vessels. One arteriole can serve ahundred capillaries. Here, in every tissue of every organ, blood's work is done whenit gives up what the cells need and takes away the waste products that they don'tneed. Now the river comparison really does apply. Capillaries join together to formsmall veins, which flow into larger main veins, and these deliver deoxygenatedblood back to the heart. Veins, unlike arteries, have thin, slack walls, because theblood has lost the pressure which forced it out of the heart, so the dark, reddish-

blue blood which flows through the veins on its way to the lungs oozes along veryslowly on its way to be reoxygenated. Back at the heart, the veins enter a specialvessel, called the pulmonary arteries, into the wall at right side of the heart. Itflows along the pulmonary arteries to the lungs to collect oxygen, and then back tothe heart's left side to begin its journey around the body again.

Structure

This is a picture of the cardio vascular system


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Blood vessels

There are 3 main types of blood vessels

y Arteriesy Veinsy Capillaries

Arteries

Arteries are blood vessels that carry blood away from the heart. The largest artery

in the human body is the aorta, the arteries carry and release blood to all of the

body, if we didnt have the arteries then the body would not be able to function as

every area needs oxygen. The aorta supplies all the other arteries with rich bloodwhich is full of oxygen; this is the supply to all the arteries so they can do their job.

Veins

The veins arte the blood vessels that carry blood from the parts of the body towards

the heart, veins receive blood from the arteries through the arterioles and

capillaries. There are 4 types of veins, pulmonary, systemic, superficial and deep

vein. Smaller veins called venules receives deoxygenated blood and delivers it to

larger veins, at the end all of it ends up at the vena cava which supplies the bloodto the right atrium and then the cardiovascular process starts again


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Capillaries

Capillaries are the smallest type of blood vessel, they are only one cell thick and

are the link from the veins to the arteries in the cardiovascular system.however,

unlike veins and arteries, their main function is not transporting blood. They are

specially designed to allow the movement of substances, mainly gases Oxygen andCarbon Dioxide into and out of the capillary.

The Heart

The heart is the core engine of the human body, without the heart, we simply

would die. It is categorised as cardiac muscle because its a muscle type on its

own, no other muscle in the human body is like it. It is also the primary organwithin the cardiovascular system, hence the system being named after the muscle.

The average human heart, beating at 72 beats per minute, will beat approximately

2.5 billion times during an average 66 year lifespan. It weighs approximately 250

to 300 grams in females and 300 to 350 grams in males, (www.wikipedia.org).

The function of the heart is to pump blood around the body. The heart is a hollow,

muscular organ divided by a vertical wall called the septum. These two chambers

are further divided into the thin walled atrium above, and a thick walled ventricle

below, making four chambers. Between each pair of chambers are valvespreventing any back flow of blood. Blood vessels leaving the heart generally carry

oxygenated blood through vessels known as arteries. These are large, hollow

elastic tubes with thick muscular walls that are designed to withstand the high

pressure with the blood leaving the heart. Their size gradually diminishes as they

spread throughout the body, ultimately reaching fine, hair-like vessels known as

capillaries. Blood vessels that return blood to the heart are known as veins which


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generally carry de-oxygenated blood to the heart. They are elastic tubes containing

valves to help prevent back flow of blood. Blood is forced through arteries by the

pressure from the heart whereas venous flow is aided by muscular contraction. The

pulmonary artery, which carries de-oxygenated blood from the heart to the lungs,

and the pulmonary vein, which carries oxygenated blood from the lungs to the

heart. The circulation is divided into two principle systems known as the general or

systemic circulation, which is the circulation around the body, and the pulmonary

circulation to and from the lungs

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the cardio vascular system