The Circulatory System
in anatomy and physiology is the course taken by
the blood through the arteries, capillaries, and veins and back to the heart. In
humans and the higher vertebrates, the heart is made up of four chambers the
right and left auricles, or atria, and the right and left ventricles. The right
side of the heart pumps oxygen-poor blood from the cells of the body back to the
lungs for new oxygen; the left side of the heart receives blood rich in oxygen
from the lungs and pumps it through the arteries to the various parts of the
body. Circulation begins early in fetal life. It is estimated that a given
portion of the blood completes its course of circulation in approximately 30
seconds.
Pulmonary ...
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is oxygenated, that
is, then it is brought back to the heart by the four pulmonary veins, which
enter the left auricle. When this chamber contracts, blood is forced into the
left ventricle and then by ventricular contraction into the aorta. The bicuspid,
or mitral, valve prevents the blood from flowing back into the auricle, and the
semilunar valves at the beginning of the aorta stop it from flowing back into
the ventricle. Similar valves are present in the pulmonary artery.
The aorta divides into a number of main branches, which in turn divide
into smaller ones until the entire body is supplied by an elaborately branching
series of blood vessels. The smallest arteries divide into a fine network of
still more minute vessels, the capillaries, which have extremely thin walls;
thus, the blood is enabled to come into close relation with the fluids and
tissues of the body. In the capillaries, the blood performs three functions then
it releases its oxygen to the tissues, it furnishes ...
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These then break
up into an elaborate capillary network in the heart muscle and valve tissue.
Blood from the coronary capillary circulation enters several small veins, which
then enter directly into the right auricle without first passing into the vena
cava.
The action of the heart consists of successive alternate contraction
and relaxation of the muscular walls of the auricles and ventricles. During the
period of relaxation, the blood flows from the veins into the two auricles,
gradually distending them. At the end of this period, the auricles are
completely dilated then their muscular walls contract, forcing almost the entire
contents through the auriculoventricular openings into ...
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The Circulatory System. (2005, April 23). Retrieved November 28, 2024, from http://www.essayworld.com/essays/The-Circulatory-System/25812
"The Circulatory System." Essayworld.com. Essayworld.com, 23 Apr. 2005. Web. 28 Nov. 2024. <http://www.essayworld.com/essays/The-Circulatory-System/25812>
"The Circulatory System." Essayworld.com. April 23, 2005. Accessed November 28, 2024. http://www.essayworld.com/essays/The-Circulatory-System/25812.
"The Circulatory System." Essayworld.com. April 23, 2005. Accessed November 28, 2024. http://www.essayworld.com/essays/The-Circulatory-System/25812.
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