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The cardiovascular system 2
The most important arteries are:
1, The aorta (Fig. 21): It is the largest artery in the body. It carries the pure oxygenated blood from the left ventricle to all parts of the body.
It is described as consisting of 3 parts:
a)Ascending aorta: from its origin from the left ventricle, it
ascends upwards, forwards and to the right.
b) Arch of aorta: it arches backwards and to the left to reach the vertebral column at the lower border of the fourth thoracic vertebra.
c) Descending aorta: which descends in the thorax behind the pericardium and diaphragm to pass from the thorax to the abdomen.
2. The pulmonary trunk: carries the deoxygenated blood from the right ventricle to the lungs. It divides under the arch of the aorta into right and left pulmonary arteries which pass to the right and left lungs respectively.
3. The coronary arteries: these are the right and left coronary arteries. They arise from the ascending aorta just after its commencement. In general, each artery supplies the atrium and ventricle of its corresponding side.
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The most important veins are:
1. The superior Vena Cava: it carries the impure deoxygenated blood from the upper limbs, the head and neck, and the brain to the right atrium.
2. The inferior Vena Cava: it carries the impure
deoxygenated blood from the lover limbs, pelvis, and trunk to right atrium.
3. The four pulmonary Veins: They are two form each lung. They carry the oxygenated blood from the lungs to the left atrium.
4. The portal vein (Fig. 22): The porta! %ein carries the blood from the alimentary canal and the spleen to the liver. It is formed by the union of the superior mesenteric vein and the splenic vein behind the neck of -37pancreas then it runs superiorly to reach the liver where it divides into two branches, right and left. Each branch -enters the corresponding lobe of the liver. The most important of its tributaries beside the two veins forming it are the inferior mesenteric vein and the gastric veins.
The blood circulation:
In the human body, the circulation of blood consists of 3 parts; the systemic circulation, the pulmonary circulation and the portal circulation.
a) The pulmonary circulation:
Through the pulmonary circulation the blood is purified (oxygenated) in the lungs.
When the right ventricle contracts, the blood is pumped to both lungs through the pulmonary trunk and pulmonary arteries.
In the lungs, purification of blood through gas exchange occurs.
The blood then returns from the lugs to the left atrium by the 4 pulmonary veins.
b) The systemic circulation:
Trough the systemic circulation, all parts of the body are supplied with pure oxygenated blood and nutrients.
When the left velltricle contracts the blood is pumped to all parts of the body through the aorta.
In the tissues of the body, exchange of gas and nutrients takes place.
The impure deoxygenated blood returns from the body tissues to the right atrium along the superior and inferior venae cavae.
c) The portal circulation (Fig. 22):
Through the portal circulation, the nutrient materials absorbed in the intestine are metabolized in the liver.
This circulation includes the outflow of pure blood from the left ventricle through the aorta to reach the stomach, intestine, pancreas and spleen.
Then the impure blood loaded with nutrients is collected from these viscera by the tributaries of the portal vein to enter the liver along its two branches.
Then the blood flows out from the liver through the two hepatic veins (right and left) to the inferior vena cava and from there to the right atrium.
The places where you can feel the pulse:
- The lower part of the radial artery.
- The brachial artery in front of the cubital fossa.
- The dorsalis pedis artery in the foot (in the interval between the metatarsals of the first and second toes.
- At the apex beat (in the interval between left 5th and 6th ribs just below and medial to the left nipple)
- The superficial temporal artery in front of the tragus of the external ear.
