Blood circulation. Types of blood circulation and vascular system

 

1. The cardiovascular system is the system of blood circulation. By the cardiovascular system we mean the heart, the arteries, the veins and the capillaries of the human body. Blood circulation is divided into 2 types: Large and small circles.

2. The centre of the circulatory system is the heart. The right heart receives blood from the veins and pumps it into the lungs by way of the lesser circulatory system. In the lungs the blood receives oxygen. Then it moves into the left heart. From the left heart the well-oxygenated blood moves into a large artery, the aorta. The blood returns to the heart by means of the veins. The walls of the capillaries are so thin that the dissolved nourishment that has come from the digestive system and the oxygen that has come from the lungs can pass through them into the tissues of the body and so nourish it. The capillaries form a close network all over the body. They gradually join together and get larger, and become veins.

3. Blood vessels that receive blood from the ventricle and lead it away from the heart and towards other organs are arteries. The vessels received this name because the early anatomists assumed that they had been empty in dead persons and had carried air.The artery that takes up the blood from the right ventricle and carries it to the lungs is the pulmonary artery. The pulmonary artery divides in two - one branch leads to the right lung, the other - to the left. The arteries continue to divide and subdivide and form smaller and smaller vessels with thinner and thinner walls. The smallest arteries are the arterioles and these finally divide into capillaries. We name them so because of their fineness, though actually they are much finer than hairs.

4. Gradually the capillaries begin to join into larger vessels. Such larger blood vessels that carry blood to the heart from the organs are the veins. The smallest of these are the venules.

5. The particular vein into which the capillaries and venules of the lungs finally unite is the pulmonary vein. The pulmonary vein carries the freshly oxygenated blood to the left auricle. The pulmonary artery and pulmonary vein make up the pulmonary circulation.

6. The contraction of the left ventricle forces the blood through a one-way valve into the aorta. The aorta is the largest artery in the body. It moves upward at first (the ascending aorta), but then arches over dorsally (the arch of the aorta). In its downward course, the aorta passes through the diaphragm.

7. The blood is a red fluid, which coagulates when escapes from a blood vessel.

 

Examining heart and circulation

 

Look at the lips, tongue and nails for the blue discoloration of cyanosis. Cyanosis may be central or peripheral. Inspect the hands for clubbing. Feel the radial pulse at the wrist and note the rate (for example 70/min) and rhythm (regular or irregular). The pulse may be irregular in force as well as time. Check that the other peripheral pulses are present. (Measure the blood pressure, and assess the jugular venous pressure). Palpate the chest tor the apex heat - the normal position is the fifth left intercostal space, one centimetre medial to the midclavicular line. Feel for any thrills. Heart size may be measured by percussion. Listen for murmurs and other abnormal sounds, for example friction rubs, beginning at the mitral area. Murmurs may he soft or loud. A harsh murmur is loud and rough.

Note the time of any murmur in relation to the cardiac cycle. The most common murmurs are:

• mid-systolic (in the middle of systole)

• pan-systolic (lasting lot the whole of systole)

• early diastolic

• mid-diastolic

• late diastolic (pre-systole)

Continue by listening at the tricuspid, aortic and pulmonary areas.

 

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