The cardiovascular system
It is the transport system of the body by which food, oxygen, water and other essential substances are carried to tissue and its waste products are carried away. It consists of three parts:
- the blood, which is the fluid in which materials are carried to and from tissue;
- the heart
1, which is the driving force which propels blood; - the blood vessels1, the routes by which the blood travels to, through and from tissue back to the heart. Blood is a connective tissue because nearly half of it is made of cells which move freely in the liquid portion of the blood, known as plasma.
The heart is a muscular pump that drives the blood through the blood vessels. A little bigger than a fist, it is a hollow organ.
The blood vessels can be classified into three groups: arteries, which carry blood from the ventricles (pumping chambers of the heart) to the capillaries in organs and tissue; veins, which drain capillaries in the tissues and organs and return the blood to the heart; capillaries which allow exchanges between the blood and body cells and between the blood and air in lung tissue.
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1 A heart to heart conversation between two people, usually dose friends, is a conversation in which they talk honestly about their feelings.
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1 Find two more meanings of the word vessel.
The respiratory system
The fundamental function of the respiratory system is to provide oxygen, which is needed to obtain energy from food, to the individual tissue cells and to remove carbon dioxide. The respiratory system is an intricate arrangement of spaces and passageways that conduct air into the lungs. These spaces include the nasal cavity, the pharynx, the larynx, the trachea and the lungs with their tubes and sacs.
Ventilation is the movement of air into and out of the lungs, as in breathing. There are two phases of ventilation:
- inhalation, the drawing of air into the lungs;
- exhalation, the expulsion of air from the lungs.
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How much does a heart normally weigh? - About ...... grams.
a. 200 b. 250 c. 300