7th Class Science Transportation in Animals and Plants Transport System in Human Being

       Transport System in Human Being

Human body also need a transport system as varieties of substances like oxygen, carbon dioxide, water, food, hormones, enzymes, etc. are needed to be transported form one part to another. In human being, the work of transportation is carried out by circulatory system. Circulatory system is made up of blood vessels and a heart.

Blood vessels are the tubular path through which blood keeps on circulating. There are three types of blood vessels, that is, arteries, veins, and capillaries. Together they form a net of blood vessels, which reaches every part of the body, making the blood to reach every parts. Blood, for reaching from heart to other parts of the body and for returning into heart from other parts of the body, use two different vessels system. The blood vessels called arteries are used by the blood to reach from heart to other parts of body .And the vessels called veins are used by the blood for coming back into heart from other parts of the body. Capillaries connect the arteries with veins. Thus blood vessels, by connecting with each other, form a tubular pathway through which blood could circulate throughout the body and can perform its functions. Blood rich in oxygen is called oxygenated blood and the blood rich in carbon dioxide is called deoxygenated blood. Arteries carry oxygenated blood and veins carry deoxygenated blood.

But one artery named pulmonary artery carries deoxygenated blood from heart to the lung and one vein name pulmonary vein carries oxygenated blood from lung to the heart.heart.

         Blood

Vessels of the circulatory system are filled with a red colored fluid called blood. Blood inside the blood vessels keeps on circulating as a transport vehicle. It receives the substances from one part of the body and carries them to the required part of the body.

Blood are made up of four components plasma, RBC (Red blood corpuscles), WBC (White blood corpuscles), and platelets. RBC contains hemoglobin, which gives red colour to blood.

         Functions of Blood

Blood performs the following functions:

(i) Blood supply all the required substances to the cells.

(ii) Blood carry the waste products out of body.

(iii) Blood maintain the body temperature at 37°c.

(iv) Blood contain the WBC, which is called the soldier of the body. WBC protects us from pathogens.

         Heart

Blood keeps on moving continuously throughout the body in order to perform its functions. For the movement of blood a force is required. Therefore, human body has developed an organ, i.e. heart, specialized for producing force necessary for the movement of the blood. When heart expands, its internal volume is increased and larger amount of blood enters into it. When heart shrinks, the internal volume is decreased and blood is expelled out of it. Hence a motion is produced in the blood, which help the blood to circulate.

Look at the following picture of heart

       Which one of the following organs produces movement in the blood?

(a) Brain

(b) Lung

(c) Kidney

(d) Heart

(e) None of these

Answer: (d)

       Water is a colorless liquid, which contributes more than 90% of plasma, a liquid part of blood. However blood appears red. Which one of the following pigments should be removed from the blood to give it colorless appearance?

(a) WBC

(b) RBC

(c) Blood plasma

(d) Platelets

(e) None of these

Answer: (b)