Archive for the ‘10th Science’ category

Biology X | LIFE PROCESSES | Transportation in Human Beings

June 23rd, 2010

Transportation in Human Beings

Activity 6.7

  1. Visit a health centre in your locality and find out what is the normal range of haemoglobin content in human beings.
  2. Is it the same for children and adults?
  3. Is there any difference in the haemoglobin levels for men and women?
  4. Visit a veterinary clinic in your locality. Find out what is the normal range of haemoglobin content in an animal like the buffalo or cow.
  5. Is this content different in calves, male and female animals?
  6. Compare the difference seen in male and female human beings and animals.
  7. How would the difference, if any, be explained?

We have seen in previous sections that blood transports food, oxygen and waste materials in our bodies. In Class IX, we learnt about blood being a fluid connective tissue. Blood consists of a fluid medium called plasma in which the cells are suspended. Plasma transports food, carbon dioxide and nitrogenous wastes in dissolved form. Oxygen is carried by the red blood cells. Many other substances like salts, are also transported by the blood. We thus need a pumping organ to push blood around the body, a network of tubes to reach all the tissues and a system in place to ensure that this network can be repaired if damaged.

OUR PUMP THE HEART

The heart is a muscular organ which is as big as our fist (Fig. 6.10). Because both oxygen and carbon dioxide have to be transported by the blood, the heart has different chambers to prevent the oxygen-rich blood from mixing with the blood containing carbon dioxide. The carbon dioxide-rich blood has to reach the lungs for the carbon dioxide to be removed, and the oxygenated blood from the lungs has to be brought back to the heart. This oxygen-rich blood is then pumped to the rest of the body. We can follow this process step by step (Fig. 6.11). Oxygen-rich blood from the lungs comes to the thin-walled upper chamber of the heart on the left, the left atrium. The left atrium relaxes when it is collecting this blood. It then contracts, while the next chamber, the left ventricle, expands, so that the blood is transferred to it. When the muscular left ventricle contracts in its turn, the blood is pumped out to the body. De-oxygenated blood comes from the body to the upper chamber on the right, the right atrium, as it expands. As the right atrium contracts, the corresponding lower chamber, the right ventricle, dilates. This transfers blood to the right ventricle, which in turn pumps it to the lungs for oxygenation.

 

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Biology X | LIFE PROCESSES | Nutrition in Human Beings

June 23rd, 2010

Nutrition in Human Beings

The alimentary canal is basically a long tube extending from the mouth to the anus. In Fig. 6.6, we can see that the tube has different parts. Various regions are specialised to perform different functions. What happens to the food once it enters our body? We shall discuss this process here.

Activity 6.3

  1. Take 1 mL starch solution (1%) in two test tubes (A and B).
  2. Add 1 mL saliva to test tube A and leave both test tubes undisturbed for 20-30 minutes.
  3. Now add a few drops of dilute iodine solution to the test tubes.
  4. In which test tube do you observe a colour change?
  5. What does this indicate about the presence or absence of starch in the two test tubes?
  6. What does this tell us about the action of saliva on starch?

We eat various types of food which has to pass through the same digestive tract. Naturally the food has to be processed to generate particles which are small and of the same texture. This is achieved by crushing the food with our teeth. Since the lining of the canal is soft, the food is also wetted to make its passage smooth. When we eat something we like, our mouth ‘waters’. This is actually not only water, but a fluid called saliva secreted by the salivary glands. Another aspect of the food we ingest is its complex nature. If it is to be absorbed from the alimentary canal, it has to be broken into smaller molecules. This is done with the help of biological catalysts called enzymes. The saliva contains an enzyme called salivary amylase that breaks down starch which is a complex molecule to give sugar. The food is mixed thoroughly with saliva and moved around the mouth while chewing by the muscular tongue.

It is necessary to move the food in a regulated manner along the digestive tube so that it can be processed properly in each part. The lining of canal has muscles that contract rhythmically in order to push the food forward. These peristaltic movements occur all along the gut.

From the mouth, the food is taken to the stomach through the food-pipe or oesophagus. The stomach is a large organ which expands when food enters it. The muscular walls of the stomach help in mixing the food thoroughly with more digestive juices.

These digestion functions are taken care of by the gastric glands present in the wall of the stomach. These release hydrochloric acid, a protein digesting enzyme called pepsin, and mucus. The hydrochloric acid creates an acidic medium which facilitates the action of the enzyme pepsin. What other function do you think is served by the acid? The mucus protects the inner lining of the stomach from the action of the acid under normal conditions. We have often heard adults complaining about ‘acidity’. Can this be related to what has been discussed above?

» Read more: Biology X | LIFE PROCESSES | Nutrition in Human Beings

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