Ans. Chocolates, sweets, soft drinks and other sugar products are the major culprits of tooth decay.
Ans. In the cells, glucose breaks down easily with the help of oxygen into carbon dioxide and water, and energy is released.
Ans. The canal can be divided into various compartments: (1) the buccal cavity, (2) foodpipe or oesophagus, (3) stomach, (4) small intestine, (5) large intestine ending in the rectum and (6) the anus.
Ans. During the act of swallowing a flap-like valve closes the passage of the windpipe and guides the food into the foodpipe. If, by chance, food particles enter the windpipe, we feel choked, get hiccups or cough.
Ans. The small intestine is highly coiled and is about 7.5 metres long. It receives secretions from the liver and the pancreas. Besides, its wall also secretes juices.
Ans. Ruminants have a large sac-like structure called rumen between the oesophagus and the small intestine. The cellulose of the food is digested here by the action of certain bacteria which are not present in humans.
Ans. No, human cannot survive only on raw, leafy vegetables, or grass because they are rich in cellulose, which is a type of carbohydrate that humans are not able to digest due to the absence of cellulose-digesting enzymes.
Ans. Grass eating animals quickly swallow the grass and store it in a part of the stomach called rumen. Here the food gets partially digested and is called cud. But later the cud returns to the mouth in small lumps and the animal chews it.
Ans. Starfish feeds on animals covered by hard shells of calcium carbonate. After opening the shell, the starfish pops out its stomach through its mouth to eat the soft animal inside the shell. The stomach then goes back into the body and the food is slowly digested.
Ans. The large intestine is wider and shorter than small intestine. It is about 1.5 metre in length. Its function is to absorb water and some salts from the undigested food material. The remaining waste passes into the rectum and remains there as semi-solid faeces.
Ans. We can prevent tooth decay in the following manner:
i. By cleaning the teeth with a brush or datun and dental floss at least twice a day and rinse the mouth after every meal.
ii. By not putting dirty fingers or any unwashed object in the mouth.
Ans. The inner walls of the small intestine have thousands of finger-like outgrowths. These are called villi (singular villus). These are found in small intestine.
Functions
i. The villi increase the surface area for absorption of the digested food.
ii. The surface of the villi absorbs the digested food materials.
Ans. Functions of the tongue in human body
i. It helps in talking.
ii. It mixes saliva with the food during chewing and helps in swallowing food.
iii. It has taste buds that detect different tastes of food.
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