Explain the process of digestion in human being with a neat and well labelled diagram.
Answers
Answer:
(i). Food is crushed and cut in the mouth with the help of teeth and is mixed with saliva that is secreted by three salivary glands(one below the tongue and two at the side of the jaw) to make it wet and slippery, this process is known as mastication.
(ii) Saliva contains amylase that breaks down complex carbohydrates and the tongue helps in pushing the food to the next part of the alimentary canal.
(iii) The soft food then passes through the oesophagus in a wave-like movement known as a peristaltic movement.
(iv) In the stomach, food mixes with gastric juices and dil. HCl. The food is broken down to simple substances with the help of digestive enzymes like pepsinogen, while mucus protects the walls of the stomach.
(v) From the stomach, the food moves into the small intestines with the help of ring-like muscles called pyloric sphincters which allow only a little food to pass through at a time.
(vi) In the small intestine, the carbohydrates, proteins, and fats are broken down with the help of juices secreted by the pancreas, liver and the small intestine itself.
(vii) Fat is converted into small globule-like forms with the help of bile juices from the liver. This process is known as emulsification.
(viii) Pancreatic juices contain trypsin enzyme that breaks down proteins and lipase that breaks down fats.
(ix) The later part of the small intestines is alkaline in nature and helps in the digestion of carbohydrates.
(x) The broken-down food is then absorbed by small projections present on the inside walls of the intestine called villi. Villi are surrounded by blood and lymph vessels that absorb the food and transport it to the rest of the body.
(xi) Finally, the food moves into the large intestine where most of the water is removed from the food and is then passed out of the body through the anus.
Answer:
SOLUTION
Humans have holozoic nutrition, that means the food is consumed as a whole and the digestion occurs internally. It can be described as:
1. Ingestion of food- The food is taken in the oral cavity in the process called the ingestion. The teeth help in grinding of the food, salivary amylase helps in partial breakdown of the starch and the tongue helps in mixing the food with saliva and helps in swallowing it. The food is now called bolus.
2. Digestion- The process of break-down of complex substances into simpler substances is called digestion and it starts with the mouth where physical break-down occurs along with some chemical digestion. The bolus is swallowed in and it arrives in stomach where the digestion of proteins occurs due to presence of the enzyme pepsin. Bolus is now called the chyme. This chyme now moves into the small intestine where rest of the process of digestion will be completed. The pancreatic juice, the intestinal juice and the bile will result in breakdown of carbohydrates, fats and the rest of the proteins. The chyme is now called the chyle and it moves to the large intestine where the water is absorbed.
3. Absorption- The digested food is absorbed via the finger-like projections present on the inner surface of the small-intestine and the reach the blood stream.
4. Assimilation- The absorbed food is then used by different tissues for the energy generation. The excess food is stored as glycogen in the liver and s fats in adipose tissue.
5. Excretion- The undigested material passes from the small-intestine to the rectum of the large-intestine, from where it is removed from the body through anus.
