Biology 3 Marks Question

The major portion of absorption takes place in the small intestines. In the stomach, simple sugars, water and alcohol are absorbed. Villi are specialised projections in the small intestine which have a large surface area for absorption. Food is fit to be absorbed only after complete digestion, so the function of villi begins after all the digestive processes are complete.

The alimentary canal is composed of the following basic layers:

1. Serosa: It is the outermost layer and is made of a thin mesothelium with some connective tissues.
2. Muscularis: It is formed by smooth muscles usually arranged into an inner circular and outer longitudinal layer.
3. Sub-mucosa: It is formed of loose connective tissues containing nerves, blood and lymph vessels.
4. Mucosa: It forms irregular folds in the stomach and small finger-like folding called villi in the small intestine.

• Marasmus is a form of protein-energy malnutrition (PEM) resulting from simultaneous deficiency of proteins and calories.
• It is caused in infants less than a year of age, when mother's milk is replaced by other foods poor in proteins and energy content; it happens when mother has a second pregnancy and child birth, when the first child is less than a year of age.
• Its symptoms include the following:

1. Protein deficiency impairs growth and replacement of tissue proteins.
2. Thinning of limbs.
3. Skin becomes thin, dry and wrinkled.
4. Growth and development of brain and mental faculties are impaired.
5. Growth rate and body weight decline rapidly.
6. Extreme emaciation of body parts.

• The neutral system and the hormones control the activities of the gastro-instestinal tract.
• The neutral system controls:

1. The secretion of saliva at the sight or smell or taste of food in the buccal cavity.
2. The secretion of gastric and intestinal glands.
3. The muscular activities of the different parts of the alimentary canal.
4. The hormones produced by the gastric and intestinal mucosa control the secretion of digestive juices and release of bile.

Role of gall bladder is to store the bile juice produced by liver the gall bladder stops functioning when gall stones gets formed over the cystic duct then the bile stored is unable to discharge its juice into the duodenum and thus the bile juice is then diffused into the nearby artery coming and causes paleness which we call it as jaundice the gall bladder is removed and the bile then cannot be stored in the gall bladder so it is advised to the patient no to eat too fat containing food as emulsification of fat is done in the liver.

1. We need different types of tools to carry out different tasks.

The role of teeth in digestion is very important. Teeth help in breaking the food into smaller particles so that it becomes easy for digestive enzymes to act on them. Moreover, swallowing the food also becomes easier after the food is properly chewed. Improper tooth-care can lead to tooth decay in the long run. Once a tooth is gone, it cannot be replaced by the body. Artificial teeth are never as good as natural teeth. Once all the teeth are gone from a person's mouth, he will not be in a position to enjoy most of the food. This will result in diminished nutrition for the person. A person may get some nutritional supplement in liquid or semi-liquid form but the fact that he cannot enjoy many of the food, would be quite depressing for him.

1. Salivary amylase catalyses the digestion of about 30% starch into maltose in the buccal cavity.
2. Pepsin acts on the proteins in the food and converts them into peptones and proteoses in the stomach.
3. Lipase digests the fats into glycerol and fatty acids in the duodenum.

Trypsin, lipase and amylase are enzymes secreted by pancreas.

• Trypsin acts on proteins, proteoses and peptones and converts them into shorter peptides.
• Lipase acts on triglycerides and converts them into diglycerides and monoglycerides along with the release of a fatty acid at every step.
• Amylase acts on starch and converts it into maltose.

Goblet cells (secrete mucus) are present in the intestinal mucosa. The secretion of these cells along with the secretions of the brush border cells of the mucosa constitutes the intestinal juice. The bicarbonate ions from the pancreas and the mucus protect the intestinal mucosa from the acidic food or chyme.

1. Anita often complains for stomachache as she does not chew her food properly.
2. Chewing has its own importance in digestion of food, as it helps in proper breakdown of food and mixing it with saliva on which enzyme ptyaline acts. If food is not chewed properly, complete breakdown of food will not take place in the mouth first of all and large pieces will enter the stomach which might cause trouble and damage to the stomach and hence, the digestive system.
3. Food moves forward through the muscle contraction movement called peristalsis.
4. Anita's mother is conscious about her daughter's health and believes in taking initiative.