DECE2-Solution(ENGLISH)-IGNOU-DAY 6-ORSP

Q1. Describe the processes of digestion, absorption and utilization of food.(10 MARK)

Ans.  Digestion of Food: Let us now take a look at the overall process of how

digestion occurs. Digestion takes place step-by-step at various sites in the digestive

tract as you will learn from the following discussion,

Mouth: As you have already noticed, the process of digestion begins in the mouth

where food is chewed by the teeth and mixed with saliva. While the food is still in

the mouth, it is acted upon by an enzyme, which acts only on cooked carbohydrates

such as starch and partially digests them or breaks them up into smaller units.

Stomach: The chewed food mixed with saliva then passes into the stomach through

the tube-like structure called the esophagus. Here it gets mixed with the digestive

juice present in the stomach called gastric juice which is acidic in nature. Mixing of

food with the gastric juice converts the food into a thin soup-like consistency. Gastric

juice contains an enzyme which acts on proteins and brings about their partial

digestion. Other nutrients in food remain chemically unchanged.

Small intestine: The next stop in the digestive tract is the small intestine. The

partially digested mass of food passes from the stomach into the small intestine. The

small intestine not only contains intestinal juice (which is secreted from the small

intestine itself) but also secretions from the liver and pancreas. The secretion from

the liver is called bile and from the pancreas is known as pancreatic juice. Bile aids in

the digestion and absorption of fats (you will learn about the role of bile in fat

digestion in the next Unit). Both pancreatic and intestinal juices contain enzymes

which break down fats, proteins and carbohydrates into simpler substances. These

simple substances ultimately reach the bloodstream.

Large intestine: The components of food which are not absorbed in the small

intestine along with a large amount of water passes on to the large intestine. Here,

most of the excess water is reabsorbed and the remaining water and solid matter is

eliminated from the body as fasces,

Absorption of Food: Where is food absorbed? You would have realized by now that

absorption takes place in the small intestine. The end products of digestion or the

nutrients present in the small intestine can be used by the body only when they enter

the bloodstream. This process of movement of digested food or nutrients across the

intestinal wall to the bloodstream is termed absorption of food. The wall of the small

intestine is made up of numerous folds or finger-like projections known as villi. The

presence of these villi tremendously increase the total area from which absorption

can take place. Most of the nutrients are absorbed from the upper part of the small

intestine though some are absorbed from the lower portion

As you know, the end products of digestion move into the bloodstream. The blood

circulating in the body and therefore, the nutrients it carries reaches every cell of the

body. Once they reach the cell, the nutrients perform their specific functions.

Utilization of Food: How is food utilized? In order to be utilized for specific

functions the absorbed end products or the nutrients from the food we eat further

undergo chemical changes. They are either further broken down to release energy or

are used to -form more complex substances. We use a certain term to refer to these

processes. Let us learn this term.

Metabolism is a general term. It refers to all the chemical changes that take place in

the cells after the end products of digestion are absorbed. You know it is of two

types breakdown of complex substances into simpler ones and manufacture of

complex substances from simple ones.