Question

What is the churning movement? Explain briefly.

Answer 1

Hint: Digestion of food in the stomach is an important step in taking up nutrients from food. Churning movement is an important step that takes in the stomach for the digestion of food. It takes place only when the stomach has food for 4 – 5 hours.

Complete answer-
All living organisms need matter to build up the body and energy to operate the metabolic reactions that sustain life. The sum total of the processes by which the living organisms obtain food and metabolise it to the materials that build up tissue and provide energy is called nutrition. Nutrition is one material that provides matter and energy to the organisms to keep alive. We generally get it by the intake of food.
The food is taken by organisms into the food vacuole or alimentary canal. So long as the food is in the food vacuole or alimentary canal, it is not truly inside the body. It will be actually within the body and will become a part of the body within the body and will become a part of the body only when it entered the cytoplasm or the blood and lymph by its passage through the membrane of the food vacuole or the mucous membrane of the alimentary canal. Absorption can occur only in solution form.
Stomach is a distensible, muscular sac like structure. The second phase of the digestion is termed as gastric phase in which the stomach temporarily stores and partially digests the food for 4-5 hours. When undistended, its inner surface shows folds, the rugae, which disappears as the stomach expands. A fully distended stomach can hold nearly 5 cm3 of food. The thick mucosa of the stomach contains numerous mucus- secreting, epithelial cells and tubular gastric glands. Food undergoes both mechanical and chemical changes in the stomach.
 Wall of the stomach undergoes periodic muscular contractions which are 15- 20 times per minute. The food mixes throughout with the acidic gastric juices in the stomach by the churning movement of its muscular wall and is called a chime. This breaks the food mechanically and mixes with the gastric juice for proper action of enzymes. For this role, the stomach wall has three smooth muscle layers: outer longitudinal, middle circular and inner oblique. The cardiac and pyloric sphincter remains closed during churning of the food.

Note-
Digestion of food has been best worked out in man. Digestion of food starts in the buccal cavity, continuous in the stomach and is completed in the small intestine. There are three main phases of digestion, salivary, gastric and intestinal. The food undergoes no changes in the pharynx and oesophagus.