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Preksha Dhyana :
circulation. Normally, 3 to 10 hours are required for chyme to pass from the pylorus to the end of the ileum.
(a) Duodenum. The first part of the small intestine is about 16 to 17 cms. long. A 'C-shaped' tube, the duodenum begins at the pylorus, passes behind the liver in front of the right kidney and across the aorta. It encircles the head of the pancreas.
The structure of this organ is similar to that of the stomach. The only difference is that its inner lining is very much wrinkled, resulting in greater surface area in a smaller space. This is an important organ in the digestive system. The pancreatic juice and the bile enter the tract about 7 cms. from the pylorus and commence their digestive action on food. Also, here--but not elsewhere-are glands, called the Bruoper's glands, beneath the mucous membrane. Small quantities of thick gruel-like mixture of semi-digested food and gastric juices are squirted into the duodenum through the gate-keeper like valve. Since this is highly acidic, too much at a time would damage the lining of the duodenum, which is notorious as a site of ulcer, since it bears the brunt of jets of acidic chyme that periodically squirt into it from the stomach. To neutralize most of the acid, alkaline digestive juices from the pancreas and gall bladder pour into the duodenum via the pancreatic duct with the characteristic split-second timing and meet the chyme. These juices contain three main enzymes which separate the proteins, fats and carbohydrates into basic building blocks.
(b) Jejunum and Ileum. There is no clear demarcation between jejunum and ileum, although their membranes differ somewhat in structure. The jejunum constitutesabout two-fifths of the smail intestine and the somewhat longer ileum, the rest. The ileum ends in a right angled T-junction with the large intestine. The greater part of food-digestion and absorption takes place in the jejunum and the ileum. The slightly acidic liquid which enters the jejunum leaves it as an alkaline one. During its passage, virtually all t'e nutrient materials are extracted. The Absorption Process
The structure of the small intestine is specialized
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