CBSE Class 11 Biology - Structure of the small intestine

CBSE Class 11 Biology - Structure of the small intestine

In this article, we are discussing ‘the structure of the small intestine’ from Class 11 Biology in order to understand the function of the small intestine in digestion and mainly absorption.

STRUCTURE OF SMALL INTESTINE : The majority of digestion and absorption of nutrients takes place in the small intestine.

Absorption is the passage of digested food material through the lining of the intestine into the blood or lymph. Lymph is a colorless fluid containing white blood cells (WBC) that circulate through our body tissues. The WBC present in lymph helps to fight any infection that enters our body.

The small intestine has four tissue layers:

• The serosa is the outermost layer of the intestine. The serosa is a smooth membrane consisting of a thin layer of cells that secrete serous fluid and a thin layer of connective tissue. Serous fluid is a lubricating fluid that reduces friction from the movement of the muscularis.
• The muscularis is a region of muscle adjacent to the submucosa membrane. It is responsible for gut movement, or peristalsis. It usually has two distinct layers of smooth muscle: circular and longitudinal.
• The submucosa is the layer of dense, irregular connective tissue or loose connective tissue that supports the mucosa, as well as joins the mucosa to the bulk of underlying smooth muscle.

Brunner’s Gland

Brunner’s glands (or duodenal glands) are compound tubular submucosal glands found in the duodenum. The main function of these glands is to produce a mucus-rich, alkaline secretion (containing bicarbonate) in order to neutralize the acidic content of chyme. The chyme is introduced into the duodenum from the stomach.  These glands provide an alkaline condition for optimal intestinal enzyme activity, thus enabling absorption to take place and lubricate the intestinal walls.

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