Small Intestine Diagram

What Is the Small Intestine?

The small Intestine is the main component of the digestive system, which absorbs the nutrients. It is a long, coiled tube that starts from the stomach, ends by the large intestine, and extends to a length of about 20 feet. Its long length and the structure efficiently process and absorb the needed nutrition for the body's functions.

Small intestine has three parts: duodenum, jejunum, and ileum. The small intestine breaks down food into nutrients with the help of digestive enzymes and absorbs those nutrients into the bloodstream. Such absorption ensures that the body receives the energy and necessary nutrients, hence being highly important.

Labelled Parts of the Small Intestine

The diagram shows the parts of the small intestine:

The various parts of the small intestine have different roles in digestion, breaking down food, and absorbing it into the bloodstream for utilisation.

Parts of the Small Intestine

The small intestine is mainly divided into three parts:

Duodenum

• First part of small intestine

• Site for maximum chemical digestion.

• Receives pancreatic juice and bile.

Jejunum

• The middle portion.

• Mainly responsible for the absorption of nutrients.

• Rich blood supply.

Ileum

• The last part.

• Responsible for absorption of vitamin B12 and bile salts.

• Opens into large intestine.

Layers of the Small Intestine (Diagram Explanation)

The diagram below shows the different layers of the small intestine.

The layers of the small intestine are divided into:

Mucosa

• The innermost layer.

• Lined with villi and microvilli

• It can increase the surface area for absorption.

Submucosa

• A supportive layer containing blood vessels, nerves and glands.

• Provides nourishment and support.

Muscularis externa

• Circular and longitudinal muscles.

• Responsible for movements of peristalsis and segmentation.

Serosa

• Outermost protective layer.

Diagram of Intestinal Villi (Key Explanation)

The diagram of the intestinal villi represents:

• Villi are finger-like projections.

• Microvilli from the brush border.

• Greatly increase surface area to promote nutrient absorption.

• Blood vessels and lymphatics are found in these structures to transport the absorbed nutrients.

Intestinal Glands

Intestinal glands are located on the inner lining of the small intestine and are responsible for digestion. They secrete:

• Digestive enzymes

• Mucus

• Hormones

These glands are composed of different cells including:

• Goblet cells that produce mucus.

• Enterocytes that are involved in nutrient absorption.

• Enteroendocrine cells that release hormones to regulate digestion.

Small Intestine NEET MCQs (With Answers & Explanations)

Important questions asked in NEET from this topic are:

• Compartment of the ruminant stomach

• Digestion in Ruminants

Practice Questions for NEET

Q1. Identify the precise nature and origin of the enzyme Enterogastrone

1. An enzyme secreted by the gastric mucosa

2. A hormone secreted by the small intestinal mucosa

3. A hormone secreted by the duodenal mucosa

4. A secretory product of an endocrine gland associated with digestion

Correct answer: 3) A hormone secreted by the duodenal mucosa

Explanation:

Enterogastrone is a collective term for various hormones produced by the mucosa of the small intestine, primarily the duodenum. These hormones, such as secretin and cholecystokinin are released in response to the presence of chyme in the small intestine and play a role in regulating digestive processes. The term "enterogastrone" specifically emphasizes its inhibitory effect on gastric motility and acid secretion, helping to slow down the emptying of the stomach and promote efficient digestion and absorption in the small intestine.

Hence, the correct answer is option 3) A hormone secreted by the duodenal mucosa.

Q2. Assertion: The serosa is a smooth membrane made up of a thin layer of cells that release serous fluid and a thin layer of connective tissue.

Reason: Serous fluid is a lubricating fluid that minimises friction caused by muscularis action

1. Assertion and reason are both true, and reason is an accurate account of assertion.

2. Both assertion and reason are accurate, but reason does not adequately explain assertion.

3. The assertion is correct, but the reasoning is incorrect.

4. Both the assertion and reason are incorrect.

Correct answer: 1) Assertion and reason are both true, and reason is an accurate account of assertion.

Explanation:

The serosa is the outermost layer of the small intestine and is composed of a thin layer of cells that secrete serous fluid and a layer of connective tissue. The serous fluid serves as a lubricant that reduces friction caused by the movement of the muscularis layer, which helps the small intestine mix and propel its contents along its length. Therefore, both the assertion and reason are true, and reason accurately explains the assertion.

Hence, the correct answer is option 1) Assertion and reason are both true, and reason is an accurate account of assertion.

Q3. Last section of large intestine is

1. Caecum

2. Colon

3. Rectum

4. Anus

Correct answer: 3) Rectum

Explanation:

The rectum is the final part of the large intestine, situated just before the anus. It plays a vital role in the elimination of waste from the body. The rectum stores formed faeces, which are the byproducts of digestion and absorption until they are ready to be expelled from the body during defecation.

Hence, the correct answer is option 3) Rectum.

Also Read:

• MCQs on Small Intestine

• Pancreas Function in Human Body

• Salivary Glands

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