Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

23. The Digestive System

Small Intestine

Anatomy & Physiology

23. The Digestive System

Small Intestine

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Problem 6

Textbook Question

What are the three folds of the small intestine called? What is their purpose?

Verified step by step guidance

The small intestine has three main folds that increase its surface area for absorption: plicae circulares, villi, and microvilli.

Step 1: Plicae circulares are large, circular folds of the mucosa and submucosa. These folds slow down the movement of chyme, allowing more time for nutrient absorption.

Step 2: Villi are small, finger-like projections on the surface of the plicae circulares. Each villus contains blood vessels and a lymphatic vessel (lacteal) to absorb nutrients like amino acids, sugars, and lipids.

Step 3: Microvilli are tiny, hair-like structures on the surface of the epithelial cells of the villi. They form the brush border, which contains enzymes that aid in the final stages of digestion and further increase the surface area for absorption.

Step 4: Together, these folds maximize the efficiency of nutrient absorption by significantly increasing the surface area of the small intestine.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Duodenum

The duodenum is the first section of the small intestine, measuring about 25-30 centimeters long. It plays a crucial role in digestion by receiving chyme from the stomach and mixing it with bile from the liver and pancreatic juices. This combination helps to neutralize stomach acid and further break down food, allowing for nutrient absorption.

Jejunum

The jejunum is the middle section of the small intestine, approximately 2.5 meters long. Its primary function is the absorption of nutrients, including carbohydrates, proteins, and fats. The jejunum has a highly folded inner surface, which increases the surface area for absorption, making it highly efficient in nutrient uptake.

Ileum

The ileum is the final section of the small intestine, about 3-4 meters long. It is primarily responsible for the absorption of vitamin B12 and bile salts, as well as any remaining nutrients not absorbed by the jejunum. The ileum connects to the large intestine at the ileocecal valve, regulating the flow of material into the colon.

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Related Practice

Multiple Choice

A lacteal can be found within each:

Which of the following statements is true?

The most numerous type of epithelial cells in the small intestine are the

Most digestion occurs in the small intestine.

The major site for nutrient absorption is the __________.

Alimentary canal and related accessory digestive organs

Both Paneth cells and Peyer’s patches are more numerous in the ileum than in the jejunum or the duodenum. Which statement below correctly describes why that may be?

Which of the following is/are absorbed in the small intestine by the Na+/glucose cotransporter?

a. Glucose

b. Galactose

c. Fructose

d. Both a and b are correct

e. All of the above are correct

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