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 22

Textbook Question

How does absorption of lipids differ from absorption of carbohydrates and proteins in the small intestine?
a. Lipids are absorbed into a capillary; carbohydrates and proteins are absorbed into a lacteal.
b. Lipids are not absorbed in the small intestine.
c. Lipids are absorbed into a lacteal; carbohydrates and proteins are absorbed into a capillary.
d. They are all absorbed into the same structure.

Verified step by step guidance

Understand the basic anatomy of the small intestine: The small intestine is the primary site for nutrient absorption. It contains villi and microvilli, which increase the surface area for absorption. Each villus contains a capillary network and a lacteal (a lymphatic vessel).

Review the absorption process for carbohydrates and proteins: Carbohydrates are broken down into monosaccharides (e.g., glucose), and proteins are broken down into amino acids. These small molecules are water-soluble and are absorbed directly into the capillaries of the villi, where they enter the bloodstream.

Review the absorption process for lipids: Lipids (fats) are broken down into monoglycerides and free fatty acids. These molecules are not water-soluble, so they are packaged into structures called micelles for transport to the intestinal cells. Inside the cells, they are reassembled into triglycerides and packaged into chylomicrons, which are absorbed into the lacteals (lymphatic vessels) rather than the capillaries.

Compare the absorption pathways: Carbohydrates and proteins are absorbed into the capillaries, which transport them to the liver via the hepatic portal vein. Lipids, on the other hand, are absorbed into the lacteals, which transport them through the lymphatic system before they enter the bloodstream.

Identify the correct answer: Based on the differences in absorption pathways, the correct answer is that lipids are absorbed into a lacteal, while carbohydrates and proteins are absorbed into a capillary. This corresponds to option c.

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Key Concepts

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

Lipid Absorption

Lipid absorption primarily occurs in the small intestine, where dietary fats are emulsified by bile salts and broken down by pancreatic lipase into fatty acids and monoglycerides. These products then diffuse across the intestinal epithelial cells and are reassembled into triglycerides, which are packaged into chylomicrons and absorbed into the lymphatic system via lacteals.

Carbohydrate and Protein Absorption

Carbohydrates and proteins are absorbed in the small intestine through different mechanisms. Carbohydrates are broken down into monosaccharides, which are absorbed directly into the bloodstream via capillaries. Proteins are digested into amino acids and small peptides, which are also absorbed into the capillaries of the intestinal villi, entering the bloodstream for distribution.

Lacteals vs. Capillaries

Lacteals are specialized lymphatic vessels found in the intestinal villi that primarily absorb lipids and fat-soluble vitamins, transporting them into the lymphatic system. In contrast, capillaries are small blood vessels that absorb water-soluble nutrients, such as carbohydrates and proteins, directly into the bloodstream, highlighting the distinct pathways for nutrient absorption in the small intestine.

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Related Practice

Textbook Question

Regional movements that occur in the small intestine and function to churn and fragment the digestive material are called:

(a) Segmentation

(b) Pendular movements

(d) Mass movements

(e) Mastication

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Multiple Choice

The __________ is the first segment of the small intestine.

Where are bile salts reabsorbed in the small intestine?

Lactose, a sugar found in milk, can only be digested by lactase, a brush border enzyme. All babies produce lactase, but only some adults do. Adults who do not produce lactase are referred to as lactose intolerant, as the presence of undigestible lactose can lead to uncomfortable digestive side effects such as gas and diarrhea. Based on your understanding of the small intestine, where would you expect to find the most lactase in babies and those adults that can digest lactose?

Celiac disease is a condition where the body has an abnormal immune response to the protein gluten found in wheat and other grains. A result of this, the body’s immune response can cause damage to the villi. Based on your knowledge of the small intestine, what function would this this most directly affect?

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

e. During eating, the small intestine exhibits motion in the migrating motor complex pattern.

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Multiple Choice

What intestinal structure(s) consist(s) of protective aggregated nodules of lymphocytes and macrophages?

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