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Ch. 22 The Digestive System
Amerman- Human Anatomy & Physiology 3e
Amerman3rd EditionHuman Anatomy & PhysiologyISBN: 9780138247201, 9780138247928, 9780138201814Not the one you use?Change textbook
All textbooksAmerman 3rd EditionCh. 22 The Digestive SystemProblem 7
Chapter 22, Problem 7

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
1
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.
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Lipids

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.
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Carbohydrates

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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Introduction to Capillaries
Related Practice
Textbook Question

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

The muscularis externa of most of the alimentary canal consists of inner circular and outer longitudinal layers of smooth muscle.

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Textbook Question

Match the following terms with the correct definition. 

__Chief cells          

__Parietal cells           

__Gastrin           

__Pyloric sphincter         

__Diffuse neuroendocrine (DNES) cells         

__Gastroesophageal sphincter         

__Pepsin         

__Chyme

a. Hormone that stimulates multiple digestive processes

b. Enzyme that begins protein digestion

c. Produce acid and intrinsic factor

d. Liquid produced as a result of stomach churning

e. Produce pepsinogen

f. Cells in gastric glands that produce hormones

g. Controls passage of bolus from esophagus to stomach

h. Controls passage of stomach contents to duodenum

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Textbook Question

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

The mucosa of the esophagus, pharynx, and oral cavity contains simple squamous epithelium to protect it from abrasion.

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Textbook Question

Which of the following statements about accessory organ secretions is not true?

a. Hepatocytes produce bile, which drains out of the liver via the common hepatic ducts.

b. Saliva contains secretory IgA and lysozyme, which play an important role in preventing the growth of pathogenic bacteria in the oral cavity.

c. Pancreatic juice contains digestive enzymes and bicarbonate ions to neutralize the acidic chyme.

d. The gallbladder produces bile, which drains out of the gallbladder via the cystic duct.

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Textbook Question

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

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Textbook Question

The primary hormone that triggers the secretion of pancreatic juice and bile is:

a. Gastric inhibitory peptide

b. Cholecystokinin

c. Motilin

d. Somatostatin

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