Question 1

Which of the following best describes the primary function of the structure shown in the first image (the long tube running from the mouth to the anus)?

Accepted Answer

It is the alimentary canal, which ingests, digests, absorbs nutrients, and eliminates waste.

Question 2

In the second image, several layers of the alimentary canal are shown. Which layer is responsible for peristalsis and segmentation, and what is its composition?

Accepted Answer

The muscularis externa; composed of inner circular and outer longitudinal smooth muscle layers.

Question 3

The third image shows a large, fatty structure draping over the intestines. What is this structure and what is one of its main functions?

Accepted Answer

It is the greater omentum; it cushions abdominal organs and contains immune cells.

Question 4

In the fourth image, which structure prevents food from entering the nasal cavity during swallowing?

Accepted Answer

The uvula and soft palate

Question 5

The fifth image shows the oral cavity. Which teeth are primarily responsible for grinding food, and at what age do they typically appear?

Accepted Answer

Molars; first molar at 10–15 months (deciduous) and 6–7 years (permanent)

Question 6

In the sixth image, which part of the tooth is the hardest substance in the body, and what is its main limitation?

Accepted Answer

Enamel; it is brittle and cannot be replaced if damaged.

Question 7

The seventh image shows the esophagus and stomach. What is the function of the cardioesophageal sphincter?

Accepted Answer

It prevents the backflow of stomach contents into the esophagus.

Question 8

The eighth image shows the internal folds of the stomach. What is the name of these folds, and what is their function?

Accepted Answer

Rugae; allow the stomach to expand when filled with food.

Question 9

The ninth image shows a cross-section of the stomach wall. Which cells secrete hydrochloric acid, and what is the role of this secretion?

Accepted Answer

Parietal cells; create an acidic environment to activate pepsinogen and kill microbes.

Question 10

The tenth image shows the process of gastric motility. What is the correct sequence of events for moving chyme into the small intestine?

Accepted Answer

Propulsion, grinding, retropulsion

Question 11

The eleventh image shows the liver, gallbladder, and pancreas. Which organ produces bile, and what is the primary function of bile in digestion?

Accepted Answer

Liver; emulsifies fats to aid in their digestion and absorption

Question 12

The twelfth image shows the structure of a villus in the small intestine. Which type of vessel absorbs most dietary fats, and where do these fats go first?

Accepted Answer

Lacteals (lymphatic vessels); into the lymphatic system before entering the bloodstream

Question 13

The thirteenth image shows the microvilli of the small intestine. What is the main function of these structures?

Accepted Answer

To increase the surface area for nutrient absorption

Question 14

The fourteenth image shows segmentation in the small intestine. How does segmentation differ from peristalsis?

Accepted Answer

Segmentation mixes chyme with digestive juices and increases contact with absorptive surfaces, while peristalsis propels food forward.

Question 15

The fifteenth image shows carbohydrate digestion and absorption. Which enzyme is responsible for beginning starch digestion in the mouth?

Accepted Answer

Salivary amylase

Question 16

The sixteenth image shows protein digestion. Which enzyme is responsible for initiating protein digestion in the stomach, and what condition is required for its activation?

Accepted Answer

Pepsin; acidic pH

Question 17

The seventeenth image shows fat digestion and absorption. What is the role of bile salts in fat digestion?

Accepted Answer

They emulsify large fat globules into smaller droplets, increasing surface area for pancreatic lipase.

Question 18

The eighteenth image shows the hepatic portal system. Why is blood from the digestive tract routed to the liver before entering the general circulation?

Accepted Answer

To allow the liver to detoxify substances and process nutrients before they reach the rest of the body.

Question 19

The nineteenth image shows the large intestine. Which of the following is NOT a function of the large intestine?

Accepted Answer

Absorption of most nutrients

The Digestive System: Structure and Function

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