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Which of the following is not involved in chemical digestion?

A.

Oral cavity

B.

Stomach

C.

Small intestine

D.

Large intestine

Answer and Explanation

The Correct Answer is D

A. Oral cavity is involved in chemical digestion through the action of salivary enzymes like amylase. 

 

B. Stomach is involved in chemical digestion with gastric acids and pepsin.

 

C. Small intestine is a major site for chemical digestion and nutrient absorption. 

 

D. Large intestine is primarily involved in the absorption of water and electrolytes and the formation of feces. It is less involved in chemical digestion compared to the other organs listed. 
 


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Correct Answer is B

Explanation

A. Mucosa (mucous membrane): The mucosa is the innermost layer of the digestive tract, not the outermost. It includes the epithelium, lamina propria, and muscularis mucosae.

B. Serosa (mesentery): The serosa is the outermost layer of the digestive tract in parts where it is covered by peritoneum. It consists of a thin layer of areolar tissue topped by simple squamous epithelium.

C. Muscularis externa: The muscularis externa is a layer of muscle in the digestive tract, located beneath the serosa. It is not the outermost layer.

D. Submucosa: The submucosa is a layer of connective tissue located between the mucosa and muscularis externa. It is not the outermost layer.

Correct Answer is B

Explanation

A. Chief cells secrete pepsinogen, not HCl.

B. Parietal cells in the stomach lining are responsible for secreting hydrochloric acid (HCl). This acid is crucial for digestion and killing pathogens.

C. Mucous cells secrete mucus, which protects the stomach lining from the acidic environment. They do not secrete HCl.

D. Regenerative (stem) cells are involved in the renewal of the stomach lining, but they do not secrete HCl.