Question

Absorption of salt and water is the principal function of which region of the GI tract? a. Esophagus b. Stomach c. Duodenum d. Jejunum e. Large intestine

Short answer

The correct answer is e. Large intestine, as its primary function is to absorb water and electrolytes from the remaining indigestible food matter.

Step-by-step solution

Review the role of each GI tract region

To solve this exercise, first, review the roles each region of the GI tract plays in the process of digestion: a. Esophagus: This part of the GI tract is responsible for transporting food from the mouth down to the stomach. b. Stomach: The stomach mainly functions to break down food into a liquid mixture and start the breakdown of proteins. c. Duodenum: This part of the small intestine receives the liquid mixture from the stomach and begins the absorption of nutrients, including fats, carbohydrates, and proteins. d. Jejunum: The jejunum is another part of the small intestine responsible for the absorption of nutrients. e. Large intestine: The primary function of the large intestine is to absorb water and electrolytes from the remaining indigestible food matter and to store and then eliminate waste.

Identify the region responsible for salt and water absorption

Looking at the roles of each GI tract region, we can see that the large intestine (part e) is the primary site for water and salt absorption. So, the correct answer is: e. Large intestine

Key concepts

Gastrointestinal Tract

The gastrointestinal (GI) tract is a vital part of the digestive system, comprising a long, continuous tube that extends from the mouth to the anus. Its primary role is to process food, extract nutrients, absorb water, and eliminate waste. The journey starts in the mouth, moves to the esophagus, and progresses through the stomach and intestines.

The GI tract can be broken down into several key regions:

• Esophagus: A muscular tube that transports food from the mouth to the stomach.
• Stomach: A muscular organ where food mixes with digestive juices to form a semi-liquid substance called chyme.
• Small Intestine: Comprised of the duodenum, jejunum, and ileum, it is pivotal for nutrient absorption.
• Large Intestine: Involves the cecum, colon, and rectum, and plays a crucial role in water absorption and waste elimination.

Understanding these components and their functions provides a clear picture of how our bodies utilize food to fuel various biological processes.

Large Intestine Function

The large intestine, also known as the colon, serves key functions in the digestive system. Its main role is to absorb water and electrolytes from the indigestible residues of food, transforming liquid waste into a more solid form.

Within the large intestine, there are several parts:

• Cecum and Ascending Colon: Initiates the process of absorbing fluids and electrolytes.
• Transverse and Descending Colon: Continues absorption and starts to form stool.
• Sigmoid Colon and Rectum: Stores fecal waste until it's ready to be expelled.

The large intestine also supports gut flora that ferment undigested carbohydrates and produce essential vitamins like vitamin K and biotin. Although nutrient absorption mainly occurs in the small intestine, the large intestine plays a critical role in regulating the body's water balance.

Water Absorption in Digestion

Water absorption in digestion is a vital function mainly managed by the large intestine. As the digestive process progresses, most nutrients are absorbed in the small intestine, leaving largely water-based waste behind.

Several processes facilitate water absorption:

• Osmosis: Water freely moves across intestinal membranes to balance fluid concentrations between the lumen and blood vessels.
• Ion Transport: Active absorption of positive ions, like sodium, promotes water uptake because water follows the movement of these ions.
• Bacterial Fermentation: Gut bacteria help break down substances that draw additional water into the large intestine, which is then reabsorbed.

The ability of the large intestine to absorb water and salts effectively is crucial for preventing dehydration and ensuring the excretion of waste in a manageable form.