The breakdown of food continues after it reaches the stomach. The point

Question

where the stomach connects with the esophagus is a structure (muscle)
called the _________________________________.
i. What is the importance of this structure?
ii. Once the food is in the stomach, the stomach has three important
tasks. Describe each of these in your own words.
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iii. What are the specific roles of hydrochloric acid (HCl) and pepsin in
the stomach?
iv. Very few molecules are actually absorbed in the stomach. When
food is ready to leave the stomach, a sphincter at the bottom of the
stomach called the ___________________sphincter opens to release
the liquified food (called chyme) into the small intestine.
e. Food completes its digestion in the small intestine
i. The liver and the pancreas provide key elements to digest

Answer 1

The breakdown of food continues after it reaches the stomach. The point where the stomach connects with the esophagus is a structure (muscle) called the lower esophageal sphincter (LES).

i. Importance of the Lower Esophageal Sphincter: The lower esophageal sphincter is crucial because it acts as a valve to prevent the backflow of stomach contents into the esophagus. By maintaining a barrier between the stomach and the esophagus, it helps protect the esophagus from the corrosive effects of stomach acid, and it contributes to proper digestion by ensuring that food moves in the right direction.

ii. Three Important Tasks of the Stomach:

• Storage: The stomach serves as a temporary storage facility for food after it is ingested. This allows the body to regulate the release of food into the small intestine, enabling effective digestion and nutrient absorption.

• Mixing and Churning: The stomach mixes food with gastric juices, including hydrochloric acid and digestive enzymes, to break down food into a semi-liquid form called chyme. This mechanical mixing also helps to expose food particles to digestive enzymes for more thorough digestion.

• Digestion: The stomach is responsible for the initial stages of digestion, particularly the enzymatic breakdown of proteins. The acidic environment and the presence of enzymes begin the process of breaking down complex food into simpler compounds that can be further digested in the small intestine.

iii. Roles of Hydrochloric Acid (HCl) and Pepsin in the Stomach:

• Hydrochloric Acid (HCl): HCl creates an acidic environment (pH ~1.5 to 3.5) in the stomach, which is essential for activating digestive enzymes, maintaining the proper pH for enzyme activity, and killing harmful bacteria and pathogens present in food. It also helps to denature proteins, making them easier for enzymes to digest.

• Pepsin: Pepsin is an enzyme produced by the stomach that begins the digestion of proteins into smaller peptides. It is initially secreted in an inactive form called pepsinogen, which is activated by the acidic environment in the stomach. Pepsin specifically breaks down peptide bonds, facilitating the digestion of protein-rich foods.

iv. Sphincter at the Bottom of the Stomach: When food is ready to leave the stomach, a sphincter at the bottom of the stomach called the pyloric sphincter opens to release the liquified food (called chyme) into the small intestine.

e. Food Completes Its Digestion in the Small Intestine: i. The liver and the pancreas provide key elements to digest food in the small intestine.

• The liver produces bile, which is stored in the gallbladder and released into the small intestine to emulsify fats, making them easier to digest.
• The pancreas secretes digestive enzymes (such as amylase for carbohydrates, lipase for fats, and proteases for proteins) and bicarbonate to neutralize stomach acid, creating an optimal environment for enzymes to function in the small intestine.