In the stomach:

Answer Explanation

a) mouth

- Correct: The mouth is not considered an accessory digestive structure; it is an integral part of the alimentary canal (digestive tract). The mouth is where the process of digestion begins, as food is ingested, chewed, and mixed with saliva. Saliva, produced by the salivary glands, contains enzymes (such as amylase) that initiate the breakdown of carbohydrates. Once food is sufficiently broken down in the mouth, it is formed into a bolus and swallowed, entering the esophagus and continuing its journey through the digestive system.

b) salivary glands

- Incorrect: Salivary glands are accessory digestive structures that secrete saliva into the mouth. Saliva contains enzymes and lubricants that aid in the mechanical and chemical digestion of food.

c) pancreas

- Incorrect: The pancreas is an accessory digestive structure that plays a crucial role in digestion by producing and secreting digestive enzymes into the small intestine. These enzymes aid in the breakdown of carbohydrates, proteins, and fats.

d) liver

- Incorrect: The liver is also an accessory digestive structure that contributes to digestion by producing bile, which is stored in the gallbladder and released into the small intestine to aid in the emulsification and digestion of fats. Additionally, the liver plays a role in processing nutrients absorbed from the small intestine and regulating glucose metabolism.

Answer Explanation

a. making enzymes; making bile and processing nutrients; and storing bile

- Correct: The pancreas, liver, and gallbladder help digestion in the following ways:

1. The pancreas produces and secretes digestive enzymes into the small intestine to aid in the breakdown of carbohydrates, proteins, and fats. These enzymes include amylase (for carbohydrates), proteases (for proteins), and lipases (for fats).

2. The liver produces bile, a digestive fluid that emulsifies fats by breaking them down into smaller droplets, which increases the surface area for enzymes to act upon. The liver also processes nutrients absorbed from the small intestine, including carbohydrates, proteins, and fats.

3. The gallbladder stores and concentrates bile produced by the liver. When needed for digestion, the gallbladder releases bile into the small intestine via the common bile duct to aid in the emulsification and digestion of fats.

Therefore, option a accurately describes the roles of the pancreas, liver, and gallbladder in digestion.

Answer Explanation

b) propulsion

- Correct: Propulsion is the movement of food along the length of the alimentary canal, from the mouth to the anus. This process occurs throughout most of the alimentary canal and includes both swallowing (deglutition) and peristalsis. Swallowing moves food from the mouth to the esophagus, while peristalsis involves rhythmic contractions and relaxations of smooth muscles in the walls of the digestive organs, pushing food forward through the esophagus, stomach, and intestines.

a) Ingestion: Ingestion refers to the intake of food into the mouth, which occurs at the beginning of the alimentary canal.

c) Segmentation: Segmentation involves the mixing and churning of food within certain regions of the digestive tract, particularly the small intestine. It does not occur throughout most of the alimentary canal but rather in specific areas where mechanical digestion and absorption are optimized.

d) Absorption: Absorption is the process by which nutrients and water are taken up from the digestive tract into the bloodstream or lymphatic system. While absorption occurs primarily in the small intestine, it also occurs in other parts of the alimentary canal, particularly in the large intestine, but it is not a continuous process throughout most of the alimentary canal like propulsion.