Question

#1. A food has been ingested. Identify all of the anatomic structures and substructures it travels through, in order, from the mouth to the anal opening.

#2. Describe the physiologic processes that act on the food in question #1, as it passes through each of the structures and substructures you identified. Include all of the enzymes and other chemicals.

Answer 1

Answer

1) Anatomical structures through which food travels :

1. Mouth
2. Esophagus
3. Cardiac sphincter
4. Stomach
5. Pyloric sphincter
6. Small intestine
7. Ileocecal valve
8. Large intestine
9. Rectum
10. Anal canal
11. Anal opening

2) Physologic processes acting on the food :

In the mouth :

• Mastication perfoms mechanical digestion and cut the food into smaller pieces.
• Salivary amylase is an enzyme released by salivary glands.
• It acts on complex carbohydrates (starch) in the mouth and break then down into disaccharides.

The food enters the stomach via esophagus.

In the stomach :

• Stomach releases gastric acid (HCl) and pepsinogen, an inactive enzyme.
• HCl acts on pepsinogen and converts it into pepsin.
• Pepsin acts on large protein molecules and break then down into smaller peptides.

The food enters duodenum, the first part of small intestine via pyloric sphicter.

In the small intestine :

• Bile from the gallblader and pancreatic enzymes from exocrine pancreas are released into the duodenum via hepatopancreatic ampulla.
• Bile acts on large lipid molecules and emulsify them into smaller fat droplets. This is a mechanical digestion.
• Pancreatic enzymes include :
  - Pancreatic amylase : It acts on polysaccharides and convert them to disaccharides.
  - Pancreatic lipase : It acts on smaller fat droplets and convert them into fatty acid and glycerol.
  - Chemotrypsin, Caboxypeptidase, Typsin : They are proteolytic enzyme that convert smaller peptides into peptones.

Brush border of the small intestine secretes :

- Maltase, sucrase, lactase : To convert disaccharides into glucose.
- Dipeptidases : They act on dipeptides and release amino acids.

The undigested matter moves into large intestine via ileocecal valve.

In large intestine

• Water from the undigested matter is absorbed in the large intestine.
• The undigested matter is sodified in order to produce fecal matter.

The fecal matter is stored in rectum.

The fecal matter is released out of the body by a process of defecation through anal canal and anal opening.