Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

23. The Digestive System

Introduction to the Digestive System

Anatomy & Physiology

23. The Digestive System

Introduction to the Digestive System

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Multiple Choice

Which of the following is a primary stimulus for defecation?

Absorption of nutrients in the small intestine

Secretion of gastric acid in the stomach

Release of bile from the gallbladder

Distension of the rectum by feces

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Verified step by step guidance

Understand the process of defecation: Defecation is the elimination of feces from the rectum through the anus. It is primarily controlled by the nervous system and involves both voluntary and involuntary mechanisms.

Identify the primary stimulus for defecation: The rectum is a muscular tube that stores feces temporarily. When feces accumulate in the rectum, they cause distension (stretching) of the rectal walls, which serves as the primary stimulus for defecation.

Explain the role of rectal distension: Distension of the rectum activates stretch receptors in the rectal walls. These receptors send signals to the spinal cord, initiating the defecation reflex, which involves relaxation of the internal anal sphincter and contraction of the rectal muscles.

Clarify why other options are incorrect: Absorption of nutrients in the small intestine, secretion of gastric acid in the stomach, and release of bile from the gallbladder are unrelated to the defecation process. These functions are part of digestion and nutrient absorption, not waste elimination.

Summarize the correct answer: The primary stimulus for defecation is the distension of the rectum by feces, which triggers the defecation reflex and facilitates the elimination of waste.