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

25. The Urinary System

Introduction to the Urinary System

Anatomy & Physiology

25. The Urinary System

Introduction to the Urinary System

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1:52 minutes

Problem 21

Textbook Question

How do the internal and external urethral sphincters differ structurally and functionally?

Verified step by step guidance

Identify the location of the internal and external urethral sphincters: The internal urethral sphincter is located at the junction of the bladder and urethra, while the external urethral sphincter is located further down the urethra, surrounding it.

Understand the structural differences: The internal urethral sphincter is composed of smooth muscle, which is involuntary, whereas the external urethral sphincter is composed of skeletal muscle, which is under voluntary control.

Explore the functional differences: The internal urethral sphincter helps maintain urinary continence by preventing the involuntary release of urine, while the external urethral sphincter allows for voluntary control over urination.

Consider the nervous system control: The internal urethral sphincter is controlled by the autonomic nervous system, specifically the sympathetic nervous system, which keeps it contracted. The external urethral sphincter is controlled by the somatic nervous system, allowing conscious control.

Summarize the roles in micturition: During urination, the internal sphincter relaxes as part of the involuntary reflex, while the external sphincter is consciously relaxed to allow urine to pass through the urethra.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Internal Urethral Sphincter

The internal urethral sphincter is a smooth muscle structure located at the junction of the bladder and urethra. It is involuntary and controlled by the autonomic nervous system, allowing for the retention of urine. Its primary function is to maintain continence by preventing the flow of urine from the bladder until voluntary urination is initiated.

External Urethral Sphincter

The external urethral sphincter is composed of striated muscle and is located around the urethra, below the internal sphincter. It is under voluntary control, allowing individuals to consciously decide when to urinate. This sphincter plays a crucial role in urinary continence, enabling the fine-tuning of urination in response to social and environmental cues.

Structural Differences

Structurally, the internal urethral sphincter is made of smooth muscle, which is not under conscious control, while the external urethral sphincter consists of striated muscle, which is under voluntary control. This distinction is essential for understanding how these sphincters function in coordination to regulate urine flow and maintain bladder control.