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

27. The Reproductive System

Anatomy of the Male Reproductive System

Anatomy & Physiology

27. The Reproductive System

Anatomy of the Male Reproductive System

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Problem 18

Textbook Question

Describe the erectile tissues of the penis. How does erection occur?

Verified step by step guidance

The penis contains three cylindrical erectile tissues: two corpora cavernosa and one corpus spongiosum. The corpora cavernosa are located on the dorsal side of the penis, while the corpus spongiosum surrounds the urethra and forms the glans at the distal end.

Erectile tissues are composed of a network of vascular spaces (sinusoids) surrounded by smooth muscle and connective tissue. These spaces can fill with blood during sexual arousal, leading to an erection.

Erection is initiated by parasympathetic nervous system activation, which releases nitric oxide (NO). Nitric oxide stimulates the production of cyclic guanosine monophosphate (cGMP) in the smooth muscle cells of the erectile tissues.

cGMP causes relaxation of the smooth muscle in the walls of the sinusoids and the arteries supplying the erectile tissues. This relaxation allows blood to flow into the sinusoids, causing them to expand and compress the veins that drain the penis, trapping blood within the erectile tissues.

The increased blood flow and trapped blood result in the penis becoming engorged and rigid, which is the physiological process of erection. The process is reversed when the enzyme phosphodiesterase type 5 (PDE5) breaks down cGMP, leading to smooth muscle contraction and the return of the penis to its flaccid state.

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Key Concepts

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

Erectile Tissues

The penis contains three main erectile tissues: the corpora cavernosa and the corpus spongiosum. The corpora cavernosa are two cylindrical structures that run along the length of the penis, while the corpus spongiosum surrounds the urethra and extends to form the glans. These tissues are rich in blood vessels and can expand significantly when filled with blood.

Mechanism of Erection

Erection occurs through a complex process involving the nervous system and blood flow. When sexual arousal happens, the brain sends signals that relax the smooth muscles in the erectile tissues, allowing blood to fill the spaces within them. This engorgement causes the penis to enlarge and become rigid, resulting in an erection.

Role of Nitric Oxide

Nitric oxide (NO) plays a crucial role in the erection process by acting as a signaling molecule. It is released in response to sexual stimulation and promotes the dilation of blood vessels in the penis, enhancing blood flow. This increase in blood flow is essential for achieving and maintaining an erection, as it allows the erectile tissues to fill with blood.