QuestionSBA
QuestionChoice
The distal expansion of the corpus spongiosum forms the glans penis.
10014265
c
Glans penis
QuestionChoice
The male urethra runs through the corpus spongiosum which lies ventrally. The corpus spongiosum remains pliable during erection by filling at a reduced pressure in comparison to the corpus cavernosum, to prevent the urethra from pinching closed, maintaining it as a channel for ejaculation.
10014263
a
Corpus spongiosum
QuestionChoice
This is a lining that covers the testis and epididymis
10014266
d
Tunica vaginalis
QuestionChoice
Lies above the annotated structure and is contained within the corpus spongiosum.
10014264
b
Spongy urethra
QuestionChoice
This is formed by erectile tissue on the dorsal surface of the penis extending from root of the penis into the body of the penis.
10014267
e
Corpus cavernosum
Concept
Chapter
## Summary

The penis is a male appendage used for reproduction and urination. It is formed of the two corpora cavernosa and corpus spongiosum. When filled with blood it becomes erect.

## Anatomy

Superficial to the perineal membrane in the male is the **root of the penis**. The root of the penis is formed by **three masses** of **erectile tissue**, each surrounded by a tough fibrous sheath. The **crura** of the penis are **attached** to the **inner surface** of each **ischiopubic ramus**. The crura become the **two corpora cavernosa** of the shaft. There is **free communication of blood vessels between the two through perforations** in the fibrous septum along the length of the shaft.

The third component is the **bulb of the penis**. It lies in the midline against the undersurface of the perineal membrane. The bulb continues in the free shaft of the penis as the **corpus spongiosum** and it extends to form the **glans penis** at the top. The bulb of the penis and **two crura are covered by muscles**, which, when they contract, may assist in initiating and maintaining **erection** of the penis.

Erectile tissue contains cork-screw like or **helicline arterioles** that open into **fibrous spaces**. As a result of **parasympathetic stimulation** the smooth muscles of the **arterioles dilate** and the fibrous spaces become taut and distended with arterial blood, resulting in erection of the penis.

Two **ischiocavernosus** muscles **enclose** the crura over the ischiopubic rami and the **bulbospongiosus** muscle cover the bulb of the penis in the midline. The bulbospongiosus muscle has a **midline raphe** or seam that has a sphincteric action that assists in ejaculation and urination.

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## Blood supply

The **deep and dorsal arteries** of the penis divide into many branches, and some end in capillary networks. Blood from **cavernous spaces converges** in vessels from the base of the glans penis, to **form the deep dorsal vein.**

## Innervation

The nerves of the penis come from the **pudendal and pelvic nerve plexuses.**

## Clinical points
Rupture of the corpus cavernosum (called a ruptured or fracture penis) causes immediiate loss of erection, severe pain and deformity. If it is not surgically repaired it can lead to permanent deformity of the penis when erect.
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penis2.gif
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Penis
Topic
237
Pelvic Anatomy
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Picture
1984
14 - Penis (corpus spongiosum).png
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Topic
237
Pelvic Anatomy
Identify the annotated structure.

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a