Perineum

Atlas References

• Netter: 358–365, 377, 378, 387, 389, 393, 395, 486–489

• McMinn: 276–279

• Gray's Atlas: 255–263, 266, 267, 270

Before You Begin

Dissection of the male and female pelvis is discussed separately in this chapter.

Dissection of the Male Cadaver

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  Place the cadaver in the supine position. Place a block under the sacrum and abduct the thighs as far as possible. A wooden block or rod is placed between the thighs at the level of the femoral condyles to maintain them in abduction ( Fig. 15.1 ).

  

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  Identify the adductor longus and gracilis muscles. These muscles can be transected so that the thighs can be abducted more easily. In this specimen, it was not necessary to transect these muscles ( Fig. 15.2 ).

  

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  Draw imaginary lines outlining the borders of the urogenital triangle: a line between the ischial tuberosities and two lines along the ischiopubic rami to the pubic symphysis ( Fig. 15.3 ). At the midpoint of a line connecting the two ischial tuberosities, palpate a fibromuscular mass of tissue, the perineal body .

  

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  Remove the skin of the urogenital region, including the scrotum. Reflect the testis toward the inguinal ligament, and expose the urogenital triangle. Lift the penis upward, and remove the adipose tissue and the rich venous network ( Fig. 15.4 ).

  

Anatomy Note

The fat that is removed here is located in the superficial perineal fascia (of Colles). This fascia is the continuation of Scarpa's fascia (membranous layer of anterior abdominal wall) into the perineum ( Figs. 15.5 and 15.6 ). Camper's fascia (fatty layer of anterior abdominal wall) continues into the perineum ( Plate 15.1 ).

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  Remove Colles’ fascia, and identify the corpus cavernosum laterally and the corpus spongiosum medially (see Fig. 15.6 ).

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  Expose the bulbospongiosus muscle covered with a fascial layer, the deep perineal fascia (Gallaudet's fascia).

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  Continue the exposure of the bulbospongiosus inferiorly, exposing the deep perineal fascia. The potential space between the superficial perineal fascia and deep perineal fascia is called the superficial perineal cleft (space between Colles’ and Gallaudet's fasciae) ( Figs. 15.7 and 15.8 ).

  
  

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  Dissect lateral to the bulbospongiosus muscle and identify the ischiocavernosus muscle arising from the ischiopubic rami (see Fig. 15.8 ). The ischiocavernosus surrounds the crus of the penis (corpora cavernosa), a bilateral collection of erectile tissue ( Fig. 15.9 ).

  

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  The inferior portion of the corpus spongiosum becomes dilated, forming the bulb of the penis. At the level of the bulb, remove the superficial perineal fascia and identify the superficial perineal muscle laterally ( Figs. 15.10 and 15.11 ).

  
  

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  Clean the superficial transverse perineal muscles, and superior to them, expose the perineal membrane ( Fig. 15.12 ).

  

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  Inferior and lateral to the transverse perineal muscles, expose the perineal nerve and perineal artery, which are branches of the pudendal nerve and internal pudendal artery, respectively (see Figs. 15.11 and 15.12 ).

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  Expose the ischiocavernosus muscle along the ischiopubic rami ( Fig. 15.13 ).

  

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  Lift the penis and expose the crus. Make an incision into the crus and expose its spongy matrix and its tunica albuginea , the outer covering of the corpus ( Fig. 15.14 ). Observe the pubic symphysis for the suspensory ligament of the penis, arising from deep fascia of the anterior abdominal wall, and the fundiform ligament , arising from the membranous layer of the superficial fascia of the abdomen.

  

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  Cut the ischiocavernosus muscle and reflect it anteriorly to expose the perineal membrane ( Fig. 15.15 ).

  

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  Cut the suspensory and fundiform ligaments of the penis and push the penis downward ( Fig. 15.16 ).

  

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  With a scalpel, cut through the bulb of the penis at the perineal membrane and remove the penis ( Fig. 15.17 ).

  

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  Identify the deep dorsal vein of the penis, the urethra, and the perineal body, and appreciate the dimensions of the perineal membrane.

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  Palpate the perineal membrane between the deep dorsal vein of the penis and the urethra, and note its thickening, the transverse perineal ligament (see Fig. 15.17 ).

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  Reflect the deep perineal membrane, and expose the underlying musculature, the deep transverse perineal muscle and sphincter urethrae ( Fig. 15.18 ).