Topographic anatomy of male pelvis (draw sagittal section)

Introduction

The male pelvis houses critical components of the urinary, reproductive, and digestive systems. Its spatial configuration is essential for understanding surgical approaches, pelvic trauma, and urologic procedures. In this article, we explore the topographic anatomy of the male pelvis, focusing on a median sagittal section to illustrate the positional relationships of pelvic structures.

1. General Topography of the Male Pelvis

The pelvis is divided into:

• Greater (false) pelvis, located above the pelvic brim, and
• Lesser (true) pelvis, located below the brim and containing the pelvic organs.

In the median sagittal section, the anatomical structures are arranged from anterior to posterior as follows:

1. Pubic symphysis – the anterior bony landmark of the pelvis
2. Urinary bladder – located just posterior to the pubic symphysis; lies in the true pelvis when empty and may extend into the false pelvis when full
3. Prostate gland – located directly beneath the bladder; surrounds the prostatic urethra
4. Membranous urethra – short segment that passes through the urogenital diaphragm (deep perineal pouch)
5. Bulb of the penis – continuous with the spongy (penile) urethra
6. Rectum – located posterior to the bladder and prostate; follows the curvature of the sacrum
7. Anal canal – terminal part of the digestive tract, located within the anal triangle
8. Sacrum and coccyx – form the posterior bony boundary

2. Pelvic Peritoneum and Pouches

In males, the peritoneum covers the superior surfaces of the pelvic organs and forms a single deep pouch:

• Rectovesical pouch – located between the posterior surface of the bladder and the anterior surface of the rectum; this is the lowest point of the peritoneal cavity in males when in supine position

Unlike in females, there is no uterine structure, so the number of peritoneal pouches is reduced.

3. Pelvic Floor and Urogenital Diaphragm

The pelvic floor (pelvic diaphragm) supports the pelvic viscera and consists of:

• Levator ani muscles: including puborectalis, pubococcygeus, and iliococcygeus
• Coccygeus muscle

These muscles form a funnel-shaped structure and play a key role in supporting the pelvic organs, maintaining continence, and providing passage for the urethra and rectum.

The urogenital diaphragm (deep perineal pouch) lies inferior to the pelvic floor and contains the:

• Deep transverse perineal muscles
• External urethral sphincter (voluntary muscle for urinary continence)

4. Sagittal Section: Organs and Relations

In a median sagittal section of the male pelvis, these organs and structures are visible:

From anterior to posterior:

• Pubic symphysis
• Urinary bladder (superior to prostate)
• Prostate gland (inferior to bladder)
• Urethra: divided into prostatic, membranous, and spongy segments
• Penis (bulb and shaft – spongy urethra continues through here)
• Rectum (curving along sacrum)
• Anal canal
• Sacrum and coccyx

Additional structures visible in sagittal views:

• Seminal vesicles – located posterior to the bladder and anterior to the rectum
• Vas deferens – ascends from the scrotum, arches over the ureter, and joins the duct of the seminal vesicle to form the ejaculatory duct, which opens into the prostatic urethra

5. Clinical Relevance

• Prostatic enlargement (BPH or cancer) can compress the urethra, causing urinary obstruction
• The rectovesical pouch is a site where fluid or infection may collect and can be accessed surgically
• Urethral catheterization and surgeries require detailed knowledge of urethral anatomy, especially the membranous portion, which is the narrowest and most vulnerable

6. Suggested Drawing: Sagittal Section of the Male Pelvis

Your drawing should depict a midline sagittal view, showing the sequential anatomy:

Anterior structures:

• Pubic symphysis
• Bladder
• Prostate
• Urethra (with its segments)
• Penis (cut to reveal spongy urethra)

Posterior structures:

• Seminal vesicle
• Rectum
• Anal canal
• Sacrum and coccyx

Include these planes and structures:

• Pelvic diaphragm (levator ani)
• Urogenital diaphragm
• Peritoneal covering forming the rectovesical pouch

(Ensure your drawing is based on official resources such as Sobotta or Gray’s Anatomy.)

Conclusion

The male pelvis contains closely packed structures vital to urinary and reproductive functions. A thorough understanding of their topographic relations, especially as visualized in the sagittal plane, is essential for clinical application in urology, proctology, and pelvic surgery.

References

1. Paulsen, F., Waschke, J. Sobotta Atlas of Human Anatomy, Vol. 2, 16th ed. Elsevier.
2. Drake, R.L., Vogl, A.W., Mitchell, A.W.M. Gray’s Anatomy for Students, 4th ed. Elsevier.
3. Moore, K.L., Dalley, A.F., Agur, A.M.R. Clinically Oriented Anatomy, 8th ed. Wolters Kluwer.