Anatomy, Abdomen and Pelvis, Superficial Perineal Space

Article Author:
Michael Fahmy
Article Editor:
Sunil Munakomi
Updated:
5/25/2019 4:42:15 PM
PubMed Link:
Anatomy, Abdomen and Pelvis, Superficial Perineal Space

Introduction

The urogenital triangle is made up of a superficial and deep layer of fascia, with a middle layer of skeletal muscle called the urogenital diaphragm. The superficial perineal space or pouch is a small compartment of the perineum. The superficial perineal space is inferior to the urogenital diaphragm and its inferior fascia, which is enveloped by Colles fascia.[1]

The superficial perineal space is an open compartment that is open anteriorly. Here it communicates freely with the potential space lying between the anterior abdominal muscles and the superficial fascia of the anterior abdominal wall. This space contains erectile tissue, muscles, and neurovascular structures associated with the external genitalia.[2]

Structure and Function

Anatomic boundaries:

Anterior: by communicating freely with the potential space lying between the superficial fascia of the anterior abdominal wall and anterior abdominal muscles

Superior: by the perineal membrane which is the inferior fascia of the urogenital diaphragm

Inferior: by Colles fascia, which is the deep membranous layer of the superficial perineal space. This fascia covers the muscles located in the superficial perineal pouch

Contents of the superficial perineal space in both sexes:

Although they have different functions in males and females, the ischiocavernosus, bulbospongiosus, and the transverse perineal muscle are present in the superficial perineal space in both sexes as well as the urethral artery.[3]

Contents of the superficial perineal space in males:

  • Corpus cavernosum of the penis: a sponge-like erectile tissue that fills with blood during a penile erection
  • Corpora spongiosus of the penis: a mass of spongy tissue that surrounds the male urethra and works to prevent the urethra from closing shut so that it can continue to be a viable channel for ejaculation
  • Posterior scrotal arteries: branches of the internal pudendal artery and directs blood flow to the penis, testicles, and scrotum
  • Artery of the bulb of the penis: arises from the internal pudendal artery between the two layers of the superior and inferior fascia of the urogenital diaphragm and directs blood flow to the bulb of the urethra
  • Posterior scrotal nerves: is a branch of the perineal nerve and runs to innervate the skin of the scrotum 
  • Crura of the penis: is the posterior portion of the corpus cavernosum that then attaches to the ischiopubic ramus
  • Bulb of the penis: forms the internal structure of the penis and appears as a prominent ridge on the shaft of the penis 

Contents of the superficial perineal space in females:

  • Corpus cavernosum of the clitoris: a sponge-like erectile tissue that fills up with blood in the clitoris during clitoral erection 
  • Posterior labial arteries: are branches of the internal pudendal artery and directs blood flow to the posterior portions of the labia majora and minora
  • Artery to the vestibule: is a branch of the internal pudendal artery and supplies the vestibular bulb 
  • Posterior labial nerves: branches of the pudendal nerve and supplies the skin of the labia majora
  • Crura of the clitoris: is an erectile tissue structure that is attached to the pubic arch and neighbors the vestibular bulbs. During sexual arousal, they become engorged with blood
  • Bulb of the vestibule: is an elongated mass of erectile tissue that lies on either side of the vaginal opening. During sexual arousal, the bulbs fill up with blood causing an erection causing the vulva to expand outward 
  • Bartholin's Gland: are two pea-sized circular glands that are located posterior and to the left and right of the vagina. They secrete mucus to lubricate the vagina

Embryology

All component of the urogenital system derives from the intermediate mesoderm.

Blood Supply and Lymphatics

The superficial perineal space receives vascular supply from the internal pudendal artery, which branches off the internal iliac artery.[4] The perineal artery supplies the transverse perineal muscle in both males and females. In males, the posterior scrotal artery supplies the posterior portion of the scrotal sac, the artery to the bulb of the penis supplies the urethra, the dorsal artery of the penis supplies the glans penis and prepuce of the penis, and the deep artery of the penis supplies the corpus cavernosum of the penis.[5] In females, the posterior labial artery supplies the posterior portion of both the labia majora and minora, the artery to the bulb of the vestibule supplies the vestibular bulbs, the dorsal artery of the clitoris supplies the clitoral crura, and the deep artery of the clitoris also supplies the clitoral crura.[5] 

Lymphatics from the superficial perineal space accompanies the internal pudendal artery and its branches, which then drain into the internal iliac lymph nodes.

Nerves

Pudendal nerve branches are present in the superficial perineal space: In females, the posterior labial nerve has a medial and lateral branch and runs along the lateral part of the urethral triangle to supply the skin of the labia majora. In males, the posterior scrotal nerve also has a medial and lateral branch and also runs along the lateral part of the urethral triangle to innervate the skin of the scrotum.[6][7]

Muscles

Ischiocavernosus muscle: is a muscle that is just below the surface of the perineum and is present in both men and woman. It is innervated by the perineal nerve which is a branch of the pudendal nerve. In males, it aids in stabilizing an erect penis, and it tenses the vagina during orgasm in females.[8] 

Bulbospongiosus muscle: is a superficial muscle in the perineum. In males, it covers the penile bulb, and in woman, it covers the vestibular bulb. In both men and woman, receives its nerve supply from the deep branch of the perineal nerve. In males, it contributes to erection and the contraction of orgasm and ejaculation. In females, it also contributes to clitoral erection and the contraction of orgasm and ejaculation.[9]

Transverse perineal muscle: is part of the pelvic floor. Its innervated by the pudendal nerve and functions to support the pelvic floor fixates the perineal body and aids in the expulsion of semen in males and the expulsion of the last drops of urine in both males and females.[10]

Surgical Considerations

In cases of traumatic rupture of the bulbous urethra, there is extravasation of urine within the superficial perineal space. However, urine can pass into the penile region (outside of Buck fascia) as well as scrotal and lower abdominal wall (outside of the Colles and Scarpa fascia). Historically, the prevention of the uremia and the sepsis that can eventually follow was by the application of the 'perineal section.'[11]

Same anatomic pathways account for the progression of necrotizing fascitis - Fournier gangrene within the perineal region. The Buck fascia and the Colles fascia account for limiting the further progression of the fascitis beyond and beneath their attachments, which is secondary to obliterative endarteritis of the arteries supplying the region due to endotoxemia.[12][13]

Clinical Significance

The Bartholin glands are within the superficial perineal space. These glands secrete a fluid that lubricates the vagina. In normal circumstances, the Bartholin glands are not visible, but if the glands are blocked, they can swell and present as a fluid-filled cyst. If the fluid gets infected, a condition known as bartholinitis occurs. The most common organisms associated with bartholinitis is Staphylococcus spp. and Escherichia coli. The diagnosis requires a pelvic exam, and the treatment is incision and drainage with marsupialization. Unfortunately, a simple incision and drainage are associated with recurrences.[14][15]


References

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[3] The secondary external inguinal ring and associated fascial planes: surgical anatomy, embryology, applications., Mirilas P,Mentessidou A,, Hernia : the journal of hernias and abdominal wall surgery, 2013 Jun     [PubMed PMID: 23404213]
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[14] Cobo F,Rodríguez-Granger J,Sampedro A,Navarro-Marí JM, Bartholin's abscess due to Dialister micraerophilus in a woman presenting with repetitive bartholinitis episodes. Medecine et maladies infectieuses. 2018 May;     [PubMed PMID: 29397243]
[15] Reis HL,Pinho CR,Ferreira Dde C, Diagnosis and management of acute puerperal bartholinitis caused by Escherichia coli. Revista da Sociedade Brasileira de Medicina Tropical. 2014 Nov-Dec;     [PubMed PMID: 25626668]