Anatomy of the Perineum

Study Notes

Lies between the sides of the pubic arch
Protected by the urogenital diaphragm
Contents:
- Anal canal
- Ischio-anal fossa
- Urogenital pouches (superficial and deep)

Lies behind the urogenital triangle
Contents:
- The ano-coccygeal body, located in the anal triangle, is a part of the pelvic region. It forms the floor of the anal canal and is part of the anorectal junction, which is the connection between the anus and the rectum.
- Anal canal
- Ischio-anal fossa

Wedge-shaped fossa
Base: downwards, formed by the skin
Edge: upwards, at the tendinous arch
Medial boundary: formed by external anal sphincter and levator ani
Lateral boundary: formed by obturator internus, fascia, and ischial tuberosity
Anterior boundary: formed by urogenital triangle
Posterior boundary: formed by sacro-tuberous ligament, covered by gluteus maximus
Contents:
Pudendal canal containing pudendal nerve, internal pudendal vessels
Inferior rectal nerve and vessels
Perineal branch innervates external anal sphincter, playing a crucial role in regulating bowel movements and maintaining continence.
The urogenital pouches are two sac-like structures that contain the urethra and vagina in males and females, respectively. They are separated by the scrotum in males and the labia in females.
Superficial pouch: covered only by skin and superficial fascia
Deep pouch: covered by deep fascia, stretched between the sides of the pubic arch
Contents of deep pouch:
- Urethra surrounded by external urethral sphincter (in female)
- Vagina surrounded by deep transverse perineal muscles (in female)
- Nerves and vessels (dorsal nerve clitoris and vessels of clitoris) (in female)
- Membranous urethra surrounded by external urethral sphincter and bulbourethral glands (in male)
- Deep transverse perineal muscles (in male)
- Nerves and vessels (dorsal nerve penis and penis vessels) (in male)

Thickened inferior fascia of urogenital diaphragm
Separates the two perineal pouches
Pierced by:
- Vagina and urethra (in female)
- Clitoris artery, vessels of the bulb, deep vessels of clitoris, dorsal vessels of clitoris, dorsal nerve of clitoris (in female)
- Membranous urethra, bulbourethral ducts, bulb vessels, urethral vessels, deep vessels of penis, dorsal vessels of penis, dorsal nerve of penis (in male)

Position: below the perineal membrane, between the perineal membrane and membranous layer of superficial fascia
Opened anteriorly and continuous with the anterior abdominal wall
Closed posteriorly
Contents:
- Root of penis or clitoris
- Superficial perineal muscles (bulbospongiosus, ischiocavernosus, superficial transverse perineal)
- Branches of pudendal nerve and internal pudendal vessels
- Part of urethra
- Testis or vagina and greater vestibular gland

Fibromuscular mass in the center of the perineum
Receives the following muscles:
- Levators ani
- External anal sphincter
- Bulbospongiosus
- Transverse perineal muscles

Origin: inside the pelvis, from sacral plexus (S2,3,4)
Leaves the pelvis through the greater sciatic foramen
Enters the perineum through the lesser sciatic foramen
Passes in the pudendal canal and ends at the lower end of the canal
Branches:
- Inferior rectal nerve
- Dorsal nerve of penis or clitoris
- Perineal nerve, which gives muscular and posterior scrotal nerves