Human Anatomy: Perineum and Associated Structures

Study Notes

Perineum
The perineum is the region between the pelvic outlet and the pelvic floor, divided into two triangles: Urogenital triangle and Anal triangle.
Urogenital Triangle
Lies between the pubic arch and is protected by the pelvic floor.
Contains the urogenital canal and ischio-anal fossa.
Anal Triangle
Lies between the coccyx and ischio-anal fossa.
Contains the anal canal, ischio-anal fossa, and ano-coccygeal body.
Ischio-anal Fossa
A wedge-shaped fossa with a base formed by the skin and an edge formed by the tendinous arch.
Medial boundary formed by external anal sphincter and levator ani, and lateral boundary formed by obturator internus, fascia, and ischial tuberosity.
Anterior boundary formed by the urogenital triangle, and posterior boundary formed by the sacro-tuberous ligament covered by gluteus maximus.
Contents include pudendal canal, inferior rectal nerve and vessels, perineal branch of 4th sacral nerve, and pad of fat.
Urogenital Triangle Pouches
Superficial pouch formed by skin and superficial fascia.
Deep pouch formed by deep fascia stretched between the sides of the pubic arch, named urogenital diaphragm.
Deep Perineal Pouch
A flattened closed space stretched between the sides of the pubic arch, forming the urogenital diaphragm.
Fascia of the closed pouch includes superior and inferior fascia of urogenital diaphragm, with transverse perineal ligament formed by fusion of superior and inferior fascia.
Deep Perineal Pouch Contents
In females: urethra surrounded by external urethral sphincter, vagina surrounded by deep transverse perineal muscles, and nerves and vessels.
In males: membranous urethra surrounded by external urethral sphincter and bulbourethral glands, deep transverse perineal muscles, and nerves and vessels.
Perineal Membrane
Thickened inferior fascia of urogenital diaphragm separating the two perineal pouches.
In females, pierced by vagina, urethra, clitoris artery, deep vessels of clitoris, dorsal vessels of clitoris, and dorsal nerve of clitoris.
In males, pierced by membranous urethra, bulbourethral ducts, bulb vessels, urethral vessels, deep vessels of penis, dorsal vessels of penis, and dorsal nerve of penis.
Superficial Perineal Pouch
Lies below the perineal membrane and between the perineal membrane and membranous layer of superficial fascia.
Opened anteriorly and continuous with the anterior abdominal wall, closed posteriorly.
Superficial Perineal Pouch Contents
In males: root of penis, superficial perineal muscles, branches of pudendal nerve and internal pudendal vessels, part of urethra, and testis.
In females: root of clitoris, superficial perineal muscles, branches of pudendal nerve and internal pudendal vessels, urethra, vagina, and greater vestibular gland.
Perineal Body
A fibromuscular mass in the center of the perineum, receiving the following muscles: levators ani, external anal sphincter, bulbospongiosus, and transverse perineal muscles.
Pudendal Nerve
Originates from the sacral plexus (S2,3,4) inside the pelvis.
Leaves the pelvis through the greater sciatic foramen and enters the perineum through the lesser sciatic foramen, passing in the pudendal canal.
Dorsal Nerve of Penis/Clitoris
A branch of the pudendal nerve, supplying the penis or clitoris.
Branches of Pudendal Nerve
In males: inferior rectal nerve, dorsal nerve of penis, and perineal nerve.
In females: inferior rectal nerve, dorsal nerve of clitoris, and perineal nerve.
Internal Pudendal Artery
Has the same course as the pudendal nerve.
Branches include inferior rectal nerves, artery of penis, and perineal artery.
Artery of Penis
Gives four branches: artery of the bulb, urethral artery, deep artery of penis, and dorsal artery of penis.
Internal Pudendal Vein
Ends in internal iliac vein.
Deep dorsal vein of penis or clitoris ends in pelvic plexuses, and superficial dorsal vein of penis ends in external pudendal vein.