The perineum is the diamond-shaped region between the pelvic outlet and the thighs. It is divided into an anterior urogenital triangle and a posterior anal triangle by an imaginary line between the ischial tuberosities. The anal triangle contains the external anal sphincter and is supplied by the inferior rectal branches of the pudendal nerve. The urogenital triangle contains erectile tissue that forms the clitoris or penis, as well as muscles and glands. The main blood supply is from the internal pudendal artery and its branches, while lymphatic drainage involves the superficial and deep inguinal nodes as well as internal iliac nodes.

1. Perineum
Themba Hospital FCOG(SA) Part 1 Tutorials
By Dr N.E Manana

2. Perineum
• Diamond shape, inferior to the pelvic floor, medial to the thighs
• Its peripheral boundaries is the pelvic outlet, its ceiling is the pelvic
diaphragm
• Its is divided into an anterior urogenital triangle and a posterior anal
triangle
• The 2 triangle are divided by an imaginary line between the ischial
tuberosities, the 2 triangle are not in the same plain
• The major nerve and artery supply is by the Pudendal nerve and the
Internal pudendal artery respectively

3. Ischio-anal fossae
• Pic 5.69

4. Anal triangle
• Faces posteroinferiorly, defined laterally by the margins of the STL,
anteriorly by the line btn the 2 ischial tuberosities and posteriorly by
the coccyx
• The anal aperture occurs centrally and is related with the ischio-anal
fossa on either side
• The major muscle in the triangle it’s the external anal sphincter,
which is formed by skeletal muscles and surrounds the anal canal
• Consists of 3 parts; deep, superficial and subcutaneous (Superior to
inferior), innervated by the inferior rectal branches of the pudendal
nerve and branches from the anterior ramus of S4

5. Urogenital triangle
• It’s the anterior half of the perineum and is oriented in a horizontally plain
• Contains the roots of the external genitalia and the opening of the
urogenital system
• Boarders
• Unlike the anal triangle it contains a strong fibromuscular support platform
• Anterior extensions of the ischio-anal fossae occur btn the deep perineal
pouch and the levator ani muscle on each side
• The superficial perineal pouch contains erectile tissue and assoc skeletal
muscles

6. • Pic5.71

7. Erectile tissue
• Two sets of erectile tissue join to form the penis or clitoris
• Cylindrically shaped, corpora cavernosa one on each side of the
urogenital triangle, anchored by the proximal end of the pubic arch
• The attached parts are termed crura (legs), the distal end of the
corpora forms the body of the clitoris of dorsal body of the penis
• The second set surround the opening of the urogenital system; in
women its termed the bulbs of vestibule, attached to the clitoris by
small bends of erectile tissue forming the glans clitoris
• In men, a large erectile mass the corpora spongiosum which encloses
the urethra, anchored at its base by perineal membrane

8. Erectile tissue
Penis
• Root of the penis consist of 2 crura and the bulb of the penis,
supported by 2 ligaments the suspensory ligament of penis and
fundiform ligament of penis
• Body of the penis composed of two corpora cavernosa and the single
corpus spongiosum
Clitoris
• Root, consist only of two crura
• Body, formed by the 2 corpora cavernosa, angles posteriorly and is
embedded in the connective tissue of the perineum

9. Greater vestibular glands (Batholin’s)
• They are small, pea-shaped mucous glands
• They lie posterior to the bulbs of the vestibule on each side of the
vaginal opening
• They are located in the superficial perineal pouch unlike the
bulbourethral glands in males which are in the deep urethra pouch
• The glands open into the vestibule along the posterolateral margin of
the vaginal opening
• Like the bulbourethral glands in men, they produce secretion during
sexual arousal

10. Muscles
• The superficial perineal pouch contains 3 pairs of muscles; the
ischiocavernosus, bulbospongiosus and superficial transverse
perineal muscles
• Table 5.6

11. • Pic 5.72

12. Superficial external genitalia
• Pic 5.73

13. Nervous supply
Somatic nerves : Pudendal nerve
• It originates from the sacral plexus, carries fibers from S2-S4
• It leaves the pelvic cavity via the greater sciatic foramen inferior to the
piriformis muscle, passes around the SSL, the enters the anal triangle via
the lesser sciatic foramen
• Entering the perineum it lies on the lateral wall of the ischio-anal fossa
(Pudendal canal)
• It has 3 terminal branches: inferior rectal nerve, perineal nerve and dorsal
nerve of the penis or clitoris
• Others: Ilio-inguinal, genitofemoral, posterior femoral cutaneous and
anococcygeal nerve

14. • 5.76

15. Blood vessels
Arteries
1. Internal pudendal artery: originates as a branch of the anterior trunk
of the internal iliac artery
• It moves along the pudendal nerve, lies lateral to the nerve around
the iliac spine
• Its branches are similar to those of the pudendal nerve
• Inferior rectal is a branch of the internal pudendal artery, crosses the
ischio-anal fossa medially
• The anastomose with middle and superior rectal arteries from the
internal iliac artery and inferior mesenteric artery respectively

16. Blood vessels
Perineal artery
• Originated near the anterior end of the pudendal canal and gives a
transverse branch and a posterior scrotal or labial artery
Terminal internal pudendal artery
• Accompanies the dorsal nerve of the penis/clitoris
• Supply tissue in the deep perineal pouch and the erectile tissue; arteries of
the bulb of vestibule, deep arteries of the clitoris and dorsal arteries of the
clitoris
• 2. External pudendal arteries: originates from the femoral artery, has a
deep and superficial vessel, course medially to supply the clitoris and labia
majora

17. • 5.77

18. • 5.78

19. Lymphatic drainage
• Lymph vessels from deep parts of the perineum drain mainly into internal
iliac nodes
• Superficial tissues of the clitoris and labia majora drain into the superficial
inguinal nodes
• Glands of the clitoris, labia minora and the terminal end of the vagina drain
into deep inguinal nodes and external iliac nodes
• Lymphatics from the testis drain into the lateral aortic and preaortic nodes
(L1-L2)

20. • 5.79

21. Thank you