Pelvis and Perineum Lecture Notes
Pelvis and Perineum Lecture Notes
Pelvis and Perineum Lecture Notes
Learning Objectives
Lumbosacral joints
o Intervertebral disc between L5 and S1
and facet joints between their articular
surfaces
o Iliolumbar ligaments
Sacroiliac joints
o Reinforced by anterior and posterior
sacroiliac ligaments
Strongest ligament of the body
Sacrococcygeal joint
o Reinforced by anterior,
posterior, and lateral
sacrococcygeal ligaments
Sacrotuberous ligament
o Transforms the sciatic notch into the sciatic
foramen
Sacrospinous ligament
o Divides the sciatic foramen
into greater and lesser sciatic foramina
Symphysis pubis
o Between the pubic bones
Pelvic Walls
Anterior
o Symphysis pubis and bodies and rami of pubic bones
Lateral
o Hip bone, obturator foramen, sacrospinous and sacrotuberous ligaments, and
obtuartor internus mm.
Posterior
o Sacrum and coccyx, ilia, sacroiliac joints and associated ligaments
o Covered by the piriformis mm.
Inferior
o Formed by the pelvic diaphragm
Muscles of the Pelvis
Obturator internus
o Origin: obturator membrane
o Leaves the pelvis through the lesser sciatic foramen
o Inserts: greater trochanter
o Action: lateral rotation of the hip
o Nerve Supply: nerve to the obturator internus
Piriformis
o Origin: pelvic surface of the sacrum
Sacral Plexus
o Anterior rami of spinal nerves L4 and L5
and S1-S4
o Branches to the lower limbs
Sciatic
Superior gluteal
Inferior gluteal
Nerve to obturator internus & superior
gemellus
Nerve to quadrates femoris & inferior
gemellus
Perforating cutaneous
nerve
Posterior cutaneous nerve
of thigh
o Branches to pelvic muscles,
viscera and perineum
Pudendal nerve (S2, 3, 4)
Motor muscles of the
perineum
Sensory lower
half of anal canal,
perianal skin,
external genitalia
Nerve to piriformis
Pelvic splanchnic nerves parasympathetic innervation to pelvic viscera
Perforating cutaneous nerve
Branch from the lumbar plexus obturator nerve (L2, 3, 4)
Autonomic nerves
o Superior hypogastric plexus contains
sympathetic, parasympathetic, and visceral
afferent fibers
o Inferior hypogastric plexuses contains
postganglionic sympathetic, preganglionic
parasympathetic and visceral afferent fibers
o Sacral splanchnic nerves from sacral portion of
sympathetic trunks
o Pelvic splanchnic nerves sacral outflow of
parasympathetic division of ANS
Clinical Correlation
Piriformis Syndrome
o ~15% of the population, sciatic nerve
travels throughpiriformis causing
sciatica and pain in gluteal region made worse by sitting,
climbing stairs, or performing squats
Injury to Pelvic Nerves
o Compression of mothers sacral plexus by
fetal head during delivery causing pain
in the mothers lower limbs
o Injury to obturator nerve during
surgical removal of cancerous lymph
nodes from lateral pelvic wall causing weakness or
paralysis of adductor muscles of thigh and sensory
deficits in medial thigh region
Urogenital Triangle
Layers
o
Skin
o Superficial fascia
Fatty layer (Campers)
Membranous layer (Colles fascia; scarpa)
Continuous with dartos fascia of the penis and Scarpas fascia of the
anterior abdominal wall
Attached to fascia lata just distal to the inguinal ligament; inferior
fascia of the urogenital diaphragm
o Inferior fascia of the urogenital
diaphragm perineal membrane
o Urogenital diaphragm composed of the sphincter urethrae and deep transverse
perineal muscles
o Superior fascia of the urogenital diaphragm
Perineal Spaces
o Superficial perineal space between Colles fascia and the inferior fascia of the
urogenital diaphragm
o Deep perineal space between the superior and inferior fascia of the urogenital
diaphragm (perineal membrane)
Superficial Perineal Space
o Contents in males
Root of the penis and associated muscles
Proximal portion of the spongy
urethra
Superficial transverse perineal
muscle
Branches (tributaries) of
the internal pudendal
artery and vein
Perineal branch of
pudendal nerve
o Contents in females
Root of the clitoris and associated
muscles bulbospongiosus
and ischiocaveronsus
Part of the urethra
Superficial perineal
muscle
Branches (tributaries) of the internal
pudendal artery and vein
Perineal branch of the
pudendal nerve Figure 1 Superficial Perineal space - males
Greater vestibular glands (Bartholins) glands
Deep Perineal Space
o Content in males
Membranous portion of
the urethra
Urogenital diaphragm
Deep transverse
Branches (tributaries) of
the internal pudendal
artery and vein
Dorsal nerve of the penis
Bulbourethral (Cowpers)
glands
o Content in females
Part of the urethra and vagina
Urogenital diaphragm
Branches (tributaries) of Figure 2 Superficial Perineal space - females
the internal pudendal artery and
vein
Dorsal nerve of the clitoris
Anal Triangle
Contents
o Anal canal
o Ischioanal fossae
o External anal sphincter
Ischioanal Fossa
Branches:
o Inferior rectal motor to external anal
sphincter
o Dorsal nerve of the penis (clitoris)
o Perineal nerve motor to muscles in urogenital
triangle; sensory to skin on posterior
surface of the scrotum (labia
majora)
Pudendal Nerve Block
o Injecting local anesthesia around the
pudendal nerve as it
exits the pudendal canal near the
ischial spine
o Provides anesthesia over S2-S4
dermatomes and lower of
vagina Figure 4 Deep Perineal Space - females
Ischioanal Abscess
May result from inflammation of the anal sinuses, a tear in the anal mucous membrane, or
a penetrating would on the anal region
Fullness and tenderness between the anus and ischial tuberosity