Pelvis anatomy Flashcards
Obturator internus
Supplied by L5 and S1, attaches to GT of femur
Lateral rotation of femur and abduction of flexed hip
Piriformis
Supplied by S1 and S2, attaches to GT of femur above obturator internus
Lateral rotation of femur and abduction of flexed hip
Separates greater sciatic foramen into two regions (one above and one below)
Obturator canal
Bordered by obturator membrane, associated obturator muscles and superior pubic ramus. Obturator nerve and vessels pass from pelvic cavity to the thigh through this canal.
Greater sciatic foramen
Formed by greater sciatic notch, sacrotuberous and sacrospinous ligaments and spine of ischium.
Superior gluteal nerves and vessels passes through foramen above piriformis
Inferior gluteal nerves and vessels, sciatic nerve, pudendal nerve, internal pudendal vessels, posterior femoral cutaneous nerves and nerves to obturator internus and quadratus femoris muscle passes below piriformis
Lesser sciatic foramen
Formed by lesser sciatic notch, ischial spine, sacrospinous ligament, sacrotuberous ligament.
Tendon of obturator internus passes through this foramen to enter gluteal region.
Below attachment of pelvic floor, act as route of communication between perineum and gluteal region.
Pudendal nerve and internal pudendal vessels pass through here as well + greater sciatic foramen
Pelvic floor
Formed by pelvic diaphragm, perineal membrane and muscles in deep perineal pouch
Greater sciatic foramen above pelvic floor
Lesser sciatic foramen below pelvic floor
Pelvic diaphragm
Levator ani (iliococcygeus, pubococcygeus and puborectalis) and coccygeus muscles from both sides Innervated by branches of anterior ramus of S4 and branches of pudendal nerve S2-S4
External urethral sphincter
All muscles in deep perineal pouch
Innervated by perineal branches of pudendal nerve
Ureters
Enters pelvic cavity anterior to bifurcation of common iliac artery and joins base of bladder.
Crossed by
uterine artery in women
ductus deferens in men
Bladder
Retroperitoneal structure
apex, two inferolateral surfaces, base and superior surface
Neck is most fixed part of the bladder. Anchored onto posteroinferior aspect of pubic bone by pubovesical ligaments (women) or puboprostatic ligaments (men)
Deep perineal pouch
Space between pelvic diaphragm (superior) and perineal membrane at the bottom
Bladder cancer spreads via
internal iliac lymph nodes
Urethra in women
Short, about 4cm.
Urethra in men
Long, about 20cm, bends twice along its course.
Preprostatic, prostatic, membranous and spongy.
Preprostatic part of urethra
1cm long, associated with internal urethral sphincter
Prostatic part
3-4cm long, site of connection between reproductive and urinary part of men
membranous part
passes through deep perineal pouch.
Surrounded by external urethral sphincter
Spongy part
longest part of urethra
Sacral plexus
formed by anterior rami of S1-S4 and lumbosacral trunk (L4 and L5).
Plexus formed in relation to anterior surface of piriformis muscle.
Lumbosacral trunk
part of L4 and all of L5.
Passes into pelvic cavity anterior to sacroiliac joint
Sacral splanchnic nerves
Contribute to inferior hypogastric plexus
Branches of sacral
Sciatic nerve - tibial part, common fibular part
Pudendal S2-S4
Superior gluteal L4-S1
Inferior gluteal L5-S2
Nerve to obturator internus and superior gemelli L5-S2
Nerve to quadriceps femoris and inferior gemelli L4-S1
Posterior femoral cutaneous nerve S1, S3
Perforating cutaneous nerve
Nerve to piriformis S1-S2
Nerves to levator ani, coccygeus and external anal sphincter S4
Pelvic splanchnic nerves S2-S4
Branch of coccygeal plexus
Anococcygeal nerves
Sciatic nerve - tibial part
L4 to S3
Forms on anterior surface of piriformis and leaves through greater sciatic foramen inferior to piriformis
Motor:
posterior compartment of thigh (including hamstring of adductor magnus) except for short head of biceps
All muscles of posterior compartment of leg
All muscles in sole of foot
Sensory:
Skin on posterolateral and lateral surface of foot and sole of foot
Sciatic nerve - common fibular part
L4 to S2
Motor:
Short head of biceps
All muscles in anterior and lateral compartment of leg
Extensor digitorum brevis in foot
Sensory:
Skin on anterolateral surface of leg and dorsal surface of foot
Pudendal nerve
S2-S4
Motor:
Skeletal muscles in perineum including urethral and anal sphincters and levator ani
Sensory:
Most skin of perineum, penis and clitoris
Superior gluteal
L4 to S1
Motor: gluteus medius, gluteus minimus and tensor fasciae latae
Inferior gluteal
L5 to S2
Motor: gluteus maximus
Pelvic splanchnic nerves
Motor visceral:
erection, mobility in GI system distal to left colic flexure, inhibitory to internal urethral sphincter
Sensory visceral:
Pelvic viscera and distal parts of colon.
Obturator nerve
L2 to L4 - branch of lumbar plexus.
Passes posterior to common iliac artery and medially to the internal iliac artery at the pelvic inlet and along lateral pelvic wall.
Travel through obturator canal and supplies adductor region of thigh
Pelvic prevertebral plexus hypogastric nerves
Enters pelvis as two hypogastric nerves, cross the pelvic inlet medial to internal iliac vessels.
Formed by splitting of superior hypogastric plexus into right and left bundles.
Inferior hypogastric plexus
Formed when hypogastric nerves joined by pelvic splanchnic nerves S2 to S4.
Course medially to major vessels and somatic nerves
Gives rise to:
rectal, uterovaginal, prostatic and vesical plexus
Innervate erectile tissue of penis and clitoris in perineum.
Sympathetic fibers of inferior hypogastric plexus
Mainly T10 to L2 Innervate blood vessels Contraction of internal anal/urethral sphincters Contraction of reproductive tract Ejaculation
Parasympathetic fibers of pelvic plexus
From pelvic splanchnic nerves S2-S4 Generally vasodilatory Stimulate bladder contraction Stimlate erection Modulate activity of enteric nervous system of colon distal to left colic flexure
Major artery supply to pelvis and perineum
Internal iliac artery
Site of origin of internal iliac artery
Level of L5-S1, anteromedial to sacro-iliac joint
Divides into anterior and posterior trunk at superior border of greater sciatic foramen
Branches of posterior trunk of internal iliac artery
Supply lower posterior abdominal wall, posterior pelvic wall and gluteal region
Iliolumbar artery, lateral sacral artery and superior gluteal artery
Branches of anterior trunk of internal iliac artery
Pelvic viscera, perineum, gluteal, adductor of thigh, placenta
Superior vesical artery, umbilical artery, inferior vesical artery/vaginal, middle rectal artery, uterine artery, obturator artery, internal pudendal and inferior gluteal
Obturator artery
In between obturator nerve (above) and obturator vein (below) enters and supplies adductor region of thigh
internal pudendal artery
Leaves pelvic cavity through greater sciatic foramen inferior to piriformis muscle
With pudendal nerve on its medial side, passes laterally to ischial spine and through lesser sciatic foramen to enter perineum.
Main artery of the perineum.
Inferior gluteal artery
Passes through greater sciatic foramen beneath piriformis to enter gluteal region
Pelvic veins
Follow course of arteries except for umbilical and iliolumbar artery
Drain into internal iliac veins which leave the pelvic cavity to join common iliac veins just superior and lateral to the pelvic inlet
Deep dorsal vein
Drains erectile tissues of clitoris and penis, joins prostatic plexus in men and vesical plexus in women.
Superficial veins that drain skin of penis and corresponding regions of clitoris drain into external pudendal veins (tributaries of saphenous vein in thigh)
Lymphatics in pelvis
Lymphatics from most pelvic viscera drain mainly into lymph nodes distributed along internal iliac and external iliac arteries and their associated branches
Internal iliac nodes
Also receive drainage from gluteal region and deep areas of perineum
