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Anatomy - Pelvis
Pelvic Girdle
Pelvis formed of: 2 hips bones (each made up of ilium, ischium, pubis), Sacrum, Coccyx
Joined anteriorly at symphysis pubis
Pelvis major (greater or false pelvis) – superior to superior pelvic aperture; Pelvis minor (lessor or true pelvis)
Superior pelvic aperture separates major from minor. Edge of this called pelvic rim.
Inferior pelvic aperture
Pelvic joints
Sacroiliac joint
Type Synovial joint
Articulation articular surfaces ilium/ sacrum
Capsule Bound to articular margins
Ligaments
Anterior sacroiliac ligament Flat band
Interosseous sacroiliac ligament
Posterior sacroiliac ligament
Movement Very little movement
Stability Entirely depends on ligaments
Sacrotuberous ligament Post ilium/sacrum/coccyx to ischial tuberosity
Sacrospinous ligament Lower sacrum and coccyx to ischial spine
Iliolumbar ligament Iliac crest/ant SI ligament to transverse process L5
Lumbosacral joints; Sacrococcygeal joint
Pubic symphysis Secondary cartilaginous joint, Fibrocartilaginous disc
Lumbar and sacral plexuses
Lumbar plexus L1-4
Formed in psoas major → lower abdo wall, skin/muscles leg
Sacral plexus L4-S4
Formed in front of piriformis → leg, pelvic floor, perineum
Bladder
flattened 3 side pyramid within pelvis, extending into abdo when full
Nerve supply
Motor Parasymp via pelvic splanchnic – vasomotor and motor to trigone
Symp from L1/2 via superior and inferior hypogastric plexus
Sensation Parasympathetic mostly, Symp involved with pain transmission
Micturition
Bladder filling initially does not increase tension → Tension increase stimulates stretch receptors
Pelvic splanchnic nerves transmit to sacral cord then efferents to detrusor to contract and external sphincter/levator ani relax
Cortical inhibition from hemispheres
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Male urethra
Prostatic part 3-4cm long
Membranous part
Spongy/penile part 15cm long
Within corpus spongiosum – subdivided into bulbous (enlarged posterior part of the corpus) and pendulous parts
Right angled forward turn after passing through perineal membrane within bulbous part
Narrowest point is external meatus
Rectum
Terminal portion of GI tract, 12cm long
Anorectal junction slung forwards by loop puborectalis that merges with external anal sphincter
Relations
Posterior Sacrum and coccyx, ischial spines posterolaterally
Anterior Rectovesical pouch - Base of bladder, Prostate, Ureters, Ductus deferens
Pouch of Douglas - Upper vagina, Cervix
Blood supply
Arterial Superior rectal artery (from inferior mesenteric artery), Middle/inferior rectal, Median sacral
Venous Free anastomosis occurs with all branches draining the rectum
Pelvic floor
Levator ani, obturator internus, piriformis
Reproductive organs
Uterus and fallopian tubes
Fundus
Body Enclosed by peritoneum that lat becomes broad lig
Rests on bladder, vesico-uterine pouch between
Cervix
Lateral, anterior and posterior fornices
Post surface covered with peritoneum, forms ant
wall pouch of Douglas
Anterior surface is deep to vesicouterine pouch.
Fallopian tubes
10cm long, Lies in upper edge of broad ligament
Divided into isthmus, ampulla and infundibulum
Blood supply Uterine artery from internal iliac
Lymph External and internal iliac nodes, sacral nodes, superficial inguinal nodes
Ovary
3x2x1cm, ovoid structure in angle between internal and external iliac vessels
Obturator nerve is lateral, Ureter is posterior, Tube is medial
Blood supply Ovarian artery from abdominal aorta
Lymph Para-aortic lymph nodes
Vagina
10cm long fibromuscular tube, Directed up and back
Anterior to rectum, anal canal and perineal body; Posterior to bladder and urethra
Blood supply Vaginal branch of internal iliac artery, Uterine artery, Inferior vesical artery, Middle rectal artery
Lymph External and internal iliac nodes, sacral nodes, superficial inguinal nodes
Nerve Sensation – pudendal nerve and ilioinguinal nerve
Vaginal examination cervix, Bladder, urethra/pubic synthesis anteriorly, Pouch of Douglas and rectum posteriorly
Body of uterus, ovaries and tubes felt with abdominal pressure
Penis
Root
Body Two corpus cavernosum bound side by side with corpus spongiosum behind
Urethra runs within corpus spongiosum
Blood supply Three pairs of arteries from internal pudendal artery
Lymph Glans drain to deep inguinal nodes, Skin drains to superficial inguinal nodes
Nerve Skin – pudendal nerves (S2), ilioinguinal nerve (L1)
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Internal Iliac Artery
Origin: common iliac, level disc L5/S1
Course: posteriorly into pelvis for 4cm then branches into anterior and posterior divisions
Anterior relations: ureter and fallopian tube and ovary
Posterior relations: internal iliac vein, lumbosacral trunk, SI joint
Lateral relations: external iliac artery and vein, obturator nerve, psoas major
Medial relations: parietal peritoneum and small bowel
Internal pudendal artery:
From anterior division, descends on lateral wall of the pelvis. Leaves pelvis through greater sciatic foramen, inferior to
piriformis, then over tip of ischial spine to enter ischo-anal fossa via lesser sciatic foramen.
Round ligament supplied by the uterine artery, vas deferens is usually supplied by inferior vesical or superior vesical.
Anterior division
Superior vesicle
Inferior vesicle
Obturator - Adductor longus/brevis/magnus, Obturator externus, Gracilis
Middle rectal
Uterine
Internal pudendal
Inferior rectal; Deep artery of penis; Dorsal artery of penis; Urethral; Artery to bulb; Perineal
Posterior division
Iliolumbar
Lateral sacral
Superior gluteal
Superficial branch → glut max; Deep branch → glut med/min, TFL
Inferior gluteal
Muscular branch → glut max, obturator
Anastomotic
Coccygeal
Arteria comitans nervi ischiadici
Lymphatic drainage of pelvis
Upper rectum and rectal mucosa to dentate line → inferior mesenteric
Gonad plus fallopian tube, superior lateral uterus, ureter → para-aortic
Lower rectum and dentate line, bladder, urethra, lower ureter, uterus/cervix/upper vagina/clitoris/labia minora, vas
deferens/seminal vesicles/prostate/bulk of penis → lateral pelvic nodes
Lumbar plexus – branches
T12 – subcostal
L1 – iliohypogastric, ilioinguinal
L1-2 – genitofemoral
L2-3 – lat fem cutaneous
L2-3-4 – post division: femoral; anterior division: obturator
L4-5 – lumbosacral trunk
Sacral plexus
From: lumbosacral trunk (L4,5) and anterior primary rami from S1-5
Lies on piriformis on posterior pelvic wall deep to internal iliac vessels, protected by sheet of pelvic fascia
Superior gluteal nerve(L4-S1)
Sacrum
5 fused bones + coccyx
4 pairs sacral foramina – S1-4 anterior larger than posterior
Ala, SI joint, superior articular facets, lumbosacral joint, 5 vertical lines – median, intermediate, lateral
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