Anatomy of the Pelvis Amel Ibrahim MBBS BSc [email protected].
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Transcript of Anatomy of the Pelvis Amel Ibrahim MBBS BSc [email protected].
Contents• Intro and definitions• Bones et al• Muscles• Vasculature• Lymphatics• Nerves• Organs• Special places • QUIZ• Preview• Further reading
Intro & Definitions • Pelvic Brim (green line)• Imagine a line drawn between
promontory of the sacrum, arcuate line of the ilium, pectineal line (pectin of pubis) and pubic crest.
• Greater (False) pelvis• All of the bony pelvis ABOVE
pelvic brim
• Lesser (True) pelvis• All of pelvis BELOW pelvic
brim.
Bones et alBones• Ilium (one on each side): crest,
anterior superior and inferior iliac spines and greater sciatic notch.
• Pubic bone (one on each side): lesser sciatic notch, tubercle and symphysis
• Ischium (one on each side): lesser sciatic notch, spine and tuberosity
• Sacrum: foramina for spinal nerves
• Coccyx
More bones
Ischium
Pubic bone
Ilium
• Vertebral column: 5 fused sacral and 3-5 fused coccygeal vertebrae
• Ilium, pubic bone and ischium meet to form acetabulum for hip joint
• Obturator foramen made by articulation of ischium with pubic bone
Ligaments• Anterior longitudinal: runs
down entire vertebral column. Prevents hyperflexion
• Inguinal ligament: arched fibres of external oblique
• Pubic Symphysis: secondary cartilaginous joint
• Sacroiliac joints anteriorly• Posterior: sacrotuberous,
posterior sacrospinous and sacrospinous
• Ligaments provide strengthand stability of hip
Male Vs FemaleBones: pelvis taller, narrower and more compact. Evolutionary optimised for bipedal locomotion. Acute angle between pubic rami (70 degrees). Contents: rectum, bladder, prostate, anus and male reproductive organs
Bones: wider and broader with larger inlet. Optimised for childbirth without compromising bipedal locomotion. Wide angle between pubic rami (100 degrees). Wider acetabulum.Contents: rectum, bladder, anus and female reproductive apparatus
Muscles• Greater Pelvis:• Quadratus Lumborum: from iliac crest to insert into
12th rib and L1-4. Lateral flexor• Psoas Major: from lumbar veterbrae to lesser
trochanter of femur. Hip flexor.• Iliacus: from internal iliac fossa to lesser trochanter.
Joins with Psoas major = ILIOPSOAS (hip flexor and trunk flexor)
• Piriformis : from greater sciatic notch and anterior sacrum to greater trochanter. Lateral rotator
• Lesser Pelvis:• MUSCLES CONTROL SPHINCTERS• Diaphragm: pubococcygeus, coccygeus,
puborectalis, (pubovaginalis) and illiococcygeus• Levtor ani = a sling made by puborectalis, pubo- and
ilio-coccygeus. Prevents incontinence. • Sphincter urethrae• (Sphincter prostatae)• External anal sphincter• pubovaginalis elevates vagina
iliacus
Psoas major
pubococcygeus
iliococcygeus
coccygeus
piriformis
Vasculature: Arteries
• Gonadal artery (branch of abdo aorta, origin L2)• Internal Iliac (anterior + posterior divisions):• Superior vesical • Inferior vesical (vaginal artery in female)• Middle and inferior rectal (superior rectal from
inferior mesenteric)• Inferior and superior gluteal • Uterine (uterus, vagina, ureter)• Internal Pudendal (perineum, penis and urethra)
(from instant anatomy website)
veins
• Veins from pelvis follow arteries• Drain to IVC (common iliac joins at L5)
• Left testicular drains to left renal not directly into IVC
(From Instant anatomy)
lymphatics
• Lateral pelvic drain everything EXCEPT:• Para aortic drain: gonad + fallopian tube +
uterus + ureter• Inferior mesenteric drain: upper rectum• All ultimately drain into lymphatic duct and
cisterna chyli
Nerves• Dermatomes: T12 (suprapubic), L1
(groin), L2 (upper thigh), S1, 2, 3, 4, 5 (buttocks, perineal and perianal). S1, 2 (genitals).
• Sympathetic: from lumbo-sacral trunk (L1-S5).
• Parasympathetic: S2-4• Lumbar plexus: L1-5 roots lie on
Psoas M. Branches: – 3 lateral to Psoas (lateral cutaneous
nerve, iliohypogastric, ilioinguinal and – 1 anterior to Psoas: genitofemoral– 2 medial to psoas: femoral, obturator
• Sacral Plexus: S1-4• Pudendal: S2-4. mixed
sensory/autonomic• Coccygeal
Dermatomes
Autonomic
Sympathetic• Hypogastric nerves:
preganglionic fibres travel to hypogastric plexus and synapse there then travel to viscera as hypogastric nerves.
• Sacral splanchnic nerves: fibres synapse at sympathetic chain and postganglionic fibres travel to hypogastric plexus as a splanchnic nerve.
Parasympathetic• Pudendal nerve: mixed
autonomic and sensory. S2-4• Pelvic splanchnic nerves:
preganglionic fibres from S2-4 travel to hypogastric plexus ad from there nerves travel to and synapse at viscera.
• Cause erection and sphincter relaxation for micturition/defaecation
Divisions of Lumbar plexuslateral cutaneous nerve: sensory to
lateral thighIliohypogastric: motor to transversus
and internal oblique, sensory to mon pubis
Ilioinguinal: motor to internal oblique, transversus and conjoint tendon. Sensory to upper medial thigh, labia majora, scrotum and root of penis
Genitofemoral: motor to cremaster. Sensory to scrotum, anterior thigh, spermatic fascia and tunica vaginalis.
Femoral (L2,3,4): motor to iliacus, pectineus and quadriceps femoris. Sensory to anterior thigh.
Obturator :
Sacral Plexus• Formed by L4, 5, S1-5• Lies on piriformis• Branches:• 6 nerves from sacral roots
– Nerve to piriformis– Posterior femoral– Perforating cutaneous– Perineal branch to levator ani– Pelvic splanchnic– Pudendal
• Anterior division:– Nerve to Quadratus femoris– Nerve to Obturator internus– Tibial branch of sciatic nerve
• Posterior division:– Superior gluteal– Inferior gluteal– Common peroneal branch of sciatic nerve
Pudendal Nerve• Somatic and autonomic• Origins S2-4• Exits through greater sciatic
foramen and re-enters pelvis via lesser sciatic foramen
• Travels with pudendal vessels along ischiorectal fossa in Alcock’s canal
• Supplies sphincters and genitalia via perineal, dorsal root of penis/clitoris and inferior anal nerves
• Promotes ejaculation, sexual arousal, anal and bladder sphincter control.
Coccygeal Nerve
• 31st spinal nerve• Forms coccygeal plexus
with S5• Coccygeal plexus gives
rise to annococcygeal nerve which supplies sacroccygeal joint and skin over coccyx.
Organs• RENAL TRACT:• Ureters:
– Originate at renal hilum at L2– Path initially medial to vertebrae and at pelvic
brim take infero-posterior path – Oblique entry into bladder avoids urinary
reflux– Crossed by gonadal artery in pelvis– Posterior to it are psoas and genitofemoral
nerve– Under it are uterine artery and vas deferens– Arterial supply via gonadal, renal, vesical,
vaginal and aortic branches– Autonomic innervation
• Bladder:– Trigonal structure.– Wall has 3 layers of smooth muscles: inner
circular and middle/outer longitudinal layers– Arterial supply from superior and inferior
vesicalnerves: sympathetic closes bladder neck whilst parasympathetic relaxes detrusor muscle to allow for miturition
Rectum and anus• Rectum
– Columnar epithelium– Superior 1/3 covered by peritoneum
anteriorly and laterally, middle 1/3 anterior peritoneum only and inferior 1/3 bare
– Arteries: superior rectal from inferior mesenteric and middle rectal from internal iliac +inferior rectal from pudendal artery
– Veinous drainage from internal venous plexus which drains to:
– superior rectal which then drains to inferior mesenteric vein, middle rectal which drains to internal iliac vein and inferior rectal vein which drains into pudendal vein
• Anus:– Starts at anorectal junction aka dentate line– Squamous epithelium continuous with skin
gradually transforming to columnar as rectum approached
– External anal sphincter is skeletal muscle with somatic innervation thus voluntary
– Internal anal sphincter is smooth muscle and under autonomic control
Female pelvic viscera• Uterus:
– Held at lateral walls by double fold of peritoneum aka broad ligament
– Uterine artery– Sympathetic and parasympathetic innervation from pelvic
plexus– Venous plexus drain to rectal and vesical veins
• Ovaries:– Attached to posterior aspect of broad ligament– Ovarian artery– Right ovarian vein drains to IVC whilst left to left renal vein– Sympathetics from aortic plexus and parasympathetics from
pelvic plexus• Fallopian tubes:
– Run in free edge of broad ligament– Ovarian and uterine arteries
• Vagina:– Opens into vaginal vestibule– Vaginal artery– Sympathetic supply from pelvic plexus and somatic sensory
innervation from ilioinguinal and pudendal nerves– Venous drainage from pelvic floor plexus to internal iliac
• Clitoris:– Female equivalent of penis– Nerve supply via pudendal
Male pelvic viscera• Scrotum:
– layers are skin, dartos muscle, external spermatic fascia, cremaster muscle, internal spermatic fascia, tunica vaginalis and tunica albuginea
• Testis: – Testicular (gonadal artery)– pampiniform plexus drain to testicular veins– Testicular vein drains to IVC on right and left renal artery on left
• Prostate:– Multi-lobar (5) with posterior groove. Apex at the bottom and base
at top – Smooth muscle– Entered by the vasa deferens and seminal vesicals– Contains prostatic urethra– Arterial supply from inferior vesical, middle rectal and occasionally
pudendal arteries– Drains to venous plexus and then to internal iliac vein– Sympathetic nerves promote ejaculation and smooth muscle
contraction whilst parasympathetics promote erection
• Penis and Urethra:– Pre-prostatic, prostatic, membranous and penile urethra– Receives ejaculatory ducts, bulbourethral and urethral glands– Arterial supply from urethral artery, deep artery to penis and
dorsal artery of penis– Drainage via superficial and deep dorsal veins of penis– Nerves are sympathetic and parasympathetics for ejaculation and
erection. Sensory supply to skin and glans of penis from pudendal nerve
Special places• Inguinal canal:
– 4 cm long running from Anterior superior iliac spine and pubic tubercle.– Contains spermatic cord (or round ligament) and ilioinguinal nerve.– Spermatic cord contains: 3 structures (vas deferens, cremaster muscle and pampiniform plexus), 3 arteries (artery to vas, artery
to cramster and testicular artery) and 3 nerves (sympathetic, parasympathetic and genitofemoral)– Floor: fibres of external oblique = inguinal ligament– Roof: transversus abdominis and internal oblique– Anterior: external oblique and internal oblique– Posterior: transversalis fascia and conjoint tendon
• Alcock’s canal: – Where pudendal nerve, vein and inetrnal pudendal artery run.– Formed by obturator internus fascia– Runs on the lateral wall of ischiorectal fossa– Femoral canal:– Contains lymphatic vessels and cloquet’s lymph node– Anterior border is inguinal ligament– Posterior border is pectineal ligament– Medial border is lacunar ligament– Lateral border is femoral vein– Site of bowel herniation
• Pubic tubercle:• Herniae above ad medial are inguinal and those below and lateral are femoral
Quiz
Q1) On the bony pelvis:• A) true pelvis lies between iliac crests T/F• B) the acetabulum formed by contributions from
all parts of hip bone T/F• C) male pelvic inlet more oval than female in
shape T/F• D) angle between pubic rami wider in male T/F• E) pelvic out let is between symphysis pubis and
sacral tuberosity T/F
Quiz
Q1) On the bony pelvis:• A) true pelvis lies between iliac crests T/F• B) the acetabulum formed by contributions from
all parts of hip bone T/F• C) male pelvic inlet more oval than female in
shape T/F• D) angle between pubic rami wider in male T/F• E) pelvic out let is between symphysis pubis and
sacral tuberosity T/F
Q2) Levator Ani• A) has fibres which assist continence by
pulling rectum backwards T/F• B) lies inferior to ischiorectal fossa T/F• C) is supplied by anterior rami of S1-2 T/F• D) Contracts during defaecation T/F
Q2) Levator Ani• A) has fibres which assist continence by
pulling rectum backwards T/F• B) lies inferior to ischiorectal fossa T/F• C) is supplied by anterior rami of S1-2 T/F• D) Contracts during defaecation T/F
Q3) On sphincters of the anus• A) the anus contains longitudinal and circular
muscle T/F• B) External sphincter composed of involuntary
muscle T/F• C) external sphincter continuous with muscle
of rectum T/F
Q3) On sphincters of the anus• A) the anus contains longitudinal and circular
muscle T/F• B) External sphincter composed of involuntary
muscle T/F• C) external sphincter continuous with muscle
of rectum T/F
• Q4) on the inguinal canal:• A) contains spermatic cord and splanchnic
nerve T/F• B) posterior border is transversus abdominis
and internal oblique T/F• C) floor is inguinal ligament T/F• D) carries round ligament in females T/F
• Q4) on the inguinal canal:• A) contains spermatic cord and splanchnic
nerve T/F• B) posterior border is transversus abdominis
and internal oblique T/F• C) floor is inguinal ligament T/F• D) carries round ligament in females T/F
Q5) on origins of nerves• A) lumbar plexus from L1-5 T/F• B) pudendal arises from S2-4 T/F• C) parasympathetic plexus arises from S2-4
T/F• D) hypogastric nerves carry postganglionic
fibres T/F
Q5) on origins of nerves• A) lumbar plexus from L1-5 T/F• B) pudendal arises from S2-4 T/F• C) parasympathetic plexus arises from S2-4
T/F• D) hypogastric nerves carry postganglionic
fibres T/F
Preview
Fin • Useful books:• Instant anatomy: good for surface anatomy, blood vessels and nerves• Netter’s atlas• (Anatomy recall)
• Websites:• www.iwanttobeasurgeon.com (down for construction at present)• www.iwanttobeasurgeon.blogspot.com• www.instantanatomy.net
• Apps:• Gray’s anatomy (2 quid!)• Netter’s flash cards (twenty pounds but useful for revision on tube)
• DVD:• Acland’s (AMAZING and free from Warwick University website or youtube. £130 for DVD set)
• Exam Material:• Pastest has over 800 anatomy questions and even more useful when you sit finals Have to pay though :(• http://ect.downstate.edu/courseware/haonline/quiz/practice/u7/quiztop7.htm (excellent for uestions on
cadaveric dissections)