Anatomy of the Pelvis

1. Anatomy of the Pelvis Amel Ibrahim MBBS BSc www.iwanttobeasurgeon.blogspot.com www.iwanttobeasurgeon.com Amel.ibrahim@imperial.ac.uk

2. Contents • Intro and definitions • Bones et al • Muscles • Vasculature • Lymphatics • Nerves • Organs • Special places • QUIZ • Preview • Further reading

3. 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.

4. Bones et al Bones • 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

5. More bones • 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 Ilium Pubic bone Ischium

6. 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

7. Male Vs Female Bones: 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

8. Muscles pubococcygeus • Greater Pelvis: • QuadratusLumborum: 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 • Levtorani = a sling made by puborectalis, pubo- and ilio-coccygeus. Prevents incontinence. • Sphincter urethrae • (Sphincter prostatae) • External anal sphincter • pubovaginalis elevates vagina iliococcygeus coccygeus Psoas major piriformis iliacus

9. 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)

10. (from instant anatomy website)

11. veins • Veins from pelvis follow arteries • Drain to IVC (common iliac joins at L5) • Left testicular drains to left renal not directly into IVC

12. (From Instant anatomy)

13. 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

14. 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

15. Dermatomes

16. Autonomic Sympathetic 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 • 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.

17. Divisions of Lumbar plexus lateral cutaneous nerve: sensory to lateral thigh Iliohypogastric: 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 :

19. 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 levatorani • Pelvic splanchnic • Pudendal • Anterior division: • Nerve to Quadratusfemoris • Nerve to Obturatorinternus • Tibial branch of sciatic nerve • Posterior division: • Superior gluteal • Inferior gluteal • Common peroneal branch of sciatic nerve

20. 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 ischiorectalfossa 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.

21. 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.

22. 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

23. 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

24. 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

25. 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

27. 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: transversusabdominis and internal oblique • Anterior: external oblique and internal oblique • Posterior: transversalis fascia and conjoint tendon • Alcock’s canal: • Where pudendal nerve, vein and inetrnalpudendal artery run. • Formed by obturatorinternus fascia • Runs on the lateral wall of ischiorectalfossa • 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

29. 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

30. 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

31. 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

32. 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

33. 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

34. 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

35. 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

36. 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

37. 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

38. 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

39. Preview

40. 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)