FOCA 2023 Lecture 8.Pelvis 2023-08-24 REDUCED.pdf

FOCA 2023 Pelvis Dr. Mark Hankin Professor & Senior Anatomist [email protected] Radiopedia Disclosures & Conflicts of Interest Authorship Anatomy & Physiology Revealed v4 2019, McGraw-Hill Clinical Anatomy: A Case Study Approach 2013, McGraw-Hill Test Prep for the USMLE® – Clinical Anatomy Q&A 2019, T...

FOCA 2023 Pelvis Dr. Mark Hankin Professor & Senior Anatomist [email protected] Radiopedia Disclosures & Conflicts of Interest Authorship Anatomy & Physiology Revealed v4 2019, McGraw-Hill Clinical Anatomy: A Case Study Approach 2013, McGraw-Hill Test Prep for the USMLE® – Clinical Anatomy Q&A 2019, Thieme Medical Publishers If you have used any of these resources, I hope you found them helpful. 2 Conceptual Objectives 1. Describe the skeleton and ligaments of the pelvis, and the pelvic inlet and outlet. Explain sexual differences in pelvic skeletal anatomy. 2. Describe the pelvic diaphragm, including the structures that pass through it. 3. Describe the organs in the pelvis in males and females. 4. Describe the anatomy of the ureter, bladder, and urethra in males and females. 5. Describe the female internal genital organs, including the ovaries, uterine (Fallopian) tubes, uterus, and vagina. 6. Describe the male internal genital organs, including the vas (ductus) deferens, seminal gland, ejaculatory duct, and prostate gland. 7. Describe the blood vessels that supply the pelvic organs. 8. Describe the lumbosacral plexus, including the origin, course and distribution of the pudendal nerves and the sites of pudendal nerve block. 9. Describe the autonomic and visceral sensory innervation of the pelvic organs, including how referred pain is related to the pelvic pain line. 3 Context The goal in FOCA of the lectures and labs on pelvis and perineum is to present the basic anatomy derived from XX or XY genotypes. As you are aware, gender is fluid. In the next two lectures, we will be referring to “male” and “female” anatomy: “female anatomy” will refer to someone whose sex assigned at birth is female or cisgender female; a similar understanding will apply to “male anatomy”. The goal is for this information to provide a foundation for later learning that considers gender-affirming care, including gender reassignment surgery, in which surgeons can address authoritatively the anatomical gender-affirming changes done intraoperatively. 4 Pelvic Skeleton & Muscular Walls 5 Pelvis Part of trunk, inferior to abdomen The pelvis is surrounded, at least in part, by the bony pelvic girdle 6 Pelvis & Perineum Pelvis Inferior part of abdominopelvic cavity PELVIS Obturator internus m. Area of transition between the trunk & lower limbs Perineum Pelvic diaphragm Perineum Perineal region Shallow compartment, inferior to pelvic diaphragm and deep to the perineal region Perineal region Surface area between thighs & buttock, from pubis to coccyx (basically, the area that includes external genitalia and anus) 7 Greater & Lesser Pelvis Pelvis divided into upper & lower parts Upper: False/Greater Pelvis Superior to pelvic inlet Occupied by inferior abdominopelvic viscera Lower: True/Lesser Pelvis Bowel shaped area inferior to pelvic inlet Continuation of abdominal cavity, via the pelvic inlet Occupied by inferior abdominopelvic & pelvic viscera Greater (false) pelvis Lesser (true) pelvis 8 Hip Bone & Pelvic Girdle Each hip bone (os coxa) is formed by 3 bones 1. Ilium 2. Ischium 3. Pubis Pelvic girdle is a bowl-shaped, ring of bones formed by the hip bones & sacrum Ilium Orientation of the pelvis Ischium Pubis 9 Pelvic Inlet & Pelvic Outlet Pelvic inlet (brim) formed by: Sacrum + Ilium + Pubis Pelvic outlet formed by: Pubic symphysis Ischiopubic rami & ischial tuberosities Sacrotuberous ligaments Coccyx Inferior view Male vs. Female Bony Pelvis Female Male 11 Sacrotuberous & Sacrospinous Ligaments Create Sciatic Foramina Greater sciatic foramen Sacrotuberous lig. Sacrospinous lig. Lesser sciatic foramen Sacrospinous lig. Sacrotuberous lig. 12 Anatomical Capacity of Pelvis for Childbirth Capacity of pelvis for childbirth can be assessed by pelvic exam Diagonal conjugate Shortest AP diameter of lesser pelvis – sacral promontory to pubic symphysis (10.5-11 cm) Narrowest distance through which a baby’s head must pass during vaginal delivery – it cannot be measured directly by palpation Conjugate is distance between two points Diagonal conjugate Promontory to inferior symphysis (13.5 cm); only conjugate measured by palpation 13 Clinical Application Obstetric (true) conjugate diameter Muscles of the Pelvic Floor & Walls Antero-inferior wall Pubic bone Puborectalis plays important role in fecal continence Urethra Lateral walls Obturator membrane Obturator internus m. Vagina Rectum Posterior wall Piriformis muscle Ischial spine - Covers sacrum & forms a muscular bed for sacral plexus Pelvic floor Pelvic diaphragm - Levator ani + (ischio)coccygeus mm. Levator ani Puborectalis Pubococcygeus Iliococcygeus Coccyx 14 Two Openings in the Pelvic Floor Urogenital hiatus ♀ urethra & vagina ♂ urethra only Anorectal hiatus Location of anorectal junction 15 Pelvic Viscera…in General 16 Uterine tube Ureter Vas deferens Pelvic Viscera Ureter Ovary Uterus Rectum Bladder Bladder Rectum Vagina Prostate FEMALE BOTH SEXES MALE Ovaries Uterine (Fallopian) tubes Uterus Vagina Bladder Ureter Urethra Rectum Vas (ductus) deferens Prostate Seminal glands Ejaculatory ducts Seminal gland Pelvic Organs Common to Both Sexes 18 Ureter, Bladder and Urethra 19 Urinary Bladder is Subperitoneal Parts & surfaces of the bladder Parts: Apex, fundus, body & neck Surfaces: Superior, inferolateral, posterior (= base/fundus) Ureter passes obliquely through bladder wall Creates a one-way flap valve (internal pressure of bladder filling compresses the ureter) During micturition, bladder contractions further act like a sphincter that prevents reflux of urine into the ureters. 20 Openings in the Bladder (2) Ureteric orifices (1) Internal urethral orifice Ureteric orifices Ureteric orifices Trigone is a triangular area between ureteric & urethral openings Urethra Female Male Prostate surrounds urethra 21 Female urethra (4 cm) Male urethra (18-22 cm) Intramural (preprostatic) Prostatic Membranous Penile (spongy) Urethra Vestibule External urethral orifice located in the perineum (in the vaginal vestibule) Two parts (clinically) 1. Posterior urethra Prostatic & membranous 2. Anterior urethra Penile (spongy) Bulbar urethra (expanded part of penile urethra) Muscles of the Bladder & Urethra Bladder wall (smooth muscle) Detrusor muscle Detrusor muscle Internal urethral sphincter - Ensures urinary continence & prevents retrograde ejaculation Internal urethral sphincter Urethra (striated/skeletal muscle) External urethral sphincter External urethral sphincter (sphincter urethrae) 23 Muscles that Control the Male Urethra Internal urethral sphincter surrounds internal urethral orifice External urethral sphincter forms a sleave & a “disc” of muscle Compressor urethrae Prostate Internal urethral sphincter External urethral sphincter Compressor urethrae Muscles Compressing the Female Urethra Urethrovaginal sphincter complex encircles the urethra & vagina External urethral sphincter forms a sleave (not a simple “disc” of muscle) that encircles urethra Compressor urethrae Urethrovaginal sphincter Urethral sphincter complex usually sufficient alone to maintain urinary continence Compressor urethrae External urethral sphincter Urethrovaginal sphincter 25 Bladder filling and emptying require sympathetic, parasympathetic and somatic activities Bladder filling Detrusor relaxes: sympathetics inhibit parasympathetics (parasympathetics stimulate detrusor to empty bladder) Urethral sphincters contract ⎼ Internal sphincter (sympathetics +) ⎼ External sphincter (pudendal nerve/somatic motor +) Bladder emptying Sense of “fullness” (visceral afferents) Detrusor contracts (parasympathetic +) Urethral sphincters relax ⎼ Internal sphincter (sympathetics –) ⎼ External sphincter (pudendal –) https://www.news-medical.net/health/Micturition-Reflex-Neural-Control-of-Urination.aspx Rectum & Anal Canal Take-Home: The rectum & anal canal are the terminal parts of the GI tract. Rectum (12 cm) Rectum, the terminal part of large intestine, is located in the pelvic cavity. Primarily retroperitoneal & subperitoneal Begins at rectosigmoid junction (S3 vertebral level) Ends at anorectal line (at superior end of anal columns Has dilated terminal ampulla & transverse folds External anal sphincter External anal sphincter 28 Anal Canal (2-4 cm) Anorectal line ↓ Anus (external opening) Anal columns Ridges in upper anal canal Pectinate (dentate) line Divides upper & lower parts of anal canal - Upper part derived from endoderm - Lower part derived from ectoderm (called anoderm) Two anal sphincters External sphincter: skeletal m. Internal sphincter: smooth m. Anorectal jn. (@S3) Anal columns Internal anal sphincter Pectinate (dentate) line Anoderm External anal sphincter 29 Neurovascular Supply of the Anal Canal Nerves & vessels are different above vs. below the pectinate Visceral afferents: Sensitive only to stretch Pectinate line Somatic afferents: Sensitive only to pain, touch, temperature Pectinate line Anorectal Flexure & Defecation Anorectal flexure maintained by puborectalis (part of levator ani muscle) At rest Puborectalis contracts to create increase the anorectal flexure Rectum Pubic bone Puborectalis m. External anal sphincter Anal canal Puborectalis m. Internal anal sphincter During defecation Puborectalis relaxes to allow anorectal flexure to straighten 31 Anal Sphincters & Fecal Continence Internal anal sphincter (involuntary) Responsible for 70-85% of fecal continence (resting anal pressure) Smooth muscle (sympathetic inn.) Tonic activity helps constrict anal canal Distension of rectal ampulla inhibits (relaxes) tone of internal anal sphincter External anal sphincter (voluntary) Skeletal muscle (somatic inn. via pudendal → inferior rectal nerve) 32 Female Internal Genital Organs 33 Ovaries During development, ovaries & their neurovasculature descend along the posterior abdominal wall to location just inferior to pelvic brim (inlet) Suspensory lig. of ovary (contains ovarian neurovasculature) Ovary Uterine tube Retroperitoneal Ovaries held in place by the suspensory ligament of ovary - Fold of peritoneum that surrounds ovarian nerves & vessels Uterus Bladder - Clinical term: infundibulopelvic (IP) ligament 34 Uterine Tube (10 cm) Ovarian fimbria, attached to the ovary ts e par terin u & us Isthm 1. Ampulla – widest & longest part Infundibulum Fimbriae Fertilization & most ectopic pregnancies usually occur here 3. Infundibulum (L. trumpet) – opens into peritoneal cavity 4. Fimbriae – finger-like mucosal folds at end of infundibulum Fertilized egg usually stays in the tube for 3-4 days Uterine tube & ovary are motile: infundibulum and fimbriae “cup” the ovary that contains a Graafian (pre-ovulatory) follicle 35 Ectopic Pregnancy Tubal pregnancy most often in the ampulla Ruptured tubal pregnancy will bleed into the peritoneal cavity. Severe hemorrhage is life-threatening. ü Peritonitis that can result may be diagnosed as acute appendicitis since parietal peritoneum in RLQ may become inflamed Uterine tube Uterine tube Uterus Ovary Uterine tube 36 Clinical Application Implantation of the embryo anywhere outside the uterus Uterus & Uterine Tubes Body: superior 2/3 of uterus Fundus: (above uterine tubes) Surrounded by broad ligament Cervix: inferior 1/3 of uterus Central cervical canal Internal os (uterine cavity → cervical canal) External os (cervical canal → vagina) Uterine wall Endometrium (inside) Myometrium (smooth muscle) Parametrium (peritoneum) Two layers of peritoneum [again] Internal os External os 37 Normal Position of Uterus is anteflexed & anteverted Flexion Retroflexion 1 Angle in uterus between body & cervical canal (body tipped over superior surface of empty bladder) Version 2 Retroversion Angle between cervical canal & vagina (cervix “inserts” into anterior side of vagina) Bladder Round Ligament of the Uterus Round ligament, between layers of peritoneum (broad ligament), attaches to uterus at junction with uterine tube Round ligament Ovarian ligament Round ligament passes through the deep inguinal ring & inguinal canal It exits the superficial inguinal ring and attaches to the labium majus Broad ligament 39 Vagina (6-9 cm) a Musculomembranous Tube Superior end of vagina Surrounds the uterine cervix Vaginal fornices (grooves) surround the cervix ⎼ Posterior vaginal fornix is the deepest part; it is separated from the recto-uterine pouch by a thin layer of pelvic fascia and peritoneum Inferior end of vagina Opens into the vestibule of the vagina 40t Culdocentesis Clinical Application Procedure to aspirate and collect peritoneal fluid from the rectouterine pouch (the cul-de-sac; pouch of Douglas) To access the recto-uterine pouch is through the posterior vaginal fornix 41 Support of Uterus & Vagina Uterosacral ligament Passive support Condensations of endopelvic fascia (ligaments) Most important: Cardinal ligament (transverse cervical) Cardinal ligament Round ligament of uterus Pelvic diaphragm Anterior view Uterosacral ligament Dynamic support Pelvic diaphragm Cardina l m Liga ent Pelvic diaphragm 42 Uterine & Vaginal Arteries in Cardinal Ligament Uterine & vaginal arteries (from internal iliac) course in the cardinal ligament, along the base of the broad ligament Pulse of uterine artery can be palpated through vaginal wall Anterior view Uterine & vaginal arteries in cardinal ligament Ureter crosses under uterine vessels 43 Male Internal Genital Organs 44 Vas (Ductus) Deferens Transports sperm from epididymis to ejaculatory duct Passes through inguinal canal Pelvic end expanded, posterior to the bladder, called the ampulla Vas deferens joins duct of seminal gland to form the ejaculatory duct, which delivers sperm into urethra 45 Vas Deferens & Seminal Gland Paired vas deferens & duct of seminal gland join to form the [short] ejaculatory duct Bladder Vas deferens Seminal gland Vas deferens Ejaculatory ducts Ampulla of vas Ureter Seminal gland Prostate Ejaculatory duct 46 Prostate: Largest Male Accessory Reproductive Gland “Normal” size: ~ walnut or golf ball Inferior to urinary bladder & superior to perineal membrane Surrounds prostatic urethra Palpable via digital rectal exam (DRE) Fibrous capsule of prostate Perineal membrane 47 Prostate Cancer & BPH BPH: usually in the central lobe, around proximal prostatic urethra Clinical Application 70% prostate CA in the posterior lobe; nodules are palpable CA BPH 48 Pelvic Arteries Branch from the Internal Iliac Artery 49 Pelvic Organs Supplied by Internal Iliac Internal iliac a. Internal iliac a. 50 Female Pelvic Arteries Pelvic viscera supplied by branches from anterior division Anterior division Umbilical (patent & obliterated) Superior vesical (2-3) Obturator Uterine Vaginal (= inferior vesical in ♂) Internal pudendal Middle rectal Inferior gluteal Posterior division Superior gluteal Typical relationships of gluteal arteries Superior gluteal a. usu. between LS trunk & S1 ventral ramus Inferior gluteal a. usu. between S2 & S3 ventral rami 51 Male Pelvic Arteries Pelvic viscera supplied by branches from anterior division Anterior division Umbilical (patent & obliterated) Superior vesical (2-3) Obturator Internal pudendal Inferior vesical (= vaginal in ♀) Middle rectal Inferior gluteal Posterior division Superior gluteal Typical relationships of gluteal arteries Superior gluteal a. usu. between LS trunk & S1 ventral ramus Inferior gluteal a. usu. between S2 & S3 ventral rami Arteries to the Bladder Internal iliac Arteries to the bladder arise the from internal iliac Superior vesical aa. from umbilical a. Inferior vesical a. from internal iliac a. directly ⎼ Female: When present, inferior vesical is a branch of vaginal a. Superior gluteal Umbilical Inferior gluteal Superior vesical Internal pudendal Inferior vesical (vaginal in ♀) Bladder 53 Arteries to the Ovary, Uterus & Vagina Anastomotic network of arteries supply the female internal genitalia Ovary Ovarian a. (from abdominal aorta) Uterine a. (from internal iliac) Uterus Uterine a. Vagina Upper part: Vaginal branch of uterine a. Middle: Vaginal a. Lower: Internal pudendal a. At the vaginal fornices, the ureter passes “under” the uterine artery (“water under the bridge”) Ureter may be injured iatrogenically during hysterectomy when ligating the uterine artery 54 Blood Supply of Rectum & Anal Canal Vessel Branch/Term Supplies Superior rectal IMA Superior rectum Middle rectal Internal iliac Middle & inferior rectum ARTERIES Inferior rectal Internal pudendal Anorectal jn. & anal canal Superior rectal IMV (→ Portal) Superior rectum Middle rectal Internal iliac (→ IVC) Middle & inferior rectum Inferior rectal Internal pudendal (→ IVC) Anorectal jn. & anal canal IMA To Portal v. Superior rectal a. Superior rectal v. VEINS To IVC Int. iliac a. Middle rectal v. Int. iliac v. Middle rectal a. Internal pudendal a. Inferior rectal a. Internal pudendal v. Inferior rectal v. Anal Cushions and Fecal Continence At rest Internal anal sphincter contracted and prevents outflow of blood from “anal cushions” (sub-mucosal hemorrhoidal plexus) Apposition of anal cushions ensures a liquid- and gas-tight closure of rectum Hemorrhoidal plexus (“anal cushions”) At rest Apposed mucosa of “anal cushions” forms tight closure Internal anal sphincter During defecation Internal anal sphincter relaxes and allows blood to drain from hemorrhoidal plexus During defecation Mucosa over anal cushions “unstick” and helps opens the anal canal 56 Internal hemorrhoids Dilation of internal rectal venous plexus (anal cushions) Occur in lower rectum & anal canal Rectal bleeding typically bright red due to high blood O2 in arteriovenous anastomoses Normal: submucosal varicosities (dilations) of rectal veins are present Pathologic: enlarged varicosities with symptoms (inflammation, thrombi, or prolapses) Not painful (visceral afferents only); they can bleed & prolapse through anus, which results in deposition of irritants on perianal skin that may cause perianal itching & irritation External hemorrhoids Dilation of external rectal venous plexus Painful (somatic afferents via inferior rectal/pudendal nn.) Clinical Application Hemorrhoids Rectal Varices Rectal varices typically occur in the mid-rectum Due to reversal of blood flow between middle & superior rectal veins Prevalence of rectal varices is 38%56% in patients with cirrhosis, and 63%-94% in a patient with extrahepatic portal vein obstruction. Although rare, bleeding from rectal varices can be life threatening Clinical Application Varices result from engorgement of submucosal veins where portal & caval (systemic) venous circulation connect Innervation of Pelvic Organs 59 Somatic Plexuses & Nerves in the Pelvis Lumbosacral trunk Contributions from L4 & L5 ventral rami to the sacral plexus Sacral plexus (S1-S4) Sciatic nerve (L4-S3) Pudendal nerve (S2-S4) Pelvic splanchnic nerves, which are preganglionic parasympathetic fibers conveyed by S2-S4 ventral rami LS S1 S2 S3 S4 60 Autonomics to Pelvic Organs Sympathetics Preganglionic fibers from T12-L2(3) spinal cord → lumbar splanchnics → hypogastric plexuses Synapse in small ganglia in pelvic plexus (inferior hypogastric) Postganglionic fibers supply organs Parasympathetics Preganglionic fibers from S2-S4 spinal cord → pelvic splanchnics → pelvic plexus → organs Postganglionic fibers synapse in intramural ganglia Visceral Afferents & Pelvic Referred Pain Pelvic pain is related to peritoneum Pelvic organs that contact peritoneum are above the pelvic pain line Visceral afferents follow sympathetics back to T12L2(3) spinal cord → pain referred to L1-L2 dermatomes Upper rectum, upper bladder; ovaries, uterine tubes, uterine body; vas deferens, prostate, seminal glands Pelvic organs NOT in contact with peritoneum are below the pelvic pain line Visceral afferents follow parasympathetics (pelvic splanchnics) back to S2-S4spinal cord → pain referred to S2-S4 dermatomes Lower rectum, upper anal canal, lower bladder; uterine cervix, upper vagina, clitoris/penis 62 END 63