K.E. Byrd X620 2017 10-16-2017 HS 2017 MED-X620 Intro to Pelvis & Perineum; Anal Triangle Kenneth E. Byrd, PhD [email protected] 274-3355 HS 2017 MED-X620 IUSOM Osteology Bony Pelvis – hip bones, sacrum and coccyx •Protect Pelvic Viscera •Support Body Weight. Superior •Attachments: muscles for Abdomen & LE Hip Bones - Os Coxae -Innominate Bone • Start as 3 bones separated by hyaline ilium cartilage called the Tri-radiate cartilage; located at the acetabulum. • They complete fusion at ~12 years for Posterior Anterior girls and ~14 years for boys. pubis ischium Lateral View of immature Ox Coxa Inferior P&P_1_Intro Pelvis-Perineum; Anal Triangle 1 of 17 K.E. Byrd X620 2017 10-16-2017 Sagittal Section Abdominal Pelvic Cavity Pelvic Inlet (pelvic brim) = skeletal (striated) muscles, GSE innervated…… aka Pelvic Diaphragm!!!!!!! Osteology Pelvic Girdle • 2 hip bones • sacrum • coccyx • sacroiliac joints • pubic symphysis (fibrocartilage) Pelvic Inlet (brim) Linea Terminalis (obstetrical term) - from pubic symphysis (anterior) to sacroiliac (SI) joint and the sacral promontory (SP) (posterior) Pectineal line completes the pelvic inlet Pubic tubercle P&P_1_Intro Pelvis-Perineum; Anal Triangle 2 of 17 K.E. Byrd X620 2017 10-16-2017 Pelvic Fractures & Common Causes Pelvic Fractures • High‐Energy Trauma • Congenital Bone Development • Osteoporosis • Avulsion – ischial tuberosity (hamstring) • Acetabulum • Types: Stable vs. Unstable Unstable fracture. In this type of fracture, there are usually two or more breaks in the pelvic ring and the ends of the broken bones do not line up correctly (displacement). Stable fracture. In this type of This type of fracture is more likely to occur due to fracture, there is often only one a high‐energy event. break in the pelvic ring and the broken ends of the bones line up adequately. Low‐energy fractures are often stable fractures. http://orthoinfo.aaos.org/topic.cfm?topic=a00520 Anteriorposterior compression injury. Pelvic radiograph on the right demonstrates disruption of the symphysis pubis (open book – widening) and widening of left sacroiliac (SI) joint. There is also a displaced fracture of the right femoral shaft . QUIZ!!!!!!! What type of pelvic fracture?? P&P_1_Intro Pelvis-Perineum; Anal Triangle 3 of 17 K.E. Byrd X620 2017 10-16-2017 Pelvic Outlet outlined in green Pubic arch Bordering structures in red GSF & LSF formed by Sacrospinous Lig. attach. GSF = Greater Sciatic Foramen to ischial spine!!!!! LSF = Lesser Sciatic Foramen (separates Greater & Lesser sciatic notches! LV5 Ant. Post. -Standing ASIS -Pelvic Tilt - Vertical Plane GSF (ASIS anteriosuperior pubic symphysis) Sacrospinous Ligament I.S. LSF Sacrotuberous Ligament I.T. I.S. = Ischial Tuberosity I.S. = Ischial Spine (mid-pelvic level!) P&P_1_Intro Pelvis-Perineum; Anal Triangle 4 of 17 K.E. Byrd X620 2017 10-16-2017 Pelvis Axis: normal path the fetus takes during childbirth Thus “pelvic diameters” are important. Frontal Section Sagittal Section Pelvic Tilt http://ecodevoevo.blogspot.com/2015/03/the-obstetric-dilemma-hypothesis.html The obstetrical dilemma hypothesis attempts to explain the increased potential difficulty in childbirth for modern humans. Humans often require assistance from other members of the species during childbirth to avoid complications. Whereas most non-human primates give birth alone with relatively little difficulty. P&P_1_Intro Pelvis-Perineum; Anal Triangle 5 of 17 K.E. Byrd X620 2017 10-16-2017 1. Ant.- Post. 2. Transverse 3. Oblique Ischial Spine (Mid-Pelvic) Pelvic Inlet Diameters pubic tubercle 1. Ant.- Post. (True Conjugate diameter) 2. Transverse 3. Oblique Pelvic Outlet pubic arch ischial tuberosities coccyx 2. Transverse 1. Ant.- Post. Ischial Spine (Mid-Pelvic) Pelvic Outlet Diameters 1. Ant. – Post. 2. Transverse P&P_1_Intro Pelvis-Perineum; Anal Triangle 6 of 17 K.E. Byrd X620 2017 10-16-2017 A. – True Conjugate median sagittal view B. – Obstetrical Conjugate = shortest A.-P. dia. A. C. – Diagonal (-----) C. = approx. estimate D. – AP Outlet D. B. NOTE: A, B, & C are Inlet diameters! Pelvis Axis: normal path the fetus takes during childbirth Obstetric conjugate • shortest AP diameter for fetal head C> A > B Diagonal conjugate ------------ (approximation/estimate of True and Obstetric conjugate diameters) Three conjugates: Pelvic A - True conjugate = Exam anteroposterior (AP) dia. B - Obstetric conjugate C - Diagonal conjugate P&P_1_Intro Pelvis-Perineum; Anal Triangle 7 of 17 K.E. Byrd X620 2017 10-16-2017 Caldwell-Moloy Classification – Gender Differences ~50% females ~33% females •Typical ♀ pelvis •Typical ♂ pelvis •Inlet – oval •Inlet – - shaped •Mid-pelvis – wide •Mid-pelvis – constricted •Sacrum – neutral position/outlet •Sacrum – contracted position •Cavity to Outlet – round & more room • Cavity to Outlet – oblong & funnel shaped ♀ ♂ ♀ ♂ Transversely oval vs. Heart-shaped INLET Roomy + round vs. Narrow +oblong CAVITY (funnel-shaped) Roomy + shallow vs. Narrow + deep OUTLET Subpubic angle – Pubic Arch Wider (80º+) vs. Narrower (50-60º) ARCH P&P_1_Intro Pelvis-Perineum; Anal Triangle 8 of 17 K.E. Byrd X620 2017 10-16-2017 Gluteal Region Medial Perineum Compartment Thigh Walls of the Pelvic Cavity (True Pelvis) •Bones •Ligaments •Muscles & Fascia Pelvic Wall Lateral – Obturator Internus Posterior – Piriformis & Sacrum Anterior Wall: Pubic Symphysis P&P_1_Intro Pelvis-Perineum; Anal Triangle 9 of 17 K.E. Byrd X620 2017 10-16-2017 Frontal Section Pelvic Wall Lateral – Obturator internus Posterior – Piriformis & Sacrum Pelvic Floor Pelvic Diaphragm – I. Levator Ani (3 parts) G II. Coccygeus I = Perineum Pelvic Wall and Floor Pelvic Diaphragm (I. and II. parts) I. Levator Ani (Pubococcygeus, Puborectalis, UG Iliococcygeus) A IS IS II. Coccygeus nn. VPR S4,5 (GSE) Sac Pelvic Wall Muscles nn. VPR (L5),S1,2 (GSE) Lateral – Obturator Int. Posterior - Piriformis nn. VPR S1,2 (GSE) nn. VPR S(2),3,4 Superior view (GSE) P&P_1_Intro Pelvis-Perineum; Anal Triangle 10 of 17 K.E. Byrd X620 2017 10-16-2017 Midsagittal view Pelvic Floor (muscular) Pelvic Diaphragm – I. Levator Ani (3 muscles) II. Coccygeus (1 muscle) Piriformis Obturator Internus Coccygeus fascia “muscular funnel inside bony pelvis” Pelvic Wall Lateral – obturator internus Posterior – piriformis Pelvic Diaphragm -A paired skeletal muscle that has an opening or hiatus in the midline, forms a muscular sling that: 1. Supports Pelvic Viscera. 2. Separates Pelvis from the Perineum (** in figs below). 3. Acts together to raise pelvic floor (forced expiration, coughing, vomiting, urinating, defecating). 4. Allows for the passage of the portions of the urinary, genital and G.I. systems. 5. Act as a sphincter. 6. Motor & sensory innervation: direct VPR S(2),3,4 – both GSE and GSA nerve fibers!!!!!!! “muscular funnel inside bony pelvis” NO UGD in posterior Anal Region!!!! Anal Region (UGD) ** ** ** skin ** Anterior frontal x-section skin Posterior frontal x-section P&P_1_Intro Pelvis-Perineum; Anal Triangle 11 of 17 K.E. Byrd X620 2017 10-16-2017 Puborectalis • Part of Levator Ani (ergo skeletal muscle) • Form U-shaped sling around anorectal angle (junction or perineal flexure) • Acts as a sphincter • Maintain fecal continence • Relaxation of this muscle……….. SUP. Puborectalis Beginning of Anal Canal: ANT. POST. End of Anal Canal: SUP. Anal WLH - transition point from non- canal keratinized stratified squamous epithelium of the anal canal to keratinized stratified squamous epithelium of the anus and perianal skin. (MORE later……..) INF. P&P_1_Intro Pelvis-Perineum; Anal Triangle 12 of 17 K.E. Byrd X620 2017 10-16-2017 Introduction to the Perineum Frontal (posterior) Section Resp. Diaphragm Perineum: Costal margin Posterior part = Anal Triangle Iliac crest Anterior part = Urogenital Triangle Abdominal cavity Pelvic inlet Obturator Pelvic Diaphragm Internus = Perineum Pelvic Diaphragm Perineum!!!!! P&P_1_Intro Pelvis-Perineum; Anal Triangle 13 of 17 K.E. Byrd X620 2017 10-16-2017 Perineum - A diamond shaped area inferior to the pelvic outlet (inferior pelvic aperture). Lithotomy position, inferior view. (“bent diamond”) Perineal region divided into 2 triangles with an imaginary line across the ischial tuberosities. 1. Urogenital Triangle 2. Anal Triangle UGUG ∆∆ UG ∆ A ∆ A ∆ Perineum is not flat but angled ~ 20 degrees between the 2 triangles (at arrow) Frontal Section of Anal Triangle/Region pelvic diaphragm (medial wall) Obturator Internus = Inf. rectal aa. muscle (lateral wall = Inf. rectal nn. of pelvis) = Ischiorectal Fossa External anal sphincter P&P_1_Intro Pelvis-Perineum; Anal Triangle 14 of 17 K.E. Byrd X620 2017 10-16-2017 Anal - Ischiorectal Fossa Pudendal nerve and internal pudendal aa./vv. leave the pelvis by the greater sciatic foramen and enter the gluteal region. These structures will leave the gluteal region via the lesser sciatic foramen and enter anal triangle of the perineum. How does an infection in this area (*) spread anteriorly (or into nearby recesses)? * * P&P_1_Intro Pelvis-Perineum; Anal Triangle 15 of 17 K.E. Byrd X620 2017 10-16-2017 In Lab TODAY (1/2)………. Do BOTH SIDES Anal Triangle Dissection Female Male In Lab TODAY (2/2)………. Reflection of Gluteus Maximus Glut. Medius P&P_1_Intro Pelvis-Perineum; Anal Triangle 16 of 17 K.E. Byrd X620 2017 10-16-2017 Anal Triangle – Ischiorectal (anal) Fossa Contents 1. Fat…. 2. ……MORE fat…… 3. ….and EVEN MORE fat!!! 4. Inferior Rectal Nerves & Vessels. 5. Function – permits distension of anal canal during defecation. P&P_1_Intro Pelvis-Perineum; Anal Triangle 17 of 17.