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
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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
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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??
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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!)
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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.
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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
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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
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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
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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
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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)
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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
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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.
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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!!!!!
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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
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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)?
* *
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In Lab TODAY (1/2)……….
Do BOTH SIDES
Anal Triangle Dissection
Female Male
In Lab TODAY (2/2)………. Reflection of Gluteus Maximus
Glut. Medius
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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.
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