K.E. Byrd X620 2017 10-16-2017

HS 2017 MED-X620 Intro to & Perineum; Anal Triangle

Kenneth E. Byrd, PhD [email protected] 274-3355 HS 2017 MED-X620 IUSOM

Osteology Bony Pelvis – hip , and •Protect Pelvic Viscera •Support Body Weight. Superior

•Attachments: muscles for Abdomen & LE

Hip Bones - Os Coxae -Innominate • Start as 3 bones separated by hyaline cartilage called the Tri-radiate cartilage; located at the .

• They complete fusion at ~12 years for Posterior Anterior girls and ~14 years for boys.

Lateral View of

immature Ox Coxa Inferior

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Sagittal Section Abdominal

Pelvic Inlet ()

= 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) completes the pelvic inlet

Pubic tubercle

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Pelvic Fractures & Common Causes Pelvic Fractures • High‐Energy Trauma • Congenital Bone Development • Osteoporosis • Avulsion – (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 !!!!! 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 1. Ant.- Post. (True Conjugate diameter) 2. Transverse 3. Oblique

Pelvic Outlet 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 Anterior part = Urogenital Triangle 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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