Greater Sciatic Foramen	Lesser Sciatic Foramen
Piriformis muscle	Tendon of obturator internus
Sciatic nerve	Nerve to obturator internus
Inferior gluteal nerve and artery	Pudendal nerve
Internal pudendal nerve, artery, and vein	Internal pudendal artery
Nerve to obturator internus muscle
Nerve to quadratus femoris
Posterior cutaneous nerve of the thigh

Sex Differences of Pelvis

• Differences linked to function

• Pregnancy and childbirth in females

• Heavier build and larger muscles of men

• Main differences

• Pelvis is heavier and has more pronounced muscle attachment sites in men than in women.

• Pubic arch is narrower and subpubic angle more acute in men than women.

• Ischial tuberosities are closer in men than in women, and pelvis outlet is thus comparatively smaller.

• All of the ilia are less flared in men than in women, so the greater pelvis is deeper.

• Pelvic inlet is heart-shaped in men and more transversely oval in women.

• Obturator foramen is round in men and oval in women.

• Female pelvis is broader than in men to allow passage of fetal head.

Anatomical Points

Measurements of the Pelvic Inlet

• Used to determine capacity of female pelvis for childbearing

• True conjugate diameter

• Measured radiologically on a lateral x-ray

• Distance from superior border of pubic symphysis to sacral promontory

• Transverse diameter: widest distance of pelvic inlet

• Oblique diameter: distance from sacro-iliac joint to contralateral iliopectineal line

Clinical Points

Fractures of the Pelvis

• A large force is required to fracture the pelvis, and fractures usually result from direct trauma, such as occurs in automobile accidents.

• The bony pelvis may fracture at any point and there may be associated damage to pelvic viscera; for example, bladder and urethral rupture can occur with fractures involving the pubis.

• Pelvic fractures are classified as stable or unstable.

• In a stable fracture, the pelvis remains stable and there is only one break-point in the pelvic ring with minimal hemorrhage.

• In an unstable fracture, the pelvis is unstable with two or more break-points in the pelvic ring with moderate to severe hemorrhage.

• Signs of a fractured pelvis include pain in the groin, hip, or lower back; difficulty walking; urethral, vaginal, or rectal bleeding; scrotal hematoma; and shock as a result of concealed hemorrhage (contained bleeding into the pelvic cavity)

• A fracture can be confirmed on radiograph and is seen as a break in continuity of the pelvic ring.

Decubitus Ulcers

• Also called pressure sores

• Can be a partial- or full-thickness loss of skin, underlying connective tissue, and can extend into muscle, bone, tendons, and joint capsules

• Two thirds of pressure sores occur in patients older than 70 years.

• Results from prolonged pressure on an area of skin, connective tissue, and muscle from a mattress, wheelchair seat, or bed rail

• Commonly occur in those with poor mobility, bed-bound, poor nutrition, and incontinence.

• Can become infected with bacteria from poor skin care or fecal or urinary incontinence

• The hip and buttock regions account for 67% of all pressure sores, with ischial tuberosity, trochanteric, and sacral locations being most common.

• In the sitting position, the ischial tuberosity bears the weight of the whole body and thus is a prime site of ulceration.

5.3 Pelvic Floor and Contents

Study Aims

At the end of your study, you should be able to:

• State the structures that form the pelvic floor

• Describe the two main muscles that form the pelvic floor and their attachments

• List the functions of the pelvic floor muscles

• Describe the attachments of the peritoneum within the pelvis and the location of the vesico-uterine and recto-uterine pouches in females and rectovesical pouch in males

• Understand the organization and function of the pelvic fascia

• Describe the clinical problems that may arise with weaknesses of the pelvic floor muscles

Guide

Pelvic Floor

• Formed by pelvic diaphragm

• Funnel-shaped

• Muscular partition from pubis to coccyx and from lateral wall to lateral wall

• Separates pelvic cavity from perineum inferiorly

• Transmits urethra, vagina (in females), and anal canal

Muscles of Pelvic Floor

• Pelvic diaphragm is composed of two paired muscles

• Principal muscle of pelvic floor

• Supports pelvic contents

• Actively maintains position of pelvic viscera

• Arcus tendineus: thickened line of fascia over obturator internus muscles running in arching line from pubis to ischial spine

• Central perineal tendon or perineal body

• Fibromuscular body extending from perineum into urogenital hiatus

• Site of numerous muscle attachments in the perineum

• Components of levator ani muscle

• Pubococcygeus

• Is anterior part of levator ani

• Main contributor to levator ani

• Arises from posterior body of pubic bone and anterior part of arcus

• Tendineus

• Runs posteriorly to attach to anococcygeal ligament and coccyx

• Iliococcygeus

• Posterior part of levator ani

• Thin and poorly developed

• Arises from posterior part of arcus tendineus and ischial spine

• Attaches to anococcygeal raphe and coccyx

• Puborectalis

• Thickened band of muscle best seen inferior to pubococcygeus

• Unites with its partner to make U-shaped sling around rectum at its junction with anus

• Has sphincterlike action by pulling anorectal junction forward and contributing to anal continence

• Medial muscle fibers of the pubococcygeus border the urogenital hiatus

• Most anterior fibers insert into urethra

• Other fibers sweep behind vagina or prostate and insert into central perineal tendon—called levator prostatae, or pubovaginalis.

• Coccygeus muscle

• Reinforces pelvic floor posteriorly

• Arises from ischial spine

• Inserts on lower two sacral and upper two coccygeal segments

• Blends with sacrospinous ligament on its external surface

• Innervation of levator ani and coccygeus muscles

• Levator ani innervated by branches from anterior rami of S3–S4 spinal nerves.

• Puborectalis also innervated by branch of pudendal nerve (S2,3,4).

• Coccygeus supplied by branches of anterior rami of S4–S5 spinal nerves.

• Functions of levator ani

• Acting together, raise pelvic floor to increase abdominal pressure, such as when coughing, sneezing, urinating, defecating, lifting heavy objects

• Important in voluntary control of micturition (urinating)

• Supports pelvic viscera

• Supports head of fetus

Muscles Lining Lateral Walls of Pelvis

• Obturator internus muscle

• Proximal attachment: pelvic surfaces of ischium and ilium and obturator membrane

• Distal attachment: greater trochanter of femur

• Innervated by nerve to obturator internus (L5, S1–S2)

• Lateral rotator of thigh

• Piriformis muscle

• Proximal attachment: pelvic surfaces of S2-4 segments of sacrum, sacrotuberous ligament

• Distal attachment: greater trochanter of femur

• Innervated by ventral rami of S1–S2 spinal nerves

• Lateral rotator of this

Muscle	Proximal Attachment (Origin)	Distal Attachment (Insertion)	Innervation	Main Actions	Blood Supply
Obturator internus	Pelvic surface of obturator membrane and surrounding bone	Medial surface of greater trochanter of femur	Nerve of obturator internus	Laterally rotates extended thigh, abducts flexed thigh at hip	Internal pudendal and obturator arteries
Piriformis	Anterior surface of sacral segments 2–4, sacrotuberous ligament	Superior border of greater trochanter of femur	Ventral rami of upper L5, S1, S2	Laterally rotates extended thigh, abducts flexed thigh at hip	Superior and inferior gluteal arteries, internal pudendal artery
Levator ani	Body of pubis, tendinous arch of obturator fascia, and ischial spine	Perineal body, coccyx, anococcygeal raphe, walls of prostate or vagina, rectum, anal canal	Ventral rami of lower sacral nerves, perineal nerve	Supports pelvic viscera; raises pelvic floor	Inferior gluteal artery, internal pudendal artery and its branches (inferior rectal and perineal arteries)
Coccygeus (ischiococcygeus)	Ischial spine, sacrospinous ligament	Inferior sacrum, coccyx	Ventral rami of lower sacral nerves	Supports pelvic viscera, draws coccyx forward	Inferior gluteal artery

Pelvic Fascia

• Occupies space between peritoneum and muscles of pelvic floor and walls

• Parietal pelvic fascia lines internal surface (facing pelvic cavity) of muscles of floor and walls.

• Visceral pelvic fascia invests each of the pelvic organs.

• Visceral and parietal fascia are continuous where organs penetrate pelvic floor.

• Where they are continuous, fascia thickens to form tendineus arch of pelvic fascia (arcus tendinous fasciae pelvis).

• Arches are bilateral bands running from pubis to sacrum, adjacent to viscera.

• Puboprostatic ligament

• Pubovesical ligament

• Sacrogenital ligaments

• Between parietal and visceral fascia is endopelvic fascia

• Matrix or filler material

• In certain areas, condenses and becomes more fibrous to form fascial “ligaments,” or septa

• Major condensation is hypogastric sheath.

• Runs from lateral pelvic wall to pelvic viscera

• Separates retropubic space from presacral space

• Serves as a conduit for vessels and nerves

• Transverse cervical (cardinal) ligaments are part of hypogastric sheath.

• Run from lateral wall to uterine cervix and vagina

• Uppermost part is beneath broad ligament and transmit uterine artery

• Sufficiently fibrous to provide passive support for uterus

• Uterosacral (female) or genitosacral (male) ligaments

• Septa separate the pelvic organs and include

• Vesicovaginal septum

• Rectovesical septum

• Rectovaginal septum

• Weakness of pelvic floor muscles or in pelvic fascia, which support the pelvic organs, can result in prolapse of pelvic organs (e.g., vaginal or rectal prolapse).

Pelvic Contents

• Female pelvic viscera and perineum

• Section 5.4: Urinary Bladder

• Section 5.5: Uterus, Vagina, and Supporting Structures

• Section 5.9: Rectum

• Male pelvic viscera and perineum

• Section 5.4: Urinary Bladder

• Section 5.8: Testis, Epididymis, and Ductus Deferens

• Section 5.9: Rectum

Clinical Points

Peritoneal Reflections

• Pelvic peritoneum

• Lines lateral and posterior pelvic walls and pelvic floor

• Covers rectum, urinary bladder, uterus, and adnexa in females

• Covers anterior and lateral surfaces of upper portion of rectum in both sexes

• In men

• Sweeps forward from rectum to bladder

• Creates recess between rectum and bladder: rectovesical pouch

• Continues over superior surface of bladder and ascends on internal side of anterior abdominal wall

• In women

• Sweeps forward from rectum onto posterior fornix of uterus and posterior uterine wall

• Creates recess between rectum and uterus: recto-uterine pouch (of Douglas)

• Covers posterior, superior, and anterior surfaces of uterus before reflecting onto superior surface of bladder

• Ascends on internal side of anterior abdominal wall

• Fluid (blood, pus) can collect in rectovesical or recto-uterine pouches, causing infection and forming pelvic abscesses.

5.4 Urinary Bladder

Study Aims

At the end of your study, you should be able to:

• Describe the course of the pelvic ureters

• Outline the gross structure of the bladder

• Describe the relations of the bladder

• Describe the structure of the male urethra

• Describe the structure of the female urethra

Guide

Ureters

• Cross pelvic brim at level of sacro-iliac joint, anterior to bifurcation of common iliac artery to pierce posterior surface of bladder

• Enter posterolateral surface of bladder and run obliquely through bladder wall, creating flap valve

• In males: pass under ductus deferens, superior to seminal vesicles

• In women: descend posterior to ovary and into base of broad ligament, passing under uterine artery (“water under the bridge”)

• Supplied by branches of common and internal iliac arteries and uterine artery (inferior vesicle artery in males) and drained by veins with same names.

• Innervated by fibers from adjacent autonomic plexuses

Urinary Bladder

General Structure

• Lies posterior to pubic bones and pubic symphysis

• When empty is tetrahedron in shape and lies entirely within true pelvic cavity; spherical when full and may reach as high as umbilicus

• When empty has base (posterior surface) and one superior and two inferolateral surfaces

• Base (posterior surface) of bladder defined internally by two ureteric openings at superolateral corners and internal urethral opening inferiorly

• Triangular area defined by these openings is vesicle trigone.

• Ridge between two urethral openings is interureteric fold.

• Neck of bladder is where base and inferolateral sides meet, inferiorly.

• Anterior angle or apex is site of attachment of urachus—fibrous remnant of fetal allantois, which is seen as median umbilical ligament on anterior abdominal wall.

• Bladder wall is composed of thick layer of interwoven bundles of smooth muscle running transversely, longitudinally, and obliquely—detrusor muscle.

• In region of neck, detrusor muscle runs circularly as involuntary internal sphincter.

• Bladder mucosa is thrown into rugae except within trigone, which is smooth.

Relations of the Urinary Bladder

Border	Structure
Superior	Peritoneum Ileum Sigmoid colon
Inferolateral	Obturator internus muscle Levator ani muscle Obturator nerve Obturator artery and vein Superior vesical artery and vein
Anterior	Retropubic space—containing adipose tissue and veins Pubic crest
Posterior—male	Seminal vesicles Ampulla of ductus deferens Rectovesical pouch Ampulla of rectum
Posterosuperior—female	Vesico-uterine pouch Body of uterus
Posterior—female	Cervix Anterior wall vagina
Inferior—male	Prostate Prostatic venous plexus

Arterial Supply

• Superior vesicle arteries (branches of internal iliac artery) supply apex and superior part of bladder.

• Inferior vesical arteries supply fundus and neck in males.

• Vaginal arteries (branches of uterine arteries) supply fundus and neck in females.

• Obturator arteries (branches of internal iliac artery) provide arterial twigs.

Venous Drainage

• Vesical venous plexus drains to internal iliac plexus via inferior vesical veins.

• Communicates with prostatic venous plexus in males and uterovaginal venous plexus in females

Female Urethra

• 3- to 4-cm long fibromuscular tube bound to anterior vaginal wall

• Extends from internal urethral meatus of bladder to external meatus situated just anterior to vaginal opening in vestibule

• Descends with vagina through urogenital hiatus and pelvic diaphragm and through perineal membrane, where it is surrounded by external sphincter urethrae

• Para-urethral glands, homologs to the prostate, open on either side near external urethral orifice

• Supplied by internal pudendal and vaginal arteries

• Drained by veins of same name

• Innervated by branches of pudendal nerve via S2–S4 spinal cord segments and afferents run with pelvic splanchnic

Male Urethra

• 25-cm fibromuscular tube

• Conveys both urine and semen

• Extends from internal urethral meatus of bladder to external urethral meatus in glans penis

• Divided into three parts: prostatic, membranous, and spongy urethra

Comparison of Prostatic, Membranous, and Spongy Parts of the Male Urethra

	Prostatic Urethra	Membranous Urethra	Spongy Urethra
Length	3 cm	2 cm	15 cm
Extent	Internal urethral meatus to apex of prostate	Apex of prostate to perineal membrane	Bulb of penis to glans penis
Key anatomical features	Urethral crest (midline ridge) Prostatic sinuses (site of opening prostatic ducts) Prostatic utricle (blind-ending sac on urethral crest; remnant of fetal duct forming uterus in females) Ejaculatory duct (opens either side of the utricle)	Surrounded by striated muscle of external urethral sphincter Bulbo-urethral glands lie posterolaterally Pubic symphysis lies anteriorly attaching via pubourethral ligaments
Blood supply	Inferior vesical and rectal arteries	Inferior vesical and rectal arteries	Internal pudendal artery via dorsal arteries of penis
Venous drainage	Veins of same names and prostatic venous plexus	Veins of same names and prostatic venous plexus	Prostatic venous plexus and internal pudendal veins
Nerve supply	Pudendal nerve (S2–S4) and prostatic plexus	Pudendal nerve (S2–S4) and prostatic plexus	Pudendal nerve (S2–S4) and prostatic plexus