[MOORE] Pelvis and Perineum - Clinically Oriented Anatomy

Contain and protect pelvic viscera and inferior abdominal viscera, support abdominopelvic viscera, provide attachment for erectile bodies, and provide attachment for muscles and membranes of the pelvic floor.

What are the main functions of the pelvis?

Ilium, ischium, and pubis.

What three bones fuse after puberty to form the hip bone?

Pubic symphysis.

Where do the right and left hip bones join anteriorly?

Promontory and ala of the sacrum, linea terminalis, arcuate line, pecten pubis, and pubic crest.

What bony structures form the pelvic brim?

Right and left ischiopubic rami.

What bony structures form the pubic arch?

Distance between the right and left ischial tuberosities.

What determines the width of the subpubic angle?

Pubic arch, ischial tuberosities, and sacrotuberous ligaments.

What structures bound the pelvic outlet (inferior pelvic aperture)?

Anterior superior iliac spines (ASISs) and the anterior aspect of the pubic symphysis.

When a person is in the anatomical position, what structures lie in the same vertical plane regarding the pelvic girdle?

True (obstetrical) conjugate.

What is the minimum anteroposterior diameter of the lesser pelvis called?

From the middle of the sacral promontory to the posterosuperior margin of the pubic symphysis.

Where does the true conjugate extend?

Diagonal conjugate.

What diameter is measured by palpating the sacral promontory with the tip of the middle finger during a pelvic exam?

11.0 cm or greater.

What should the true conjugate measure to be considered adequate for vaginal delivery?

The plane of the pelvic inlet (defined by the pelvic brim).

What demarcates the greater and lesser pelvis?

Musculofascial pelvic diaphragm.

What limits the pelvic cavity inferiorly?

Ureters, urinary bladder, rectum, pelvic genital organs, blood vessels, lymphatics, and nerves.

What structures are contained within the pelvic cavity?

Antero-inferior wall, two lateral walls, a posterior wall, and a floor.

What are the walls of the pelvic cavity?

Pubic bones, ilia, sacrum, and coccyx.

What structures is the pelvic diaphragm suspended from?

Sacrotuberous ligament and sacrospinous ligament.

What ligaments attach the coccyx and inferior sacrum to the ischial tuberosity and ischial spine, respectively?

Obturator membrane.

What membrane fills the obturator foramen?

Greater sciatic foramen.

Through what foramen does the piriformis muscle leave the lesser pelvis?

Bodies of the pubic bones, ischial spines, and tendinous arch of the levator ani.

To what structures does the levator ani attach?

Urogenital hiatus.

What anterior gap in the levator ani allows passage of the urethra and vagina (in females)?

Puborectalis, pubococcygeus, and iliococcygeus.

What are the three parts of the levator ani muscle?

Maintaining the anorectal angle (perineal flexure).

What is the function of the puborectalis muscle?

Anococcygeal body or ligament (levator plate).

What structure do the medial fibers of the pubococcygeus muscle merge with?

Supporting the abdominopelvic viscera and maintaining urinary and fecal continence.

What are the main functions of the levator ani?

Loose areolar (fatty) layer between the transversalis fascia and the parietal peritoneum.

What allows the bladder to expand as it fills with urine?

Supravesical fossa.

What is created when the peritoneum reflects onto the superior surface of the bladder?

Recto-uterine pouch (of Douglas).

In females, what pouch is formed as the peritoneum reflects from the uterus onto the rectum?

Rectovesical pouch.

In males, what pouch is formed as the peritoneum reflects from the bladder onto the rectum?

Broad ligament of the uterus.

What double peritoneal fold extends between the uterus and the lateral pelvic wall?

Retropubic (prevesical) and retrorectal (presacral) spaces.

What are the potential spaces formed by loose fatty tissue anterior and posterior to the pelvic viscera?

Hypogastric sheath.

What fascial condensation gives passage to vessels and nerves passing from the lateral wall of the pelvis to the pelvic viscera?

Lateral ligament of the bladder, lateral rectal ligament, and cardinal ligament.

Into what three laminae does the hypogastric sheath divide?

Cardinal ligament.

What ligament provides the main passive support for the uterus?

Pelvirectal space.

What surgically important potential space exists superior to the pelvic diaphragm?

Rectosacral ligaments.

What divides the pelvirectal space into anterior and posterior spaces?

Perineum, levator ani, and ligaments of the pelvic fascia.

What structures may be injured during childbirth that can lead to prolapse of pelvic organs or fecal incontinence?

The pelvic cavity, between the pelvic inlet superiorly and the pelvic diaphragm inferiorly.

Where is the pelvic cavity located?

Pubic symphysis and bones of the lesser pelvis.

What structures bound the pelvic cavity anteriorly and posterosuperiorly?

Obturator internus muscles.

What pads the lateral walls of the pelvic cavity?

Sacrotuberous and sacrospinous ligaments.

What forms the greater sciatic foramen in the posterolateral walls of the pelvic cavity?

Levator ani and coccygeus muscles.

What muscles compose the pelvic diaphragm?

Puborectalis, pubococcygeus, and iliococcygeus.

What muscles form the tripartite levator ani?

Lateral ligament of the bladder.

What is the anteriormost lamina of the hypogastric sheath called?

Lateral rectal ligament.

What is the posteriormost lamina of the hypogastric sheath called?

Cardinal ligament.

In females, what is the middle lamina of the hypogastric sheath called?

Rectovesical septum.

In males, what is the middle lamina of the hypogastric sheath called?

Laterally,

Where do the somatic nerves lie in relation to the neurovascular structures of the pelvis?

Medial to the somatic nerves.

Where do the vascular structures lie in relation to the somatic nerves of the pelvis?

Lateral to the arteries.

Where do the veins lie in relation to the arteries in the pelvis?

Internal iliac artery.

What is a major source of arterial supply to the pelvis?

Gonadal arteries, superior rectal artery.

Name arteries that supply the pelvis, but not via the internal iliac artery.

Superior rectal artery.

What artery is the direct continuation of the inferior mesenteric artery?

Internal iliac veins.

What veins drain the pelvic viscera?

Common iliac veins.

What do the external and internal iliac veins merge with?

Superior gluteal veins.

Besides the uterine veins during pregnancy, what are the largest tributaries of the internal iliac veins?

External iliac, internal iliac, sacral, and common iliac lymph nodes.

What are the four primary groups of lymph nodes in the pelvis?

External iliac lymph nodes.

What nodes receive lymph mainly from the inguinal lymph nodes but also from pelvic viscera?

Internal iliac lymph nodes.

What nodes receive drainage from the inferior pelvic viscera, deep perineum, and gluteal region?

Sacral lymph nodes.

What nodes receive lymph from postero-inferior pelvic viscera?

Common iliac lymph nodes.

What nodes receive drainage from the other three main groups of pelvic lymph nodes?

Lumbosacral trunk.

What is formed by the union of the L4 and L5 nerves at or superior to the pelvic brim?

Sciatic and pudendal nerves.

What are the two main nerves arising from the sacral plexus?

Greater sciatic foramen.

Through what foramen do most branches of the sacral plexus leave the pelvis?

L4-S3.

What spinal nerve roots form the sciatic nerve?

S2, S3, and S4.

From what spinal nerves do the pelvic splanchnic nerves originate?

Pelvic viscera.

What do the pelvic splanchnic nerves innervate?

Ureter.

What structure is crossed by the uterine artery near the lateral part of the fornix of the vagina?

Vasomotion and contraction of internal genital organs during orgasm, inhibition of rectal peristalsis.

What are the effects of sympathetic fibers on the pelvic organs?

Bladder and rectal emptying, erection of the external genitalia.

What are the effects of parasympathetic fibers on the pelvic organs?

Distal parts of the urinary system and gastrointestinal tract, and the reproductive system.

What organ systems are included as pelvic viscera?

Abdomen.

Where are the superior portions of the ureters located?

At the bifurcation of the common iliac artery.

Where do the ureters cross to enter the lesser pelvis?

Internal iliac arteries.

To what arteries are the pelvic parts of the ureters parallel?

Vesical venous plexus.

What surrounds the inferior ends of the ureters?

Oblique passage through the muscular wall of the urinary bladder.

What forms a one-way "flap valve" to prevent backflow of urine into the ureters?

T10-L2 or L3.

What spinal cord segments do afferent (pain) fibers from the ureters follow?

Ipsilateral lower quadrant of the abdomen, especially to the groin (inguinal region).

Where is ureteric pain usually referred?

Lesser pelvis, partially superior and partially posterior to the pubic bones.

Where is the urinary bladder located when empty?

Retropubic space.

What separates the bladder from the pubic bones?

Apex, body, fundus, and neck.

What are the four parts of the urinary bladder?

Pubic bones and fascia covering the levator ani and superior obturator internus muscle.

What structures form the bladder bed?

Detrusor muscle.

What muscle forms the wall of the urinary bladder?

Ureteric orifices and the internal urethral orifice.

What are the angles of the trigone of the bladder?

Internal iliac veins.

What veins do the veins draining blood from the bladder correspond to?

Hypogastric plexuses and nerves.

Through what structures are sympathetic fibers conveyed to the vesical (pelvic) plexuses?

Pelvic splanchnic nerves and the inferior hypogastric plexus.

Through what structures are parasympathetic fibers conveyed to the vesical (pelvic) plexuses?

T11-L2 or L3.

What spinal cord segments do pain fibers from the superior bladder follow?

18-22 cm.

What is the length of the male urethra?

Internal urethral orifice of the urinary bladder to the external urethral orifice.

Where does the male urethra extend?

Intramural (preprostatic), prostatic, intermediate (membranous), and spongy.

What are the four parts of the male urethra?

Urethral crest.

What is the most prominent feature of the prostatic urethra?

Seminal colliculus.

On what structure do the ejaculatory ducts open?

4 cm.

What is the length of the female urethra?

Pelvic diaphragm, external urethral sphincter, and perineal membrane.

Through what structures does the urethra pass?

S3 vertebra.

At what level does the rectosigmoid junction lie?

Sacral flexure of the rectum.

What flexure does the rectum follow?

Anorectal flexure.

What flexure occurs as the gut perforates the pelvic diaphragm (levator ani)?

Puborectalis muscle.

What maintains the anorectal flexure?