Structure of the Pelvic Wall Flashcards
What is the Sacral Promontory?
The anterior-superior margin of vertebra S1 that projects forward
What is the sacral canal?
Continuation of the vertebral canal
Contains the Cauda equina
What is sacral hiatus?
The inferior opening to the sacral canal
Site of entry of needle for caudal injection/epidural
What is the Coccyx?
4 coccygeal vertebrae fused together
Serves as site for muscle and ligament attachment
What structures form the Pelvic Brim?
Promontory and ala of sacrum
Right and Left linea terminalis:
-arcuate line of the ilium, Pecten pubis, pubic crest
What is the difference between the true and false pelvis?
True Pelvis - lies below the pelvic brim, contains lower GI tract and urogenital organs
False Pelvis - located above the pelvic brim, part of posterior wall of abdominal cavity
Why are pelvic fractures associated with high mortality?
Pelvic organ damage and hemorrhage
One must assume damage to urinary bladder and urethra
What is the sacroiliac joint?
Transmits the weight of most of the body to the hip bones
Held together by interosseous ligaments and anterior and posterior sacro-iliac ligaments
What is the sacrotuberous ligament?
Broad attachment to sacrum and narrows inferiorly to attach to the ischial tuberosity
Located posterior to the sacrospinous ligament
What is the sacrospinous ligament?
Triangular shape
Attaches to the lateral margin of sacrum and ischial spine
What is the function of the sacrotuberous and sacrospinous ligament?
Prevent upward tilting of sacrum due to weight of trunk
Convert the greater and lesser sciatic notches into greater and lesser sciatic foramina
What is the obturator membrane?
Covers obturator foramen, serves as a site of muscle attachment
What are the three measurements for obstetrics?
Obstetric Conjugate
Diagonal Conjugate
Interspinous Distance
What is the obstetric conjugate?
Minimum AP diameter of the lesser pelvis and narrowest fixed distance through which baby’s head must pass in a vaginal delivery
Sacral promontory to thickest margin of the pubic symphysis
Can’t be measured during pelvic exam*
What is the diagonal conjugate?
Measured by palpating the sacral promontory with the tip of the middle finger while using other hand to mark the level of the inferior margin of the pubic symphysis on the examining hand
What is the interspinous distance?
Distance between the ischial spines
Narrowest part of the pelvic canal
What is the difference between the pelvic inlet, outlet, cavity and angle of pubic arches in males and females?
Pelvic inlet - F-oval, M - kidney shaped
Pelvic outlet - F-Large, M-Small
Pelvic cavity - F-Wide, M-Narrow
Angle of Pubic Arches - F-Wide, M-Narrow
What are the walls of the true pelvis?
Lateral - Pelvic bones, Obturator Internus, Sacrospinous and Sacrotuberous ligaments
Anterior - Pubic symphysis and bodies of pubic bones
Posterior - Sacrum, coccyx, and piriformis muscle
What is the pelvic diaphragm?
Thin muscle layer that forms the floor of the true pelvis
Contains urogenital hiatus for passage of urethra in both sexes
Supports pelvic viscera
What are the origins and insertions of the Levator Ani?
Origin: Body of pubis, Tendinous arch, Ischial spine
Insertion: Coccyx, Anococcygeal body, Perineal body
What is the significance of the perineal body?
Important for maintaining support of the pelvic viscera
If torn during childbirth, could result in organ prolapse
What are the subdivisions off the Levator Ani?
Puborectalis
Pubococcygeus
Iliococcygeus
What are the origin, insertion, and action of the coccygeus?
Origin: Ischial Spine
Insertion: Sacrum and Coccyx
Supports the pelvic viscera
What is the endopelvic fascia?
Lines pelvic cavity and covers pelvic organs
Composed of parietal and visceral pelvic fascia
Parietal - covers muscles of pelvic wall
Visceral - located on surface of viscera
What is the nervous supply provided by the Sacral Plexus?
Motor - lower limb muscles, pelvic diaphragm, muscles of perineum, pelvic viscera,
Cutaneous sensory to lower buttock and back of thigh
What is the cause/result of compression of the sacral plexus?
Cause - pelvic tumor, compression by head of fetus during childbirth
Result - Pain to the lower limb (Sciatica)
What composes the sacral plexus?
Anterior Rami of L4,L5 and S1-S4
Sacral nerves emerge from sacral canal via anterior sacral foramina
What is the location of the sacral plexus (relative to a muscle)?
Anterior to the piriformis muscle
What branches of the sacral plexus exit the true pelvis through the greater sciatic foramen?
Superior gluteal nerve - above piriformis*
Inferior gluteal nerve - below piriformis*
Sciatic Nerve - below piriformis*
Posterior Cuteaneous nerve of the thigh
What branches of the sacral plexus pass through both the greater and lesser sciatic foramina?
Pudendal nerve
Nerve to Obturator Internus Muscle
