Anatomy of the pelvis Flashcards
What 4 bones make up the pelvis?
Sacrum
Ilium
Ischium
Pubis
Where are the 2 coxal hip bones joined?
Pubic symphysis anteriorly
SI joint posteriorly
What 3 bones unite to form the acetabulum?
Ilium
Ischium
Pubis
What important structures/landmarks does the ilium contain?
Ala of ilium
4 iliac spines: posterior superior and inferior
Anterior superior and inferior
Greater sciatic notch
What important structures/landmarks does the ischium contain?
The ischial spines
Ischial tuberosity
Lesser sciatic notch
What are the components of the pubis?
Pubic symphysis
Pubic tubercle
Pubic crest
What 2 structures of the anterior pelvis are on the same plane?
anterior superior iliac spine is on the same plane as the pubic tubercle
What is the difference between the greater and lesser pelvis?
Greater pelvis is above pelvic inlet and lesser pelvis is inside pelvic inlet
What is another name for the greater pelvis?
False pelvis and the opposite is true (pun intended)
What are the boundaries of the greater pelvis?
Posteriorly the lumbar spine
Posterolaterally the ala of the illium
The abdominal wall anteriorly
What are the boundaries of the pelvic inlet?
Sacral promontory + sacral alae posteriorly
Arcuate + pectineal lines laterally
Upper margin of pubic symphysis anteriorly
What are the boundaries of the pelvic outlet?
Tip of coccyx posteriorly
Sacrotuberous ligament posterolaterally
Ischial tuberosity laterally
Ischiopubic ramus anterolaterally
Lower margin of pubic symphysis anteriorly
What are the boundaries of the pelvic cavity?
Sacrum + Coccyx posteriorly
Ilium + ischium laterally
Body of pubic bone, pubic rami, and pubic symphysis anteriorly
What is in the pelvic cavity?
Pelvic viscera
Nerves
Blood vessels
Muscles
What is the most common pelvic shape in males?
Android
What is the most common pelvic shape in females?
Gynecoid
What is a pelvic shape sometimes seen in males and black females?
Anthropoid
What is the transverse diameter of the pelvic inlet?
11cm
What is the transverse diameter of the pelvic outlet?
13cm
What is the anteroposterior diameter of the pelvic inlet?
13 cm
What is the anteroposterior diameter of the pelvic outlet?
11cm
What is the oblique diameter of both the inlet and outlet?
12cm
What is the interspinous distance?
10cm
Do the pelvic inlet and outlet lie in a completely horizontal plane in anatomical position?
No the inlet is oblique angle of 55 degrees with horizontal plane whereas outlet is at an angle of 45 degrees with horizontal plane
How is the female pelvis different to the male pelvis?
Outlet is wider
Inlet is open and circular
Ischial spines are more distant
Wider greater sciatic notch
Longer pubis and shorter ischium
Sacrum is flatter and shorter
Broader hips and tailbone
Pubic arch/ subpubic angle is greater than 90 degrees
lighter bones
Where does the sacrospinous ligament attach?
laterally attached to the ischial spine
Medially attached to the sacrum and coccyx
Where does the sacrotuberous ligament attach?
Ischial tuberosity inferiorly
Posterior superior iliac spine, lower part of posterior surface of sacrum and upper part of coccyx
What landmarks constitute the surfaces of the pelvic cavity?
Anterior wall
Pelvic floor: levator ani and coccygeus
Posterior wall is composed of pelvic surface of the sacrum and coccyx
Lateral walls composed of pelvic surface of ilium and obturator internis and its fascia
Where does the piriformis muscle originate?
On the sacrotuberous ligament
The gluteal surface of the ilium
The sacrum at S2 - S4
Where does the piriformis insert?
Greater trochanter of the femur
What spinal nerves innervate the piriformis?
The anterior rami of S1 - S2
What does the piriformis do?
Rotates femur laterally and holds femur head in acetabulum
Where does the obturator internis originate?
Obturator membrane and pelvic surface of the ilium and ischium
Where does the obturator internis insert?
Greater trochanter of the femur
What does the obturator internis do?
Laterally rotates femur and keeps head of femur in acetabulum
Where does obturator internus get its nerve supply?
Anterior rami of L5 S1 and S2
What are the main muscles of the pelvic floor?
Levator ani
coccygeus
What are the levator ani muscles?
Pubococcygeus (consists of puborectalis and puboprostaticus/pubovaginalis)
Iliococcygeus
Coccygeus
Where does the iliococcygeus originate and insert?
Origin: tendinous arch of obturator fascia and iscial spine
Inserts: anococcygeal raphe and coccyx
Where does the coccygeus originate?
Ischial spine
Where does the coccygeus insert?
lower sacrum and coccyx
Where does nerve supply of coccygeus come from?
S4 and S5 spinal nerves
Where does levator ani get its nerve supply?
S4 branches
Inferior anal nerve
Coccygeal plexus
What is the closest muscle to the center around anus ?
Puborectalis
What is the role of the pelvic floor?
Supports viscera of pelvis
Equalizes intraabdominal pressure during defacation and parturition
Which muscle is most often torn during childbirth?
Pubococcygeus
What does puborectalis do?
Forms sling around anus that helps with fecal continence
What is a possible consequence of injury to pelvic floor muscles?
Prolapse in uterus or rectum
Neck of bladder can be moved resulting in urinary incontinence.
Where is the uterovesical pouch?
Anterior to the uterus
Posterior to the bladder
Where is the rectouterine pouch?
Between rectum and uterus
What is another name for the rectoterine pouch?
Pouch of douglas
What does the rectouterine pouch cover?
Anterior part of middle third of the rectum and upper rectum
The uterus anteriorly
The posterior fornix of the vagina inferiorly
Describe the rectovesical pouch and who has it?
The male peritoneal pouch covers the base of the bladder as well as the superior portion of the bladder it also covers the anterior part of the middle third of the rectum and continues to cover it superiorly until it becomes continuous with the posterior abdominal wall
What is the clinical significance of the abdominal pouches?
Any free fluid accumulates in those pouches. For example, pus from abscesses or blood from rupture of blood vessels.
What are the paravesical fossae?
Some peritoneum is reflected laterally into lateral pelvic wall from superior bladder wall and is continuous with the pelvic wall.
What is the broad ligament?
Membrane is folded over fallopian tubes in such a way that underneath them the membrane meets itself in the form of a double membrane. As a result this tissue connects the ovary to the uterus and is called the broad ligament. It also covers the ovary
What is the difference between male and female peritoneal cavity?
In males the lower extent the peritoneal cavity is closed. In females inferiorly the peritoneal communicates with exterior atmosphere via the uterine tube. Any infection in vagina or uterine tube could spread into the peritoneam called peritonitis.
