Gross anatomy: overview of pelvis and perineum

Question 1

Pelvic cavity

Answer 1

• Is continuous w/ abd cavity and the separation plane is the plane of pelvic inlet
• This runs from the sacral promontory to the pubic symphysis
• The pelvic brim (inlet) is the bony margin that defines the plane of the pelvic inlet
• The pelvic inlet contains (from front to back) the pubic symphysis, pubic crest, pectinate line, arcuate line, sacral ala, and sacral promontory
• The pelvic outlet (inferior to inlet) is lined by the pubic symphysis, ischiopubic ramus, ischial tuberosity, sacrotuberous ligament, and coccyx
• The pelvic outlet defines the border to the perineum

Question 2

Perineum

Answer 2

• Inferior to the pelvic cavity is the perineum (outside of the pelvic cavity where external genitals, erectile bodies and SkM controlling erection, orgasm, defecation, and micturition/peeing are)
• The separation of the pelvic cavity and the perineum is the pelvic diaphragm: a thin partition of SkM that extends from the lateral pelvic walls downward and medially
• Of the muscles that make up the pelvic diaphragm the most important one is levator anii (broadest muscle)

Question 3

Female peritoneal cavity

Answer 3

• Contains 2 openings: the paired uterine tubes
• These openings are the only places where there are gaps in there peritoneum (covers all other intraperitoneal structures in the pelvic cavity)
• Some structures in pelvic cavity are partly intraperitoneal and retroperitoneal

Question 4

Female pelvic viscera 1

Answer 4

• The peritoneum extends down to surround most of the uterus and the top of the bladder
• But the vagina and cervix are inferior to the inferior margin of the peritoneum and thus are subperitoneal
• Subperitoneal space is continuous w/ retroperitoneal space
• The space between the bladder and the uterus is the vesicouterine pouch
• The space btwn the uterus and the rectum is the rectouterine pouch (pouch of douglas)

Question 5

Female pelvic viscera 2

Answer 5

• The ovarian ligament attaches the ovary to the uterus, and the uterine tube surrounds part of the ovary and allows the oocyte to migrate to the uterus during ovulation
• The round ligament of the uterus connects the uterus to labia majora, and is the only structure that passes thru the inguinal canal in the female
• Both the round ligament and the ovarian ligament are remnants of the gubernaculum: the structure that pulls the gonads (ovaries) down during development so they can assume their mature position

Question 6

Broad ligament and its mesenteries

Answer 6

• The broad ligament extends laterally from the uterus and contains an ovary, ovarian ligament, uterine tube, and round ligament
• The broad ligament contains 3 mesenteries named after which structure it is surrounding
• The mesentery that surrounds the uterine tube is the mesosalpinx
• The one that surrounds the ovary is the mesovarium
• The one that spans btwn the ovaries and the uterine tubes is the mesometrium

Question 7

Male pelvic viscera

Answer 7

• The peritoneum extends inferiorly to cover the superior margin of the bladder and part of the rectum/seminal vesicle
• The space btwn the bladder and the rectum is the rectovesical pouch

Question 8

Emission and ejaculation

Answer 8

• 4 SmM structures involved in emission (getting sperm from epididymis to urethra): vas deferens, seminal vesicle, prostate, prostatic urethra
• All of these SmM structures are under sympathetic innervation
• Ejactulation is from prostatic urethra to external urethral meatus and is under somatic control
• No emission = no ejaculation

Question 9

Sympathetic pathways controlling pelvic/perineal organs 1

Answer 9

• From lateral horns of the spinal cord the sym/pres go into the ventral root-> spinal nerve (briefly) then enter the white rami to enter the sympathetic trunk
• From the trunk the sym/pre will either exit via lumbar splanchnic nerve or go down the trunk and exit via lumbar splanchnic nerve at the proper level
• The sym/pre will reach the superior hypogastric plexus where they synapse w/ the sym/post cell bodies

Question 10

Sympathetic pathways controlling pelvic/perineal organs 2

Answer 10

• The sym/post axons continue down the hypogastric nerves to the inferior hypogastric plexuses
• VS pain will be running with the sympathetics but going the opposite direction and never synapsing until spinal cord
• The superior hypogastric plexus is sym/mixed (both pre and post fibers, only post cell bodies) + VS pain
• The inferior hypogastric plexus is sym/post and VS pain

Question 11

Disruption of the superior hypogastric plexus

Answer 11

• In males: absence of ejaculation due to denervation of vas deferens, seminal vesicles, and prostate
• In females: interrupting pain pathways from some pelvic organs