Download Pelvis and Perinum Forum 2009

Gross Anatomy, Fall 2009
Pelvis & Perineum Forum
1. Trace the pudendal nerve and it terminal branches. What structures are innervated? What
landmarks / spaces are important along the course (ID landmarks)? Where would you inject
an anesthetic agent to perform a pudendal nerve block? What landmark(s) would be used to
guide the injection?
Inferior rectal nerve, dorsal nerve of penis, perineal nerve
Innervates: Motor – external urethral and anal sphincters and levator ani (overlaps with
branches of ventral division of S4 for levator ani and external sphincter)
Sensory – Most skin of the perineum. Penis and clitoris.
Landmarks: Leaves pelvic cavity through greater sciatic foramen, inferior to the piriformis
muscle, and enters the gluteal region. Courses into the perineum by immediately
passing around the sacrospinous ligament, where the ligament joins the ischial spine,
and through the lesser sciatic foramen (this course takes the nerve out of the pelvic
cavity, around the peripheral attachment of the pelvic floor, and into the perineum)
Is accompanied throughout its course by the internal pudendal vessels
Pudendal Nerve Block: Performed to relieve pain associated with childbirth. Injection is
usually given where the pudendal nerve crosses the lateral aspect of the sacrospinous
ligament near its attachment to the ischial spine. The needle is passed transcutaneously
to the medial aspect of the ischial spine and around the sacrospinous ligament.
2. Where is cancer of the bladder likely to spread? What structures can be affected?
Rectum, uterus, prostate, and lateral walls of the pelvic cavity. Venous plexus. Spreads via
local internal iliac lymph nodes, but can also affect external iliac lymph nodes. Can
spread to bone.
3. A 37 year old patient complains of urine leakage when she creates intrabdominal pressure.
Patient history reveals she has given a breech birth. MRI reveals a malpositioned neck of the
bladder. What structure is damaged?
(Breech position is when baby enters birth canal feet first, instead of the normal head first)
Neck of bladder anchored into position by a pair of tough, fibromuscular bands. In women
they are called “pubovesical ligaments”; in men “puboprostatic ligaments”
Apex is anchored by median umbilical ligament
4. Why are internal hemorrhoids painless and external hemorrhoids painful? What nervous
system structures are involved with each type? What structure divides the anal canal
regions?
Internal hemorrhoids (inside the rectum) are painless because there is only visceral
innervation inside the rectum (hypogastric plexus: autonomic, not for pain)
External hemorrhoids (at the anal verge, distal boundary of the anal canal) are painful
because there is somatic and sensory innervation from the inferior rectal nerve
(innervates the skin of the anal triangle)
Pectinate line is dividing line
5. A patient has blockage in the middle rectal vein. What vessels provide collateral circulation?
Trace the flow path for each collateral vessel.
Superior rectal vein, internal pudendal vein, and inferior rectal vein
6. When performing an episiotomy, what perineal structure is cut? What perineum structures
attach to this structure?
Midline – cuts perineal body
Medio-lateral – cuts vaginal epithelium, skin, and muscles (superficial transverse perineal
muscle and bulbospongiosus muscle
7. While performing a pap smear what structures can be assessed?
Vagina, cervix, and external os
8. A 10-year-old male presents from an accident where he fell and straddled his bike. Since the
time of the accident he has pain and swelling of his perineal & scrotal skin. What part of the
urethra is damaged? In what structure is the extravation occurring?
Spongy urethra. Superficial space (between superficial fascia, inferior, and perineal
membrane, superior)
9. What structures distinguish these two photos?
A
B
Angle of pubic arch and shape of pelvic inlet
A men 50-60 degree arch, with heart-shaped pelvic inlet and more prominent ischial spines
B women 50-80 degree pubic arch circular pelvic inlet
10. Uterine prolapse can be a direct result from injury to what structures?
Transverse cervical ligament, pelvic floor (of pelvic diaphragm; pelvic diaphragm is the
most important, and greatest, support to all organs in the pelvic cavity)
The bladder helps keep the uterus in its normal position (along with the other
organs/structures in the cavity)
11. What structures are in danger in the instance of a pelvic fracture of the superior pubic
ramus?
Bladder, spermatic cord, femoral artery (obturator foramen), aberrant obturator artery
(not everyone has, but is important as this vessel is under a lot of pressure; should be
aware of possibility of presence)
12. A patient is shot in the gluteal region with the bullet passing through the great sciatic
foramen. What structures could be injured?
Piriformis muscle, Superior and inferior gluteal n., v., and a., the sciatic n., pudendal n,
internal pudendal vessels (v. and a.), posterior femoral cutaneous nerves, obturator
internus and quadratus femoris
13. A patient is complaining about knee pain, after extensive testing and knee examinations, it is
determined that there is nothing wrong with the knee… where is the problem?
Compression/damage at greater sciatic foramen, not referred pain, from L4-S3.
14. A female patient has a blockage in her uterine artery. What vessels provide collateral
circulation?
Ovarian and vaginal arteries (some from internal pudendal artery)
15. You suspect your patient’s testicular cancer has spread. What lymph nodes need checking?
Lateral aortic/lumbar nodes and pre-aortic nodes in abdomen
16. You are reviewing MRI images from a patient who had upper abdominal surgery. The
patient is now showing signs of pelvic infection, which is confirmed in the MR images. What
are the sites in the male/female where these pelvic infections are likely to localize?
Female – recto-uterine pouch
Male – recto-vesical pouch
17. A patient complains of vaginal dryness. What structures may be at fault?
Greater vestibular glands (Bartholin’s glands)
18. A 16 year old male is kicked in the groin during a soccer match. Swelling occurs in the
scrotum. MRI reveals blood in the veins training the scrotal skin. What is the next vessel where
a thrombosis is most likely pass from this injured area?
External pudendal veins  greater saphenous