SDL - Vessels and Nerves in Pelvis Flashcards
What vertebral level is the bifurcation of the abdominal aorta?
L4
Where does the external iliac artery pass? What artery does it give off?
Passes underneath the inguinal ligament to become to femoral artery
Gives off the inferior epigastric artery before it passes under the inguinal ligament
What does the inferior epigastric artery anastomose with?
Superior epigastric artery
What arteries supply structures in the pelvis?
Internal iliac artery, gonadal artery, ureteric artery, IMA
How does the internal iliac artery commonly branch?
It divides into a small posterior trunk, which supplies the body wall and gluteal region, and a larger anterior trunk that supplies the pelvic viscera, the perineum, the gluteal region and the thigh.
What do the visceral branches of the internal iliac artery supply?
All of the pelvic organs except the gonads
What does the first visceral branch off the anterior division of the internal iliac give rise to?
Superior vesical arteries (branches of umbilical artery)
What is contained in the medial umbilical ligament?
Obliterated umbilical artery
What forms the median and lateral umbilical ligaments?
Median - urachus
Lateral - inferior epigastric artery
The inferior vesical artery of the male supplies part of the bladder. What else does it supply?
Prostate
Which branches of internal iliac artery pass out of the pelvis? Which area does each of these branches supply?
Internal pudendal –> perineum
Gluteal –> gluteal region
Which branches of the internal pudendal artery supply the erectile tissue of the penis in males and of the clitoris and vestibule in females?
Male –> dorsal arteries of penis, deep arteries of penis, arteries of the bulb of penis
Female –> dorsal arteries of the clitoris, deep arteries of clitoris
How is venous blood passed from pelvic viscera to internal iliac veins?
Most of the pelvic viscera are surrounded by networks of veins, into which they drain.
From these networks, venous blood passes via vessels which mirror the arteries to reach the internal iliac veins.
Which vessels do the gonadal veins drain into?
Left gonadal vein –> left renal vein
Right gonadal vein –> IVC
Where does lymph from most of the pelvic viscera drain to?
internal iliac lymph nodes.
Where do the internal iliac nodes then drain?
External iliac nodes..
Into which nodes do the gonads drain?
Left and right lumbar lymph nodes. This is different from the skin of the labia and scrotum.
What are the nerves present in the pelvis?
The obturator nerve, the sacral plexus and its branches and sympathetic and parasympathetic autonomic nerves.
Describe the course of the obturator nerve
The obturator nerve runs behind the ovary and leaves the pelvis (through an opening in the obturator muscle called the obturator canal) and enters the thigh
What is the sacral plexus formed by?
The ventral rami of the first four sacral nerves. It also receives a contribution from the ventral rami of the fourth and fifth lumbar nerves.
What nerves does the sacral plexus give off?
The plexus gives off a number of branches supplying the lower limb, including the very large sciatic nerve.
Where does the sciatic nerve run?
Leaves the pelvis via the greater sciatic foramen
Where does the internal pudendal nerve run?
Runs together with the internal pudendal artery to supply perineal structures. Leaves the pelvis through the greater sciatic foramen.
What is the pudendal nerve a branch of?
The sacral plexus
What is the sciatic nerve a branch of?
The sacral plexus
What parasympathetic outflow does the sacral plexus give rise to in the pelvis?
The pelvic splanchnic nerves
Which nerves are responsible for genital erection?
Pelvic splanchnic nerves
Where are the pelvic splanchnic nerves formed from?
Branches of 2nd, 3rd, 4th sacral segmental nerves
What pelvic plexus do the pelvic splanchnic nerves contribute to?
The inferior hypogastric plexus in the fascia around the rectum, as they travel to the pelvic viscera
What role do these parasympathetic pelvic splanchnic nerves play in micturition?
Urinating –> contraction of detrusor muscle
What are sympathetic fibres to the pelvic viscera supplied by?
The thoracic and lumbar splanchnic nerves
Where do the thoracic and lumbar splanchnic nerves branch off? Where do they travel?
Branch off the sympathetic chain and travel down into the pelvis via a number of midline plexuses, eventually joining the pelvic plexus
What is the pelvic outlet almost completely occluded by?
Muscles of the pelvic floor
Where does the piriformis arise from?
The anterior aspect of the sacrum and passes out of the greater sciatic foramen
Where does the obturator internus muscle originate?
From the deep surface of the obturator membrane and the bone surrounding the obturator foramen
How does the tendon of the obturator internus leave the pelvic cavity?
Via the lesser sciatic foramen
Where do the tendons of obturator internus and piriformis insert?
Greater trochanter of femur
What are the actions of these muscles (obturator internus and piriformis)?
Lateral rotation and abduction of femur at hip joint
Where is the obturator canal? What travels through it?
Passageway through obturator fascia that creates communication between pelvis and medial thigh
Obturator artery, nerve and vein (neurovascular bundle)
What is the pelvic floor formed by?
Levator ani muscles and coccygeus
The levator ani muscles and coccygeus are attached laterally to the pelvic wall; to which structures?
Pubic bone, tendinous arch, ischial spine
What is the coccygeus muscle sometimes known as?
Ischiococcygeus
Where does the iliococcygeus arise from?
Arises from the ischial spine and from the posterior part of the tendinous arch of the pelvic fascia, and is attached to the coccyx
Where does the puborectalis arise from?
From pubic bone (lateral to pubic symphysis on both sides) and encircles the rectum
Where does the pubococcygeus arise?
From the body of the pubic bone and the anterior aspect of the tendinous arch.
The fibres travel around the margin of the urogenital hiatus and run posteromedially, attaching at the coccyx
Where does the coccygeus arise?
Arises by its apex from the ischial spine and sacrospinous ligament, and inserts into the coccyx and into the side of the lowest piece of the sacrum.
How do the levator ani and coccygeus converge in the midline?
They interdigitate around the urogenital and anal hiatuses
What is the perineal body? What is its function?
Fibrous structure posterior to urogenital hiatus and in front of rectum.
Point of convergence for levator ani muscles. Helps to stabilise the pelvic floor.
What are the attachments of coccygeus muscle?
Arises from ischial spine to inferior end of sacrum and coccyx
What is the coccygeus ligament adherent to on its gluteal surface?
The sacrospinous ligament
What is effect of puborectalis muscle?
Forms a ‘sling’ around the rectum as it pierces the pelvic diaphragm, pulling the gut tube anteriorly, so that the anal canal descends at an angle of approximately 900 to the rectum
Why is this arrangement of puborectalis muscle important?
This angle is important in maintaining faecal continence
What is an episiotomy? When and why is it carried out?
A cut through the pelvic floor between the vagina and rectum (perineal body) to enlarge the vaginal.
Which bones make up the bony pelvis?
Pubis, ischium and ilium
Which bony features define the pelvic brim?
Promontory of sacral ala
Arcuate line
Pecten pubis
Pubic crest
What runs between the ASIS and pubic tubercle?
Inguinal ligament
Which ligaments contribute to the borders of the greater sciatic foramen?
Sacrospinous ligament
Which ligaments contribute to the borders of the lesser sciatic foramen?
Sacrotuberous ligament
