ANAT 316: Lecture 22 - The Neurovascular Supply to the Pelvis

Sympathetic innervation to the pelvis:

- Decrease GI tract motility - Contraction of sphincters - Detrusor relaxation - Uterine contraction - Contraction of erectile tissues (ejaculation)

Parasympathetic Innervation to the pelvis:

- Increase GI tract motility - Relaxation of sphincters - Contraction of detrusor muscle - relaxation of uterine musculature - vasodilation in erectile tissues (erection)

The Anterior Division of the Internal Iliac artery:

Branches of the anterior division: 1. The Umbilical artery: was attached to the umbilicus.. in the adult the artery becomes obliterated so that there is no longer blood coming to the artery. HOWEVER, there are arteries that branch off of the umbilical artery in the portion where it is not obliterated: - Superior vesicle arteries: come to the superior portion of the bladder 2. Obturator Artery: comes out of the pelvis through the obturator foramen to give blood supply to the medial thigh. 3. Middle Rectal Artery: going towards the rectum (nothing else is going towards the rectum from the anterior division) 4. Inferior Gluteal A: exits the greater sciatic foramen BELOW the piriformis to bring blood supply to the gluteus maximus 5. Internal Pudendal Artery: exits the greater sciatic foramen BELOW the piriformis. To differentiate this from the inferior gluteal, you know that the pudendal artery will exit closer to the later side of the pelvis because it needs to wrap around the spinous process and com back through the lesser sciatic foramina to go to the external genitalia.

The Posterior Division of the Internal Iliac artery:

Branches of the posterior division: 1. Iliolumbar A: wraps back up off the posterior division, to bring blood supply to the iliacus, psoas, quadrates lumbormum muscles. 2. Lateral Sacral :descends down the lateral side of the sacrum into sacral foramina 3. Superior Gluteal Artery: blood supply to the gluteal muscles (gluteus medium and minimum). Exits the pelvis via the greater sciatic foramen, ABOVE the piriformis

Path of the Pudendal Artery:

Exits the pelvis from the greater sciatic foramen (underneath the piriformis muscle), wraps around the spinous process (the ischial spine) of the pubic bone, enters back into the pelvis via the lesser sciatic foramen and travels deep to the levator ani muscle to give off branches to the rectum and external genitalia (perineum). When the pudendal artery comes back into the pelvis it will travel anteriorly to the ischialpupic ramus. When the internal pudendal artery enters back into the pelvis via the lesser sciatic foramen, it will be covered by a protective sheath called the pedestal canal. The pudendal canal carries the: - Pudendal nerve - Internal Pudendal Artery **The Internal pudendal artery will give off branches both before and after entering the pudendal (alcock's) canal. Before the canal: - Rectal branches After the canal: - Perineal branches (penile and scrotal branches in the male; clitoral and labial branches in the female).

Innervation to the Pelvis:

Superior hypogastric Plexus near the bifurcation of the aorta into the common iliac branches. - The superior hypogastric plexus gives off the right and left hypogastric nerves that give rise to the inferior hypogastric plexus. Lumbar and sacral sympathetic chain run along the lateral aspects of the sacrum. - From the lumbar sympathetic chain: there is the lumbar splanchnic nerves which will synapse in the inferior mesenteric ganglia and are associated with sympathetic innervation to the hind gut, as well as in the superior hypogastric plexus in order to bring SYMPATHETIC innervation to the pelvis. - From the sacral sympathetic chain: will give off sacral splanchnic nerves which will synapse in either the hypogastric nerves or the inferior hypogastric plexus carrying SYMPATHETIC innervation to the pelvis. - From the sacral spinal nerves: will give off pelvic splanchnic nerves that synapse in the inferior epigastric plexus and give rise to PARASYMPATHETIC innervation.

Course of the Pudendal Nerve (S2-S4):

The Pudendal Nerve gives SOMATIC innervation to the external genitalia. - Exits the pelvis via the greater sciatic foramen, enters beneath elevator ani via the lesser sciatic foramen. Gives rise to rectal branches then passes through pudendal canal traveling towards the external genitalia in both males and females.

The Female Pelvic Blood Supply:

Trends: - The piriformis muscle will be covered by sacral spinal nerves (L4-S2) *Typically the superior gluteal nerve will dive between the lumbosacral trunk and S1, and the inferior gluteal nerve will dive between S1 and S2 Unique to the female pelvis: 1. The uterine and vaginal arteries: the uterine artery will travel over the ureter (traveling to the bladder) to get to the uterus.

The Male Pelvic Blood Supply:

Trends: - locate the umbilical artery to orientate yourself - find the apex of coccyges to locate the greater sciatic foramen. Unique to the male pelvis: 1. Inferior Vesical Artery: comes off of the anterior division of the internal iliac targeting the inferior surface of the bladder and the prostate.

Variations in the Obturator Artery:

Typically, the obturator artery will stem off of the anterior branch of the internal iliac artery, traveling through the obturator foramen (with the nerve) to give blood supply to the medial thigh. *sometimes an accessory obturator artery will come off of the external iliac artery to meet with obturator artery (or travel separate) and go through the obturator foramen to bring accessory branches to the medial thigh. *in other cases, there can be NO obturator artery coming from the internal iliac, rather there will ONLY be an artery coming from the external iliac artery. In this situation, the obturator branch is named the Aberrant obturator artery.

Blood Supply to the Uterus:

Typically: there is one common branch off the inferior iliac artery that splits to give the uterine and vaginal branches. - the uterine branch will then split again, giving off the ascending branch of the uterine artery (blood supply up to the uterus) AND the vaginal branch of the uterine artery (down towards the cervix and vagina) *The ascending branch will come up the uterus towards the fallopian tube, splitting again to the ovarian and tubal branches going to the ovary and fallopian tube, respectively. Note that the ovary also receives blood supply from the ovarian artery (gonadal artery coming from the abdominal aorta). The ovarian artery will also give off branches that will anastomose with the ovarian and tubule arteries from the ascending uterine branch from the uterine artery coming from the inferior iliac artery. The uterine and vaginal artery can arise from one main artery, or as their own separate individual branches from the internal iliac artery. ALWAYS LOOK AT WHERE THEY ARE GOING!

The Blood Supply to the Pelvis:

Use piriformis as a landmark for the blood supply. At L4/L5, the aorta will split into the common iliac artery. After this split the common iliac arteries (left and right) will split into the internal and external iliac arteries. The external iliac will travel under the inguinal ligament, becoming the femoral artery in the thigh. After this, the internal iliac (staying within the pelvis) will spit into anterior and posterior divisions, each giving off further branches.