Pelvic Neurovasculature week 4 Flashcards
What are the branches of the posterior division of the internal iliac aa? If applicable, state the proximity of these aa’s to other anatomical structures in the pelvis.
- Iliolumbar artery - runs superolaterally
- Lateral sacral arteries - gives rise to spinal branches, which enter the anterior sacral foramina.
- Superior gluteal artery - usually runs between lumbosacral trunk (L4-L5) and S1. This vessel leaves the pelvis through greater sciatic foramen above the piriformis mm
What are the anterior divisions of the internal iliac artery in males? What structures do these aa’s supply? If applicable, state their proximity to other anatomical strucutres and/or the pathways they take in the pelvis.
Internal Iliac Artery- anterior division (MALES)
- Umbilical: Obliterated in the adult. Goes into the median umbilical fold.
- Obturator: (supplies the medial thigh); It leaves the pelvis through the obturator canal. Always travels with the obturator nerve.
- Vesicular: (supplies the bladder and prostate); superior, middle and inferior. Superior vesicular is a branch of the obliterated umbilical aa.
- Middle rectal: (supplies the rectum); anastomoses with the superior and inferior rectal arteries.
- Inferior gluteal: (supplies the gluteal region); between S2 and S3 and leaves the pelvis through the greater sciatic foramen inferior to the piriformis mm.
- Internal pudendal: (supplies structures in the perineum); leaves the pelvis through the greater sciatic foramen; passes lesser sciatic foramen to enter the ischioanal fossa.
What are the 2 branches of the anterior division of the internal iliac that are only present in females?
What aa’s do they anastomose with? If applicable, state their proximity to other anatomical structures.
Vaginal: only present in females and anastomoses with uterine artery.
Uterine: homologous to artery to vas deferens and anastomoses with vaginal artery and ovarian artery. Travels superior to the ureters. (Water travels under the bloody bridge.)
Name the 4 branches of the internal pudendal artery and what they supply.
Internal pudendal – exits greater sciatic foramen and enters the ischiorectal fossa via the lesser sciatic foramen.
Branches of the internal pudendal artery include:
- inferior rectal artery
- perineal artery→posterior scrotal/labial artery
- artery of bulb of penis/vestibular bulb
- terminal branches → deep & dorsal arteries of penis/clitoris
The vessels (and nerves) to perineal structures travel in the _____ canal and under the protection of the _____ _____.
The vessels (and nerves) to perineal structures travel in the pudendal canal and under the protection of the ischiopubic ramus.
see reverse
What vein drains most of the pelvic structures? What forms the pelvic venous plexuses?
The pelvis drained mainly by the internal iliac veins and their tributaries. Pelvic venous plexuses are formed by the interjoining of veins in the pelvis (rectal, vesical, prostatic, uterine, and vaginal).
What is the lumbosacral trunk formed by?
What is the sacral plexus formed by? Where is it located within the pelvis?
What is the sciatic nerve formed by? Where does the sciatic nerve exit the pelvis?
What are the superior and inferior gluteal nerves formed by?
- Lumbosacral trunk is formed by L4 and L5.
- . Key concept: The sacral plexus is formed by the ventral rami of L4, L5, S1, S2, S3 and S4. It lies roughly on the internal surface of the piriformis mm.
- The sciatic nerve (L4-S3) is the major nerve arising from these levels. It leaves the pelvis through the greater sciatic foramen, just below the piriformis muscle.
The following nerves are also derived from L4-S3:
- Superior Gluteal* (dissect and identify)
Inferior Gluteal* (dissect and identify)
Also present will be Posterior Femoral Cutaneous - nerve to Obturator Internus - Nerve to Quadratus Femoris - Nerve to piriformis - nerves to levator ani and coccygeus - nerve to external anal sphincter (Do not dissect)
Identify the labeled structures.
Fibers from what spinal levels form the pudendal nerve?
What are the 3 main branches of the pudendal nerve? What do they innervate?
What travels with the pudendal nerve?
The pudendal nerve (S2-S4) is the main nerve of the perineum and chief sensory nerve of the external genitalia. It is accompanied by the internal pudendal artery and vein.
There are 3 main branches of the pudendal nerve:
- inferior rectal nerve
- perineal nerve (which gives rise to the posterior scrotal/labial nerve) (do not dissect)
- dorsal nerve of penis/clitoris
***perineal nn innervates bulbospongiosus, ischiocavernosus, superficial and deep transverse perineal, sphincter urethrae muscles.
see reverse
What spinal cord levels do pelvic splanchnic nerves originate from?
What intestinal structures are innervated by pelvic splanchnic nerves? How do these fibers ascend?
Are pelvic splanchnic nerves sympathetic or parasympathetic? Are these fibers pre or postganglionic?
PP: pelvic splanchnics are parasympathetic.
- Vagus Nerve (CN X): there is no vagus nerve stimulation of structures in the pelvis.
- Pelvic Splanchnic Nerves:
- arise from neuron cell bodies found in the 2nd, 3rd, and 4th sacral spinal cord segments.
- convey preganglionic parasympathetic fibers which synapse on postganglionic neurons in terminal ganglia in the descending colon, sigmoid colon, and rectum.
- these fibers ascend in the hypogastric nerves and the superior hypogastric plexus to reach the parts of the colon they will innervate.
What nerves provide sympathetic innervation to pelvic viscera?
Are they pre or postganglionic?
Lumbar and Sacral Splanchnic nerves
Preganglionic
Where do Lumbar and Sacral splanchnics synapse?
Once synapsing, how do postganglionic nerves reach their target organs?
- Preganglionic sympathetic innervation for abdominal viscera is conveyed via splanchnic nerves which synapse on postganglionic sympathetic neurons in prevertebral ganglia.
- Lumbar and Sacral Splanchnic Nerves carry sympathetic preganglionic innervation to the pelvic viscera via synapses in prevertebral ganglia (e.g. inferior mesenteric ganglia).
- Fibers from these postganglionic neurons will travel to reach these target organs via autonomic plexuses which follow branches of blood vessels. (These autonomic plexuses are mixed meaning they contain both sympathetic and parasympathetic fibers as well as afferent fibers from the organs, a.k.a. GVA fibers.)
- Fibers from these postganglionic neurons will travel via the superior hypogastric plexus and branches of blood vessels to reach these target organs.
State wheter the following are sympathetic, parasympathetic, or mixed autonomic:
Sacral splanchnic nerves
hypogstric nerves
superior hypogastric plexus
pelvic splanchnic nerves
inferior hypogastric plexus
- Superior Hypogastric Plexus (mixed autonomic) – right and left hypogastric nerves
- Inferior Hypogastric Plexus (mixed autonomic)
- Hypogastric nerves (mixed autonomic)
- Sacral Splanchnic nerves (sympathetic)
- Pelvic Splanchnic nerves (parasympathetic)
What nerves are responsible for producing an erection? How are they distributed to the penis?
What nerves are responsible for producing an ejaculation? What structures contract during ejaculation? Is their innervation sympathetic or parasympathetic?
Parasympathetic nerve fibers are responsible for the vasodilation of arteries supplying the erectile tissue of the penis. As a result, the erectile tissue becomes engorged resulting in an erect penis. The parasympathetic fibers originate from the S2-S4 spinal cord segments, extend into the inferior hypogastric plexuses, and then to the prostatic plexus. The parasympathetic fibers continue their journey from the prostatic plexus as greater and lesser cavernous nerves. The cavernous nerves pass under the pubic arch and pierce the deep perineal pouch and perineal membrane to reach the corpora cavernosa and spongiosum of the penis.
Sympathetic stimulation through the prostatic plexus reaches the ductus deferens and seminal glands for a peristaltic contraction which delivers semen via the ejaculatory ducts into the prostatic urethrae. Ejaculation results from closure of the internal urethral sphincter at the neck of the urinary bladder (mediated via sympathetics), contractions of the urethral smooth muscle (mediated via parasympathetics) and contraction of the bulbospongiosus muscle (via pudendal nerves-somatic)
