Sem 2 - D - Pelvic Nerves and Vessels - Sacral plexus, Autonomic nerves, Dermatomes, Branches of Internal Iliac Artery Flashcards
What are the roots of the sacral plexus?
The sacral plexus is formed by the anterior rami of S1-S4 spinal nerves with contributions from lumbar spinal nerves L4 and L5
What are the nerves of the sacral plexus and the nerve roots?
- Superior gluteal nerve - L4,5, S1
- Inferior gluteal nerve - L5, S1,2
- Sciatic nerve - L4,5, S1,2,3
- Posterior cutaneous nerve of the thigh - S1,2,3
- Pudendal nerve - S2,3,4
- Nerve to piriformis - S1,2
- Nerve to obturator internus - L5, S1
- Nerve to quaratus femoris - L5, S1
- Nerve to levator ani - S4
* Superior gluteal nerve - L4,5, S1 * Inferior gluteal nerve - L5, S1,2 * Sciatic nerve - L4,5, S1,2,3 * Posterior cutaneous nerve of the thigh - S1,2,3 * Nerve to obturator internus - L5, S1 * Nerve to quaratus femoris - L5, S1 * Nerve to piriformis - S1,2 * Pudendal nerve - S2,3,4 * Nerve to levator ani - S4
What does the superior gluteal nerves supply? Where does it lie in relation to the piriformis ? How does it leave the pelvis?
The superior gluteal nerve (L4,5, S1) leaves the pelvis via the greater sciatic foramen entering the gluteal region superiorly to the piriformis to supply the gluteus medius, gluteus minimus and the tensor fascia lata
It is accompanied by the superior gluteal artery and vein for much of its course.
* Inferior gluteal nerve - L5, S1,2 * Sciatic nerve - L4,5, S1,2,3 * Posterior cutaneous nerve of the thigh - S1,2,3 * Nerve to obturator internus - L5, S1 * Nerve to quaratus femoris - L5, S1 * Nerve to piriformis - S1,2 * Pudendal nerve - S2,3,4 * Nerve to levator ani - S4
What does the inferior gluteal nerves supply? Where does it lie in relation to the piriformis ? How does it leave the pelvis?
The inferior gluteal nerve (L5, S1,2) leaves the pelvis via the greater sciatic foramen entering the gluteal region inferiorly to the piriformis to supply the gluteus maximus
It is accompanied by the inferior gluteal artery and vein for much of its course.
* Sciatic nerve - L4,5, S1,2,3 * Posterior cutaneous nerve of the thigh - S1,2,3 * Nerve to obturator internus - L5, S1 * Nerve to quaratus femoris - L5, S1 * Nerve to piriformis - S1,2 * Pudendal nerve - S2,3,4 * Nerve to levator ani - S4
How is the sciatic nerve formed?
The sciatic nerve is the largest nerve in the body
It is formed by the lumbosacral trunk (the distal roots of the lumbar plexus which also contribute to the sacral plexus) crossing the pelvic brim to join with S1,2,3 to form the sciatic nerve
* Sciatic nerve - L4,5, S1,2,3 * Posterior cutaneous nerve of the thigh - S1,2,3 * Nerve to obturator internus - L5, S1 * Nerve to quaratus femoris - L5, S1 * Nerve to piriformis - S1,2 * Pudendal nerve - S2,3,4 * Nerve to levator ani - S4
How does the sciatic nerve get from the pelvis to gluteal region? What does the sciatic nerve supply?
The sciatic nerve passes through the greater sciatic foramen and arises inferior to the piriformis where it descends down posterior thigh deep to long head of biceps femoris
Motor innervation to the posterior thigh and all muscles leg/foot, sensory to everything below knee except saphenous nerve distribution
* Sciatic nerve - L4,5, S1,2,3 * Posterior cutaneous nerve of the thigh - S1,2,3 * Nerve to obturator internus - L5, S1 * Nerve to quaratus femoris - L5, S1 * Nerve to piriformis - S1,2 * Pudendal nerve - S2,3,4 * Nerve to levator ani - S4
What are the terminal branches of the sciatic nerve and what are there nerve roots?
Sciatic nerve two terminal branches - Common fibular nerve, Tibial nerve Common fibular nerve - L4-S2 Tibial nerve - L4-S3
* Posterior cutaneous nerve of the thigh - S1,2,3 * Nerve to obturator internus - L5, S1 * Nerve to quaratus femoris - L5, S1 * Nerve to piriformis - S1,2 * Pudendal nerve - S2,3,4 * Nerve to levator ani - S4
What does the posterior cutaneous nerve of the thigh supply?
Posterior cutaneous nerve of the thigh leaves the pelvis via the greater sciatic foramen and enters the gluteal region inferior to the piriformis It has no motor functions and provides sensory innervation to the skin on the posterior surface of the thigh and upper leg
* Nerve to obturator internus - L5, S1 * Nerve to quaratus femoris - L5, S1 * Nerve to piriformis - S1,2 * Pudendal nerve - S2,3,4 * Nerve to levator ani - S4
What are the attachments of the obturator internus muscle?
The obturator internus muscles attaches to the pelvic surface of the obturator membrane and the surrounding bones and passes through the lesser sciatic foramen to insert at the medial side of the greater trochanter
* Nerve to obturator internus - L5, S1 * Nerve to quaratus femoris - L5, S1 * Nerve to piriformis - S1,2 * Pudendal nerve - S2,3,4 * Nerve to levator ani - S4
What are the attachments of the gemelli muscles and what do they sandwich?
Superior gemelli muscle- arises at ischial spine Inferior gemelii muscles - arises at ischial tuberosity
They sandwich the obturtor internus muscle belly and blend with the tendon of the obturator internus to insert at the medial side of the greater trochanter
* Nerve to obturator internus - L5, S1 * Nerve to quaratus femoris - L5, S1 * Nerve to piriformis - S1,2 * Pudendal nerve - S2,3,4 * Nerve to levator ani - S4
What are the attachments of the quadratus femoris muscle?
The quadratus femoris attaches from the ischial tuberosity to the quadrate tubercle on the intertrochanteric crest of the femur
* Nerve to obturator internus - L5, S1 * Nerve to quaratus femoris - L5, S1 * Nerve to piriformis - S1,2 * Pudendal nerve - S2,3,4 * Nerve to levator ani - S4
What does the nerve to obturator internus supply?
What does the nerve to quadratus femoris supply?
Nerve to obturator internus supplies the obturator internus and superior gemellus muscle
Nerve to quadratus femoris supplies the quadratus femoris and inferior gemellus muscle
* Nerve to obturator internus - L5, S1 * Nerve to quaratus femoris - L5, S1 * Nerve to piriformis - S1,2 * Pudendal nerve - S2,3,4 * Nerve to levator ani - S4
Describe the course of the nerve to obturator internus?
Nerve to obturator internus arises direct from L5 , S1 and leaves the pelvis via the greater sciatic foramen inferior to the piriformis giving branches to the superior gemellus before re-entering the pelvis via the lesser sciatic foramen after crossing over the ischial spine to pierce the pelvic aspect of the obturator internus
* Nerve to obturator internus - L5, S1 * Nerve to quaratus femoris - L5, S1 * Nerve to piriformis - S1,2 * Pudendal nerve - S2,3,4 * Nerve to levator ani - S4
Describe the course of the nerve to quadratus femoris?
The nerve to quadratus femoris arises from L5,S1 and leaves the pelvis via the greater sciatic foramen inferior to the pififormis
It runs anterior to the sciatic nerve before giving branches to the quadratus femoris and inferior gemellus muscle
* Nerve to piriformis - S1,2 * Pudendal nerve - S2,3,4 * Nerve to levator ani - S4
What is the course of the nerve to prifiromis?
Nerve to pirfiromis arises from sacral nerves S1 and S2 and travels directly backwards to pierce the anterior surface of the piriformis
Couldnt find a pic showing nerve to piriformis
* Pudendal nerve - S2,3,4 * Nerve to levator ani - S4
What is the muscular part of the pelvic floor also known as?
What muscles make it up and what is there nerve supply?
Muscular part of the pelvic floor is the pelvic diaphragm
Pelvic diaphragm = levator ani + coccygeus
- Levator ani nerve supply - pudendal nerve (S2,3,4) + nerve to levator ani (s4)
- Coccygeus - direct S4,5 spinal nerves
Pudendal nerve - S2,3,4 What is the course of the pudendal nerve?
The pudendal nerve arises at S2,3,4 spinal level and exits the pelvis via the greater sciatic foramen inferior to the piriformis before curving around the ischial spine to pass through the lesser sicatic foramen back into the pelvis . It passes through the pudendal canal - canal in the fascia of the obturator internus to reach the perineum
What nerves arise from the pudendal nerve?
The inferior rectal nerve is given off in the pudendal canal which heads towards the levator ani & external anal sphincter
Pudendal nerve gives off superficial and deep perineal branches
- Deep - dorsal nerve of penis and clitoris
- Superficial - posterior scrotal or labial nerves
What does the pudendal nerve supply via its branches? Split into motor and sensory supply
Pudendal nerve motor innervation:
- * Perineal neve - levator ani, external urethral sphincter, bulbospongiosus and ischiocavernosus, superficial and deep transverse perineal muscles
- * Inferior rectal nerve - external anal sphincter
Pudendal nerve sensory innervation:
- * Perineal nerve - skin of perineum , skin of labia majora and minora (posterior labial nerves), posterior scrotum (posterior scotal nerves)
- * Inferior rectal - perianal skin, lower 1/3rd anal canal * Dorsal nerve of penis/clitoris - skin of penis/clitoris
Where are the superior and inferior hypogastric plexuses situated in males and females?
The superior hypogastric plexus is located anterior to the bifurcation of the aorta at L4
From the plexus, sympathetic fibres descend as right & left hypogastric trunks which then travels to the inferior hypogastric plexus which is located either side of the rectum in males, and either side of the rectum/vagina in females
What sympathetic nerves will contribute towards the superior and inferior hypogastric plexus?
What plexus do the pelvic splanchnic nerves contribute to?
Lumbar splanchnic nerves give sympathetics to superior hypogastrc plexus
Pelvic splanchnic nerves (S2-S4) contribute parasympathetics towards the inferior/superior hypogastric plexus and inferior mesenteric plexus
Sacral splanchnic nerves give sympathetics to the inferior hypogastric plexus, as well as right/left hypogastric trunks
What function does the sympathetics have on the rectum? What do sympathetic cause to the internal anal/urethral sphincters? Do sympathetics cause ejaculation or erection? What effects do sympathetics have on the bladder, uterus and arteries?
Sympathetics are important in fight and flight and therefore decrease non essential bodily functions * Sympathetics decreases rectal movement * They cause contraction of the internal urethral (sphincter vesciae) and anal sphincters * Sympathetics cause ejaculation - contraction of vas deferens and seminal vesicles * Sympathetics relax the bladder and both relax/contract the uterus * Sympathetics cause vasoconstriction of the arteries
What function does the parasympathetics have on the rectum? What do parasympathetic cause to the internal sphincters? Do parasympathetics cause ejaculation or erection? What effects do parasympathetics have on the bladder, uterus and arteries?
* Parasympathetics in the pelvis are from S2-S4 pelvic splanchnic nerves * They increase motility in the rectum and anal canal * Parasympathetics relax the internal anal sphincter, cause contraction of the detursor whilst inhibiting contraction of the internal urethral sphincter * Parasympathetics have no effect on seminal vesicles, ductus deferens and uterus) * Parasympathetics cause vasodilaton of arteries - erection
State the origin of each of the nerves for male innervation of the perineum
- Dorsal nerve of penis origin - deep perineal branch of pudendal nerve
- Perineal branch supplying the perineal muscles - pudendal nerve
- Anterior scrotal nerves - ilioinguinal and genitofemoral nerve
- Posterior scrotal nerves - perineal branch of pudendal nerve
