Nerves of posterior abdominal wallspinal nerves Lumbar Plexus
Nerves of posterior abdominal wall(spinal nerves): Lumbar Plexus ØRoots: It is formed from anterior (ventral) rami of upper 4 lumbar nerves. ØSite : It is formed within the substance of psoas major muscle. ØIts branches emerge from lateral & medial borders of the muscle and its anterior surface. ØIt is one of the main nervous supplying the lower limb. ØAll anterior rami receive gray rami communicantes from sympathetic trunk, and the upper 2 lumbar nerves give off white rami communicantes to symp. trunk.
Branches of Sympathetic trunk (Abdominal part) : §White rami communicantes : the upper 2 ganglia receive a white rami communicantes from 1 st & 2 nd lumbar spinal nerves, they contain preganglionic N. Fs. & sensory N. Fs. §Gray rami communicantes (postganglionic Fs. ) to all lumbar spinal nerves. A grey ramus contains postganglionic N. Fs. These Fs. are distributed through the branches ØA- N. Fs. Synapse in a symp. chain ganglion of spinal nerves to skin : at same level. 1 -blood vessels (vasomotor) ØB- N. Fs. synapse in a symp. chain 2 -sweat glands ganglion at a different level. 3 -arrector pili muscles of skin. ØC- N. Fs. Synapse in a collaterl (aortic) ganglion as sup. mesenteric ganglion.
Branches of Lumbar plexus ØIliohypogastric, ilioinguinal, lateral cutaneous N. of thigh and femoral N. emerge from lateral border of psoas muscle, in order that from above downward. ØIliohypogastric & ilioinguinal nerves (L 1) : -Iliohypogastric N. supplies skin of lower part of anterior + lateral abdominal wall, while -ilioinguinal N. passes through inguinal canal to supply skin of groin (upper medial part of thigh) + scrotum or labium majus. ØLateral cut. N. of thigh (L 2, 3) : passes in front of iliacus muscle and enter thigh behind lateral end of inguinal ligament to supply skin of lateral surface of thigh.
Branches of Lumbar plexus ØFemoral N. ( dorsal division of ventral rami of L 2, 3, 4): is the largest branch of lumbar plexus. it descends between psoas & iliacus and enters thigh behind inguinal lig. and lateral to femoral vessels & sheath. -In abdomen : It supplies iliacus +psoas major. -In lower limb : It supplies muscles of front of thigh + skin of anterior & lateral surface of thigh + skin of medial side of leg & foot through saphenous N. ØObturator N. (ventral division of ventral rami of L 2, 3, 4) : emerge from medial border of psoas muscle. it descends in front of sacroiliac joint and behind common iliac vessels in the pelvis. It enters thigh through obturator foramen.
Branches of Lumbar plexus Ø 4 th lumbar root of lumbosacral trunk : -it takes part in sacral plexus formation. -it descends anterior to ala of sacrum to join 1 st sacral nerve. ØGenitofemoral nerve (L 1, 2) : -emerges from anterior surface of psoas major. -it descends in front of psoas and above inguinal ligament it divides into genital branch, which enters spermatic cord and supplies cremaster muscle + skin of scrotum, and a femoral branch, which supplies a small area of skin in the uppermost part of front of thigh. -Genitofemoral nerve is involved in cremateric reflex, in which stimulation of skin of thigh in male results in reflex contraction of cremaster muscle and drawing upward of testis within the scrotum,
Lymph Nodes of posterior ØThey are closely related to aorta to abdominal wall: form a preaortic and a right & left lateral aortic (para-aortic or lumbar) chain. ØPreaortic L. Ns. lie around origins of celiac, superior mesenteric, and inferior mesenteric arteries. They drain lymph from G. I. T. from lower 1/3 of esophagus to halfway down anal canal, and also from spleen, pancreas, gallbladder & liver. Efferent lymph vessels form large intestinal lymph trunk. ØLateral aortic (para-aortic or lumbar) L. Ns. : drain lymph from kidneys & suprarenals, from testes or ovaries, uterine tubes & fundus of uterus, from deep lymph vessels of abdominal walls, and from common iliac Ns. Efferent lymph vessels form right & left lumbar trunks.
Lymph vessels of posterior abdominal wall: ØCisterna chyli : -it is a narrow sac , opens upwards into thoracic duct. –it collects lymph from abdomen & lower limbs. -Tributaries : it receives intestinal trunk, right & left lumbar trunks and some lymph vessels from lower thorax. ØThoracic duct : begins in the abdomen as an elongated lymph sac, cisterna chyli, which lies below diaphragm, in front of first 2 lumbar vertebrae and on right site of aorta.
Thoracic duct ØIt runs upward to enter thorax through aortic opening of diaphragm, then into root of neck to end in left brachiocephalic vein. ØIt conveys all lymph from lower limbs, pelvic cavity, abdominal cavity, left side of thorax + left side of head, neck & left upper limb to blood of left brachio-cephalic vein. Ø(A), Tributaries of thoracic duct & right lymphatic duct. Ø(B), The areas of body drained into thoracic duct (clear) and right lymphatic duct (black). ØThe right side of head , neck & right uper limb are drained by right lymph trunk into right brachio-cephalic vein.
Structures of pelvic walls ØAnterior pelvic wall : it is a shortest wall, it is formed by : -posterior surface of pubic bodies bones. -symphysis pubis. Ø posterior pelvic wall : It is formed by : –sacrum & coccyx. -Piriformis muscle. -Parietal pelvic fascia which covers bones & piriformis muscles.
Piriformis muscle ØOrigin : front of middle 3 pieces (S 2, 3, 4) of sacrum. ØInsertion : it leaves pelvis to enter gluteal region by passing through greater sciatic foramen to be inserted into top (upper border) of of greater trochanter of femur. ØN. suply : branches from sacral plexus (S 1, 2). ØAction : lateral rotator of femur at hi joint.
Structures of Pelvic walls ØLateral pelvic wall : it consists of : -Part of hip bone below pelvic inlet. -Obturator membrane. -Obturator internus & its covering fascia. -Sacrotuberous & sacrospinous ligaments. ØInferior pelvic wall (Pelvic floor ) or (pelvic diaphragm) : -it supports pelvic viscera, it divides pelvis into : -upper part : it is the main pelvic cavity. -lower part : it is the perineum (structures that fill outlet of true pelvis) -pelvic floor is formed of : 1 -levator ani muscles. 2 -coccygeus muscles. 3 -fascia covering these muscles. -the pelvic floor is incompletle anteriorly to allow passage of urethra in male + urethra & vagina in female.
Pelvic walls ØSacrotuberous ligament : is strong. –its medial upper end is attched to : 1 -posterior inferior iliac sine. 2 -lateral surface of sacrum & coccyx. -its lateral lower end : is attached to : 1 -medial margin of ischial tuberosity. Sacrospinous ligament : is a strong triangular ligament. -its apex : is attached to ischial spine. -its base : is attched to last piece of sacrum + first piece of coccyx. ØThe function of 2 ligaments : 1 -they convert greater & lesser sciatic notches into foramina, greater & lesser sciatic foramina. 2 - they prevent lower end of sacrum & coccyx from being rotated upwards at sacroiliac joint by the weight of body.
Obturator membrane, Canal Ø obturator membrane : is & muscle : completely closes the obturator foramen except at the upper part where it leaves a small gap called obturator canal. ØObturator N. & vessels leave the pelvis to enter thigh by passing through obturator canal. ØObturator internus muscle : -origin : pelvic surface of obturator membrane + adjoining part of hip bone. -insertion : its tendon leaves pelvis through lesser sciatic foramen to be inserted into upper border of greater trochanter of femur. -N. supply : N. to obturator internus (sacral plexus). -action : lateral rotation of thigh at hip joint.
Obturator Fascia ØIt is a part of parietal pelvic fascia. ØIt covers pelvic surface of obturator internus muscle. ØA tendinous arch is formed by thickening of pelvic fascia (obturator fascia) covering the obturator internus, and gives a linear origin for levator ani muscle.
Levator ani muscle ØIt is a wide thin sheet that has linear origin from : 1 -back of body of pubis. 2 -obturator fascia (tendinous arch). 3 -ischial spine. ØInsertion : by 3 fibres. 1 -anterior fibres : (levator prostatae or sphincter vaginae). : form a sling around prostate or vagina and inserted into perineal body in front of anal canal (a mass of fibrous tissue). its function is to support the prostate or to constrict the vagina + to stabilize the perineal body.
Levator ani muscle ØIntermediate fibres : 1 -(puborectalis) : it forms a sling around the junction of rectum & anal canal to meet other fibres. 2 -(Pubococcygeus) : passes posteriorly to be inserted into anococcygeal body, (a small fibrous mass) between tip of coccyx & anal canal. ØPosterior fibres : ( iliococcygeus) : passes posteriorly to be inserted into anococcygeal body & coccyx.
Pelvic Walls ØThe bony pelvis consists of 4 bones : - 2 hip bones : form lateral & anterior walls. - Sacrum & coccyx : form posterior wall. ØPelvic brim : is formed by - Sacral promontory : posteriorly. - Ilio-pectineal lines : laterally. - Symphysis pubis : anteriorly. Ø Sacral promontory : is the projecting forwards of the anterior margin of body of S 1 vertebra. ØParts of pelvis : 1 -False (greater) pelvis : above pelvic brim, it forms part of abdominal cavity, it consists mainly of right & left iliac fossae. 2 -True (lesser) pelvis : below pelvic brim, it is a curved canal which has an inlet, outlet & a cavity.
Pelvic walls ØPelvic inlet : is formed by boundaries of pelvic brim. ØPelvic outlet : -coccyx : posteriorly. -ischial tuberosities + sacrotuberous ligament : laterally. -pubic arch + symphysis ppubis : anteriorly. ØPelvic cavity : it is a curved canal, lies between inlet & outlet, and has a short anterior wall and longer posterior wall.
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