[ANATOMY #12] April 28, 2013

Transcription

1 Sympathetic chain : Sympathetic chain is each of the pair of ganglionated longitudinal cords of the sympathetic nervous system; extend from level of atlas (base of skull) till coccyx. It is paravertebral (next to the vertebral column ) in location. Situated on either side of the vertebral column or in front of the neck of the ribs.( Between the neck of the rib and lateral side of the vertebra). The sympathetic chain is divided into the following parts, depending on the region of the body where the chain is present: 1) Cervical part ( in the neck region) : Three ganglia (3) : superior / middle / inferior sympathetic ganglia. 2) Thoracic part ( in the chest) : 12 ganglia. 3) Abdominal part : 4-5 sympathetic ganglia. 4) Sacral region: 4-5 sympathetic ganglia. 5) Coccyx: 1 sympathetic ganglion ( it is called ganglion impar ). The summation: 26 sympathetic ganglia. The origin of sympathetic nerves: thoracolumber origin. ( thoraco : all the thoracic vertebrae / lumber : L1 & L2 ). The origin of parasympathetic nerves: craniosacral. ( cranio : through cranial nerves brain stem / sacral : S2,S3,S4 ). preganglionic fibers : Originated from sympathetic nucleus present in the lateral horn of gray matter of spinal cord. (Note ) -gray matter : H- shaped area of the spinal cord where many types of neurons synapse. - composed of 3 horns : anterior horn/posterior horn/lateral horn. They leave the spinal cord to go through the ventral roots >> spinal nerve >> sympathetic ganglion. white ramus : contains a preganglionic fibers through the spinal nerve. (The afferent fibers to the ganglia). How many spinal nerves that contain white rami? ( 14 on each side ) Why 14?? ( because the nuclei in the lateral horns are 14 in number. And each nucleus gives a preganglionic fiber (white ramus). From wiki : Each of the thoracic, and the first and second lumbar nerves contribute a white ramus

2 communicans to the adjoining sympathetic ganglion. 12 thoracic nerves + L1+L2=14 These preganglionic fibers may: 1- Synapse in the Corresponding ganglion. 2- Ascend upward to synapse in higher ganglion. 3- Descend downward to synapse in lower ganglion. 4- Not synapse in the sympathetic chain. *Note the ascending preganglionic fiber in this picture. These preganglionic fibers that don t synapse in the sympathetic chain go to prevertebral ganglia to synapse there. - These are called ( splanchnic nerves) - They synapse in the prevertebral ganglia : 1- Celiac ganglion. 2- Superior mesenteric ganglion.

3 Postganglionic fibers : 3- Inferior mesenteric ganglion. They arise from the sympathetic ganglia and go backwards through the spinal nerve to the spinal cord. Gray ramus : contains postganglionic fibers through the spinal nerve. ( the efferent fibers of the sympathetic ganglia). How many gray rami? 31 Why 31? ( because each spinal nerve contains postganglionic sympathetic fiber). Gray rami are present in all segments. Note : sympathetic fibers go to : 1- Bllod vessels. ( mainly ) 2- Smooth muscles. 3- erector spinae muscles in the skin. Nervs which leave the sympathetic chain : 1) Gray rami ( 31 post ganglionic fibers join spinal nerves ) **Note : the cervical part of sympathetic chain possesses 3 ganglia : superior/middle/ inferior. 1) From Superior cervical ganglion : Gray rami communicans are given to lower 4 cranial nerves and anterior rami of upper four cervical spinal nerves ( C1,C2,C3,C4) 2)From Middle cervical ganglion : Gray rami communicans are given to the anterior rami of 5th and 6th cervical spinal nerves ( C5,C6). 3)From Inferior cervical ganglion: Gray rami communicans: These are given to the anterior rami of seventh and eighth cervical spinal nerves ( C7,C8). 2) visceral nerves: 1) Internal and external carotid nerves: from superior cervical sympathetic ganglia to corresponding arteries ( external and internal arteries which supply the parotid/submandibular glands. 2) pharyngeal branch : from superior cervical sympathetic ganglia to pharyngeal plexus. 3) pulmonary nerves : from 2 nd, 3 rd & 4 th thoracic ganglia 4) cardiac nerves : from 2 nd, 3 rd & 4 th thoracic ganglia + 3 cervical ganglia. 5) splanchnic nerves : greater, lesser and lowest splanchnic nerves

4 3) Splanchnic nerves : 1) Greater splanchnic nerve. - From T5-T9 and maybe T10 thoracic ganglia. - Pierces the cruss of the diaphragm to synapse in the celiac ganglia. - Carries sympathetic fibers. - The postganglionic fibers accompany the branches of the celiac artery and follow them to their distribution. - There are 2 celiac ganglia surrounds the celiac trunk making the celiac plexus. - The parasympathetic fibers from the vagus nerve also accompany the branches of the celiac artery. 2) Lesser splanchnic nerve : - From T9,T10 thoracic ganglia. - Pierces the cruss of the diaphragm. - Synapse in the superior mesenteric ganglia. - Distributed with branches of superior mesenteric artery. - Postganglionic fibers supply the smooth muscles, glands of small intestine, ascending and transverse parts of colon. - Carries sympathetic fibers to the midgut. - The parasympathetic fibers from the vagus nerve. 3) The lowest splanchnic nerve : - From T12 or from both T11 and T12. - Pierces the diaphragm to end in the renal plexus. - poseganglionic fibers to the suprarenal glands. - It may not present - The parasympayhetic fibers from the vagus nerve. 4) Lumber splanchnic nerve : - Arise from L1& L2 ganglia. - Ends in inferior mesenteric ganglia. - Postgangilionic fibers go to sigmoid and pelvic colon. - Distributed through the branches of inferior mesenteric artery as a plexus ( hypogastric plexus) - Other postgangilionic fibers arise from the hypogastric plexus to supply bladder, rectum and genetalia. -The hypogastric plexus has both sympathetic and parasympathetic fibers. The parasympathetic fibers arise from S2,S3,S4.

5 5) sacral branch : Arises from the sacral part of sympathetic chain. Goes to pelvic viscera mainly. Distributed through the hypogastric plexus of nerves. The abdominal part of the sympathetic chain : - It possesses 4-5 ganglia. - It descends downward along the medial border of the psoas major muscle. - Enters the abdomen behind the medial arcuate ligament of the diaphragm.

6 - It continues as the pelvic part in the pelvis behind common iliac vessels. - The right sympathetic part : lies behind the right border of inferior vena cava ( can't be seen). - The left sympathetic part: lies close to the left border of the aorta ( can be seen). Nerves in the posterior abdominal wall : 1) Subcostal nerve : ( lacated below the last rib) 2) Ilioinguinal nerve + iliohypogastric nerve ( originated from L1 ) These three nerves (mentioned above) are located posterior to the kidneys. 3) Genitofemoral nerve ( from L1,L2 ) Genital branch : goes through the inguinal canal to supply the cremasteric muscle. femoral branch : supplies the skin over the upper medal side of the thigh. Cremasteric reflex : This reflex is elicited by scratching the upper medial side of the thigh sensory fibers of the femoral branch are stimulated and carry impulses to L1,L2 activation of the motor fibers of genital branch contraction of the cremasteric muscle cremasteric muscle pulls the testis upwards. 4) Lateral cautaneous nerve of the thigh : (from L2,L3) To anterior suoerior iliac spine goes below the inguinal ligament then to the lateral side of the thigh. 5) Femoral nerve : From the posterior division of anterior rami of L2,L3 amd L4. 6) obturator nerve : Supplies the anterior compartment of the thigh. It has both sensory and motor fibers. from the anterior division of the anterior rami of L2,L3 and L4. supplies the medial compartment of the thigh. it has both sensory and motor fibers. 6) lumbosacral trunk ( L4,L5 and S1 )

7 the nerves in the posterior abdominal wall are related to the psoas major muscle : 1) On the medial side : obturator nerve / lumbosacral trunk. 2) Anterior : genitofemoral nerve ( it goes throgh the fibers of psoas majo muscle ). 3) On the lateral side : femoral nerve/ iliohypogastric nerve/ ilioinguinal nerve. Note : ** the innervation of psoas major muscle : from the anterior rami of L1,L2,L3 and L4. ** the innervation of the quadratous lumborum : from the ventral rami of T12,L1,L2 and L3. The second part of lecture is about embryology. It will be included within the next sheet (#13) by our colleague اسراء أبو هنية I m sorry for being late to write this sheet :/ Sorry for any mistake