Spinal nerve - wikipedia Spinal nerve Spinal nerve The formation of the spinal nerve from the posterior and anterior roots Details Identifiers Latin nervus spinalis MeSH D013127 TA A14. 2.00. 027 A14. 2.02. 001 FMA 5858 Anatomical terms of neuroanatomy ( edit on Wikidata ) A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into the corresponding cervical, thoracic, lumbar, sacral and coccygeal regions of the spine. There are eight pairs of cervical nerves, twelve pairs of thoracic nerves, five pairs of lumbar nerves, five pairs of sacral nerves, and one pair of coccygeal nerves. The spinal nerves are part of the peripheral nervous system. Contents 1 Structure 2 Regional nerves 2.1 Cervical nerves 2.2 Thoracic nerves 2.3 Lumbar nerves 2.4 Sacral nerves 2.5 Coccygeal nerve 3 Function 4 Clinical significance 5 Additional Images 6 References Structure Spinal nerve Typical spinal nerve location Each spinal nerve is formed from the combination of nerve fibers from its dorsal and ventral roots. The dorsal root is the afferent sensory root and carries sensory information to the brain. The ventral root is the efferent motor root and carries motor information from the brain. The spinal nerve emerges from the spinal column through an opening ( intervertebral foramen ) between adjacent vertebrae. This is true for all spinal nerves except for the first spinal nerve pair ( C1 ), which emerges between the occipital bone and the atlas ( the first vertebra ). Thus the cervical nerves are numbered by the vertebra below, except spinal nerve C8, which exists below vertebra C7 and above vertebra T1. The thoracic, lumbar, and sacral nerves are then numbered by the vertebra above. In the case of a lumbarized S1 vertebra ( aka L6 ) or a sacralized L5 vertebra, the nerves are typically still counted to L5 and the next nerve is S1. Scheme showing structure of a typical spinal nerve 1. Somatic efferent. 2. Somatic afferent. 3, 4, 5. Sympathetic efferent. 6, 7. Sympathetic afferent Outside the vertebral column, the nerve divides into branches. The dorsal ramus contains nerves that serve the posterior portions of the trunk carrying visceral motor, somatic motor, and somatic sensory information to and from the skin and muscles of the back ( epaxial muscles ). The ventral ramus contains nerves that serve the remaining anterior parts of the trunk and the upper and lower limbs ( hypaxial muscles ) carrying visceral motor, somatic motor, and sensory information to and from the ventrolateral body surface, structures in the body wall, and the limbs. The meningeal branches ( recurrent meningeal or sinuvertebral nerves ) branch from the spinal nerve and re-enter the intervertebral foramen to serve the ligaments, dura, blood vessels, intervertebral discs, facet joints, and periosteum of the vertebrae. The rami communicantes contain autonomic nerves that serve visceral functions carrying visceral motor and sensory information to and from the visceral organs. Some anterior rami merge with adjacent anterior rami to form a nerve plexus, a network of interconnecting nerves. Nerves emerging from a plexus contain fibers from various spinal nerves, which are now carried together to some target location. Major plexuses include the cervical, brachial, lumbar, and sacral plexuses. Regional nerves Further information : Spinal cord § Spinal cord segments Cervical nerves Cervical nerves The cervical nerves are the spinal nerves from the cervical vertebrae in the cervical segment of the spinal cord. Although there are seven cervical vertebrae ( C1 - C7 ), there are eight cervical nerves C1 -- C8. All cervical nerves except C8 emerge above their corresponding vertebrae, while the C8 nerve emerges below the C7 vertebra. Elsewhere in the spine, the nerve emerges below the vertebra with the same name. The posterior distribution includes the suboccipital nerve ( C1 ), the greater occipital nerve ( C2 ) and the third occipital nerve ( C3 ). The anterior distribution includes the cervical plexus ( C1 - C4 ) and brachial plexus ( C5 - T1 ). The cervical nerves innervate the sternohyoid, sternothyroid and omohyoid muscles. A loop of nerves called ansa cervicalis is part of the cervical plexus. Thoracic nerves The thoracic nerves are the twelve spinal nerves emerging from the thoracic vertebrae. Each thoracic nerve T1 - T12 originates from below each corresponding thoracic vertebra. Branches also exit the spine and go directly to the paravertebral ganglia of the autonomic nervous system where they are involved in the functions of organs and glands in the head, neck, thorax and abdomen. Anterior divisions : The intercostal nerves come from thoracic nerves T1 - T11, and run between the ribs. At T2 and T3, further branches form the intercostobrachial nerve. The subcostal nerve comes from nerve T12, and runs below the twelfth rib. Posterior divisions : The medial branches ( ramus medialis ) of the posterior branches of the upper six thoracic nerves run between the semispinalis dorsi and multifidus, which they supply ; they then pierce the rhomboid and trapezius muscles, and reach the skin by the sides of the spinous processes. This sensitive branch is called the medial cutaneous ramus. The medial branches of the lower six are distributed chiefly to the multifidus and longissimus dorsi, occasionally they give off filaments to the skin near the middle line. This sensitive branch is called the posterior cutaneous ramus. Lumbar nerves Further information : List of lumbar nerves Lumbar plexus and branches The lumbar nerves are the five spinal nerves emerging from the lumbar vertebrae. They are divided into posterior and anterior divisions. Posterior divisions : The medial branches of the posterior divisions of the lumbar nerves run close to the articular processes of the vertebrae and end in the multifidus muscle. The laterals supply the erector spinae muscles. The upper three give off cutaneous nerves which pierce the aponeurosis of the latissimus dorsi at the lateral border of the erector spinae muscles, and descend across the posterior part of the iliac crest to the skin of the buttock, some of their twigs running as far as the level of the greater trochanter. Anterior divisions : The anterior divisions of the lumbar nerves ( rami anteriores ) increase in size from above downward. They are joined, near their origins, by gray rami communicantes from the lumbar ganglia of the sympathetic trunk. These rami consist of long, slender branches which accompany the lumbar arteries around the sides of the vertebral bodies, beneath the psoas major. Their arrangement is somewhat irregular : one ganglion may give rami to two lumbar nerves, or one lumbar nerve may receive rami from two ganglia. The first and second, and sometimes the third and fourth lumbar nerves are each connected with the lumbar part of the sympathetic trunk by a white ramus communicans. The nerves pass obliquely outward behind the psoas major, or between its fasciculi, distributing filaments to it and the quadratus lumborum. The first three and the greater part of the fourth are connected together in this situation by anastomotic loops, and form the lumbar plexus. The smaller part of the fourth joins with the fifth to form the lumbosacral trunk, which assists in the formation of the sacral plexus. The fourth nerve is named the furcal nerve, from the fact that it is subdivided between the two plexuses. Sacral nerves Plan of sacral and pudendal plexuses The sacral nerves are the five pairs of spinal nerves which exit the sacrum at the lower end of the vertebral column. The roots of these nerves begin inside the vertebral column at the level of the L1 vertebra, where the cauda equina begins, and then descend into the sacrum. There are five paired sacral nerves, half of them arising through the sacrum on the left side and the other half on the right side. Each nerve emerges in two divisions : one division through the anterior sacral foramina and the other division through the posterior sacral foramina. The nerves divide into branches and the branches from different nerves join with one another, some of them also joining with lumbar or coccygeal nerve branches. These anastomoses of nerves form the sacral plexus and the lumbosacral plexus. The branches of these plexus give rise to nerves that supply much of the hip, thigh, leg and foot. The sacral nerves have both afferent and efferent fibers, thus they are responsible for part of the sensory perception and the movements of the lower extremities of the human body. From the S2, S3 and S4 arise the pudendal nerve and parasympathetic fibers whose electrical potential supply the descending colon and rectum, urinary bladder and genital organs. These pathways have both afferent and efferent fibers and, this way, they are responsible for conduction of sensory information from these pelvic organs to the central nervous system ( CNS ) and motor impulses from the CNS to the pelvis that control the movements of these pelvic organs. Coccygeal nerve The coccygeal nerve is the 31st pair of spinal nerves. It arises from the conus medullaris, and its anterior root helps form the coccygeal plexus. It does not divide into a medial and lateral branch. It is distributed to the skin over the back of the coccyx. Function Areas of distribution of the cutaneous branches of the posterior divisions of the spinal nerves. The areas of the medial branches are in black, those of the lateral in red Actions of the spinal nerves edit Level Motor function C1 -- C6 Neck flexors C1 -- T1 Neck extensors C3, C4, C5 Supply diaphragm ( mostly C4 ) C5, C6 Move shoulder, raise arm ( deltoid ) ; flex elbow ( biceps ) C6 externally rotate ( supinate ) the arm C6, C7 Extend elbow and wrist ( triceps and wrist extensors ) ; pronate wrist C7, C8 Flex wrist ; supply small muscles of the hand T1 -- T6 Intercostals and trunk above the waist T7 -- L1 Abdominal muscles L1 -- L4 Flex thigh L2, L3, L4 Adduct thigh ; Extend leg at the knee ( quadriceps femoris ) L4, L5, S1 abduct thigh ; Flex leg at the knee ( hamstrings ) ; Dorsiflex foot ( tibialis anterior ) ; Extend toes L5, S1, S2 Extend leg at the hip ( gluteus maximus ) ; flex foot and flex toes Clinical significance The muscles that one particular spinal root supplies are that nerve 's myotome, and the dermatomes are the areas of sensory innervation on the skin for each spinal nerve. Lesions of one or more nerve roots result in typical patterns of neurologic defects ( muscle weakness, abnormal sensation, changes in reflexes ) that allow localization of the responsible lesion. There are several procedures used in sacral nerve stimulation for the treatment of various related disorders. Sciatica is generally caused by the compression of lumbar nerves L4, or L5 or sacral nerves S1, S2, or S3, or by compression of the sciatic nerve itself. Additional images A portion of the spinal cord, showing its right lateral surface. The dura is opened and arranged to show the nerve roots. Distribution of the cutaneous nerves. Ventral aspect. Distribution of the cutaneous nerves. Dorsal aspect. The spinal cord with dura cut open, showing the exits of the spinal nerves. The spinal cord showing how the anterior and posterior roots join in the spinal nerves. A longer view of the spinal cord. Projections of the spinal cord into the nerves ( red motor, blue sensory ). Projections of the spinal cord into the nerves ( red motor, blue sensory ). Schematic diagram of cervical plexus. Dissection images Cerebrum. Inferior view. Deep dissection. Cerebrum. Inferior view. Deep dissection. Spinal nerves. Spinal cord and vertebral canal. Deep dissection. References Jump up ^ `` Spinal Nerves ''. National Library of Medicine. Retrieved 12 April 2014. Jump up ^ 1. Anatomy, descriptive and surgical : Gray 's anatomy. Gray, Henry. Philadelphia : Courage Books / Running Press, 1974 Jump up ^ 2. Clinically Oriented Anatomy. Moore, Keith L. Philadelphia : Wolters Kluwer Health / Lippincott Williams & Wilkins, 2010 ( 6th ed ) Jump up ^ 1. Anatomy, descriptive and surgical : Gray 's anatomy. Gray, Henry. Philadelphia : Courage Books / Running Press, 1974 Jump up ^ 1. Anatomy, descriptive and surgical : Gray 's anatomy. Gray, Henry. Philadelphia : Courage Books / Running Press, 1974 Jump up ^ 3. Human Neuroanatomy. Carpenter, Malcolm B. Baltimore : Williams & Wilkins Co., 1976 ( 7th ed ) Jump up ^ 3. Human Neuroanatomy. Carpenter, Malcolm B. Baltimore : Williams & Wilkins Co., 1976 ( 7th ed ) Blumenfeld H. ' Neuroanatomy Through Clinical Cases '. Sunderland, Mass : Sinauer Associates ; 2002. Drake RL, Vogl W, Mitchell AWM. ' Gray 's Anatomy for Students '. New York : Elsevier ; 2005 : 69 - 70. Ropper AH, Samuels MA. ' Adams and Victor 's Principles of Neurology '. Ninth Edition. New York : McGraw Hill ; 2009. Nervous system Central nervous system Meninges Spinal cord Brain Rhombencephalon Medulla Pons Cerebellum Midbrain Forebrain Diencephalon Retina Optic nerve Cerebrum Limbic system Peripheral nervous system Somatic Sensory nerve Motor nerve Cranial nerve Spinal nerve Autonomic Sympathetic Parasympathetic Enteric Spinal nerves Cervical C1 C2 C3 C4 C5 C6 C7 C8 anterior Cervical plexus Brachial plexus posterior Posterior branches of cervical nerves Suboccipital -- C1 Greater occipital -- C2 Third occipital -- C3 Thoracic T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 anterior Intercostal Intercostobrachial -- T2 Thoraco - abdominal nerves -- T7 -- T11 Subcostal -- T12 posterior Posterior branches of thoracic nerves Lumbar L1 L2 L3 L4 L5 anterior Lumbar plexus Lumbosacral trunk posterior Posterior branches of the lumbar nerves Superior cluneal L1 -- L3 Sacral S1 S2 S3 S4 S5 anterior Sacral plexus posterior Posterior branches of sacral nerves Medial cluneal nerves Coccygeal anterior Coccygeal plexus posterior Posterior branch of coccygeal nerve GND : 4256684 - 8 Retrieved from `` https://en.wikipedia.org/w/index.php?title=Spinal_nerve&oldid=825336513 '' Categories : Peripheral nervous system Spinal nerves Hidden categories : Pages with unresolved properties Wikipedia articles with GND identifiers Talk Contents About Wikipedia Bosanski Català Čeština Dansk Deutsch Eesti Español Esperanto فارسی Français Հայերեն Hrvatski Italiano עברית Latina Magyar Nederlands 日本 語 Norsk Polski Português Română Slovenčina Српски / srpski Suomi Svenska తెలుగు Українська 20 more Edit links This page was last edited on 12 February 2018, at 20 : 42. 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Question: what are the nerves called that emerge from the thoracic region of the spinal cord
Answer: T1 -T12