Spinal nerves how many

There are five sacral nerve pairs. The first nerve root exits between S1 and S2. One pair of coccygeal Co1 nerves meets in the area of the tailbone. By way of the peripheral nervous system PNS , nerve impulses travel to and from the brain through the spinal cord to a specific location in the body. The PNS is a complex system of nerves that branch off from the spinal nerve roots. These nerves travel outside of the spinal canal to the upper extremities arms, hands and fingers , to the muscles of the trunk, to the upper and lower extremities arms, hands, fingers, legs, feet and toes and to the organs of the body.

Any interruption of spinal cord function by disease or injury at a particular level may result in a loss of sensation and motor function below that level. Depending on the severity of the disease or injury, the loss of function may be permanent. Did you know you can support education and research for neurosurgical conditions while you shop, at no extra cost to you? Register with AmazonSmile to designate the NREF as your charity, and a percentage of your purchase is donated automatically.

Annulus fibrosus — The fibrous, ring-like outer portion of an intervertebral disc. Arachnoiditis — Inflammation of the arachnoid membrane the middle of the three protective layers called the meninges ; most commonly seen around the spinal cord and cauda equina. Arthritis — Inflammation of a joint, usually accompanied by swelling, pain and restriction of motion.

Bone spur — Bony growth or rough edge of bone. Cauda equina — The collection of nerves at the end of the spinal cord that resembles a horse's tail. Cervical spine — The neck region of the spine consisting of the first seven vertebrae.

Coccyx — More commonly known as the tailbone, this is a bony structure in the region of the spine below the sacrum. Conus medullaris — The cone-shaped bottom of the spinal cord, usually at the level of L1. Disc Intervertebral — A tough, elastic cushion located between the vertebrae in the spinal column; acts as a shock absorber for the vertebrae. Disc degeneration — The deterioration of a disc. A disc in the spine may wear out over time.

A deteriorated disc may or may not cause pain. Facet — A joint formed when a posterior structure of a vertebra that joins with a facet of an adjacent vertebra; this joint allows for motion in the spinal column.

Each vertebra has a right and left superior upper facet and a right and left inferior lower facet. Foramen — An opening in the vertebrae of the spine through which the spinal nerve roots travel. Joint — The junction of two or more bones that permits varying degrees of motion between the bones. Lamina — The flattened or arched part of the vertebral arch that forms the roof or back part of the spinal canal.

The vagus nerve is responsible for contributing to homeostatic control of the organs of the thoracic and upper abdominal cavities. The spinal accessory nerve is responsible for controlling the muscles of the neck, along with cervical spinal nerves. The hypoglossal nerve is responsible for controlling the muscles of the lower throat and tongue.

Three of the cranial nerves also contain autonomic fibers, and a fourth is almost purely a component of the autonomic system. The oculomotor, facial, and glossopharyngeal nerves contain fibers that contact autonomic ganglia. The oculomotor fibers initiate pupillary constriction, whereas the facial and glossopharyngeal fibers both initiate salivation. The vagus nerve primarily targets autonomic ganglia in the thoracic and upper abdominal cavities. Visit this site to read about a man who wakes with a headache and a loss of vision.

His regular doctor sent him to an ophthalmologist to address the vision loss. The ophthalmologist recognizes a greater problem and immediately sends him to the emergency room.

Once there, the patient undergoes a large battery of tests, but a definite cause cannot be found. A specialist recognizes the problem as meningitis, but the question is what caused it originally. How can that be cured?

The loss of vision comes from swelling around the optic nerve, which probably presented as a bulge on the inside of the eye. Why is swelling related to meningitis going to push on the optic nerve?

Another important aspect of the cranial nerves that lends itself to a mnemonic is the functional role each nerve plays. The nerves fall into one of three basic groups. They are sensory, motor, or both see Table The remainder of the nerves contain both sensory and motor fibers.

The nerves that convey both are often related to each other. The trigeminal and facial nerves both concern the face; one concerns the sensations and the other concerns the muscle movements. The facial and glossopharyngeal nerves are both responsible for conveying gustatory, or taste, sensations as well as controlling salivary glands.

The vagus nerve is involved in visceral responses to taste, namely the gag reflex. This is not an exhaustive list of what these combination nerves do, but there is a thread of relation between them.

Skip to content Spinal Nerves The nerves connected to the spinal cord are the spinal nerves. Figure The cervical plexus supplies nerves to the posterior head and neck, as well as to the diaphragm. The brachial plexus supplies nerves to the arm. The lumbar plexus supplies nerves to the anterior leg. The sacral plexus supplies nerves to the posterior leg. Cranial Nerves The nerves attached to the brain are the cranial nerves, which are primarily responsible for the sensory and motor functions of the head and neck one of these nerves targets organs in the thoracic and abdominal cavities as part of the parasympathetic nervous system.

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 lateral branches supply the erector spinae muscles. The anterior divisions of the lumbar nerves rami anteriores consist of long, slender branches that accompany the lumbar arteries around the sides of the vertebral bodies, beneath the psoas major. 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 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. 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 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. The pudendal nerve and parasympathetic fibers arise from S2, S3, and S4. They supply the descending colon and rectum, urinary bladder, and genital organs.

These pathways have both afferent and efferent fibers. The coccygeal nerve is the 31st pair of spinal nerves and arises from the conus medullaris. Its anterior root helps form the coccygeal plexus.

The spinal nerves branch into the dorsal ramus, ventral ramus, the meningeal branches, and the rami communicantes. Course and branches of thoracic spinal nerve : This diagram depicts the course and branches of a typical thoracic spinal nerve. The posterior division dorsal ramus is labeled at the top right.

A nerve plexus is a network of intersecting nerves; multiple nerve plexuses exist in the body. Nerve plexuses are composed of afferent and efferent fibers that arise from the merging of the anterior rami of spinal nerves and blood vessels. There are five spinal nerve plexuses—except in the thoracic region—as well as other forms of autonomic plexuses, many of which are a part of the enteric nervous system. The cervical plexus is formed by the ventral rami of the upper four cervical nerves and the upper part of fifth cervical ventral ramus.

The network of rami is located deep within the neck. The brachial plexus is formed by the ventral rami of C5—C8 and the T1 spinal nerves, and lower and upper halves of the C4 and T2 spinal nerves.

The plexus extends toward the armpit axilla. The lumbar plexus is formed by the ventral rami of L1—L5 spinal nerves with a contribution of T12 form the lumbar plexus. This plexus lies within the psoas major muscle. The sacral plexus is formed by the ventral rami of L4-S3, with parts of the L4 and S4 spinal nerves.

It is located on the posterior wall of the pelvic cavity. The coccygeal plexus serves a small region over the coccyx and originates from S4, S5, and Co1 spinal nerves. It is interconnected with the lower part of sacral plexus. Brachial plexus : Cervical C5—C8 and thoracic T1 nerves comprise the brachial plexus, which is a nerve plexus that provides sensory and motor function to the shoulders and upper limbs.

Lumbar plexus : The lumbar plexus is comprised of the ventral rami of the lumbar spinal nerves L1—L5 and a contribution from thoracic nerve T The posterior green and anterior yellow divisions of the lumbar plexus are shown in the diagram. The intercostal nerves are part of the somatic nervous system and arise from anterior divisions rami anteriores, ventral divisions of the thoracic spinal nerves T1 to T The intercostal nerves are distributed chiefly to the thoracic pleura and abdominal peritoneum.

Intercostal nerves : An image of the intercostal brachial nerves. They differ from the anterior divisions of the other spinal nerves in that each pursues an independent course without plexus formation. These are limited in their distribution to the parietes wall of the thorax.

The anterior divisions of the second, third, fourth, fifth, and sixth thoracic nerves, and the small branch from the first thoracic, are confined to the walls of the thorax and are named thoracic intercostal nerves. Near the sternum, they cross in front of the internal mammary artery and transversus thoracis muscle, pierce the intercostales interni, the anterior intercostal membranes, and pectoralis major, and supply the integument of the front of the thorax and over the mamma, forming the anterior cutaneous branches of the thorax.

The branch from the second nerve unites with the anterior supraclavicular nerves of the cervical plexus. The seventh intercostal nerve terminates at the xyphoid process, at the lower end of the sternum. The anterior divisions of the seventh, eighth, ninth, tenth, and eleventh thoracic intercostal nerves are continued anteriorly from the intercostal spaces into the abdominal wall; hence they are named thoraco-abdominal nerves or thoracicoabdominal intercostal nerves.

Unlike the nerves from the autonomic nervous system that innervate the visceral pleura of the thoracic cavity, the intercostal nerves arise from the somatic nervous system. This enables them to control the contraction of muscles, as well as provide specific sensory information regarding the skin and parietal pleura.

This explains why damage to the internal wall of the thoracic cavity can be felt as a sharp pain localized in the injured region. Damage to the visceral pleura is experienced as an unlocalized ache. A dermatome is an area of skin that is supplied by a single spinal nerve, and a myotome is a group of muscles that a single spinal nerve root innervates. A dermatome is an area of skin that is supplied by a single spinal nerve. There are eight cervical nerves, twelve thoracic nerves, five lumbar nerves and five sacral nerves.

Each of these nerves relays sensation, including pain, from a particular region of the skin to the brain. Dermatomes : Dermatomes are areas of skin supplied by sensory neurons that arise from a spinal nerve ganglion. Dermatomes and the associated major cutaneous nerves are shown here in a ventral view.

Along the thorax and abdomen, the dermatomes are like a stack of discs, with each section supplied by a different spinal nerve. Along the arms and the legs, the pattern is different. The dermatomes run longitudinally along the limbs, so that each half of the limb has a different dermatome. Although the general pattern is similar in all people, the precise areas of innervation are as unique to an individual as fingerprints.

Dermatomes have clinical significance, especially in the diagnosis of certain diseases. Symptoms that follow a dermatome, such as pain or a rash, may indicate a pathology that involves the related nerve root. Examples include dysfunction of the spine or a viral infection. Viruses that remain dormant in nerve ganglia, such as the varicella zoster virus that causes both chickenpox and shingles, often cause either pain, rash, or both in a pattern defined by a dermatome.