What is the significance of enlargement of the spinal cord

Hacking, C. Lumbar enlargement. Reference article, Radiopaedia. Spine , Central Nervous System. URL of Article. Clinically oriented anatomy. Read it at Google Books - Find it at Amazon 2. Susan Standring. Gray's Anatomy. ISBN: Related articles: Anatomy: Spine. The radial nerve innervates muscles and receives sensation from the posterior arm and forearm, including the dorsal region of the lateral three digits not including their tips.

The ulnar nerve innervates anterior forearm muscles as well as intrinsic hand muscles. It receives sensation from the dorsal and palmar regions of the medial one and a half digits. The lumbar plexus arises from all the lumbar spinal nerves L1 to L5 and gives rise to nerves innervating the pelvic region and the anterior leg.

The femoral nerve is one of the major nerves from this plexus, which gives rise to the saphenous nerve as a branch that extends through the anterior lower leg.

The femoral nerve innervates anterior thigh muscles and receives sensory information from the anterior and medial aspects of the thigh. The sacral plexus comes from the lower lumbar nerves L4 and L5 and the sacral nerves S1 to S4. The most significant systemic nerve to come from this plexus is the sciatic nerve , which is a combination of the tibial nerve and the fibular nerve.

The sciatic nerve extends across the hip joint and is the largest and longest nerve of the body. Through the tibial and fibular nerves, the sciatic nerve innervates the muscles and receives sensation of the posterior thigh and lower leg.

It is most commonly associated with the condition sciatica , which is the result of compression or irritation of the nerve or any of the spinal nerves giving rise to it. Spinal nerves of the thoracic region, T2 through T11, are not part of the plexuses but rather emerge and give rise to the intercostal nerves found between the ribs, which articulate with the vertebrae surrounding the spinal nerve. The intercostal nerves innervate the intercostal muscles and receive sensation from the skin of the anterior and lateral sides of the thoracic region.

The last nerves T7 to T12 also innervate the abdominal muscles and their overlying skin. For example, the fibers of eighth cervical nerve innervate the medial surface of the forearm and extend out to the fingers.

All spinal nerves except C1 innervates a region on the skin. Dermatomes are important in a clinical setting as they can help identify potential damage to spinal nerves. In a sensory exam, the dermatome of a specific area is tested for sensation for example the stroking of a cotton ball to evaluate the functioning of the spinal nerve connected to that dermatome. Dermatomes are also associated with referred visceral pain, as the spinal nerves innervated the regions of the skin also innervate internal organs.

Pain from the internal organ can then be mistakenly referred to a dermatome. For example, myocardial infarction is perceived as referred pain in the chest, left shoulder and left arm. This is because the sensory fibers that innervate the cardiac tissue travel through the T1-T4 spinal nerves, which also innervate the medial and anterior side of the body. The spinal cord is covered and protected by the spinal meninges, similar to the cranial ones.

However, the spinal dura mater presents only one layer of tissue. Moreover, the epidural space is a real space that houses areolar and adipose connective tissues, and blood vessels. The spinal cord is divided into segments that take the same name as the vertebral regions. Inferior to the conus medullaris, the spinal nerves form a bundle called the cauda equina.

The spinal cord presents two enlargements at the cervical and lumbar level. In cross section, the gray matter is deep within the spinal cord and is separated into horns. The sensory axons coming from the posterior root ganglia enter the spinal cord through the posterior nerve root and synapse in the posterior horn, where interneurons are found. Autonomic motor neurons are found in the lateral horns, while somatic motor neurons are found in the anterior horns.

Motor neurons send their axons out of the spinal cord through the anterior nerve root. The posterior and anterior root fuse to form the spinal nerve, which contains mixed sensory and motor information. The white matter is separated into columns which contain axons of sensory and motor neurons. The posterior columns contain ascending sensory tracts which are bundles of axons going towards the brain.

The lateral and anterior column contain ascending sensory tracts as well as descending motor tracts, which carry the motor responses from the brain. Overall, the posterior regions of the spinal cord are responsible for ascending sensory information, while the anterior regions are responsible for descending motor information.

Spinal nerves are all mixed nerves with both sensory and motor fibers. Spinal nerves emerge from the spinal cord and reorganize through plexuses, which then give rise to systemic nerves. Thoracic spinal nerves are not part of any plexus, but give rise to the intercostal nerves directly. What region of the spinal cord contains motor neurons that direct the movement of skeletal muscles? By the end of this section, you will be able to: Describe the structures that protect and supply the spinal cord Describe the structures of the spinal cord and their functions Explain the arrangement of gray and white matter in the spinal cord Compare and contrast how white and gray matter process information Describe the sensory and motor components of spinal nerves and the plexuses that they pass through Explain what a dermatome is and its clinical significance.

Protective Coverings of the Spinal Cord The spinal cord, as the brain, is protected by meninges, which are continuous with the cranial meninges. Blood Supply to the Spinal Cord The spinal cord is supported by an extensive collateral supply and drainage of blood.

Spinal Cord The description of the CNS is concentrated on the structures of the brain, but the spinal cord is another major organ of the system. The spinal cord is divided into four regions: cervical, thoracic, lumbar and sacral. The sacral region has a tapered end called the conus medullaris. The bundle of axons inferior to the conus medullaris is the cauda equina. The cauda equina is anchored to the coccyx by the filum terminale, a thin strand of pia mater.

The superior view of a cross section of spinal cord within the vertebra shows the dorsal and ventral roots emerging from the spinal cord and fusing to form the spinal nerve. On the dorsal root, a dorsal root ganglion contain sensory neurons. The spinal cord is wrapped in meninges, as shown in the figure enlargement.

The cross-section of a thoracic spinal cord segment shows the posterior, anterior, and lateral horns of gray matter, as well as the posterior, anterior, and lateral columns of white matter. A micrograph shows the histology of the spinal cord.

White Columns Just as the gray matter is separated into horns, the white matter of the spinal cord is separated into columns. Dorsal Root Ganglion A ganglion ganglia for plural is a group of neuron cell bodies in the peripheral nervous system.

The cell bodies of sensory neurons, which are unipolar neurons by shape, are seen in this micrograph. Also, the fibrous region is composed of the axons of these neurons that are passing through the ganglion to be part of the dorsal nerve root tissue source: canine. LM x The spinal cord is a part of the central nervous system and is a continuation of the medulla passing out of the cranial vault through the foramen Magnum. It runs continues caudally in the vertebral canal that forms from the adjacent vertebral foramina.

Simply put, the spinal cord is a bunch of nerves carrying electric signals between the brain and the rest of the body. Therefore, one of the most significant jobs of the cervical spine is the protection of the spinal cord as it advances through the neck to activate the rest of the body. It has a length that ranges between 16 to 18 inches or 41 to 45 cm. However, its diameter changes in the different regions because of the changes in the white and gray matter.