Chapter 13 - Section 13.2 - Study Guide - Assess Your Learning Outcomes - Page 504: 5

**5. Number of Spinal Nerves**: - There are typically 31 pairs of spinal nerves in the human nervous system. - These spinal nerves are classified into five regions based on their location in the vertebral column: 1. 8 pairs of cervical nerves (C1-C8). 2. 12 pairs of thoracic nerves (T1-T12). 3. 5 pairs of lumbar nerves (L1-L5). 4. 5 pairs of sacral nerves (S1-S5). 5. 1 pair of coccygeal nerves (Co). **6. Anatomy of the Posterior and Anterior Roots of a Spinal Nerve; the Rootlets; and the Posterior Root Ganglion Relationship to the Spinal Cord and Intervertebral Foramina**: **Anatomy of a Spinal Nerve**: - Each spinal nerve emerges from the spinal cord through two roots: the posterior (dorsal) root and the anterior (ventral) root. **Posterior Root**: - The posterior root contains sensory (afferent) nerve fibers that carry sensory information from the body's periphery to the spinal cord. - It is associated with a swelling known as the posterior root ganglion, which contains cell bodies of sensory neurons. - The ganglion is located just outside the spinal cord, within the vertebral foramen (the bony canal through which the spinal nerve passes). **Anterior Root**: - The anterior root contains motor (efferent) nerve fibers that carry motor commands from the spinal cord to muscles and glands. - Unlike the posterior root, it does not have a ganglion associated with it. **Rootlets**: - Both the posterior and anterior roots are composed of multiple rootlets. Rootlets are smaller nerve bundles that converge to form the main roots. - The posterior rootlets originate from individual sensory neurons within the posterior root ganglion, while the anterior rootlets originate directly from the ventral horn motor neurons in the spinal cord. **Relationship to the Spinal Cord and Intervertebral Foramina**: - The posterior root ganglion is situated just outside the spinal cord and within the vertebral foramen of the respective vertebra. It is an enlargement or swelling along the posterior root. - After passing through the intervertebral foramen (the opening formed by adjacent vertebrae), the spinal nerve divides into its anterior and posterior roots. - The posterior root ganglion and the posterior rootlets are found within the intervertebral foramen, while the anterior rootlets and the anterior root emerge from the spinal cord and join the posterior root to form the spinal nerve. In summary, each spinal nerve has both posterior and anterior roots. The posterior root contains sensory nerve fibers and is associated with the posterior root ganglion, located within the intervertebral foramen. The anterior root contains motor nerve fibers and originates directly from the spinal cord. These roots come together to form the spinal nerve shortly after passing through the intervertebral foramen, and from there, they distribute sensory and motor information to and from various parts of the body.

**5. Number of Spinal Nerves**: - There are typically 31 pairs of spinal nerves in the human nervous system. - These spinal nerves are classified into five regions based on their location in the vertebral column: 1. 8 pairs of cervical nerves (C1-C8). 2. 12 pairs of thoracic nerves (T1-T12). 3. 5 pairs of lumbar nerves (L1-L5). 4. 5 pairs of sacral nerves (S1-S5). 5. 1 pair of coccygeal nerves (Co). **6. Anatomy of the Posterior and Anterior Roots of a Spinal Nerve; the Rootlets; and the Posterior Root Ganglion Relationship to the Spinal Cord and Intervertebral Foramina**: **Anatomy of a Spinal Nerve**: - Each spinal nerve emerges from the spinal cord through two roots: the posterior (dorsal) root and the anterior (ventral) root. **Posterior Root**: - The posterior root contains sensory (afferent) nerve fibers that carry sensory information from the body's periphery to the spinal cord. - It is associated with a swelling known as the posterior root ganglion, which contains cell bodies of sensory neurons. - The ganglion is located just outside the spinal cord, within the vertebral foramen (the bony canal through which the spinal nerve passes). **Anterior Root**: - The anterior root contains motor (efferent) nerve fibers that carry motor commands from the spinal cord to muscles and glands. - Unlike the posterior root, it does not have a ganglion associated with it. **Rootlets**: - Both the posterior and anterior roots are composed of multiple rootlets. Rootlets are smaller nerve bundles that converge to form the main roots. - The posterior rootlets originate from individual sensory neurons within the posterior root ganglion, while the anterior rootlets originate directly from the ventral horn motor neurons in the spinal cord. **Relationship to the Spinal Cord and Intervertebral Foramina**: - The posterior root ganglion is situated just outside the spinal cord and within the vertebral foramen of the respective vertebra. It is an enlargement or swelling along the posterior root. - After passing through the intervertebral foramen (the opening formed by adjacent vertebrae), the spinal nerve divides into its anterior and posterior roots. - The posterior root ganglion and the posterior rootlets are found within the intervertebral foramen, while the anterior rootlets and the anterior root emerge from the spinal cord and join the posterior root to form the spinal nerve. In summary, each spinal nerve has both posterior and anterior roots. The posterior root contains sensory nerve fibers and is associated with the posterior root ganglion, located within the intervertebral foramen. The anterior root contains motor nerve fibers and originates directly from the spinal cord. These roots come together to form the spinal nerve shortly after passing through the intervertebral foramen, and from there, they distribute sensory and motor information to and from various parts of the body.