Chapter_14_-_Spinal_Cord_and_Nerves_Student

Chapter 14: Spinal Cord and Spinal Nerves

Overview

• Author: Kenneth S. Saladin

• Edition: Sixth Edition

• Publisher: McGraw-Hill Education (2020)

Surface Anatomy of the Spinal Cord

Regions

• Cervical

• Thoracic

• Lumbar

• Sacral

Enlargements

• Cervical Enlargement: Responsible for innervating the arms.

• Lumbosacral Enlargement: Responsible for innervating the lower limbs.

Key Structures

• Medullary Cone: Tapered end of the spinal cord.

• Cauda Equina: Bundle of spinal nerve roots extended beyond the spinal cord.

• Terminal Filum: Fibrous extension anchoring the spinal cord.

Spinal Meninges

Layers of Meninges

• Dura Mater (Dural Sheath)

  • Tough, outer layer.

  • Contains the epidural space.

• Arachnoid Mater

  • Middle layer.

  • Subarachnoid Space: Contains cerebrospinal fluid (CSF).

• Pia Mater

  • Delicate, inner layer, supports blood vessels to the spinal cord.

  • Denticulate Ligaments: Anchors spinal cord to vertebrae.

Cross-Sectional Anatomy of the Spinal Cord

Gray Matter

• Regions:

  • Posterior Horn

  • Lateral Horn (only in thoracic region)

  • Anterior Horn

• Gray Commissure: Connects left and right sides.

• Characteristics: Contains few myelinated axons.

White Matter

• Columns (Funiculi):

  • Posterior Funiculus

  • Lateral Funiculus

  • Anterior Funiculus

• Contains the myelinated axons; connected by the white commissure.

Spinal Tracts

Types of Tracts

• Ascending Tracts: Carry sensory information to the brain.

• Descending Tracts: Carry motor information from the brain.

  • Decussation: Many tracts cross midline, which means origin and destination are on opposite sides of the body.

  • Some tract connections remain ipsilateral (same side).

General Anatomy of Nerves and Ganglia

Structure of Nerves

• Components:

  • Epineurium: wraps the entire nerve.

  • Perineurium: wraps a fascicle of axons.

  • Endoneurium: wraps around a single axon.

Anatomy of a Ganglion

• Ganglion: Cluster of cell bodies outside of the CNS.

Spinal Nerves

Overview

• Total of 31 pairs:

  • Cervical: C1–C8

  • Thoracic: T1–T12

  • Lumbar: L1–L5

  • Sacral: S1–S5

  • Coccygeal: Co1

Proximal Branches

• Posterior Dorsal Root: Sensory input.

• Dorsal Root Ganglion: Contains sensory neuron cell bodies.

• Anterior Ventral Root: Motor output.

Distal Branches

• Posterior Dorsal Ramus: Innervates deep muscles and skin of the back.

• Anterior Ventral Ramus: Larger, innervates front and limbs, gives rise to plexuses, especially intercostal nerves.

Spinal Nerve Plexuses

Major Plexuses

• Cervical Plexus: Includes innervation of neck and diaphragm (phrenic nerve).

• Brachial Plexus: Supplies upper limbs (includes musculocutaneous, radial, median, and ulnar nerves).

• Lumbar Plexus: Innervates lower back and legs (includes femoral and obturator nerves).

• Sacral Plexus: Supplies lower body, includes sciatic nerve.

• Coccygeal Plexus: Innervates lower sacrum and coccyx.

Specific Plexuses

Cervical Plexus

• Nerves:

  • Hypoglossal, Lesser Occipital, Great Auricular, Transverse Cervical, Phrenic Nerve.

Brachial Plexus

• Complexity of branches serving shoulder and arm:

  • Dorsal Scapular, Suprascapular, Musculocutaneous, Median, Ulnar, Radial Nerves.

Lumbar Plexus

• Important branches include:

  • Iliohypogastric, Ilioinguinal, Genitofemoral, Obturator, Femoral Nerves.

Sacral and Coccygeal Plexuses

• Key Nerves: Sciatic nerve (Common Fibular and Tibial branches), pudenal nerve.

Cutaneous Innervation and Dermatomes

• Dermatome: Area of skin innervated by specific spinal nerve.

• Maps show the skin areas corresponding to spinal nerves.

Clinical Terms to Know

• Paraplegia: Paralysis of both lower limbs (lesions from T1 to L1).

• Quadriplegia: Paralysis of all four limbs (lesions above C5 requiring ventilation support).

• Hemiplegia: Paralysis on one side of the body, often due to stroke.

Conclusion

• End of Chapter 14: Comprehensive overview of the anatomy and functions of the spinal cord and spinal nerves.