Correctly identify and label the spinal nerves and their plexuses

Correctly identify and label the spinal nerves and their plexuses

The Correct Answer and Explanation is:

Correct Answer:

Spinal Nerves and Their Plexuses:

The spinal nerves are grouped into five regions, and four major plexuses arise from these spinal nerves:

1. Cervical Plexus – formed by spinal nerves C1 to C4
2. Brachial Plexus – formed by spinal nerves C5 to T1
3. Lumbar Plexus – formed by spinal nerves L1 to L4
4. Sacral Plexus – formed by spinal nerves L4 to S4
   (Note: There is no plexus formed from the thoracic spinal nerves T2–T12; these nerves become intercostal nerves.)

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The spinal cord gives rise to 31 pairs of spinal nerves, which are part of the peripheral nervous system (PNS). These nerves are categorized into regions: 8 cervical (C1–C8), 12 thoracic (T1–T12), 5 lumbar (L1–L5), 5 sacral (S1–S5), and 1 coccygeal (Co1). Each spinal nerve emerges from the spinal cord through intervertebral foramina and contains both sensory (afferent) and motor (efferent) fibers.

From these spinal nerves, nerve plexuses are formed — networks of intersecting nerves that combine and redistribute fibers from various spinal nerves. These plexuses primarily serve the limbs and anterior body wall, ensuring efficient motor and sensory innervation.

1. Cervical Plexus (C1–C4):
   This plexus lies deep in the neck and supplies the skin and muscles of the neck, head, and shoulders. One key nerve arising from it is the phrenic nerve (C3–C5), which innervates the diaphragm, making it critical for respiration.
2. Brachial Plexus (C5–T1):
   Found in the shoulder region, it innervates the upper limb. Major branches include the musculocutaneous, median, ulnar, radial, and axillary nerves, which control the motor and sensory functions of the arm and hand.
3. Lumbar Plexus (L1–L4):
   Located in the lower back, it provides motor and sensory innervation to the anterior thigh and part of the lower abdomen. The femoral and obturator nerves are key branches.
4. Sacral Plexus (L4–S4):
   This plexus serves the pelvis, buttocks, genitals, thighs, calves, and feet. Its most prominent nerve is the sciatic nerve, the largest nerve in the body.

The thoracic nerves (T2–T12) do not form a plexus. Instead, they become intercostal nerves, which run between the ribs and help control muscles of the chest and abdominal wall.

Understanding spinal nerves and their plexuses is essential in clinical practice for assessing injuries and diagnosing neurological or muscular disorders.