Textbook Question
The connective tissue sheath that surrounds a fascicle of nerve fibers is the
a. Epineurium
b. Endoneurium
c. Perineurium
d. Epimysium
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13. The Peripheral Nervous System
Introduction to the Peripheral Nervous System
Problem 9
Textbook Question
The genitofemoral, femoral, and lateral femoral cutaneous nerves are major nerves of the
(a) Lumbar plexus
(b) Sacral plexus
(c) Brachial plexus
(d) Cervical plexus
Verified step by step guidance1
Step 1: Understand the anatomical regions and the plexuses involved. The lumbar plexus is formed by the anterior rami of the L1 to L4 spinal nerves and primarily innervates the lower abdomen, anterior and medial thigh.
Step 2: Identify the nerves listed in the problem: genitofemoral, femoral, and lateral femoral cutaneous nerves. These nerves are known to arise from the lumbar plexus.
Step 3: Recall the origins of each nerve: the genitofemoral nerve arises from L1-L2, the femoral nerve from L2-L4, and the lateral femoral cutaneous nerve from L2-L3 spinal nerves, all part of the lumbar plexus.
Step 4: Compare the other plexuses: the sacral plexus mainly supplies the posterior thigh, lower leg, and foot; the brachial plexus supplies the upper limb; the cervical plexus supplies the neck and diaphragm.
Step 5: Conclude that since all three nerves originate from the lumbar spinal nerves and serve the anterior and lateral thigh region, they are major nerves of the lumbar plexus.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Lumbar Plexus
The lumbar plexus is a network of nerve fibers originating from the lumbar spinal nerves L1 to L4. It primarily supplies the lower abdomen, thigh, and groin regions. Key nerves such as the genitofemoral, femoral, and lateral femoral cutaneous nerves arise from this plexus, making it essential for lower limb sensory and motor functions.
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Major Nerves of the Lumbar Plexus
The genitofemoral nerve provides sensation to the genital area and upper anterior thigh; the femoral nerve controls muscles that extend the knee and provides sensation to the anterior thigh; the lateral femoral cutaneous nerve supplies sensation to the outer thigh. Understanding these nerves helps identify their origin from the lumbar plexus.
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Other Nerve Plexuses and Their Regions
The sacral plexus innervates the posterior thigh, lower leg, and foot; the brachial plexus serves the upper limb; and the cervical plexus supplies the neck and diaphragm. Differentiating these plexuses by their anatomical regions aids in correctly associating nerves with their plexus.
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