Textbook Question
A sensory region monitored by the posterior rami of a single spinal segment is
(a) A ganglion
(b) A fascicle
(c) A dermatome
(d) A ramus
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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 concept of nerve plexuses. A nerve plexus is a network of intersecting nerves. The human body has several major plexuses, including the cervical, brachial, lumbar, and sacral plexuses, each associated with specific regions and functions.
Step 2: Review the anatomical location and function of the lumbar plexus. The lumbar plexus is located in the lower back (lumbar region) and primarily serves the lower abdomen, pelvis, and legs. It gives rise to several important nerves, including the genitofemoral, femoral, and lateral femoral cutaneous nerves.
Step 3: Compare the lumbar plexus to other plexuses mentioned in the options. The sacral plexus is located lower than the lumbar plexus and serves the pelvis and lower limbs. The brachial plexus serves the upper limbs, and the cervical plexus serves the neck and diaphragm.
Step 4: Identify the nerves listed in the problem. The genitofemoral nerve is involved in sensory and motor functions in the genital region and upper thigh. The femoral nerve is a major nerve for the anterior thigh, and the lateral femoral cutaneous nerve provides sensation to the lateral thigh. These nerves are all associated with the lumbar plexus.
Step 5: Conclude that the correct answer is based on the anatomical association of these nerves with the lumbar plexus, as they originate from this specific network of nerves.
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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 nerves located in the lower back, formed by the anterior rami of the first four lumbar spinal nerves (L1-L4). It supplies motor and sensory innervation to the lower abdomen, pelvis, and parts of the lower limb. Key nerves arising from this plexus include the genitofemoral, femoral, and lateral femoral cutaneous nerves, which are essential for understanding lower limb function.
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Nerve Functions
Nerves can be classified based on their functions: sensory nerves transmit sensory information from the body to the brain, while motor nerves carry signals from the brain to muscles. The genitofemoral nerve provides sensation to the skin of the groin, the femoral nerve innervates the quadriceps muscle for knee extension, and the lateral femoral cutaneous nerve supplies sensation to the outer thigh, illustrating the diverse roles of these nerves.
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Plexus Anatomy
A plexus is a network of intersecting nerves that allows for the redistribution of nerve fibers to various body regions. The lumbar plexus is specifically important for the lower body, while other plexuses like the sacral and brachial serve different regions. Understanding the anatomy and connections of these plexuses is crucial for diagnosing and treating nerve-related issues in the corresponding areas.
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