For each of the following muscles or body regions, identify the plexus and the peripheral nerve(s) (or branch of one) involved. Use choices from keys A and B.
_; _ (1) the diaphragm
_; _ (2) muscles of the posterior leg
_; _ (3) anterior thigh muscles
_; _ (4) medial thigh muscles
_; _ (5) anterior arm muscles that flex the forearm
_; _ (6) muscles that flex the hand and digits (two nerves)
_; _ (7) muscles that extend the hand and digits
_; _ (8) skin and extensor muscles of the posterior arm
_; _ (9) fibularis muscles, tibialis anterior, and toe extensors
_; _, _, _, (10) elbow joint

Key A: Plexuses
(a) brachial
(b) cervical
(c) lumbar
(d) sacral

Key B: Nerves
(1) common fibular
(2) femoral
(3) median
(4) musculocutaneous
(5) obturator
(6) phrenic
(7) radial
(8) tibial
(9) ulnar

Name: Marieb Human Anatomy & Physiology
Author: Hoehn, Haynes, Abbott
ISBN: 9780138242732

Verified step by step guidance

Step 1: Identify the plexus and nerve for the diaphragm. Recall that the diaphragm is primarily innervated by the phrenic nerve, which arises from the cervical plexus.

Step 2: For muscles of the posterior leg, determine which plexus supplies this region and the corresponding nerve. The sacral plexus innervates the posterior leg muscles, mainly through the tibial nerve.

Step 3: For anterior thigh muscles, identify the plexus and nerve involved. The lumbar plexus supplies the anterior thigh muscles, primarily via the femoral nerve.

Step 4: For medial thigh muscles, find the plexus and nerve. The lumbar plexus also innervates the medial thigh muscles, mainly through the obturator nerve.

Step 5: For anterior arm muscles that flex the forearm, determine the plexus and nerve. The brachial plexus supplies these muscles, with the musculocutaneous nerve being the main nerve involved.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Peripheral Nervous System Plexuses

Plexuses are networks of intersecting nerves that originate from spinal nerve roots and reorganize to form peripheral nerves. The main plexuses include cervical, brachial, lumbar, and sacral, each innervating specific body regions and muscles. Understanding which plexus supplies a muscle helps identify the nerve involved.

Peripheral Nerves and Their Muscle Innervations

Peripheral nerves arise from plexuses and innervate specific muscles or muscle groups. For example, the phrenic nerve from the cervical plexus controls the diaphragm, while the femoral nerve from the lumbar plexus innervates anterior thigh muscles. Recognizing nerve-muscle relationships is essential for mapping function and diagnosing nerve injuries.

Muscle Groups and Their Functional Roles

Muscle groups are categorized by location and function, such as flexors or extensors of limbs. Identifying the muscle group involved (e.g., posterior leg muscles or anterior arm flexors) guides the selection of the correct plexus and nerve. This functional classification aids in understanding motor control and clinical assessments.

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