Nerve Plexuses in Human Anatomy

Questions and Answers

Which spinal nerves contribute to the formation of the phrenic nerve?

C3-C5 (correct)

C5-T1

C1-C5

C1-C3

What is the function of the lesser occipital nerve?

Innervates peripherally the medial aspect of the upper third of the ear (correct)

Innervates the posterior neck muscles

Transmits sensory information from the skin of the neck

Supplies the medial aspect of the upper third of the ear

Which of the following pairs of plexuses receive contributions from the same spinal nerve roots?

Cervical and lumbar

Lumbar and sacral

Cervical and brachial (correct)

Brachial and sacral

What is the role of the ansa cervicalis within the cervical plexus?

Forms loops combining fibers from different spinal nerves Signup and view all the answers

Which nerve located in the cervical plexus innervates the skin around the shoulder?

Supraclavicular nerves Signup and view all the answers

Which characteristic of the diaphragm's innervation is significant when considering spinal cord injuries?

A high lesion must occur to affect diaphragmatic function. Signup and view all the answers

Where do the fibers of the greater auricular nerve originate from?

C2-C3 Signup and view all the answers

The cervical plexus provides sensory innervation to which of the following areas?

Upper pectoral region and ear Signup and view all the answers

Which plexus is responsible for the innervation of the diaphragm?

Cervical plexus Signup and view all the answers

What is the primary condition associated with cancers of the upper part of the lung?

Pancoast syndrome Signup and view all the answers

Which type of lung cancer is most commonly associated with Pancoast tumors?

Non-small cell lung cancer Signup and view all the answers

In cases of myocardial infarction, pain may radiate to which part of the body?

Left arm Signup and view all the answers

What anatomical structures are likely irritated in Pancoast syndrome?

Structures near the pulmonary apex Signup and view all the answers

The brachial plexus can be affected by irritation from which type of tumor?

Pancoast tumor Signup and view all the answers

Intercostobrachial neuralgia may result from which of the following?

Surgery involving the breast Signup and view all the answers

Which nerve system can provide pain referral to the upper arm during upper thoracic issues?

Brachial plexus Signup and view all the answers

Pancoast tumors were more commonly diagnosed in the past due to what factor?

Lack of screening tests Signup and view all the answers

Which symptom can indicate a problem with heart pathologies, particularly myocardial infarctions?

Pain radiating to the left arm Signup and view all the answers

Which term refers to the exchange of nerve fibers between branches of the brachial plexus and intercostal nerves?

Nerve anastomosis Signup and view all the answers

What forms the medial cord of the brachial plexus?

The anterior division of the lower trunk Signup and view all the answers

Which of the following nerves is NOT a direct branch from the medial cord?

Musculocutaneous nerve Signup and view all the answers

Which structure is formed by the merging of all posterior divisions?

Posterior cord Signup and view all the answers

Which ventral rami contribute to the formation of the superior trunk?

C5 and C6 Signup and view all the answers

What is the primary function of the brachial plexus?

To innervate the upper limbs Signup and view all the answers

Which of the following is a nerve that originates from the posterior cord?

Axillary nerve Signup and view all the answers

Which statement is true regarding the lateral cord?

It includes contributions from the upper and middle trunks Signup and view all the answers

The branches of the brachial plexus traverse which anatomical structure?

Interscalene triangle Signup and view all the answers

What type of nerves arise from the trunks of the brachial plexus?

Mixed nerves Signup and view all the answers

Which nerve emerges from the medial cord besides the ulnar nerve?

Medial cutaneous nerve of the forearm Signup and view all the answers

Which spinal nerve segments form intercostal nerves?

T1-T12 Signup and view all the answers

What is the main function of plexuses formed by spinal nerve branches?

To innervate muscles with fibers from multiple spinal nerves Signup and view all the answers

Which area of the body is NOT innervated by the ventral branches of spinal nerves?

Back muscles Signup and view all the answers

What is true about the intercostal nerves and the ribs?

They run parallel to each rib and supply the rib muscles Signup and view all the answers

What branches from the intercostal nerve innervate the skin overlying the rib?

Both anterior and lateral cutaneous branches Signup and view all the answers

In which regions are the spinal nerve plexuses specifically located?

Cervical, brachial, and lumbosacral Signup and view all the answers

What happens when spinal nerves mix in a plexus?

They give rise to new peripheral branches with specific routes Signup and view all the answers

What role does the dorsal ramus play in spinal nerve function?

It provides innervation to the back muscles Signup and view all the answers

What is the primary consequence of a single spinal segment damage?

Incomplete paralysis of muscles due to multi-spinal nerve innervation Signup and view all the answers

Study Notes

Nerve Plexuses Overview

Ventral branches of spinal nerves form plexuses, except for T2-T12.
Plexuses are found in cervical, brachial, and lumbosacral regions.
Each muscle typically innervated by multiple spinal nerves to prevent complete paralysis from segment damage.

Innervation of Specific Regions

Back: Innervated by dorsal branches of spinal nerves.
Thorax: Ventral branches from T1-T12 form intercostal nerves, located between ribs, supplying rib muscles, anterolateral chest, and abdominal wall.

Cervical Plexus

Formed by spinal nerves C1-C5, with fibers mixing shortly after origin.
Contains ansa cervicalis, which is adjacent to the hypoglossal nerve (XII).
Provides sensory and motor innervation to neck, shoulder, and diaphragm (phrenic nerve).

Peripheral Branches of the Cervical Plexus

Lesser Occipital Nerve: From C2, innervates skin of the upper ear.
Greater Auricular Nerve: Behind sternocleidomastoid (SCM), innervates parotid and mastoid area skin.
Transverse Cutaneous Nerve: Sensory innervation from the anterolateral neck’s skin.
Supraclavicular Nerves: Supply skin around the shoulder area.

Brachial Plexus

Originates from spinal nerves C5-T1; some contributions from C4.
Comprised of three trunks:
- Upper trunk (C5-C6)
- Middle trunk (C7)
- Lower trunk (C8-T1)
Trunks split into anterior and posterior divisions leading to three cords:
- Posterior cord: merges all posterior divisions.
- Lateral cord: anterior divisions of upper and middle trunks.
- Medial cord: anterior division of lower trunk.

Terminal Nerves of the Brachial Plexus

Lateral Cord: Musculocutaneous and lateral root of the median nerve.
Medial Cord: Ulnar nerve and roots of the median nerve.
Posterior Cord: Axillary and radial nerves.

Lumbosacral Plexus

Formed by spinal nerves L1-S4.
Lumbar plexus (L1-L4) and sacral plexus (L4-S4) provide innervation to lower limbs.

Clinical Relevance

Brachial plexus proximity to major arteries emphasizes surgical significance.
Pancoast syndrome can occur due to lung tumors affecting plexus structures.
Intercostobrachial nerves can relate to surgeries or trauma, leading to associated pain.

Additional Notes

Cervical plexus contributes fibers to the brachial plexus.
Diaphragm innervation mainly from phrenic nerve (C3-C5), lesions above C3 can affect respiration.
Burnt-out luminal -- branches of intercostal nerves may lead to referred thoracic pain during heart pathology, especially left-side injuries.

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Description

This quiz explores the structure and function of nerve plexuses formed by the ventral branches of spinal nerves. Focus will be on the cervical, brachial, and lumbosacral plexuses, detailing how spinal nerves intercommunicate and give rise to peripheral branches. Test your knowledge on these crucial components of the nervous system.