Brachial Plexus and Axillary Fossa Anatomy

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Questions and Answers

What anatomical structures are classified as supraclavicular in relation to the brachial plexus?

Trunks and Roots (correct)

Cords and Divisions

Collateral branches

Nerves and Arteries

Which muscles contribute to the anterior wall of the axillary fossa?

Intertubercular sulcus and axillary vein

Subscapularis and teres major

Latissimus dorsi and serratus anterior

Pectoralis major and minor (correct)

Which spinal nerve levels correspond to the dermatomes of the lateral aspect of the arm?

C6 and C7

C7 and C8

C4 and C5

C5 and C6 (correct)

What anatomical feature serves as the apex of the axillary fossa?

Clavicle and first rib Signup and view all the answers

What is the primary composition of the contents found within the axillary fossa?

Fat and fascial sheath Signup and view all the answers

The brachial plexus is formed by which of the following?

Ventral rami of five spinal nerves Signup and view all the answers

Which section of the brachial plexus is primarily associated with a proximal-distal gradient of innervation?

Roots Signup and view all the answers

Which two digits are primarily innervated by the C6 dermatome?

Radial two digits Signup and view all the answers

Which nerves arise from the C5 and C6 spinal levels?

Lower Subscapular nerve Signup and view all the answers

What is the function of the Latissimus dorsi muscle?

Extends, adducts, and internally rotates the arm at the glenohumeral joint Signup and view all the answers

Which of the following statements about the posterior cord is true?

It has two terminal branches. Signup and view all the answers

Which nerve is particularly vulnerable to stretching or tearing injuries?

Axillary nerve Signup and view all the answers

What skin area does the Axillary nerve innervate?

Skin over the lateral arm Signup and view all the answers

Which nerve arises from the C5 root and innervates the rhomboids?

Dorsal Scapular nerve Signup and view all the answers

What is the primary consequence of a lesion to the Long Thoracic nerve?

Medially winged scapula Signup and view all the answers

Which of the following nerves arises from the roots of the brachial plexus?

Long Thoracic nerve Signup and view all the answers

What condition is characterized by difficulty in raising the limb above the head due to scapular issues?

Long Thoracic nerve injury Signup and view all the answers

Which muscles are involved in the elevation of the scapula?

Upper trapezius and Levator scapulae Signup and view all the answers

What factor is critical for arm abduction and flexion beyond 30 degrees?

Scapular rotation Signup and view all the answers

The serratus anterior muscle is innervated by which nerve?

Long Thoracic nerve Signup and view all the answers

Which of these muscles contributes to scapular depression?

Lower Trapezius Signup and view all the answers

What joint do the intrinsic (scapulohumeral) muscles primarily move?

Glenohumeral joint Signup and view all the answers

Which muscle is responsible for initiating arm abduction at the glenohumeral joint?

Deltoid Signup and view all the answers

What common condition is associated with the radial nerve being compressed against the humerus?

Crutch palsy Signup and view all the answers

Which of the following muscles is NOT part of the rotator cuff?

Teres Major Signup and view all the answers

What is the primary function of the rotator cuff muscles during arm movement?

Stabilize the glenohumeral joint Signup and view all the answers

What type of fracture is most commonly associated with the greater tubercle of the humerus in elderly individuals?

Stable fractures with no displacement Signup and view all the answers

Which nerve innervates all muscles of the posterior arm and forearm?

Radial nerve Signup and view all the answers

Which muscles form the posterior axillary fold?

Latissimus Dorsi, Teres Major, Deltoid Signup and view all the answers

Which muscles are primarily involved in the movements of protraction and retraction of the scapula?

Rhomboids and Pectoralis minor Signup and view all the answers

What are the components of the brachial plexus following the roots?

Divisions and Cords Signup and view all the answers

What nerves arise from the trunks of the brachial plexus?

Nerve to Subclavius and Suprascapular nerve Signup and view all the answers

What is the relationship of cords in the brachial plexus to the axillary artery?

Cords are named based on their position around the axillary artery Signup and view all the answers

What primarily supplies muscles in the anterior compartment of the arm?

Fibers from the Anterior divisions Signup and view all the answers

Which condition can lead to compression of the roots and trunks of the brachial plexus?

Hypertrophy or pathology of the scalenes Signup and view all the answers

Which of the following is NOT included in the clinical manifestation of Scalene Interval Syndrome?

Pain in the shoulder girdle Signup and view all the answers

Which two structures pass between the anterior and middle scalene muscles?

Brachial plexus and Subclavian artery Signup and view all the answers

What are the anterior and posterior divisions of the brachial plexus responsible for?

Anterior division for anterior muscles, posterior division for posterior muscles Signup and view all the answers

Where does the axillary artery become the subclavian artery?

At the apex of the axilla Signup and view all the answers

Study Notes

Brachial Plexus Overview

The brachial plexus consists of 11 collateral (preterminal) branches with roots and trunks categorized as supraclavicular structures.
Divisions and cords of the plexus are classified as infraclavicular structures.

Axillary Fossa Anatomy

The axillary fossa has a pyramidal shape; its base is formed by the skin of the armpit and apex by the interval between clavicle and first rib.
The anterior wall comprises pectoralis major and minor, medial wall is formed by serratus anterior and lateral ribcage, lateral wall is the intertubercular sulcus, and posterior wall includes subscapularis, teres major, and latissimus dorsi tendon.

Key Anatomical Structures in Axillary Fossa

Contains axillary artery and vein, axillary lymph nodes, and infraclavicular elements of the brachial plexus.
Brachial plexus roots derive from five spinal nerves.

Developmental Perspective

Upper limbs originate as buds from the venterolateral body wall adjacent to caudal cervical and upper thoracic segments at the end of the fourth week of embryonic development.
Dermatomes align with this embryonic origin.

Dermatome Maps

C4 – Upper limb sensations not specified.
C5 – Lateral aspect of arm.
C6 – Lateral forearm, hand, and radial two digits.
C7 – Middle finger and middle of the hand.
C8 – Ulnar two digits and medial hand/wrist.
T1 – Medial aspect of forearm, elbow, lower arm.

Innervation Patterns

Distal innervation gradient present in somatic motor fibers: C5-C6 fibers innervate proximal muscles, intermediate rami fibers target mid-region, and C8-T1 fibers focus on distal musculature.
Dorsal scapular nerve (C5) innervates rhomboids and levator scapulae.

Long Thoracic Nerve

Arises from C5, C6, C7; damage leads to serratus anterior weakness, resulting in "winged scapula" and difficulty elevating the arm above head.

Scapulothoracic Movements

Movements include elevation/depression (upper trapezius, pectoralis minor) and protraction/retraction (serratus anterior for protraction and rhomboids for retraction).

Brachial Plexus Architecture

Roots contribute to the formation of three trunks: superior, middle, and inferior.
Each trunk branches into anterior and posterior divisions with distinct functional roles:
- Anterior division innervates anterior muscles of the arm and forearm.
- Posterior division targets posterior muscles.

Cords and Relations to Axillary Artery

Cords arise based on anatomical relationships to the axillary artery; post-trunks split into anterior and posterior divisions forming cords.
The axillary artery continues from the subclavian artery after passing the first rib.

Scalene Muscles and Compression Risks

Roots and trunks of the plexus pass between anterior and middle scalene muscles, subject to compression from scalene hypertrophy or pathology.
The interval transmits significant neuro-vascular elements for the upper limb.

Scalene Interval Syndrome Symptoms

Characterized by a cool, pale upper limb and diminished pulses; subclavian vein does not traverse this interval.

Collateral Branches of the Posterior Cord

Includes upper subscapular, thoracodorsal (C6, C7, C8), and lower subscapular nerves, each with unique innervations.

Axillary Nerve Vulnerabilities

The axillary nerve is susceptible to stretching and tearing injuries, which can impair innervation to the deltoid and teres minor.

Radial Nerve Compression Risks

Risks include compression against the tendon of latissimus dorsi or the proximal humeral shaft, potentially leading to conditions like "crutch palsy."

Rotator Cuff Muscles

Comprises deltoid, teres major, supraspinatus, infraspinatus, teres minor, and subscapularis which stabilize the glenohumeral joint during limb movements.

Avulsion Fractures

Commonly occur in the greater tubercle of the humerus due to falls; stable fractures typically require minimal external fixation and rehabilitation.

Trigger for Arm Abduction

Supraspinatus muscle initiates arm abduction at the glenohumeral joint, with the deltoid muscle assisting thereafter.

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Description

Explore the intricate anatomy of the brachial plexus and axillary fossa in this quiz. Understand the structure and function of the collateral branches, divisions, and key anatomical components within the axillary fossa. This overview provides a comprehensive look at the related nerves, arteries, and developmental perspectives of the upper limbs.