Axilla and Brachial Plexus Anatomy
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Questions and Answers

What is the primary shape of the axilla?

  • Cylindrical
  • Spherical
  • Pyramidal (correct)
  • Cuboidal

Which structure does NOT form a boundary of the axillary inlet?

  • Clavicle
  • Sternum (correct)
  • First rib
  • Scapula

What component does the axilla NOT contain?

  • Pulmonary artery (correct)
  • Brachial plexus
  • Axillary lymph nodes
  • Axillary artery

Which is the correct order of the brachial plexus stages?

<p>Roots, Trunks, Divisions, Cords, Terminal branches (D)</p> Signup and view all the answers

How many anterior rami contribute to the formation of the brachial plexus?

<p>Five (B)</p> Signup and view all the answers

Which trunk of the brachial plexus is formed by the union of C5 and C6 roots?

<p>Superior trunk (C)</p> Signup and view all the answers

Which type of division does each trunk of the brachial plexus split into?

<p>Anterior and Posterior divisions (A)</p> Signup and view all the answers

Which root is NOT part of the brachial plexus?

<p>T2 (D)</p> Signup and view all the answers

What is the contribution range of the lateral cord of the brachial plexus?

<p>C5 to C7 (A)</p> Signup and view all the answers

Which cord is positioned medial to the second part of the axillary artery?

<p>Medial cord (D)</p> Signup and view all the answers

Which of the following nerves is a branch of the posterior cord?

<p>Upper subscapular nerve (C)</p> Signup and view all the answers

Where does the axillary artery begin?

<p>Lateral border of the first rib (C)</p> Signup and view all the answers

Which branch of the axillary artery passes anterior to the surgical neck of the humerus?

<p>Anterior circumflex humeral artery (D)</p> Signup and view all the answers

What nerves originate from the upper trunk of the brachial plexus?

<p>Dorsal scapular and suprascapular nerves (D)</p> Signup and view all the answers

Which nerve has contributions from C8 and T1?

<p>Ulnar nerve (D)</p> Signup and view all the answers

Which of the following correctly identifies the components of the posterior cord?

<p>All 3 posterior divisions (C)</p> Signup and view all the answers

What is the primary muscle innervated by the axillary nerve?

<p>Deltoid (C)</p> Signup and view all the answers

Which structure exits the axilla through the quadrangular space?

<p>Axillary nerve (B)</p> Signup and view all the answers

The superior lateral cutaneous nerve of the arm is responsible for sensation from which area?

<p>Skin over the deltoid muscle (B)</p> Signup and view all the answers

What are the contents of the posterior quadrangular space?

<p>Axillary nerve and posterior circumflex humeral vessels (B)</p> Signup and view all the answers

Which of the following muscles is not innervated by the axillary nerve?

<p>Infraspinatus (D)</p> Signup and view all the answers

Which nerve is responsible for causing 'winging of scapula' when paralyzed?

<p>Long thoracic nerve (A)</p> Signup and view all the answers

Which space contains the circumflex scapular vessels?

<p>Upper triangular space (A)</p> Signup and view all the answers

Which nerve and artery are found in the lower triangular interval?

<p>Radial nerve and profunda brachii artery (C)</p> Signup and view all the answers

Flashcards

What is the axilla?

A triangular-shaped space that connects the neck and arm.

Describe the axillary inlet.

The axillary inlet is the superior opening of the axilla, formed by the clavicle, scapula, and the first rib.

What forms the floor (base) of the axilla?

The base of the axilla is formed by the skin of the armpit.

What is the brachial plexus?

A network of nerves that originate from the spinal cord and provide innervation to the upper limb.

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What spinal nerves are involved in the brachial plexus?

The brachial plexus is formed by the anterior rami of spinal nerves C5, C6, C7, C8, and T1.

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What are the stages of the brachial plexus?

The brachial plexus is organized into 5 stages: roots, trunks, divisions, cords, and terminal branches.

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What do the anterior divisions of the brachial plexus supply?

The anterior division of each trunk forms nerves that supply the anterior compartments of the arm and forearm.

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What do the posterior divisions of the brachial plexus supply?

The posterior division of each trunk forms nerves that supply the posterior compartments of the arm and forearm.

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What are the cords of the brachial plexus?

These 3 cords originate from the 3 divisions of the brachial plexus. They are positioned in relation to the 2nd part of the axillary artery.

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Explain the formation and contributions of the lateral cord.

The lateral cord is formed by the anterior divisions of the upper and middle trunks. Its contributions come from C5, C6, and C7.

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What are the origins and contributions of the medial cord?

The medial cord is a continuation of the anterior division of the inferior trunk, receiving contributions from C8 and T1.

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How is the posterior cord formed?

The posterior cord is formed by the union of all 3 posterior divisions. It receives contributions from all roots of the brachial plexus.

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What is the origin and function of the long thoracic nerve?

The long thoracic nerve originates from C5, C6, and C7 and supplies the serratus anterior muscle.

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What are the origins and function of the dorsal scapular nerve?

The dorsal scapular nerve, originating from C5, supplies the rhomboid muscles.

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What are the origins and function of the suprascapular nerve?

The suprascapular nerve, originating from C5 and C6, supplies the supraspinatus and infraspinatus muscles.

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What are the origins and function of the musculocutaneous nerve?

The musculocutaneous nerve originates from C5, C6, and C7 and is responsible for innervating the muscles of the anterior compartment of the arm.

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What is the course and function of the axillary nerve?

The axillary nerve originates from the posterior cord of the brachial plexus, traverses the quadrangular space, and reaches the posterior scapular region. It accompanies the posterior circumflex humeral vessels, passing along the surgical neck of the humerus. It innervates the deltoid and teres minor muscles. It also includes the superior lateral cutaneous nerve of the arm which provides sensation to the deltoid region.

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What are the borders of the quadrangular space?

The quadrangular space is a triangular-shaped space in the scapular region bounded by the teres minor muscle superiorly, teres major muscle inferiorly, humerus laterally, and long head of triceps brachii medially.

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What structures pass through the quadrangular space?

The axillary nerve, along with the posterior circumflex humeral vessels, passes through the quadrangular space.

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What are the actions of the muscles innervated by the axillary nerve?

The deltoid muscle is responsible for shoulder abduction, while the teres minor muscle is involved in external rotation of the shoulder joint.

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What is the function of the serratus anterior muscle and what happens when it is paralyzed?

The serratus anterior muscle is crucial for protracting and rotating the scapula upward. When this muscle is paralyzed, "winging of the scapula" occurs, where the medial border of the scapula moves away from the chest wall.

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What are the spaces in the scapular region and what structures do they contain?

The spaces of the scapular region include the posterior quadrangular space, the upper triangular space, and the lower triangular interval. Each space houses specific vessels and nerves crucial for limb function.

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Describe the boundaries and contents of the upper triangular space.

The upper triangular space is located in the scapular region, defined by the teres minor superiorly, teres major inferiorly, and the long head of triceps brachii laterally. It houses the circumflex scapular vessels.

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What structures are found within the lower triangular interval?

The lower triangular interval is found in the scapular region, bordered by the long head of triceps brachii medially, humerus shaft laterally, and teres major muscle superiorly. It contains important structures like the radial nerve and the profunda brachii artery.

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Study Notes

Axilla and Brachial Plexus

  • The axilla is the gateway to the upper limb, transitioning between the neck and arm.
  • It's pyramidal in shape, with four walls, an inlet (apex), and a base.
  • The axillary inlet (apex) connects superiorly to the neck.
  • Its boundaries include the clavicle, scapula, and first rib.
  • The floor (base) is formed by the skin of the armpit.
  • The axilla contains the brachial plexus, axillary artery, axillary vein, axillary lymph nodes, and the tail of the breast in females.

Brachial Plexus

  • Formed by the anterior rami of C5, C6, C7, C8, and most of T1.
  • The brachial plexus has five stages:
    • Roots: The ventral rami of the spinal nerves.
    • Trunks: Three trunks (superior, middle, and inferior) are formed by the union of the roots.
    • Divisions: Each trunk divides into anterior and posterior divisions.
    • Cords: The divisions combine to form three cords (lateral, medial, and posterior) within the axilla.
    • Terminal branches: These nerves ultimately branch off from the cords and supply the muscles and sensory areas of the upper limb.

Axillary Artery

  • The main blood supply to the upper limb.
  • Begins at the lateral border of the first rib, a continuation of the subclavian artery.
  • It terminates at the lower border of the teres major muscle, becoming the brachial artery.
  • It has branches: anterior and posterior circumflex humeral arteries.

Axillary Nerve

  • Originates from the posterior cord of the brachial plexus.
  • Exits the axilla through the quadrangular space, entering the posterior scapular region.
  • Related to the posterior circumflex humeral vessels and the posterior surface of the surgical neck of the humerus.
  • Innervates the deltoid and teres minor muscles.

Pectoral Region

  • Includes three major muscles: Pectoralis major, Pectoralis minor, and Subclavius.
  • Pectoralis major has clavicular, sternocostal, and abdominal heads.
  • Pectoralis minor originates on the ribs and inserts on the coracoid process.
  • Subclavius is a smaller muscle below the clavicle that stabilizes it.

Serratus Anterior

  • A muscle with its origin on the upper ribs.
  • It inserts on the medial anterior border of the scapula.
  • Its paralysis causes winging of the scapula.

Scapular Region Muscles

  • Supraspinatus, Infraspinatus, Teres minor, Teres major, and Subscapularis.

Spaces of the Scapular Region

  • Posterior quadrangular space, bordered by teres minor, teres major, humerus, and the long head of the triceps brachii.
  • Upper triangular space, superiorly teres minor, inferiorly teres major, laterally long head of triceps brachii.
  • Lower triangular space, bordered by long head of triceps brachii, shaft of humerus, teres major.
  • These spaces contain nerves and vessels related to the shoulder.

Back Muscles

  • Trapezius: This large superficial back muscle affects scapular movement.
  • Levator scapulae; The specific function of the levator scapulae muscle has to do with the upward and downward motion of the scapula.
  • Rhomboid major and minor: These muscles are located deep to the Trapezius and help in the retraction of the scapulae.
  • Latissimus dorsi: This large, broad, flat muscle extends and adducts the arm across the chest.

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Axilla & Brachial Plexus PDF - Gulf Medical University

Description

Explore the intricate anatomy of the axilla and the brachial plexus in this quiz. Learn about the structures that connect the neck to the upper limb, including their boundaries and functions. This quiz covers essential concepts related to the anatomy vital for understanding the upper extremity.

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