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Questions and Answers
Which nerve is responsible for innervating the serratus anterior muscle?
What condition is caused by damage to the C5-C6 nerve roots?
Injury to which part of the brachial plexus can lead to sensory loss and motor deficits in the upper limb?
Which nerve damage results in a condition referred to as 'clawhand'?
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What is the result of damage to the radial nerve?
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Which trunks are formed from the spinal nerve roots C5, C6, C7, C8, and T1?
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Which nerve is primarily responsible for innervating the serratus anterior muscle?
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From which level does the dorsalscapular nerve arise?
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Which nerve is a continuation from the lateral cord and innervates the pectoralis major muscle?
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What distinguishes the supraclavicular part of the brachial plexus from the infraclavicular part?
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Which cord contributes to the formation of the median nerve?
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Which nerve roots are associated with the ulnar nerve?
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What is the clinical significance of injuries to the brachial plexus?
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Which spinal nerve roots contribute to the formation of the brachial plexus?
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What structures are enclosed by the axillary sheath?
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Which group of axillary lymph nodes primarily drains lymph from the upper limb?
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Which artery is considered the thickest branch of the axillary artery?
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What is the clinical significance of injuries to the brachial plexus?
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Which vein drains into the axillary vein after piercing the clavipectoral fascia?
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What structure primarily receives lymph from the umbilicus?
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What does the anterior ramus of the spinal nerve divide into?
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What is the apex of the axillary fossa positioned relative to the base?
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Which muscle is part of the anterior wall of the axillary fossa?
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Which of the following is NOT a content of the axillary fossa?
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The axillary artery is divided into how many parts based on its position relative to the pectoralis minor muscle?
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Which structure is located in the medial wall of the axillary fossa?
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What type of connective tissue is found at the apex of the axillary fossa?
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Which artery is NOT a branch of the 3rd part of the axillary artery?
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What forms the base of the axillary fossa?
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Which condition is characterized by wrist drop due to nerve damage?
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What is the primary effect of damage to the long thoracic nerve?
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What is a common result of injury to the inferior trunk of the brachial plexus?
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What type of paralysis occurs with damage to the superior trunk of the brachial plexus?
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Which muscle is affected in a patient with a winged scapula due to nerve damage?
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Which artery is considered the first part of the axillary artery?
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What structure does the cephalic vein pierce to drain into the axillary vein?
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Which group of axillary lymph nodes primarily drains the anterior part of the upper limb?
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Which artery is known as the thickest branch of the axillary artery?
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From which spinal nerves is the brachial plexus formed?
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Which of the following is NOT a function of the axillary sheath?
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Which group of axillary lymph nodes contains the largest number?
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Which group of axillary lymph nodes assists in draining lymph from the upper extremity?
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What is the primary function of the long thoracic nerve?
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Which component of the brachial plexus does the musculocutaneous nerve arise from?
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Which nerve is directly formed from the roots of the brachial plexus and specifically innervates serratus anterior?
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Where is the supraclavicular part of the brachial plexus located?
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Which spinal nerve roots contribute to the formation of the dorsal scapular nerve?
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Which trunk of the brachial plexus is formed by the combination of C7 spinal nerve roots?
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What is the role of the suprascapular nerve within the brachial plexus?
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Which nerve originates from the medial cord and contributes to innervating the pectoralis muscles?
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Study Notes
Brachial Plexus and Upper Limb Nerves
- The brachial plexus is a network of nerves extending from the neck into the axilla, innervating the upper limb.
- It's formed by the union of anterior rami of spinal nerves C5 to T1.
- The brachial plexus is responsible for skin sensation and movement of the upper limb.
Brachial Plexus Formation
- The brachial plexus undergoes formation through a series of steps:
- Roots: C5, C6, C7, C8, and T1
- Trunks: Superior, middle, and inferior trunks formed by the combination of roots.
- Divisions: Each trunk splits into anterior and posterior divisions.
- Cords: The divisions recombine to form three cords - lateral, medial, and posterior cords - based on their position relative to the axillary artery.
Nerves Originating From the Brachial Plexus
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Nerves originating from the roots:
- Dorsal scapular nerve: Innervates rhomboids and levator scapulae muscles.
- Long thoracic nerve: Innervates serratus anterior muscle.
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Nerves originating from the trunks:
- Nerve to subclavius: Innervates the subclavius muscle
- Suprascapular nerve (C5-6): Innervates supraspinatus and infraspinatus muscles.
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Nerves originating from the lateral cord:
- Lateral pectoral nerve: Innervates pectoralis major muscle.
- Musculocutaneous nerve: Innervates biceps brachii, brachialis, and coracobrachialis muscles, providing sensation to the lateral forearm skin.
- Lateral root of the median nerve: Contributes to the formation of the median nerve.
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Nerves originating from the medial cord
- Medial root of the median nerve: Contributes to the formation of the median nerve
- Medial pectoral nerve: Innervates pectoralis major and minor muscles.
- Medial cutaneous nerve of arm: Provides sensation to the medial aspect of the arm.
- Medial cutaneous nerve of forearm: Provides sensation to the medial aspect of the forearm.
- Ulnar Nerve: Innervates flexor carpi ulnaris, flexor digitorum profundus (medial half), and intrinsic hand muscles (except thenar muscles).
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Nerves originating from the posterior cord:
- Upper subscapular nerve: Innervates the subscapularis muscle.
- Thoracodorsal nerve: Innervates the latissimus dorsi muscle.
- Lower subscapular nerve: Innervates the teres major muscle.
- Axillary nerve: Innervates the deltoid and teres minor muscles, providing sensation to the lateral shoulder skin.
- Radial nerve: Innervates the triceps brachii, anconeus, brachioradialis, extensors of the wrist and fingers, providing sensation to the posterior and lateral aspect of the arm and forearm
Brachial Plexus Injuries
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Erb-Duchenne paralysis: (C5-C6) Damage to the superior trunk, leading to a "waiter's tip" deformity, characterized by adducted shoulder, internally rotated arm, and extended elbow.
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Klumpke’s paralysis: (C8-T1) Damage to the inferior trunk, resulting in "claw hand" -- inability to extend the fingers, often accompanied by Horner’s syndrome.
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Winged scapula: Damage to the long thoracic nerve, resulting in weakness and inability to shrug the shoulder due to weakness of the serratus anterior muscle.
Axilla and Axillary Artery
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The axilla (armpit) houses the infraclavicular part of the brachial plexus, axillary artery, axillary vein, and lymph nodes.
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The axillary artery is the continuation of subclavian artery and transitions into the brachial artery after the teres minor muscle.
- It is divided into three parts:
- The first part: Supra-scapular artery, thoraco-acromial artery.
- The second part: Lateral thoracic artery.
- The third part: Anterior circumflex humeral artery, posterior circumflex humeral artery, subscapular artery (largest branch).
- It is divided into three parts:
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The axillary vein is the continuation of the basilic vein and transitions into the subclavian vein after the first rib.
- It is joined by the cephalic vein.
- The cephalic vein courses deep from the deltopectoral triangle, pierces the clavipectoral fascia.
Axillary Lymph Nodes
- Anterior (pectoral): 4-5 lymph nodes.
- Posterior (subscapular): 6-7 lymph nodes.
- Lateral: 4-6 lymph nodes.
- Central: 3-4 lymph nodes.
- Apical: 6-12 lymph nodes.
- Drainage: anterior, posterior, and lateral lymph nodes drain into the central group, which then drain into the apical group, finally draining into the subclavian trunk.
- Lymph drainage: Axillary lymph nodes receive lymph from the upper limb, breast, and abdominal wall up to the umbilicus.
Axillary Sheath
- The axillary sheath is a part of the deep cervical fascia, enclosing the axillary artery, vein, and infraclavicular part of the brachial plexus.
Axilla
- The axilla, also known as the armpit, is a pyramidal shaped area.
- The apex of the axilla points upwards and medially.
- The base of the axilla points laterally and downwards.
- The anterior wall of the axilla is formed by the pectoralis major muscle, pectoralis minor muscle, and clavipectoral fascia, as well as the intercostal muscles.
- The posterior wall of the axilla is formed by the subscapularis muscle, teres major muscle, and latissimus dorsi muscle.
- The medial wall of the axilla is formed by the 1st to 4th ribs and serratus anterior muscle.
- The lateral wall of the axilla is formed by the intertubercular sulcus.
- The contents of the axilla include loose connective tissue, the axillary artery, axillary vein, axillary lymph nodes, and the brachial plexus.
Axillary Artery
- The axillary artery is a continuation of the subclavian artery.
- The axillary artery has 3 parts:
- 1st part: Has one branch, the supreme (highest) thoracic artery.
- 2nd part: Has two branches: the thoracoacromial artery and lateral thoracic artery.
- 3rd part Has three branches: subscapular artery, anterior humeral circumflex artery, and posterior humeral circumflex artery.
- The subscapular artery is the thickest branch of the axillary artery and has two branches: thoracodorsal artery and circumflex scapular artery.
Axilliary Vein
- The axillary vein is a continuation of the brachial vein.
- The cephalic vein drains into the axillary vein.
- The cephalic vein pierces the clavipectoral fascia.
- The structures that pierce the clavipectoral fascia are the cephalic vein, thoracoacromial artery, lymph vessels, and the lateral pectoral nerve.
Axillary Lymph Nodes
- The axillary lymph nodes are divided into five groups:
- Anterior group (pectoral): 4-5 nodes
- Posterior group (subscapular): 6-7 nodes
- Lateral group: 4-6 nodes
- Central group: 3-4 nodes
- Apical group: 6-12 nodes
- The axillary lymph nodes receive lymph from the upper extremity.
Axillary Sheath
- The axillary sheath is part of the deep cervical fascia.
- The axillary sheath encloses the axillary artery, axillary vein, and the brachial plexus (infraclavicular part).
Brachial Plexus
- The brachial plexus is a network of nerves extending from the neck into the axilla.
- The brachial plexus innervates the structures in the upper limb.
- The brachial plexus is formed by the union of the anterior rami of spinal nerves C5 to T1.
Nerves Formed by the Brachial Plexus
- Some nerves are formed by the combination of branches from anterior rami of different spinal nerves.
- For example, the radial nerve is formed by C5, C6, C7, and C8.
- Some nerves are formed by branches from just one segment.
- For example, the dorsal scapular nerve is formed by C5.
- Some nerves arise directly at the roots level of the brachial plexus, such as the dorsal scapular nerve.
- Some nerves arise from the trunk level, such as the suprascapular nerve.
- Some nerves arise from the cords' level, such as the lateral pectoral nerve.
Nerves From Roots
- Dorsal Scapular Nerve: Innervates the rhomboids and levator scapulae muscles.
- Long Thoracic Nerve: Innervates the serratus anterior muscle.
Nerves From Trunks
- Nerve to Subclavius (C5-6)
- Suprascapular Nerve (C5-6)
Nerves From Lateral Cord
- Lateral Pectoral Nerve: Innervates the pectoralis major muscle.
- Musculocutaneous Nerve: Innervates the muscles in the anterior compartment of the arm.
- Lateral Root of Median Nerve: Joins the medial root of the median nerve to form the median nerve.
Nerves From Medial Cord
- Medial Root of Median Nerve: Joins the lateral root of the median nerve to form the median nerve.
- Medial Pectoral Nerve: Innervates the pectoralis minor muscle.
- Medial Cutaneous Nerve of Arm: Provides sensory input to the medial aspect of the arm.
- Medial Cutaneous Nerve of Forearm: Provides sensory input to the medial aspect of the forearm.
- Ulnar Nerve: Innervates the muscles in the medial compartment of the forearm and intrinsic muscles of the hand.
Nerves From Posterior Cord
- Subscapular Nerves: Innervate the subscapularis and teres major muscles.
- Thoracodorsal Nerve: Innervates the latissimus dorsi muscle.
- Axillary Nerve (C5-6): Innervates the deltoid and teres minor muscles.
- Radial Nerve (C5-T1): Innervates the muscles in the posterior compartment of the arm and forearm.
Common Brachial Plexus Injuries
- Erb-Duchenne Paralysis: Damage to the superior trunk of the brachial plexus, commonly affecting nerves C5 and C6.
- Klumpke's Paralysis: Damage to the inferior trunk of the brachial plexus, commonly affecting nerves C8 and T1.
- Winged Scapula: Occurs when the long thoracic nerve is damaged. This results in weakness of the serratus anterior muscle, causing the scapula to protrude.
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Description
Test your knowledge on the brachial plexus and the innervation of the upper limb. This quiz covers the formation of the brachial plexus, including its roots, trunks, divisions, and originating nerves. Perfect for students in anatomy or neurosciences.
