Anatomy (Upper Limb)

Case The cord of a plexus is positioned lateral to the second part of the axillary artery. Question What roots are the origin of this structure?

Correct answer: C5 to C7 Explanation The structure is the lateral cord of the brachial plexus, which originates from C5 to C7. Small segmental branches of the brachial plexus progress from C5 to C8 to the muscles of the neck. The posterior cord of the brachial plexus originates from C5 to T1. The medial cord of the brachial plexus originates from C8 and T1.

Case A compartment of the arm is innervated by the radial nerve. Question What muscle is contained in this compartment?

Correct answer: Triceps brachii Explanation The structure is the posterior compartment, which contains the triceps brachii. The biceps brachii, brachialis, and coracobrachialis are contained in the anterior compartment.

What nerve bundle is found deep within the pyramid-shaped axilla?

Correct answer: Brachial plexus Explanation The brachial plexus is one of the major plexuses that enters the axillary inlet at the apex of the pyramid-shaped structure. It supplies nerves to the upper extremity. The cervical, coccygeal, and celiac plexuses are located elsewhere. The brachial plexus is formed by thoracic and cervical nerve roots.

You are caring for a patient who sustained an injury to the insertion of the biceps brachii muscle. Based on this data, the injury is closest to which structure?

Correct answer: Elbow Explanation The biceps brachii muscle is the anterior muscle of the upper arm. An insertion refers to the end of the muscle that is attached to the movable bone. The radius is the insertion of the biceps brachii. The closest structure to the radius is the elbow. The clavicle, humerus, and shoulder are distal to the insertion of the biceps brachii muscle.

Case A short artery originating from the axillary artery divides into the pectoral, deltoid, clavicular and acromial branches. Question How many branches arise from the part of the axillary artery that this structure originates from?

Correct answer:2 Explanation The structure is the thoracoacromial artery, which arises from the second part of the axillary artery. The second part of the axillary artery gives rise to two branches. The first part of the axillary artery gives rise to one branch. The third part of the axillary artery gives rise to three branches. In total, six branches arise from the axillary artery.

Case The largest branch of the axillary artery supplies the posterior wall of the axilla and posterior scapular region. Question How many branches arise from the part of the axillary artery that this structure originates from?

Correct answer:3 Explanation The structure is the subscapular artery, which arises from the third part of the axillary artery. The third part of the axillary artery gives rise to three branches. The first part of the axillary artery gives rise to one branch. The second part of the axillary artery gives rise to two branches. In total, six branches arise from the axillary artery.

When positioning a patient, what intervention helps prevent problems (contractures) with the axilla?

Correct answer:Abduction Explanation When positioning a patient, there should be abduction of the axilla with a 10-15° forward flexion along with an external rotation. Positioning the patient in this manner will help to prevent contractures. This can be accomplished by suspending the arm from an IV pole or bedside table. The axilla would not be adducted, internally rotated, or neutrally rotated. These positions could cause contractures.

Case A muscle within the superficial layer of the posterior forearm is innervated by the radial nerve. Question What is a role of this muscle?

Correct answer:Abductor of the wrist Explanation This muscle is the extensor carpi radialis longus, an abductor of the wrist. The supinator is within the deep layer of the posterior forearm and supinates the forearm and hand. The abductor pollicis longus is within the deep layer of the posterior forearm and is an abductor of the thumb. The extensor indicis is within the deep layer of the posterior forearm and is an extensor of the index finger. The listed muscles are muscles of the posterior forearm. Functions of muscles in the posterior forearm include extension of the wrist and supination of the hand. Muscles of the anterior forearm allow for flexion of the wrist and pronation of the hand.

Case A bone with an S-shaped contour serves as an attachment between the trunk and the upper limb. Question Where does this attachment articulate laterally?

Correct answer:Acromial process of the scapula Explanation The bony attachment is the clavicle, which articulates laterally with the acromion of the scapula. The head of the humerus articulates with the glenoid cavity of the scapula. The scapula articulates with the head of the humerus. The clavicle articulates medially with the manubrium of the sternum and the first costal cartilage.

Case The most medial muscle in the superficial layer of the anterior forearm is innervated by the ulnar nerve. Question What is a function of this muscle?

Correct answer:Adducts the wrist Explanation This muscle is the flexor carpi ulnaris, a powerful flexor and adductor of the wrist. Abduction of the wrist is performed by the flexor carpi radialis. The palmaris longus opposes shredding forces on the skin. The pronator teres is the rotator of the radius over the ulna. The four listed muscles are muscles of the anterior forearm, which allows for flexion of the wrist and pronation of the hand. Functions of muscles in the posterior forearm include extension of the wrist and supination of the hand.

Case The transition of the neck and the arm is formed by the clavicle, scapula, upper thoracic wall, and humerus with related muscles. Question Which wall of this structure is formed by the pectoralis major, pectoralis minor, and subclavius muscles?

Correct answer:Anterior Explanation The anterior wall of the axilla is formed by the pectoralis major, pectoralis minor, and subclavius muscles. The lateral wall is formed by the intertubercular sulcus of the humerus. The medial wall is formed by the upper thoracic wall and the serratus anterior muscle. The posterior wall is formed by the scapula, subscapularis, latissimus dorsi, teres major, and the triceps brachii.

Case A muscle in the deep layer of the anterior forearm originates from the anterior and medial surfaces of the ulna. Question What is another point of origin for this muscle?

Correct answer:Anterior surface of the interosseous membrane Explanation The muscle is the flexor digitorum profundus, which originates from the anterior and medial surfaces of the ulna and the anterior surface of the interosseous membrane. This muscle inserts on the distal phalanx of digits 2, 3, 4, and 5. The flexor pollicis longus originates from the anterior surface of the radius. The pronator quadratus originates from a linear ridge located on the anterior surface of the lower end of the ulna.

Case An artery passes through the anterior compartment of the arm and terminates distal to the elbow joint. Question This structure continues from what artery?

Correct answer:Axillary Explanation The structure is the brachial artery, a continuation of the axillary artery. The brachial artery divides into the radial and ulnar arteries.

A muscle in the superficial layer of the anterior forearm originates from the medial epicondyle of the humerus and passes to the lateral side of the anterior surface of the wrist. Where does it inser

Correct answer:Bases of metacarpals II and III Explanation The muscle is the flexor carpi radialis, which inserts on the bases of metacarpals II and III. The palmaris longus inserts on the flexor retinaculum. The pronator teres inserts on the lateral surface of the radius. The flexor carpi ulnaris inserts on the pisiform bone of the wrist.

A patient presents with weakness in one of the upper limbs. The patient states that they cannot flex their arm at the elbow. Based solely on the information given, what muscle is most likely affected?

Correct answer:Biceps brachii Explanation The biceps brachii is the primary muscle for flexion at the elbow. The triceps brachii is the primary muscle for extension at the elbow. The biceps femoris is the primary muscle for flexion at the knee joint. The trapezius is the primary muscle for retraction, rotation, elevation, and depression of the scapula. The latissimus dorsi is the muscle involved in adduction; it internally rotates and extends the humerus.

What muscle performs a flexion action despite its location on the posterior forearm?

Correct answer:Brachioradialis Explanation Brachioradialis is found on the posterior aspect of the forearm and is an accessory flexor of the elbow. It acts as a flexor despite its location because it lies anterior to the elbow joint. Anconeus is located medial to the superficial extensors. Its main action is abduction of the ulna during pronation, but it also acts as an accessory extensor. Pronator teres is located in the superficial anterior forearm; it rotates the radius over the ulna during pronation. Supinator is found in the deep layer of the posterior forearm; it turns the hand palm up (supination).

Case A muscle in the anterior compartment of the arm enables flexion of the glenohumeral joint. Question Where does the short head of this muscle originate?

Correct answer:Coracoid process Explanation The short head of the biceps brachii originates from the coracoid process. The long head of the triceps brachii originates from the infraglenoid tubercle of the scapula. The brachialis originates from parts of the intermuscular septum on the medial side. The long head of the biceps brachii originates from the supraglenoid tubercle of the scapula.

Case A group of muscles is associated with flexion of the wrist joint. Question Which muscle of this group is also responsible for abduction of the wrist?

Correct answer:Flexor carpi radialis Explanation The flexor carpi radialis facilitates abduction of the wrist. The flexor carpi ulnaris, palmaris longus, flexor carpi radialis, flexor digitorum superficialis, and flexor digitorum profundus are all associated with the flexion of the wrist joint.

A group of muscles is associated with flexion of the wrist joint. Which muscle of the group is responsible for adduction?

Correct answer:Flexor carpi ulnaris Explanation The flexor carpi ulnaris facilitates adduction of the wrist. The flexor carpi ulnaris, palmaris longus, flexor carpi radialis, flexor digitorum superficialis, and flexor digitorum profundus are all associated with the flexion of the wrist joint.

A muscle in the intermediate layer of the forearm splits into two parts near the proximal phalanx of each finger. What other muscle's tendon does this structure pass around posteriorly?

Correct answer:Flexor digitorum profundus Explanation The flexor digitorum superficialis splits into two parts and passes around the tendons of the flexor digitorum profundus. The flexor pollicis longus and pronator quadratus are located in the deep layer of the forearm but are not involved with pattern of insertion.

Case The lateral angle of a large, flat, triangular bone contains a glenoid fossa. Question What does this structure articulate with?

Correct answer:Head of the humerus Explanation The bone is the scapula. The lateral angle of the scapula articulates with the head of the humerus. The clavicle articulates laterally with the acromion of the scapula and medially with the manubrium of the sternum and the first costal cartilage. The head of the humerus articulates with the glenoid cavity of the scapula.

What muscle elevates the shoulder and rotates the glenoid cavity downward whenever the scapula is in a fixed position?

Correct answer:Levator scapulae Explanation The muscle that elevates the shoulder is the levator scapulae. The action of the teres major is to extend the arm at the shoulder and assist in adduction and medial rotation of the arm at the joint. The teres minor helps to laterally rotate and extend the arm at the shoulder joint. The serratus anterior abducts and rotates the scapula upward while elevating the ribs when the scapula is stabilized.

Case A ball-and-socket joint with a large round humeral head and a shallow glenoid cavity is mobile and requires stabilization. Question What component acts as a dynamic stabilizer?

Correct answer:Rotator cuff Explanation The joint is the glenohumeral joint. Dynamic stabilization of this joint is facilitated by the rotator cuff. Static stabilization is facilitated by the capsule, glenohumeral ligaments, and labrum complex.

Case The cord of a plexus is positioned lateral to the second part of the axillary artery. Question What nerve originates from this cord?

Correct answer: Musculocutaneous nerve Explanation The structure is the lateral cord of the brachial plexus. The musculocutaneous nerve originates from this cord. The ulnar nerve originates from the medial cord of the brachial plexus. The axillary and radial nerves originate from the posterior cord of the brachial plexus.

Case An artery originating from the axillary artery supplies the glenohumeral joint and the head of the humerus. Question How many branches arise from the part of the axillary artery from which this structure originates?

Correct answer:3 Explanation The structure is the anterior circumflex humeral artery, which arises from the third part of the axillary artery. The third part of the axillary artery gives rise to three branches. The first part of the axillary artery gives rise to one branch. The second part of the axillary artery gives rise to two branches. In total, six branches arise from the axillary artery.

Case An artery passes through the anterior compartment of the arm and terminates distal to the elbow joint. Question What vessel is medial to this artery?

Correct answer:Basilic vein Explanation The structure is the brachial artery. The basilic vein has a position medial to the brachial artery before becoming the axillary vein. The basilic vein is formed by the radial and ulnar veins.

Case A musculotendinous collar surrounds the anterior, superior, and posterior aspects of the glenohumeral joint. Question Besides the tendons of the rotator cuff, what composes this structure?

Correct answer:Capsule Explanation The joint capsule blends with the tendons of the rotator cuff to form this musculotendinous collar. Glenohumeral ligaments are involved with other aspects of joint stability. The subscapularis and teres minor are muscles of the rotator cuff, not parts of the musculotendinous collar.

Case The roots and trunks of a plexus enter the posterior triangle of the neck between the anterior scalene and middle scalene. Question What forms the middle trunk of this plexus?

Correct answer:Continuation of the C7 root Explanation The structure is the brachial plexus. The middle trunk of the brachial plexus is formed by the continuation of the C7 root. The brachial plexus is formed by the anterior rami of C5 to C8 and most of the anterior ramus of T1. The superior trunk of the brachial plexus is formed by the union of C5 and C6 roots. The inferior trunk arises from the union of the C8 and T1 roots.

Case A patient diagnosed as having rotator cuff syndrome demonstrates impingement involving the supraspinatus muscle. Question What anatomical feature's failure typically causes this injury?

Correct answer:Subacromial bursa Explanation Failure of the subacromial bursa to protect the muscles of the rotator cuff is a typical cause of impingement involving the supraspinatus. The biceps brachii, joint capsule, and musculotendinous collar are sources of stability for the glenohumeral joint, but they are not typical causes of impingement involving the supraspinatus.

An osteofibrous passageway leads from the wrist to the hand. What lies in the distal row of the osseous plane of this structure?

Correct answer: Capitate Explanation The capitate, hamate, trapezium, and trapezoid are located in the distal row of the osseous plane of the carpal tunnel. The scaphoid, lunate, triquetrum, and pisiform are located in the proximal row of the osseous plane of the carpal tunnel.

Case The transition of the neck and the arm is formed by the clavicle, scapula, upper thoracic wall, and humerus with related muscles. Question This structure contains the proximal portion of what other structure?

Correct answer: Coracobrachialis Explanation The axilla contains many structures, including the coracobrachialis. The levator scapulae, rhomboid minor, and trapezius are muscles associated with the shoulder.

An osteofibrous passageway leads from the wrist to the hand. What forms the anterior wall of this structure?

Correct answer: Flexor retinaculum Explanation The flexor retinaculum forms the anterior wall of the carpal tunnel. Contained within the carpal tunnel are the flexor digitorum superficialis tendons, flexor digitorum profundus tendons, flexor pollicis tendon, and the median nerve. The tendons are surrounded by synovial sheaths.

An osteofibrous passageway leads from the wrist to the hand. What forms the medial arch of the base of this structure

Correct answer: Hamate bone Explanation The base of the carpal arch is formed medially by the pisiform bone and hamate bone. The base of the carpal arch is formed laterally by the tubercle of the scaphoid and trapezial ridge. The flexor retinaculum forms a bridge between the medial and lateral sides of the base of the carpal arch.

Case The transition of the neck and the arm is formed by the clavicle, scapula, upper thoracic wall, and humerus with related muscles. Question What leaves this structure through the fascia inferior to the pectoralis minor muscle?

Correct answer: Lateral thoracic artery Explanation The lateral thoracic artery exits the axilla through the fascia inferior to the pectoralis minor muscle. The axillary vein enters the neck and continues to become the subclavian vein. The intercostobrachial nerve passes through the axilla directly through the medial wall. The medial pectoral nerve exits directly through the pectoralis minor muscle.

Which of the following move in concert to produce flexion, one of the movements of the shoulder joint?

Correct answer: Pectoralis major Anterior deltoid Biceps brachii Explanation Pectoralis major, anterior deltoid, and biceps brachii are responsible for producing flexion movement of the shoulder joint. Posterior deltoid is responsible to produce extension movement of the shoulder joint.

Which of the following constitute clinically relevant content of the axilla region?

Correct answer: Peripheral spinal nerves of the upper limb Cephalic and basilic veins Biceps brachii and coracobrachialis muscles Explanation Peripheral spinal nerves of the upper limb (brachial plexus) are one of the contents of the Axilla region. Cephalic and basilic veins are the 2 main sub-veins of the main axillary vein draining the upper limb. Biceps brachii and coracobrachialis are the muscle tendons of the axilla region. Tendons of flexor pollicis longus are the contents of the carpal tunnel.

Case An osteofibrous passageway leads from the wrist to the hand. Question What lies in the proximal row of the osseous plane of this structure?

Correct answer: Scaphoid Explanation The scaphoid, lunate, triquetrum, and pisiform are located in the proximal row of the osseous plane of the carpal tunnel. The capitate, hamate, trapezium, and trapezoid are located in the distal row of the osseous plane of the carpal tunnel.

Case An osteofibrous passageway leads from the wrist to the hand. Question What enables free movement of tendons within this structure?

Correct answer: Synovial sheath Explanation Synovial sheaths surrounding the tendons in the carpal tunnel facilitate free movement. The tunnel is formed by the carpal arch, osseous plane, and flexor retinaculum.

Case The cord of a plexus is positioned posterior to the second part of the axillary artery. Question What nerve originates from this cord?

Correct answer: Thoracodorsal nerve Explanation The structure is the posterior cord of the brachial plexus. The thoracodorsal nerve originates from this cord. The dorsal scapular nerve originates from the C5 root of the brachial plexus. The long thoracic nerve originates from the anterior rami of C5 to C7. The musculocutaneous nerve originates from the lateral cord of the brachial plexus.

Case An osteofibrous passageway leads from the wrist to the hand. Question What lies in the distal row of the osseous plane of this structure?

Correct answer: Trapezium Explanation The capitate, hamate, trapezium, and trapezoid are located in the distal row of the osseous plane of the carpal tunnel. The scaphoid, lunate, triquetrum, and pisiform are located in the proximal row of the osseous plane of the carpal tunnel.

Case The roots and trunks of a plexus enter the posterior triangle of the neck between the anterior scalene and middle scalene. Question What forms the superior trunk of this plexus

Correct answer: Union of C5 and C6 roots Explanation The structure is the brachial plexus. The superior trunk of the brachial plexus is formed by the union of C5 and C6 roots. The brachial plexus is formed by the anterior rami of C5 to C8 and most of the anterior ramus of T1. The middle trunk arises from a continuation of the C7 root. The inferior trunk arises from the union of the C8 and T1 roots.

Case A blood vessel passes through the axilla to the inferior margin of the teres major muscle. Question What is formed by this continuation?

Correct answer: Brachial artery Explanation The axillary artery passes through the axilla and becomes the brachial artery at the inferior margin of the teres major muscle. The axillary artery begins at the lateral margin of the first rib and becomes the subclavian artery at the neck. The thoracodorsal artery supplies the latissimus dorsi.

There are muscles of the pectoral girdle located anteriorly and posteriorly in the pectoral area. Which of these muscles is located on the posterior aspect of the thorax?

Correct answer: Rhomboid minor Explanation The rhomboid minor muscle connects the spine to the medial border of the scapula in the posterior thorax. It stabilizes the scapula during pectoral girdle movement. The subclavius, pectoralis minor, and serratus anterior are all located in the anterior part of the thorax.

Case The transition of the neck and the arm is formed by the clavicle, scapula, upper thoracic wall, and humerus with related muscles. Question What blood vessel supplies this structure?

Correct answer: Subclavian artery Explanation The subclavian artery enters the axilla, becomes the axillary artery, and supplies this structure. The brachial artery supplies the shoulder. The carotid arteries supply the neck, face, and brain. The internal thoracic artery supplies the breasts and anterior wall of the chest.

Case An artery supplies the upper regions of the medial and anterior axillary walls. Question How many branches arise from the part of the axillary artery from which this structure originates?

Correct answer:1 Explanation The structure is the superior thoracic artery, which originates from the first part of the axillary artery. The first part of the axillary artery gives rise to one branch. The second part of the axillary artery gives rise to two branches. The third part of the axillary artery gives rise to three branches. In total, six branches arise from the axillary artery.

Case An artery originating from the axillary artery has branches from the inferior margin of the pectoralis major muscle that contribute to the vascular supply of the breast in women. Question How many branches arise from the part of the axillary artery from which this structure originates?

Correct answer:2 Explanation The structure is the lateral thoracic artery, which arises from the second part of the axillary artery. The second part of the axillary artery gives rise to two branches. The first part of the axillary artery gives rise to one branch. The third part of the axillary artery gives rise to three branches. In total, six branches arise from the axillary artery.

A synovial joint links the distal end of the radius and the articular disc of the ulna to the lunate, scaphoid, and triquetrum. How many axes does this joint facilitate movement around?

Correct answer:2 Explanation The wrist joint facilitates movement around 2 axes so that the hand can be abducted, adducted, flexed and extended.

Case An artery originating from the axillary artery passes through the quadrangular space of the teres major, teres minor, triceps brachii, and humerus. Question How many branches arise from the part of the axillary artery that this structure originates from?

Correct answer:3 Explanation The structure is the posterior circumflex humeral artery, which arises from the third part of the axillary artery. The third part of the axillary artery gives rise to three branches. The first part of the axillary artery gives rise to one branch. The second part of the axillary artery gives rise to two branches. In total, six branches arise from the axillary artery.

Case The muscle directly lateral to the palmaris longus in the superficial layer of the anterior forearm is innervated by the median nerve. Question What is a function of this muscle?

Correct answer:Abducts the wrist Explanation This muscle is the flexor carpi radialis, a flexor and abductor of the wrist. The flexor carpi ulnaris is a flexor and adductor of the wrist. The palmaris longus opposes shredding forces on the skin. The pronator teres is the rotator of the radius over the ulna. The four listed muscles are muscles of the anterior forearm, which allows for flexion of the wrist and pronation of the hand. Functions of muscles in the posterior forearm include extension of the wrist and supination of the hand.

Case Landmarks on the proximal end of the humerus are the site of attachment for rotator cuff muscles. Question Relative to the greater of these landmarks, where is the lesser landmark?

Correct answer:Anterior Explanation The landmark is the lesser tubercle, which is positioned anteriorly with respect to the greater tubercle. The greater tubercle is positioned laterally with respect to the head of the humerus and has superior and posterior surfaces containing facets for tendon attachment.

Case A 16-year-old boy reports right shoulder pain and the inability to move his right shoulder after a hit during a football game. He was treated in the emergency department for an anterior right shoulder dislocation. Upon follow-up with an orthopedic surgeon several weeks after the injury, he reported numbness of the outer part of his right arm and weakness of his deltoid muscle with the inability to perform overhead activities. Question What nerve has been affected, causing his current symptoms?

Correct answer:Axillary nerve Explanation Anterior shoulder dislocations are most common in young males and tend to occur after impact injuries, such as in contact sports. The shoulder most commonly dislocates anteriorly. The axillary nerve wraps around the humerus, deep to the deltoid muscles. The axillary nerve innervates the teres minor (one of the muscles of the rotator cuff) and deltoid muscle. When the humerus moves out of the socket to a forward position, the axillary nerve is pulled due to the position of the arm; this can cause symptoms of numbness and weakness at the area of innervation of the nerve. The musculocutaneous nerve innervates the coracobrachialis muscles and the skin of the anterior side of the arm. The median nerve traverses into the carpal tunnel. The radial nerve innervates the brachioradialis muscles and the forearm extensors. The radial nerve is most commonly damaged by humeral shaft fractures.

Case The cord of a plexus is positioned posterior to the second part of the axillary artery. Question What roots are the origin of this structure?

Correct answer:C5 to T1 Explanation The structure is the posterior cord of the brachial plexus, which originates from C5 to T1. The lateral cord of the brachial plexus originates from C5 to C7. Small segmental branches of the brachial plexus progress from C5 to C8 to the muscles of the neck. The medial cord of the brachial plexus originates from C8 and T1.

Case An otherwise healthy 35-year-old man presents to his primary care provider with a complaint of severe pain in his right chest wall that started acutely following a workout session where he was doing multiple repetitions of various upper body exercises. On physical exam, he is tender to palpation over his right upper chest, particularly between his sternum and mid-axillary line. There is no evidence of ecchymosis or crepitus. He has full range of motion, although adduction and medial rotation of the humerus reproduce his pain. Upper extremity strength is 5/5 bilaterally. Radial pulses are 3+ bilaterally. Question What nerve roots are involved in the innervation of the injured muscle above?

Correct answer:C5, C6, C7, C8, T1 Explanation Pectoralis major is innervated by 2 nerves: lateral and medial pectoral nerves. In contrast, pectoralis minor is innervated only by the medial pectoral nerve. Both of these nerves have roots in the brachial plexus but have different routes to their terminal named branches. The lateral pectoral nerve has contributions from C5, C6, and C7 and eventually comes off the lateral cord. The medial pectoral nerve has contributions from C8 and T1 and comes off the medial cord. The nerve to subclavius is comprised of contributions from C5 and C6 and comes off the superior trunk. The long thoracic nerve is comprised of contributions from C5, C6, and C7 and innervates serratus anterior. The thoracodorsal nerve is comprised of contributions from C6, C7, and C8 and innervates latissimus dorsi.

Case The cord of a plexus is positioned medial to the second part of the axillary artery. Question What roots are the origin of this structure?

Correct answer:C8 and T1 Explanation The structure is the medial cord of the brachial plexus, which originates from C8 and T1. The lateral cord of the brachial plexus originates from C5 to C7. Small segmental branches of the brachial plexus progress from C5 to C8 to the muscles of the neck. The posterior cord of the brachial plexus originates from C5 to T1.

Case A hinge joint with three separate articulations has a shared synovial cavity. One of the three articulations is involved in flexion and extension of the forearm. Question What structure forms an articulation with the head of the radius to enable this movement?

Correct answer:Capitulum of the humerus Explanation The articulation of the capitulum of the humerus and the head of the radius enables flexion and extension of the forearm. Flexion and extension of the forearm are also supported by the articulation between the trochlea of the humerus and the trochlear notch of the ulna, but the head of the radius is not part of this specific articulation. Pronation and supination of the forearm are supported by the articulation between the head of the radius and the radial notch of the ulna.

Joints in the upper limb, including the wrist and digits, display actions powered by flexor muscles. Which of these joints facilitates limited gliding movements?

Correct answer:Carpometacarpal joint Explanation The carpometacarpal joints (except the thumb) facilitate limited gliding movements. The interphalangeal joints generally facilitate flexion and extension as main movements. The metacarpophalangeal joints facilitate flexion, extension, abduction, adduction, circumduction, and limited rotation. The wrist joint facilitates abduction, adduction, flexion, and extension.

Case The anterolateral projection of a bone arches over the glenohumeral joint and has a small oval facet on its distal end for articulation. Question What structure does this projection articulate with?

Correct answer:Clavicle Explanation The structure is the acromion, a projection of the spine of the scapula that articulates with the clavicle. The acromion is not connected to the humerus or thorax.

Case A nerve provides the motor innervation to all muscles in the anterior compartment of the arm. Question What muscle does this nerve penetrate to enter the arm?

Correct answer:Coracobrachialis Explanation The structure is the musculocutaneous nerve, which enters the arm by penetrating the coracobrachialis. It continues between the biceps brachii and brachialis muscles. The median nerve enters at the margin of the teres major.

A muscle in the intermediate layer of the forearm contains two heads, one of which originates from the medial epicondyle of the humerus. Where is the second origin of this head?

Correct answer:Coronoid process of the ulna Explanation The humeroulnar head of the flexor digitorum superficialis originates from the medial epicondyle of the humerus and the medial edge of the coronoid process of the ulna. The radial head of the flexor digitorum superficialis originates from the anterior oblique line of the radius. The flexor digitorum superficialis splits and inserts into the margins of the middle phalanges of digits 2, 3, 4, and 5.

Case A structure communicates superiorly with the lateral wall of the axilla. Question What does this structure communicate through inferiorly?

Correct answer:Cubital fossa Explanation The structure is the arm. Inferiorly, it communicates with the forearm through the cubital fossa, a triangular depression formed by the brachioradialis and pronator teres. The brachial artery passes through the anterior compartment. The capitulum of the humerus and the trochlear notch of the ulna are components of the elbow joint.

A 65-year-old man with a history of long-standing atherosclerotic disease slowly develops an atherosclerotic blockage of the right axillary artery below the level of the first rib but above the level of the subscapular artery. What is most likely to be true in this patient?

Correct answer:Direction of blood flow in the subscapular artery will be reversed. Explanation In this patient with long-standing atherosclerotic disease who slowly develops an atherosclerotic blockage of the right axillary artery above the level of the subscapular artery, blood flow to the limb will most likely be maintained through collateral circulation involving anastomoses around the scapula with the dorsal scapular, suprascapular, and subscapular arteries. Blood flow to the distal axillary artery through this collateral circulation entails a reversal of the normal direction of blood flow through the subscapular artery. If this patient had a slowly developing blockage of the axillary artery below the level of the subscapular artery, he would likely show signs of chronic limb ischemia, such as gangrene in the fingertips or ischemic arm pain when elevated, but the location of the blockage in this patient would allow this collateral circulation to develop. If the patient had a sudden blockage of the axillary artery at this point (e.g., sudden thrombosis or trauma), he would show signs of acute limb ischemia, such as pallor, cold, and no blood flow on Duplex ultrasound. The collateral circulation described above is only established slowly over time.

Case The part of the axillary artery anterior to the subscapularis muscle and teres major muscle has 3 branches. Question How is this part oriented in relation to the pectoralis minor?

Correct answer:Distal Explanation The structure is the third part of the axillary artery, which is distal to the pectoralis minor. The pectoralis minor crosses anteriorly to the vessel. The first part of the axillary artery is proximal to the pectoralis minor. The second part of the axillary artery is posterior to the pectoralis minor.

Case A muscle in the posterior compartment of the arm is innervated by the radial nerve. Question What movement does this structure enable?

Correct answer:Extension of the elbow Explanation The triceps brachii enables extension of the elbow. The brachialis muscle enables flexion of the elbow. The pronator teres enables pronation of the forearm. The biceps brachii enables supination of the forearm when the elbow joint is flexed.

What is a deep muscle of the posterior forearm?

Correct answer:Extensor pollicus brevis Explanation Extensor pollicus brevis is a deep muscle of the posterior forearm that extends the metacarpophalangeal and carpometacarpal joint of the thumb. Extensor digitorum, extensor carpi radialis brevis, and extensor digiti minimi are superficial muscles of the posterior forearm.

What muscle forms the medial border of the anatomical snuffbox?

Correct answer:Extensor pollicus longus Explanation Extensor pollicus longus extends all joints of the thumb and forms the medial border of the anatomical snuffbox. Abductor pollicus longus and extensor pollicus brevis make up the lateral border of the anatomical snuffbox. Flexor pollicus longus is found on the anterior aspect of the forearm and does not make a border with the anatomical snuffbox, as this structure is on the posterior aspect of the forearm.

Case A square-shaped muscle in the deep layer of the distal forearm originates from a linear ridge on the lower ulna. Question Where does it insert?

Correct answer:Flat surface of the radius Explanation The muscle is the pronator quadratus, which inserts on the anterior flat surface of the radius. The flexor pollicis longus inserts on the palmar surface of the distal phalanx after passing through the carpal tunnel. The flexor digitorum profundus inserts on the distal phalanx of digits 2, 3, 4, and 5.

Case A muscle is penetrated and innervated by the musculocutaneous nerve after passing through the axilla. Question What movement does this structure enable?

Correct answer:Flexion of the arm Explanation The coracobrachialis muscle enables flexion of the arm. The triceps brachii enables extension of the elbow. The pronator teres enables pronation of the forearm. The supinator enables supination of the forearm.

Case A muscle beneath the biceps brachii is innervated by the musculocutaneous nerve. Question What movement does this structure enable?

Correct answer:Flexion of the elbow Explanation The brachialis muscle enables flexion of the elbow. The triceps brachii enables extension of the elbow. The biceps brachii enables supination of the forearm when the elbow joint is flexed. The pronator teres enables pronation of the forearm.

Case A group of muscles in the superficial layer of the forearm enables flexion of the wrist and fingers and pronation of the hand. Question Which of the muscles in the group is most medial?

Correct answer:Flexor carpi ulnaris Explanation The flexor carpi radialis, flexor carpi ulnaris, palmaris longus, and pronator teres are the four muscles in the superficial layer of the anterior forearm. The most medial is the flexor carpi ulnaris.

Case Flexion of the four digits involves the metacarpophalangeal joints and the distal interphalangeal joints. Question What muscle facilitates this movement?

Correct answer:Flexor digitorum profundus Explanation The flexor digitorum profundus facilitates flexion of the four digits for the metacarpophalangeal and distal interphalangeal joints. The flexor carpi ulnaris facilitates adduction of the wrist. The flexor digitorum superficialis facilitates flexion of the four digits for the metacarpophalangeal and proximal interphalangeal joints. The flexor pollicis longus facilitates flexion of the thumb.

A 58-year-old man cannot actively extend his left ring finger. On exam, his ring finger is flexed at the level of the metacarpophalangeal joint and proximal interphalangeal joint. What tendon is malfunctioning?

Correct answer:Flexor digitorum superficialis Explanation Flexor digitorum superficialis is located in the intermediate layer of the anterior forearm and is responsible for flexion of the metacarpophalangeal joint and the proximal interphalangeal joint. Flexor carpi radialis flexes and abducts the wrist and has no action on the fingers. Flexor pollicus longus is a tendon that is a flexor of the thumb. Palmaris longus is an accessory flexor of the wrist and does not perform any flexion of the digits.

Flexion of the four digits involves the metacarpophalangeal joints and the proximal interphalangeal joints. What muscle facilitates this movement?

Correct answer:Flexor digitorum superficialis Explanation The flexor digitorum superficialis facilitates flexion of the four digits for the metacarpophalangeal and proximal interphalangeal joints. The flexor carpi ulnaris facilitates adduction of the wrist. The flexor digitorum profundus facilitates flexion of the four digits for the metacarpophalangeal and distal interphalangeal joints. The flexor pollicis longus facilitates flexion of the thumb.

Case A muscle overlies the anterolateral surface of the forearm, forms the lateral boundary of the cubital fossa, and is innervated by the radial nerve. Question What is a role of this muscle?

Correct answer:Flexor of the elbow Explanation This muscle is the brachioradialis, a flexor of the elbow that passes anteriorly to this joint. The extensor carpi radialis longus, extensor carpi radialis brevis, extensor carpi ulnaris are muscles of the posterior forearm that are abductors of the wrist. The anconeus is an extensor of the elbow. The extensor digitorum, extensor digiti minimi, and extensor indicis are extensors of the fingers. The listed muscles are muscles of the posterior forearm. Functions of muscles in the posterior forearm include extension of the wrist and supination of the hand. Muscles of the anterior forearm allow for flexion of the wrist and pronation of the hand.

Flexion of the thumb involves the metacarpophalangeal joint and the interphalangeal joint. What muscle facilitates this movement?

Correct answer:Flexor pollicis longus Explanation The flexor pollicis longus facilitates flexion of the thumb. The flexor carpi ulnaris facilitates adduction of the wrist. The flexor digitorum superficialis facilitates flexion of the four digits for the metacarpophalangeal and proximal interphalangeal joints. The flexor digitorum profundus facilitates flexion of the four digits for the metacarpophalangeal and distal interphalangeal joints.

Case A 26-year-old man is seen in the ED after cutting his wrist while opening a package with a knife. Upon examination, he cannot flex his thumb. Question What structure was injured?

Correct answer:Flexor pollicus longus Explanation Flexor pollicus longus is a deep muscle of the anterior forearm that crosses under the carpal tunnel and allows for flexion of the thumb. Flexor carpi radialis is a superficial anterior forearm muscle that flexes and abducts the wrist. Flexor digitorum profundus is a deep muscle of the anterior forearm that passes through the carpal tunnel, but it gives rise to four tendons of the four fingers and allows flexion at the proximal interphalangeal joint, distal interphalangeal joint, and the metacarpophalangeal joint. Flexor digitorum superficialis is an intermediate muscle of the anterior forearm that passes through the carpal tunnel and allows for flexion of the proximal interphalangeal joint and metacarpophalangeal joint of the four fingers.

Case A muscle in the superficial layer of the anterior forearm originating from the medial epicondyle of the humerus. It flexes the hand at the wrist and tenses the skin of the palm. Question Where does it insert?

Correct answer:Flexor retinaculum Explanation The muscle is the palmaris longus, which inserts on the flexor retinaculum. The flexor carpi radialis inserts on the bases of metacarpals II and III. The pronator teres inserts on the lateral surface of the radius. The flexor carpi ulnaris inserts on the pisiform bone of the wrist.

Case A bone is held firmly in position by the muscles of the rotator cuff. Question What does the head of this structure articulate with?

Correct answer:Glenoid cavity of the scapula Explanation The structure is the head of the humerus, which articulates with the glenoid cavity of the scapula. The clavicle articulates laterally with the acromion of the scapula and medially with the manubrium of the sternum and the first costal cartilage. The scapula articulates with the head of the humerus.

Case An intermuscular septum divides the arm into anterior and posterior compartments and extends to the outer sleeve of deep fascia surrounding the arm. Question From what bone does this structure extend?

Correct answer:Humerus Explanation The intermuscular septum of the arm extends from the humerus to the outer sleeve of deep fascia surrounding the arm. The acromion is located in the shoulder. The radius and ulna are located in the forearm

Case The superior border of a flat triangular bone contains a hook-like structure that projects anterolaterally. Question How is this structure positioned relative to the lateral part of the clavicle?

Correct answer:Inferior Explanation The coracoid process of the scapula is inferior to the lateral clavicle. The scapula has superior, lateral, and medial borders.

Case Landmarks on the proximal end of the humerus are separated by an intertubercular sulcus. Question In what direction does this groove continue?

Correct answer:Inferior Explanation The intertubercular sulcus separates the greater and lesser tubercles and continues inferiorly to the proximal shaft of the humerus. The lesser tubercle is positioned anteriorly with respect to the greater tubercle. The greater tubercle has superior and posterior surfaces containing facets for tendon attachment.

Case A muscle innervated by the radial nerve enables extension of the forearm at the elbow joint. Question Where does the long head of this muscle originate?

Correct answer:Infraglenoid tubercle of the scapula Explanation The long head of the triceps brachii originates from the infraglenoid tubercle of the scapula. The medial head of the triceps brachii originates on the posterior surface of the shaft of the humerus, inferior to the radial groove. The lateral head of the triceps brachii originates superior to the radial groove of the humerus.

Case A tendon passes posteriorly to the glenohumeral joint and inserts on the middle facet of the greater tubercle. Question From what muscle does this tendon arise?

Correct answer:Infraspinatus Explanation The tendon of the infraspinatus follows this pattern. The tendon of the subscapularis inserts on the lesser tubercle of the humerus. The tendon of the supraspinatus inserts onto the superior facet of the greater tubercle. The tendon of the teres minor inserts on the inferior facet of the greater tubercle of the humerus.

Case The transition of the neck and the arm is formed by the clavicle, scapula, upper thoracic wall, and humerus with related muscles. Question What directly enters through the medial wall of this structure?

Correct answer:Intercostobrachial nerve Explanation The intercostobrachial nerve passes through the axilla directly through the medial wall. The axillary vein enters the neck and continues to become the subclavian vein. The lateral thoracic artery exits the axilla through the fascia inferior to the pectoralis minor muscle. The medial pectoral nerve exits the axilla directly through the pectoralis minor muscle.

Case A flexor of the forearm at the elbow joint is innervated by the radial nerve on a lateral component and the musculocutaneous nerve. Question Where does this muscle originate on the medial side?

Correct answer:Intermuscular septum Explanation The brachialis originates from parts of the intermuscular septum on the medial side. The short head of the biceps brachii originates from the coracoid process. The long head of the triceps brachii originates from the infraglenoid tubercle of the scapula. The long head of the biceps brachii originates from the supraglenoid tubercle of the scapula.

Case Joints in the upper limb, including the wrist and digits, display actions powered by flexor muscles. Question Which of them facilitates flexion and extension as main mechanisms of movement?

Correct answer:Interphalangeal joint Explanation The interphalangeal joints generally facilitate flexion and extension as main movements. The carpometacarpal joints (except the thumb) facilitate limited gliding movements. The metacarpophalangeal joints facilitate flexion, extension, abduction, adduction, circumduction, and limited rotation. The wrist joint facilitates abduction, adduction, flexion, and extension.

If a patient is standing in the correct anatomical position, where will their thumbs be relative to the rest of the body?

Correct answer:Lateral Explanation In anatomical position, the body is erect, facing forward, with arms at sides and palms facing forward. Lateral refers to a position that is away from the midline of the body. This would describe the thumbs in anatomical position. Medial refers to closest to the midline. Deep refers to further away from the surface or superficial aspect of an organism. Superficial is closer to the surface of an organism. Superior is a position that is above another landmark. In humans, this is typically towards the head.

Case Landmarks on the proximal end of the humerus are the site of attachment for rotator cuff muscles. Question Relative to the head of the humerus, where is the greater of these landmarks?

Correct answer:Lateral Explanation The landmark is the greater tubercle, which is positioned laterally with respect to the head of the humerus. The greater tubercle has superior and posterior surfaces containing facets for tendon attachment. The lesser tubercle is positioned anteriorly with respect to the humerus.

Case The transition of the neck and the arm is formed by the clavicle, scapula, upper thoracic wall, and humerus with related muscles. Question Which wall of this structure is formed by the intertubercular sulcus of the humerus?

Correct answer:Lateral Explanation The lateral wall of the axilla is formed by the intertubercular sulcus of the humerus. The anterior wall is formed by the pectoralis major, pectoralis minor, and subclavius muscles. The medial wall is formed by the upper thoracic wall and the serratus anterior muscle. The posterior wall is formed by the scapula, subscapularis, latissimus dorsi, teres major, and the triceps brachii.

Case A muscle in the superficial layer of the anterior forearm originates from the medial epicondyle and supracondylar ridge of the humerus. Question Where does it insert?

Correct answer:Lateral surface of the radius Explanation The muscle is the pronator teres, which inserts on the lateral surface of the radius. The flexor carpi radialis inserts on the bases of metacarpals II and III. The palmaris longus inserts on the flexor retinaculum. The flexor carpi ulnaris inserts on the pisiform bone of the wrist.

Case An infant with a history of upward force on arm during delivery presents with total claw hand. The lumbricals appear to be flexing the metacarpophalangeal (MCP) joints, as well as extending the distal and proximal interphalangeal joints. Question These findings result from damage to which aspect of the brachial plexus?

Correct answer:Lower trunkExplanation Damage to the lower trunk (C8-T1 roots) (Klumpke palsy) is commonly seen in infants with upward force on the arm during delivery and in adults with forceful arm trauma, such as grabbing onto a tree branch to break a fall. Klumpke palsy presents with total claw hand, as seen in this patient. Damage to roots (C5, C6, C7) damages the long thoracic nerve, which classically presents with winged scapula. Damage to the upper trunk would lead to Erb palsy (waiter's tip hand). Damage to the posterior cord would cause wrist drop.

An osteofibrous passageway leads from the wrist to the hand. What lies in the proximal row of the osseous plane of this structure?

Correct answer:Lunate Explanation The scaphoid, lunate, triquetrum, and pisiform are located in the proximal row of the osseous plane of the carpal tunnel. The capitate, hamate, trapezium, and trapezoid are located in the distal row of the osseous plane of the carpal tunnel.

Case A bone with an S-shaped contour serves as an attachment between the trunk and the upper limb. Question Where does this attachment articulate medially?

Correct answer:Manubrium of the sternum Explanation The bony attachment is the clavicle, which articulates medially with the manubrium of the sternum and the first costal cartilage. The clavicle articulates laterally with the acromion of the scapula. The head of the humerus articulates with the glenoid cavity of the scapula. The scapula articulates with the head of the humerus.

Case The transition of the neck and the arm is formed by the clavicle, scapula, upper thoracic wall, and humerus with related muscles. Question Which wall of this structure is formed by the upper thoracic wall and the serratus anterior muscle?

Correct answer:Medial Explanation The medial wall of the axilla is formed by the upper thoracic wall and the serratus anterior muscle. The anterior wall is formed by the pectoralis major, pectoralis minor, and subclavius muscles. The lateral wall is formed by the intertubercular sulcus of the humerus. The posterior wall is formed by the scapula, subscapularis, latissimus dorsi, teres major, and the triceps brachii.

Case The transition of the neck and the arm is formed by the clavicle, scapula, upper thoracic wall, and humerus with related muscles. Question How is the apex of the inlet of this structure directed?

Correct answer:Medial Explanation The structure is the axilla. The inlet of the axilla is a triangle with an apex directed medially. This structure has lateral, anterior, and posterior margins formed by the first rib, clavicle, and scapula, respectively.

Case The transition of the neck and the arm is formed by the clavicle, scapula, upper thoracic wall, and humerus with related muscles. Question What exits this structure directly through the pectoralis minor muscle?

Correct answer:Medial pectoral nerve Explanation The medial pectoral nerve exits the axilla directly through the pectoralis minor muscle. The axillary vein enters the neck and continues to become the subclavian vein. The intercostobrachial nerve passes through the axilla directly through the medial wall. The lateral thoracic artery exits the axilla through the fascia inferior to the pectoralis minor muscle.

A 32-year-old woman presents with pain in her neck and upper shoulder after being thrown from a horse and hitting the ground with the top of her left shoulder. An MRI of her neck reveals tearing of the superior roots of the brachial plexus on her right side. What is most likely true about the function or position of the right upper limb in a patient who presents with this type of nerve injury?

Correct answer:Medial rotation of entire right upper limb Explanation This patient fell and violently hit the ground with her left shoulder, likely resulting in the trauma tearing or rupture of the superior parts of the brachial plexus. This results in Erb-Duchenne palsy, which is weakness and paralysis of the muscles supplied by the C5 and C6 nerve roots: deltoid, biceps, and brachialis. It manifests clinically as adduction of the right shoulder and medial rotation of the arm, forearm, and hand. People with Erb-Duchenne palsy may show loss of sensation in the lateral, not medial, forearm. Sensation of the medial forearm is supplied by the medial cutaneous nerve of the forearm, which is a branch of the ulnar nerve (C8,T1); it would not likely be affected by an injury to the superior roots of the brachial plexus. Erb-Duchenne palsy is characterized by a medial, not lateral, rotation of the right arm and forearm. Patients who have an injury to the inferior parts of the brachial plexus have weakness and paralysis of the muscles of the hand, called Klumpke paralysis, which clinically manifests as a claw hand.

A patient presents with characteristics of carpal tunnel syndrome. Which nerve is most likely damaged?

Correct answer:Median nerve Explanation The median nerve is most frequently affected in the carpal tunnel. Typically, the median nerve enters the hand through the carpal tunnel. The extensor carpi ulnaris extends and adducts the hand. The thenar muscles are on the lateral part of the palm. The trapezius stabilizes the upper back.

Joints in the upper limb, including the wrist and digits, display actions powered by flexor muscles. Which of these joints facilitates flexion, extension, abduction, adduction, circumduction, and limited rotation?

Correct answer:Metacarpophalangeal joint Explanation The metacarpophalangeal joints facilitate flexion, extension, abduction, adduction, circumduction, and limited rotation. The carpometacarpal joints (except the thumb) facilitate limited gliding movements. The interphalangeal joints generally facilitate flexion and extension as main movements. The wrist joint facilitates abduction, adduction, flexion, and extension.

Case A patient presents with injury to the left upper limb. On physical exam, the patient shows inability to flex the forearm at the elbow and loss of sensation to the lateral forearm. Question What nerve has been damaged?

Correct answer:Musculocutaneous Explanation The musculocutaneous nerve innervates the flexors of the forearm, including coracobrachialis, biceps brachii, and brachialis. Biceps brachii is responsible for supination of the forearm. Damage to the musculocutaneous nerve is responsible for loss of forearm flexion and supination of the forearm and for loss of lateral forearm sensation. The axillary nerve innervates the deltoid muscle, which is responsible for abduction (from 15-110°), adduction, flexion, extension, and medial and lateral rotation of the arm. The radial nerve is responsible for extension of the wrist and thumb. The ulnar nerve is responsible for flexing the forearm, flexing the hand, adducting the hand and thumb.

A muscle extends from the coracoid process of the scapula to the midshaft of the humerus. Question Which nerve innervates this muscle?

Correct answer:Musculocutaneous nerve Explanation The muscle is the coracobrachialis, which is innervated by the musculocutaneous nerve. Muscles in the forearm are innervated by the median nerve. The triceps brachii muscle is innervated by the radial nerve. Muscles in the hands and forearms are innervated by the ulnar nerve

A muscle in the deep layer of the anterior forearm originates from the anterior surfaces of the radius and interosseous membrane. Where does it insert?

Correct answer:Palmar surface of the distal phalanx Explanation The muscle is the flexor pollicis longus, which inserts on the palmar surface of the distal phalanx after passing through the carpal tunnel. The flexor digitorum profundus inserts on the distal phalanx of digits 2, 3, 4, and 5. The pronator quadratus inserts on the anterior flat surface of the radius.

What muscle is responsible for depressing the scapula and elevating the ribs?

Correct answer:Pectoralis minor Explanation Pectoralis minor functions to depress the scapula and elevate the ribs. It originates at the third, fourth, and fifth ribs and inserts onto the coracoid process of the scapula. Pectoralis major is responsible for flexing, adducting, and medially rotating the arm. Both the pectoralis major and minor are innervated by the lateral and medial pectoral nerves. Subclavius depresses the lateral part of the clavicle. Serratus anterior rotates the scapula upward and is responsible for raising the arm above the horizontal plane.

Which muscle is used as an anatomical landmark in surgery to identify the levels of axillary lymph nodes?

Correct answer:Pectoralis minor Explanation The pectoralis minor is a triangular-shaped muscle lying deep to the much larger pectoralis major muscle. Important vessels and other structures of the axilla pass deep to the pectoralis minor where it forms a bridge with the coracoid process of the scapula. In identifying levels of lymph nodes in an axillary dissection, level I nodes are lateral to the lateral border of the pectoralis minor, level II nodes lie beneath the muscle, and level III nodes are medial to the medial border of the pectoralis minor. Typically the lymph nodes at level I and II are removed in a standard axillary lymph node dissection. The level III nodes would be removed if gross disease is encountered at level II. The pectoralis major, subclavius, and serratus anterior are the other 3 muscles of the pectoral girdle. They are not used as anatomical landmarks to identify lymph nodes in axillary dissections.

A muscle in the superficial layer of the anterior forearm originates from the olecranon and posterior border of the ulna. Where does it insert?

Correct answer:Pisiform bone of the wrist Explanation The muscle is the flexor carpi ulnaris, which inserts on the pisiform bone of the wrist. The palmaris longus inserts on the flexor retinaculum. The flexor carpi radialis inserts on the bases of metacarpals II and III. The pronator teres inserts on the lateral surface of the radius.

Case The transition of the neck and the arm is formed by the clavicle, scapula, upper thoracic wall, and humerus with related muscles. Question Which wall of this structure is formed by the scapula, subscapularis, latissimus dorsi, teres major, and the triceps brachii?

Correct answer:Posterior Explanation The posterior wall of the axilla is formed by the scapula, subscapularis, latissimus dorsi, teres major, and the triceps brachii. The anterior wall is formed by the pectoralis major, pectoralis minor, and subclavius muscles. The lateral wall is formed by the intertubercular sulcus of the humerus. The medial wall is formed by the upper thoracic wall and the serratus anterior muscle.

Case The part of the axillary artery that provides the thoracoacromial trunk and the lateral thoracic artery begins at the upper border of the pectoralis minor and ends at the lower border. Question How is this part oriented in relation to the pectoralis mino

Correct answer:Posterior Explanation The structure is the second part of the axillary artery, which is posterior to the pectoralis minor. The pectoralis minor crosses anteriorly to the vessel. The first part of the axillary artery is proximal to the pectoralis minor. The third part of the axillary artery is distal to the pectoralis minor.

Case A nerve innervates the skin on the lower lateral surface of the arm and the dorsal lateral surface of the hand. Question This nerve is the largest terminal branch of what formation?

Correct answer:Posterior cord of the brachial plexus Explanation The structure is the radial nerve, which is a branch of the posterior cord of the brachial plexus. The long thoracic nerve originates from the anterior rami of C5 to C7. The dorsal scapular nerve originates from the C5 root of the brachial plexus. The lateral pectoral nerve, musculocutaneous nerve, and lateral root of the median nerve originate from the lateral cord of the brachial plexus.

Case The part of the axillary artery on top of the serratus anterior provides the superior thoracic artery branch. Question How is this part oriented in relation to the pectoralis minor?

Correct answer:Proximal Explanation The structure is the first part of the axillary artery, which is proximal to the pectoralis minor. The pectoralis minor crosses anteriorly to the vessel. The second part of the axillary artery is posterior to the pectoralis minor. The third part of the axillary artery is distal to the pectoralis minor.

Question A muscle enables extension of the forearm at the elbow joint. What is the insertion site of this muscle?

Correct answer:Proximal radius Explanation The proximal radius is a site of insertion for the muscles of the arm that enable flexion and extension of the forearm at the elbow joint. The distal humerus is also involved in the movement of the arm and forearm. The distal radius and distal ulna are not insertion sites for muscles of the arms involved in flexion and extension of the forearm. The proximal ends are the insertion site for most muscles of the arm. The proximal humerus is involved with components of the shoulder and axilla.

Which artery runs through the anatomic snuffbox?

Correct answer:Radial artery Explanation The anatomic snuffbox is a triangular space that contains passage of the radial artery. The extensor pollicis longus muscle makes up the medial border. The extensor pollicis brevis and abductor pollicis longus muscles comprise the lateral border. The brachial artery runs with the median nerve through the cubital fossa and around the supracondylar ridge of the distal humerus. The fibular artery supplies blood to the lower limb. The ulnar artery is a branch of the brachial artery.

Case A hinge joint with three separate articulations has a shared synovial cavity. One of the three articulations is involved in pronation and supination of the forearm. Question What structure forms an articulation with the head of the radius to enable this movement?

Correct answer:Radial notch of the ulna Explanation Pronation and supination of the forearm are supported by the articulation between the head of the radius and the radial notch of the ulna. The articulation of the capitulum of the humerus and the head of the radius enables flexion and extension of the forearm. Flexion and extension of the forearm are also supported by the articulation between the trochlea of the humerus and the trochlear notch of the ulna.

Case A breast cancer survivor patient with a history of axillary node dissection presents with symptoms consistent with scapular winging: primarily, inability to abduct the arm above the horizontal plane. She describes pain that radiates the length of her arm and numbness and tingling that extend into the hand. Question What portion of the brachial plexus has been damaged?

Correct answer:Roots Explanation Damage to the serratus anterior is responsible for the patient's clinical presentation (winged scapula). Winged scapula represents an injury to the long thoracic nerve, weakening the serratus anterior muscle. The long thoracic nerve is derived from brachial plexus roots C5, C6, and C7. Damage to upper trunk (C5-C6 roots) is known as Erb palsy or "waiter's tip hand" due to the arm hanging by the patient's side (adducted), medially rotated, with arm extended and pronated. Damage to the lower trunk (C8-T1 roots) is known as Klumpe palsy and presents as total claw hand (distal and proximal interphalangeal joints extended). Damage to the posterior cord would damage the extensors of the arm (axillary and radial nerves), causing wrist drop.

What complication of childbirth is most likely to injure the neonate's brachial plexus?

Correct answer:Shoulder dystocia Explanation Shoulder dystocia represents "stuck shoulders" in the pelvic outlet at the time of birth. Maneuvers to deliver the shoulders can transiently or permanently injure the brachial plexus. Cephalopelvic disproportion is a birth complication that would damage the skull. A frank breech presentation may result in an increased risk of hip dysplasia. A transverse lie is a birth complication preventing vaginal delivery that would result in fetal demise without a cesarean section.

Case A tendon arises from a muscle that medially rotates the arm at the glenohumeral joint and inserts onto the lesser tubercle of the humerus. Question From what muscle does this tendon arise?

Correct answer:Subscapularis Explanation The tendon described arises from the subscapularis. The tendon of the infraspinatus inserts on the middle facet of the greater tubercle. The tendon of the supraspinatus inserts onto the superior facet of the greater tubercle. The tendon of the teres minor inserts on the inferior facet of the greater tubercle of the humerus.

Case A group of muscles arises from various locations on the scapula and inserts in the proximal humerus. Question Which muscle of this group inserts most anteriorly?

Correct answer:Subscapularis Explanation This group of muscles is the rotator cuff. The rotator cuff is composed of the infraspinatus, subscapularis, supraspinatus, and teres minor. The most anterior insertion of the group is by the subscapularis, upon the lesser tuberosity.

A muscle innervated by the radial nerve enables extension of the forearm at the elbow joint. Where does the lateral head of this muscle originate?

Correct answer:Superior to the radial groove of the humerus Explanation The lateral head of the triceps brachii originates superior to the radial groove of the humerus. The long head of the triceps brachii originates from the infraglenoid tubercle of the scapula. The medial head of the triceps brachii originates on the posterior surface of the shaft of the humerus, inferior to the radial groove.

Case A muscle innervated by the musculocutaneous nerve has a short and long head. Question What movement does this structure enable when the elbow joint is flexed?

Correct answer:Supination of the forearm Explanation The biceps brachii enables supination of the forearm when the elbow joint is flexed. The coracobrachialis muscle enables flexion of the arm. The triceps brachii enables extension of the elbow. The pronator teres enables pronation of the forearm.

Case A muscle within the deep layer of the posterior forearm is wrapped around the proximal end of the radius during protonation of the hand. Question What is a role of this muscle?

Correct answer:Supinator of forearm Explanation This muscle is the supinator, which supinates the forearm and hand. The extensor carpi radialis longus, extensor carpi radialis brevis, extensor carpi ulnaris are muscles of the superficial layer of the posterior forearm that are abductors of the wrist. The brachioradialis is a flexor of the elbow located in the superficial layer of the posterior forearm. The anconeus is an extensor of the elbow located in the superficial layer of the posterior forearm. The listed muscles are muscles of the posterior forearm. Functions of muscles in the posterior forearm include extension of the wrist and supination of the hand. Muscles of the anterior forearm allow for flexion of the wrist and pronation of the hand.

Case A muscle in the anterior compartment of the arm is innervated by the musculocutaneous nerve and enables flexion of the glenohumeral joint. Question Where does the long head of this muscle originate?

Correct answer:Supraglenoid tubercle of the scapula Explanation The long head of the biceps brachii originates from the supraglenoid tubercle of the scapula. The brachialis originates from parts of the intermuscular septum on the medial side. The short head of the biceps brachii originates from the coracoid process. The long head of the triceps brachii originates from the infraglenoid tubercle of the scapula

Case A patient with poor athletic technique has rotator cuff syndrome due to the compressive forces of subacromial impingement. Question What tendon is characteristically susceptible to these forces?

Correct answer:Supraspinatus Explanation The supraspinatus tendon is particularly susceptible to the compressive forces of subacromial impingement. The infraspinatus, subscapularis, and teres minor are less susceptible because they are not subject to the same spaces of fixed dimensions as the supraspinatus.

Case A tendon passes under the acromion and over the glenohumeral joint, inserting on the superior facet of the greater tubercle. Question From what muscle does this tendon arise?

Correct answer:Supraspinatus Explanation The tendon of the supraspinatus follows this pattern. The tendon of the infraspinatus inserts on the middle facet of the greater tubercle. The tendon of the subscapularis inserts on the lesser tubercle of the humerus. The tendon of the teres minor inserts on the inferior facet of the greater tubercle of the humerus.

Case A portion of bone oriented horizontally between the proximal humerus and the shaft is weaker than other areas. Question What is the name of this portion, which is a common fracture site?

Correct answer:Surgical neck Explanation The surgical neck is weaker than other areas of the proximal humerus (anatomical neck, head, and tubercles) and is a common site of fracture.

The tendons of the flexor digitorum superficialis, flexor digitorum profundus, flexor pollicis longus, and the median nerve are contained by an osteofibrous passageway leading from the wrist to the hand. Which structure is lateral to the tendons of the largest extrinsic flexor of the forearm?

Correct answer:Tendon of the flexor pollicis longus Explanation The largest extrinsic flexor of the forearm is the flexor digitorum superficialis. The tendon of the flexor pollicis longus muscle is lateral to the tendons of the flexor digitorum superficialis muscle. The median nerve and flexor retinaculum are anterior to the tendons. The tendons of the flexor digitorum profundus muscle are deep to the tendons of the flexor digitorum superficialis muscle.

Case The tendons of the flexor digitorum superficialis, flexor digitorum profundus, flexor pollicis longus, and the median nerve are contained by an osteofibrous passageway leading from the wrist to the hand. Question Which structure is deep to the tendons of the largest extrinsic flexor of the forearm?

Correct answer:Tendons of the flexor digitorum profundus Explanation The largest extrinsic flexor of the forearm is the flexor digitorum superficialis. The tendons of the flexor digitorum profundus muscle are deep to the tendons of the flexor digitorum superficialis muscle. The median nerve and flexor retinaculum are anterior to the tendons. The tendon of the flexor pollicis longus muscle is lateral to the tendons of the flexor digitorum superficialis muscle.

Case A group of muscles arises from various locations on the scapula and inserts in the proximal humerus. Question Which muscle of this group inserts most posteriorly?

Correct answer:Teres minor Explanation This group of muscles is the rotator cuff. The rotator cuff is composed of the infraspinatus, subscapularis, supraspinatus, and teres minor. The most posterior insertion of the group is by the teres minor, upon the greater tuberosity.

Case A tendon arises from a muscle that laterally rotates the humerus and inserts on the inferior facet of the greater tubercle of the humerus. Question From what muscle does this tendon arise?

Correct answer:Teres minor Explanation This tendon arises from the teres minor. The tendon of the infraspinatus inserts on the middle facet of the greater tubercle. The tendon of the subscapularis inserts on the lesser tubercle of the humerus. The tendon of the supraspinatus inserts onto the superior facet of the greater tubercle.

Case The joint of the first metacarpal facilitates flexion, extension, abduction, adduction, rotation, and circumduction. Question What other bone makes up this joint?

Correct answer:Trapezium Explanation The joint of the first metacarpal and trapezium is a saddle joint, which affords a greater degree of mobility to the thumb than the other carpometacarpal joints. The capitate articulates with the third metacarpal. The hamate articulates with the fifth metacarpal. The trapezoid articulates with the second metacarpal.

When the forearms are extending at the elbow, which muscle is the prime mover?

Correct answer:Triceps brachii Explanation When the forearms are extending, the triceps brachii is the prime mover; the brachialis is the antagonist. Neither the biceps brachii nor the brachioradialis is involved in extension of the arm

Case A hinge joint with three separate articulations has a shared synovial cavity. One of the three articulations is involved in flexion and extension of the forearm. Question What structure forms an articulation with the trochlear notch of the ulna to enable this movement?

Correct answer:Trochlea of the humerus Explanation The articulation of the trochlea of the humerus and the trochlear notch of the ulna enables flexion and extension of the forearm. Flexion and extension of the forearm are also supported by the articulation between the head of the radius and the capitulum of the humerus, but the trochlea of the humerus is not part of this specific articulation. Pronation and supination of the forearm are supported by the articulation between the head of the radius and the radial notch of the ulna.

An osteofibrous passageway leads from the wrist to the hand. What forms the lateral arch of the base of this structure?

Correct answer:Tubercle of scaphoid Explanation The base of the carpal arch is formed laterally by the tubercles of the scaphoid and trapezium bones. The base of the carpal arch is formed medially by the pisiform bone and hamate bone. The flexor retinaculum forms a bridge between the medial and lateral sides of the base of the carpal arch.

Case The cord of a plexus is positioned medial to the second part of the axillary artery. Question What nerve originates from this cord?

Correct answer:Ulnar nerve Explanation The structure is the medial cord of the brachial plexus. The ulnar nerve originates from the medial cord of the brachial plexus. The axillary nerve originates from the posterior cord of the brachial plexus. The dorsal scapular nerve originates from the C5 root of the brachial plexus. The musculocutaneous nerve originates from the lateral cord of the brachial plexus.

A patient presents with a characteristic claw hand. Damage to what structure would lead to this sign?

Correct answer:Ulnar nerve Explanation Ulnar nerve damage leads to characteristic claw hand. The fourth and fifth fingers are flexed at the interphalangeal joints, while the second and third fingers are extended in a pointed position. If the axillary nerve is damaged, weakness will be found in the deltoid, and abducting the humerus will be severely limited. If the musculocutaneous nerve is damaged, the patient will present with weakness in flexion of the bicep. The phrenic nerve innervates the diaphragm. If the long thoracic nerve is damaged, the patient will present with the classic sign of winging of the scapula.

Case The roots and trunks of a plexus enter the posterior triangle of the neck between the anterior scalene and middle scalene. Question What forms the inferior trunk of this plexus?

Correct answer:Union of C8 and T1 roots Explanation The structure is the brachial plexus. The inferior trunk arises from the union of the C8 and T1 roots. The brachial plexus is formed by the anterior rami of C5 to C8 and most of the anterior ramus of T1. The middle trunk of the brachial plexus is formed by the continuation of the C7 root. The superior trunk of the brachial plexus is formed by the union of C5 and C6 roots