Study Notes
World History
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Upper Limb Study Notes
The upper limb is divided into four regions: the shoulder, arm, forearm, and hand, each defined by its major joints and bones. These study notes cover upper limb anatomy from the sternoclavicular attachment to the phalanges, including the muscles that move each segment and the key passageways, such as the axilla, cubital fossa, and carpal tunnel, that carry nerves and vessels between regions.
Upper Limb Attachment
The upper limb is attached to the trunk by muscles and a small skeletal articulation at the sternoclavicular joint.
Divisions of the Upper Limb
The upper limb is divided into the shoulder, arm, forearm, and hand based on the position of its major joints and component bones.
Shoulder Definition
The shoulder is defined as the area of upper limb attachment to the trunk.
Arm Definition
The arm is the part of the upper limb located between the shoulder and the elbow joint.
Forearm Definition
The forearm is the part of the upper limb situated between the elbow joint and the wrist joint.
Hand Definition
The hand is the part of the upper limb distal to the wrist joint.
Axilla Description
The axilla is an irregularly shaped pyramidal area formed by the muscles and bones of the shoulder and the lateral surface of the thoracic wall. Its apex opens into the lower neck, and the skin of the armpit forms its floor. All major structures passing between the neck and arm traverse the axilla.
Cubital Fossa Description
The cubital fossa is a triangular depression anterior to the elbow joint, formed by muscles. It is a passage for the brachial artery and the median nerve.
Carpal Tunnel Description
The carpal tunnel is the gateway to the palm, formed by carpal bones and the flexor retinaculum. It transmits the median nerve and long flexor tendons to the digits.
Upper Limb Function: Mobility
Unlike the lower limb, the upper limb is highly mobile, primarily used for positioning the hand in space.
Scapular Movement and Reach
Sliding (protraction and retraction) and rotating the scapula on the thoracic wall alters the position of the glenohumeral joint, extending the reach of the hand.
Glenohumeral Joint Movements
The glenohumeral joint allows for a wide range of motion in three axes: flexion, extension, abduction, adduction, medial rotation, lateral rotation, and circumduction.
Elbow Joint Movements
The major movements at the elbow joint are flexion and extension of the forearm.
Forearm Pronation and Supination
Pronation is the movement where the radius crosses over the ulna, turning the palm posteriorly. Supination returns the hand to the anatomical position (palm anterior).
Wrist Joint Movements
The wrist joint allows for abduction, adduction, flexion, extension, and circumduction of the hand.
Hand as a Mechanical Tool
The hand functions as a mechanical tool for gripping and manipulating objects, involving finger flexion against the thumb and coordinated joint movements.
Hand as a Sensory Tool
The hand is a crucial sensory tool for discriminating objects by touch, due to a high density of sensory receptors in the finger pads and a disproportionately large representation in the sensory cortex.
Shoulder Bones
The bones of the shoulder include the scapula, clavicle, and the proximal end of the humerus.
Arm Bone
The humerus is the single bone of the arm.
Forearm Bones
The forearm consists of two bones: the radius (lateral) and the ulna (medial).
Elbow Joint Articulation
The elbow joint is a hinge joint formed by the distal humerus articulating with the proximal radius and ulna, allowing flexion and extension. It also permits the radius to spin on the ulna for pronation/supination.
Wrist Joint Articulation
The wrist joint is formed between the radius and carpal bones, and an articular disc distal to the ulna and carpal bones.
Hand Bones
The bones of the hand include the carpal bones (wrist), metacarpals (palm), and phalanges (digits).
Phalanges Count
The thumb has two phalanges, while the other four digits each have three phalanges.
Metacarpophalangeal Joints
These are biaxial condylar joints allowing abduction, adduction, flexion, extension, and circumduction of the fingers.
Interphalangeal Joints
These are primarily hinge joints that permit only flexion and extension of the fingers.
Shoulder Muscles Connecting to Trunk
Muscles like the trapezius, levator scapulae, and rhomboids connect the scapula and clavicle to the trunk.
Shoulder Muscles Connecting to Humerus
Muscles such as the pectoralis major, latissimus dorsi, teres major, and deltoid connect the clavicle, scapula, and body wall to the proximal humerus.
Rotator Cuff Muscles
The four rotator cuff muscles (subscapularis, supraspinatus, infraspinatus, teres minor) connect the scapula to the humerus and stabilize the glenohumeral joint.
Arm Muscle Compartments
Muscles in the arm are divided into anterior (flexor) and posterior (extensor) compartments by fascia and intermuscular septa.
Forearm Muscle Compartments
The forearm's anterior and posterior compartments are separated by a lateral intermuscular septum, the radius, ulna, and an interosseous membrane.
Intrinsic Hand Muscles
Intrinsic muscles of the hand produce delicate digit movements and modify forces from forearm tendons. The thenar muscles form the thenar eminence and allow thumb mobility.
Axillary Inlet Borders
The axillary inlet at the base of the neck is bordered by the lateral margin of rib I, the posterior surface of the clavicle, the superior margin of the scapula, and the medial surface of the coracoid process.
Nerve Supply to Upper Limb
The upper limb is innervated by the brachial plexus, formed from spinal nerves C5-T1, which originates in the neck and passes through the axillary inlet into the axilla.
Muscles Connecting Shoulder to Trunk
Muscles like the trapezius, levator scapulae, rhomboid major, rhomboid minor, and latissimus dorsi connect the shoulder girdle bones to the back and thoracic wall.
Breast and Axilla Relationship
The breast overlies the pectoralis major muscle (anterior axillary wall), and its axillary process can extend into the axilla. Lymphatic drainage from the breast often goes to axillary lymph nodes.
Brachial Plexus Formation
The brachial plexus, formed by the anterior rami of spinal nerves C5 to T1, is the primary source of innervation for the upper limb.
Clinical Significance of Brachial Plexus
Testing dermatomes, myotomes, and tendon reflexes in the upper limb is used to clinically assess lower cervical and T1 nerve function.
Dermatome Example: C5
The upper lateral region of the arm is a key area for testing sensation related to the C5 spinal cord level.
Dermatome Example: C6
The palmar pad of the thumb is a key area for testing sensation related to the C6 spinal cord level.
Dermatome Example: C7
The pad of the index finger is a key area for testing sensation related to the C7 spinal cord level.
Dermatome Example: C8
The pad of the little finger is a key area for testing sensation related to the C8 spinal cord level.
Dermatome Example: T1
The skin on the medial aspect of the elbow is a key area for testing sensation related to the T1 spinal cord level.
Myotome Example: C5
Abduction of the arm at the glenohumeral joint is predominantly controlled by the C5 nerve root.
Myotome Example: C6
Flexion of the forearm at the elbow joint is primarily controlled by the C6 nerve root.
Myotome Example: C7
Extension of the forearm at the elbow joint is mainly controlled by the C7 nerve root.
Myotome Example: C8
Flexion of the fingers is mainly controlled by the C8 nerve root.
Myotome Example: T1
Abduction and adduction of the index, middle, and ring fingers are predominantly controlled by the T1 nerve root.
Tendon Reflex Example: Biceps
Tapping the biceps tendon in the cubital fossa primarily tests the C6 spinal cord level.
Tendon Reflex Example: Triceps
Tapping the triceps tendon posterior to the elbow primarily tests the C7 spinal cord level.
Anterior Arm Muscle Innervation
All muscles in the anterior compartment of the arm are innervated by the musculocutaneous nerve.
Anterior Forearm Muscle Innervation
The median nerve innervates most muscles in the anterior forearm, with exceptions for flexor carpi ulnaris and part of flexor digitorum profundus (ulnar nerve).
Intrinsic Hand Muscle Innervation
Most intrinsic hand muscles are innervated by the ulnar nerve, except for thenar muscles and lateral lumbricals (median nerve).
Posterior Arm/Forearm Muscle Innervation
All muscles in the posterior compartments of the arm and forearm are innervated by the radial nerve.
Musculocutaneous Nerve Sensory Area
The musculocutaneous nerve provides sensation to the skin on the anterolateral side of the forearm.
Median Nerve Sensory Area
The median nerve provides sensation to the palmar surface of the lateral three and a half digits.
Ulnar Nerve Sensory Area
The ulnar nerve provides sensation to the medial one and a half digits.
Radial Nerve Sensory Area
The radial nerve supplies skin on the posterior surface of the forearm and the dorsolateral surface of the hand.
Axillary Nerve and Humerus
The axillary nerve passes around the posterior aspect of the surgical neck of the humerus, making it vulnerable to injury in fractures of this region.
Radial Nerve and Humerus
The radial nerve travels diagonally around the posterior surface of the middle of the humerus in the radial groove, making it susceptible to injury with midshaft humeral fractures.
Ulnar Nerve and Humerus
The ulnar nerve passes posteriorly to the medial epicondyle of the distal humerus, explaining the 'funny bone' sensation when this area is struck.
Superficial Veins for Access
Large superficial veins like the cephalic, basilic, and median cubital veins are commonly used for vascular access and blood withdrawal.
Cephalic Vein Path
The cephalic vein originates from the dorsal venous network of the hand, ascends laterally, crosses the elbow, and passes through the deltopectoral triangle into the axilla.
Basilic Vein Path
The basilic vein originates from the medial dorsal venous network of the hand, ascends posteromedially on the forearm, moves anteriorly below the elbow, and penetrates deep fascia in the mid-arm.
Median Cubital Vein Location
The median cubital vein connects the cephalic and basilic veins at the elbow, crossing the roof of the cubital fossa and serving as a common site for venipuncture.
Thumb Orientation
The thumb is oriented at a right angle to the other digits, allowing its movements to occur in a plane perpendicular to the other fingers.
Thumb Opposition
The ability to bring the pad of the thumb into contact with the pads of the other fingers (opposition) is crucial for normal hand function and is facilitated by the thumb's unique articulation and musculature.
Frequently Asked Questions About Upper Limb Study Notes
What is the upper limb?
The upper limb is the entire free limb attached to the trunk through muscles and the sternoclavicular joint. It is divided into the shoulder, arm, forearm, and hand based on the position of its major joints. Unlike the lower limb, it is highly mobile and primarily used for positioning the hand in space.
What bones make up the upper limb?
The upper limb bones include the scapula, clavicle, and humerus at the shoulder; the humerus alone in the arm; the radius (lateral) and ulna (medial) in the forearm; and the carpal bones, metacarpals, and phalanges in the hand. The thumb has two phalanges, while each of the other four digits has three.
What bones are found in the forearm and how do they move?
The forearm contains two bones: the radius on the lateral side and the ulna on the medial side. During pronation, the radius crosses over the ulna, turning the palm posteriorly. Supination returns the forearm to the anatomical position with the palm facing anteriorly.
What are the muscles of the upper limb and how are they organized?
Upper limb muscles are grouped by region. At the shoulder, muscles like the trapezius and rhomboids connect the scapula to the trunk, while the pectoralis major, latissimus dorsi, and deltoid connect the shoulder girdle to the humerus. The four rotator cuff muscles (subscapularis, supraspinatus, infraspinatus, and teres minor) stabilize the glenohumeral joint. In the arm, muscles are split into anterior flexor and posterior extensor compartments by fascia and intermuscular septa.
What is the carpal tunnel and what passes through it?
The carpal tunnel is the gateway to the palm, formed by the carpal bones and the flexor retinaculum. It transmits the median nerve and the long flexor tendons to the digits. Compression of the median nerve within this tunnel causes carpal tunnel syndrome.
What movements does the glenohumeral joint allow?
The glenohumeral joint allows movement in three axes, including flexion, extension, abduction, adduction, medial rotation, lateral rotation, and circumduction. Its wide range of motion is further extended by protraction and retraction of the scapula on the thoracic wall, which shifts the position of the joint itself and increases the reach of the hand.
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