Upper Limb Anatomy: Bones

• The upper limb consists of the arm, forearm, and hand, and is specialized for mobility and manipulation

Bones of the Upper Limb

• The upper limb includes the clavicle, scapula, humerus, radius, ulna, carpals, metacarpals, and phalanges

Clavicle

• The clavicle (collarbone) is a long bone that connects the upper limb to the trunk
• It articulates with the sternum (sternoclavicular joint) and the scapula (acromioclavicular joint)
• The clavicle provides attachment for muscles and transmits forces from the upper limb to the axial skeleton

Scapula

• The scapula (shoulder blade) is a flat, triangular bone that lies on the posterior aspect of the thorax
• It articulates with the humerus (glenohumeral joint) and the clavicle (acromioclavicular joint)
• The scapula provides attachment for muscles that move the upper limb and shoulder
• Key features include the spine, acromion, coracoid process, glenoid cavity, and infraspinous fossa

Humerus

• The humerus is the long bone of the arm, extending from the shoulder to the elbow
• It articulates with the scapula (glenohumeral joint) and the radius and ulna (elbow joint)
• Key features include the head, anatomical neck, surgical neck, greater and lesser tubercles, intertubercular groove, deltoid tuberosity, capitulum, trochlea, and epicondyles

Radius

• The radius is one of the two bones of the forearm, located on the lateral (thumb) side
• It articulates with the humerus (elbow joint), ulna (radioulnar joints), and carpal bones (wrist joint)
• Key features include the head, neck, radial tuberosity, and styloid process
• The radius participates in pronation and supination of the forearm

Ulna

• The ulna is the other bone of the forearm, located on the medial (little finger) side
• It articulates with the humerus (elbow joint), radius (radioulnar joints), and carpal bones (wrist joint)
• Key features include the olecranon, coronoid process, trochlear notch, radial notch, and styloid process
• The ulna is the stabilizing bone of the forearm

Carpal Bones

• The carpus (wrist) consists of eight small bones arranged in two rows
• The proximal row (from lateral to medial) includes the scaphoid, lunate, triquetrum, and pisiform
• The distal row (from lateral to medial) includes the trapezium, trapezoid, capitate, and hamate
• The carpal bones articulate with the radius and ulna (wrist joint) and the metacarpal bones

Metacarpal Bones

• The metacarpals are the five bones of the hand, located between the carpus and the phalanges
• Each metacarpal consists of a base, shaft, and head
• They articulate with the carpal bones (carpometacarpal joints) and the phalanges (metacarpophalangeal joints)
• They are numbered I-V starting at the thumb

Phalanges

• The phalanges are the bones of the fingers
• Each finger has three phalanges (proximal, middle, and distal), except for the thumb, which has only two (proximal and distal)
• Each phalanx consists of a base, shaft, and head
• They articulate with the metacarpal bones (metacarpophalangeal joints) and other phalanges (interphalangeal joints)

Joints of the Upper Limb

• The joints of the upper limb include the sternoclavicular, acromioclavicular, glenohumeral, elbow, radioulnar, wrist, carpometacarpal, metacarpophalangeal, and interphalangeal joints

Sternoclavicular Joint

• The sternoclavicular joint is a synovial joint between the clavicle and the sternum
• It allows for movements of the clavicle and scapula

Acromioclavicular Joint

• The acromioclavicular joint is a synovial joint between the clavicle and the acromion of the scapula
• It allows for movements of the scapula on the clavicle

Glenohumeral Joint

• The glenohumeral joint (shoulder joint) is a ball-and-socket synovial joint between the humerus and the scapula
• It is the most mobile joint in the body, allowing for flexion, extension, abduction, adduction, rotation, and circumduction
• The rotator cuff muscles (supraspinatus, infraspinatus, teres minor, and subscapularis) stabilize the joint

Elbow Joint

• The elbow joint is a hinge synovial joint between the humerus, radius, and ulna
• It allows for flexion and extension of the forearm

Radioulnar Joints

• The radioulnar joints (proximal and distal) are pivot synovial joints between the radius and ulna
• They allow for pronation and supination of the forearm

Wrist Joint

• The wrist joint (radiocarpal joint) is a condyloid synovial joint between the radius and the carpal bones
• It allows for flexion, extension, abduction, and adduction of the hand

Carpometacarpal Joints

• The carpometacarpal joints are synovial joints between the carpal bones and the metacarpal bones
• They allow for limited movement of the metacarpals
• The carpometacarpal joint of the thumb is a saddle joint, allowing for greater mobility

Metacarpophalangeal Joints

• The metacarpophalangeal joints are condyloid synovial joints between the metacarpal bones and the phalanges
• They allow for flexion, extension, abduction, and adduction of the fingers

Interphalangeal Joints

• The interphalangeal joints are hinge synovial joints between the phalanges
• They allow for flexion and extension of the fingers

Muscles of the Upper Limb

• The muscles of the upper limb are responsible for movements of the shoulder, arm, forearm, and hand
• They are divided into groups based on their location and function

Shoulder Muscles

• Muscles that move the shoulder include the trapezius, deltoid, latissimus dorsi, pectoralis major, and serratus anterior
• The trapezius elevates, depresses, retracts, and rotates the scapula
• The deltoid abducts, flexes, and extends the arm
• The latissimus dorsi extends, adducts, and medially rotates the arm
• The pectoralis major flexes, adducts, and medially rotates the arm
• The serratus anterior protracts and rotates the scapula

Arm Muscles

• Muscles that move the arm include the biceps brachii, triceps brachii, brachialis, and coracobrachialis
• The biceps brachii flexes and supinates the forearm
• The triceps brachii extends the forearm
• The brachialis flexes the forearm
• The coracobrachialis flexes and adducts the arm

Forearm Muscles

• The forearm muscles are divided into anterior and posterior compartments
• The anterior compartment muscles are mostly flexors and pronators
• The posterior compartment muscles are mostly extensors and supinators

Anterior Forearm Muscles

• The anterior forearm muscles include the pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris, flexor digitorum superficialis, flexor digitorum profundus, flexor pollicis longus, and pronator quadratus

Posterior Forearm Muscles

• The posterior forearm muscles include the brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, supinator, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis

Hand Muscles

• The hand muscles are divided into thenar, hypothenar, and intermediate groups
• The thenar muscles are located at the base of the thumb
• The hypothenar muscles are located at the base of the little finger
• The intermediate muscles are located between the thenar and hypothenar groups

Thenar Muscles

• The thenar muscles include the abductor pollicis brevis, flexor pollicis brevis, opponens pollicis, and adductor pollicis
• These muscles control the movements of the thumb

Hypothenar Muscles

• The hypothenar muscles include the abductor digiti minimi, flexor digiti minimi brevis, and opponens digiti minimi
• These muscles control the movements of the little finger

Intermediate Muscles

• The intermediate muscles include the lumbricals and interossei
• The lumbricals flex the metacarpophalangeal joints and extend the interphalangeal joints
• The interossei (palmar and dorsal) abduct and adduct the fingers

Nerves of the Upper Limb

• The nerves of the upper limb arise from the brachial plexus
• The brachial plexus is formed by the ventral rami of spinal nerves C5-T1
• The major nerves of the upper limb include the musculocutaneous, axillary, radial, median, and ulnar nerves

Musculocutaneous Nerve

• The musculocutaneous nerve innervates the biceps brachii, brachialis, and coracobrachialis muscles
• It also provides cutaneous innervation to the lateral forearm

Axillary Nerve

• The axillary nerve innervates the deltoid and teres minor muscles
• It also provides cutaneous innervation to the shoulder region

Radial Nerve

• The radial nerve innervates the triceps brachii and the posterior forearm muscles
• It also provides cutaneous innervation to the posterior arm, forearm, and hand

Median Nerve

• The median nerve innervates most of the anterior forearm muscles and some of the thenar muscles
• It also provides cutaneous innervation to the lateral palm and fingers
• It passes through the carpal tunnel in the wrist

Ulnar Nerve

• The ulnar nerve innervates the flexor carpi ulnaris and flexor digitorum profundus muscles, as well as most of the intrinsic hand muscles
• It also provides cutaneous innervation to the medial hand and fingers
• It passes through the cubital tunnel at the elbow

Vasculature of the Upper Limb

• The major arteries of the upper limb include the subclavian, axillary, brachial, radial, and ulnar arteries
• The subclavian artery becomes the axillary artery at the lateral border of the first rib
• The axillary artery becomes the brachial artery at the inferior border of the teres major muscle
• The brachial artery divides into the radial and ulnar arteries at the elbow
• The radial and ulnar arteries supply the forearm and hand
• The veins of the upper limb include superficial and deep veins, which drain into the subclavian vein