Upper Extremity Anatomy

• The upper extremity includes the shoulder, arm, forearm, wrist, and hand.
• It is specialized for manipulating objects in the environment.
• The upper extremity is connected to the axial skeleton at the sternoclavicular joint.

Bones

• Clavicle: A long bone that articulates with the sternum and scapula, providing attachment for muscles and transmitting forces from the upper limb to the axial skeleton.
• Scapula: A flat, triangular bone that articulates with the clavicle and humerus, forming the shoulder joint (glenohumeral joint).
• Humerus: The long bone of the arm, articulating with the scapula at the shoulder and the radius and ulna at the elbow.
• Radius: One of the two bones of the forearm, located on the thumb side. It articulates with the humerus at the elbow and the carpals at the wrist.
• Ulna: The other bone of the forearm, located on the pinky side. It articulates with the humerus at the elbow and contributes to the wrist joint.
• Carpals: Eight small bones that form the wrist, arranged in two rows.
• Metacarpals: Five bones that form the palm of the hand, articulating with the carpals and phalanges.
• Phalanges: Fourteen bones that form the fingers (three in each finger, two in the thumb).

Joints

• Sternoclavicular Joint: Connects the clavicle to the sternum.
• Acromioclavicular Joint: Connects the clavicle to the acromion of the scapula.
• Glenohumeral Joint (Shoulder Joint): Ball-and-socket joint between the head of the humerus and the glenoid fossa of the scapula, allowing for a wide range of motion.
• Elbow Joint: Hinge joint between the humerus, radius, and ulna, allowing for flexion and extension.
• Radioulnar Joints (Proximal and Distal): Allow for pronation and supination of the forearm.
• Wrist (Radiocarpal) Joint: Connects the radius to the carpal bones, allowing for flexion, extension, abduction, and adduction.
• Intercarpal Joints: Joints between the carpal bones.
• Carpometacarpal Joints: Joints between the carpal bones and the metacarpals.
• Metacarpophalangeal Joints (MCP): Joints between the metacarpals and the phalanges.
• Interphalangeal Joints (IP): Joints between the phalanges (proximal, middle, and distal).

Muscles

• Shoulder Muscles:
  • Deltoid: Abducts, flexes, and extends the arm at the shoulder.
  • Rotator Cuff Muscles (Supraspinatus, Infraspinatus, Teres Minor, Subscapularis): Stabilize the shoulder joint and contribute to rotation.
  • Teres Major: Adducts, extends, and medially rotates the arm at the shoulder.
  • Latissimus Dorsi: Extends, adducts, and medially rotates the arm.
  • Pectoralis Major: Adducts, flexes, and medially rotates the arm.
• Arm Muscles:
  • Biceps Brachii: Flexes the elbow and supinates the forearm.
  • Brachialis: Flexes the elbow.
  • Triceps Brachii: Extends the elbow.
• Forearm Muscles:
  • Anterior Compartment (Flexors):
    • Flexor Carpi Radialis: Flexes and abducts the wrist.
    • Flexor Carpi Ulnaris: Flexes and adducts the wrist.
    • Palmaris Longus: Flexes the wrist.
    • Flexor Digitorum Superficialis: Flexes the wrist and middle phalanges of the fingers.
    • Flexor Digitorum Profundus: Flexes the wrist and distal phalanges of the fingers.
    • Pronator Teres: Pronates the forearm.
    • Pronator Quadratus: Pronates the forearm.
• Posterior Compartment (Extensors):
  • Extensor Carpi Radialis Longus and Brevis: Extends and abducts the wrist.
  • Extensor Carpi Ulnaris: Extends and adducts the wrist.
  • Extensor Digitorum: Extends the wrist and fingers.
  • Extensor Digiti Minimi: Extends the little finger.
  • Supinator: Supinates the forearm.
  • Abductor Pollicis Longus: Abducts the thumb.
  • Extensor Pollicis Longus and Brevis: Extends the thumb.
  • Extensor Indicis: Extends the index finger.
• Hand Muscles:
  • Thenar Muscles (Thumb):
    • Abductor Pollicis Brevis: Abducts the thumb.
    • Flexor Pollicis Brevis: Flexes the thumb.
    • Opponens Pollicis: Opposes the thumb.
    • Adductor Pollicis: Adducts the thumb.
  • Hypothenar Muscles (Little Finger):
    • Abductor Digiti Minimi: Abducts the little finger.
    • Flexor Digiti Minimi Brevis: Flexes the little finger.
    • Opponens Digiti Minimi: Opposes the little finger.
  • Palmar Interossei: Adduct the fingers.
  • Dorsal Interossei: Abduct the fingers.
  • Lumbricals: Flex the MCP joints and extend the IP joints.

Nerves

• Brachial Plexus: A network of nerves that originates in the neck and provides innervation to the upper extremity, formed by the anterior rami of spinal nerves C5-T1.
  • Roots: C5, C6, C7, C8, T1.
  • Trunks: Superior (C5-C6), Middle (C7), Inferior (C8-T1).
  • Divisions: Anterior and Posterior divisions from each trunk.
  • Cords: Lateral, Posterior, and Medial cords.
  • Terminal Branches:
    • Musculocutaneous Nerve: Innervates the biceps brachii, brachialis, and coracobrachialis muscles, and provides sensory innervation to the lateral forearm.
    • Axillary Nerve: Innervates the deltoid and teres minor muscles, and provides sensory innervation to the skin over the deltoid.
    • Radial Nerve: Innervates the triceps brachii, brachioradialis, and extensor muscles of the forearm, and provides sensory innervation to the posterior arm, forearm, and hand.
    • Median Nerve: Innervates the flexor muscles of the forearm (except flexor carpi ulnaris and ulnar half of flexor digitorum profundus) and thenar muscles, and provides sensory innervation to the palmar side of the thumb, index, middle, and radial half of the ring fingers.
    • Ulnar Nerve: Innervates the flexor carpi ulnaris, ulnar half of flexor digitorum profundus, hypothenar muscles, interossei, and adductor pollicis, and provides sensory innervation to the little finger and ulnar half of the ring finger.

Vasculature

• Subclavian Artery: The main artery supplying the upper extremity, becoming the axillary artery after passing the lateral border of the first rib.
• Axillary Artery: Continuation of the subclavian artery, becoming the brachial artery at the lower border of the teres major muscle.
• Brachial Artery: Runs down the arm, dividing into the radial and ulnar arteries at the elbow.
• Radial Artery: Runs down the radial side of the forearm, contributing to the superficial and deep palmar arches in the hand.
• Ulnar Artery: Runs down the ulnar side of the forearm, also contributing to the superficial and deep palmar arches.
• Palmar Arches (Superficial and Deep): Networks of arteries in the palm that supply blood to the hand and fingers.
• Cephalic Vein: A superficial vein that runs along the lateral side of the arm, draining into the axillary vein.
• Basilic Vein: A superficial vein that runs along the medial side of the arm, draining into the brachial vein.
• Median Cubital Vein: Connects the cephalic and basilic veins in the cubital fossa (region in front of the elbow), commonly used for venipuncture.
• Axillary Vein: Drains blood from the upper extremity, becoming the subclavian vein.
• Subclavian veins: drains into the brachiocephalic vein

Fascia and Compartments

• Deep Fascia: A layer of connective tissue that surrounds muscles and divides the upper extremity into compartments.
• Arm Compartments:
  • Anterior Compartment: Contains the flexor muscles (biceps brachii, brachialis, coracobrachialis).
  • Posterior Compartment: Contains the extensor muscles (triceps brachii).
• Forearm Compartments:
  • Anterior Compartment: Contains the flexor and pronator muscles.
  • Posterior Compartment: Contains the extensor and supinator muscles.
• Retinacula: Thickened bands of deep fascia that hold tendons in place at the wrist (flexor and extensor retinacula).
• Carpal Tunnel: Space between the carpal bones and flexor retinaculum, through which the median nerve and flexor tendons pass.

Overview of the anatomy of the upper extremity. Includes bones of the shoulder, arm, forearm, wrist, and hand, with a focus on function and connections to the axial skeleton.