Anatomy of the Arm Muscles and Vascular System

Posted on May 4, 2024 in Biology

Muscles of the Arm

Biceps Brachii

  • Origin:
    • Short Head: Coracoid process of the scapula
    • Long Head: Glenoid of the scapula
  • Insertion: Radial tuberosity and fascia of the forearm
  • Innervation: Musculocutaneous nerve
  • Function:
    • Flexion of the shoulder joint
    • Supination of the forearm
    • Flexion of the forearm at the elbow

Brachialis

  • Origin: Anterior humerus
  • Insertion: Coronoid process of the ulna
  • Innervation: Musculocutaneous nerve
  • Function: Flexion of the forearm

Coracobrachialis

  • Origin: Coracoid process of the scapula
  • Insertion: Middle third of the medial surface of the humerus
  • Innervation: Musculocutaneous nerve
  • Function: Flexion and adduction of the arm

Anconeus

  • Insertion: Posterior surface of the ulna
  • Innervation: Radial nerve
  • Function:
    • Stabilizes the elbow joint
    • Assists the triceps brachii in extension

Triceps Brachii

  • Origin:
    • Long Head: Infraglenoid tubercle of the scapula
    • Lateral Head: Posterior surface of the humerus, superior to the radial groove
    • Medial Head: Posterior surface of the humerus, below the radial groove
  • Insertion: Olecranon process of the ulna
  • Innervation: Radial nerve
  • Function: Extension of the forearm at the elbow

Innervation of the Arm

The brachial plexus, originating from spinal nerves C5 to T1, provides innervation to the muscles and skin of the arm and forearm.

Major Nerves of the Brachial Plexus

  • Musculocutaneous Nerve: Supplies the anterior compartment muscles of the arm and sensory innervation to the lateral forearm.
  • Median Nerve: Supplies the anterior compartment muscles of the forearm and hand, and sensory innervation to the palmar hand and first three and a half fingers.
  • Ulnar Nerve: Supplies muscles of the hand and sensory innervation to the ulnar side of the palm, back of the hand, and the fifth finger and half of the fourth finger.
  • Axillary and Circumflex Nerves: Supply the deltoid and teres minor muscles.
  • Radial Nerve: Supplies the posterior compartment muscles of the arm and forearm and sensory innervation to the posterior arm and forearm, and the back of the hand.

Arterial Supply of the Arm

Major Arteries

  • Axillary Artery: Continuation of the subclavian artery, supplying the shoulder region and transitioning into the brachial artery.
  • Brachial Artery: Continuation of the axillary artery, running along the arm and dividing into the radial and ulnar arteries.
  • Deep Brachial Artery: Branch of the brachial artery, contributing to the arterial anastomosis around the elbow.
  • Radial Artery: Runs along the radial side of the forearm, supplying the hand and forming the deep palmar arch.
  • Ulnar Artery: Runs along the ulnar side of the forearm, contributing to the superficial and deep palmar arches.

Palmar Arches

  • Deep Palmar Arch: Formed by the radial artery and a branch of the ulnar artery, supplying the deep structures of the hand.
  • Superficial Palmar Arch: Formed by the ulnar artery and a branch of the radial artery, supplying the superficial structures of the hand.

Venous Drainage of the Arm

Major Veins

  • Axillary Vein: Continuation of the basilic vein, draining the shoulder region and transitioning into the subclavian vein.
  • Cephalic Vein: Runs superficially along the radial side of the arm and forearm, draining into the axillary vein.
  • Basilic Vein: Runs superficially along the ulnar side of the arm and forearm, draining into the axillary vein.
  • Median Cubital Vein: Connects the cephalic and basilic veins at the elbow, commonly used for blood draws and intravenous infusions.

Palmar Venous Arches

  • Superficial Palmar Venous Arch: Accompanies the superficial palmar arterial arch, draining superficial structures of the hand.
  • Deep Palmar Venous Arch: Accompanies the deep palmar arterial arch, draining deep structures of the hand.