Humerus

The humerus is a long bone of the upper arm. It is one of the longest bones in the body, which makes it more prone to fractures upon impact. The word “humerus” comes from the Latin word for upper arm.

The humerus bone is located in the upper arm, between the shoulder joint and the elbow joint. The shoulder joint, also known as the glenohumeral joint, is a ball and socket joint. The ball is the humeral head, and the socket is the glenoid fossa of the scapula. The joint is supported by ligaments, and surrounded by the four rotator cuff muscles and their tendons: the supraspinatus, infraspinatus, teres minor, and subscapularis. These muscles originate on the scapula and insert on the humeral head.

The proximal humerus is the part of the bone that is most prone to fracture. Below the head of the humerus is the anatomical neck of the humerus, followed by the greater and lesser tubercles, which are projections in the bone. Underneath the tubercles is the surgical neck. Proximal humerus fractures most often occur in the surgical neck, especially in older individuals with osteoporosis. 

The proximal humerus is connected through the bone shaft to the distal humerus. The distal humerus articulates at the elbow joint to the radius and ulna, the two arm bones that make up the forearm.

The humerus provides structural support and serves as an insertion point for many important muscles. The pectoralis major (“pecs”) and latissimus dorsi (“lats”) muscles attach at the intertubular sulcus, or groove, in the head of the humerus, and work to help rotate the humerus. Several other muscles that provide motion for the arm and upper body attach to the humerus, these include the deltoids, brachioradialis, coracobrachialis, pronator teres, teres major, brachialis, and common flexor and extensor tendons. Finally, the rotator cuff muscles at the shoulder connect to the humerus to stabilize the glenohumeral joint, which is freely movable, but also highly unstable and prone to dislocation, as well as rotator cuff injury. Injuries to the rotator cuff are common in people over 60 years of age. 

Various arteries and veins travel along the humerus bone. The brachial artery, the major blood vessel of the upper arm, runs along the length of most of the humerus bone. At the elbow joint, it divides into the radial and ulnar arteries which supply blood to the forearm. The basilic vein also travels close to the humerus and helps drain parts of the hand and forearm.

Moreover, nerves of the brachial plexus travel along the humerus. The radial nerve follows a similar path, rotating along the bone midway down the humeral shaft. Fractures in this region can cause damage to the radial nerve. The ulnar nerve travels along the distal end of the humerus, near the elbow. When one refers to hitting their “funny bone,” they are actually referring to striking the ulnar nerve. 

The humerus is a long bone located in the upper arm, between the shoulder joint and elbow joint. The proximal humerus connects to the shoulder through the glenoid fossa of the scapula, forming the glenohumeral joint. The distal humerus articulates at the elbow to the radius and ulna in the forearm. 

The humerus provides structural support to the arm and is an insertion point for many important muscles in the upper body, such as pectoralis major, latissimus dorsi, rotator cuff muscles, and more. The brachial artery also travels along the humerus, supplying oxygen and other nutrients in the blood to the arm while the basilic vein runs close by and helps drain parts of the hand and forearm. The radial and ulnar nerves also run close to the humerus.