The upper arm

General information

The upper arm consists of an upper arm bone (humerus) and several joint connections to both the shoulder (shoulder joint) and the bones of the forearm (elbow joint). The upper arm also has numerous

  • Muscles,
  • Nerves
  • Vessels

The upper arm bone (humerus)

The humerus is a long tubular bone, which is divided into different parts. The main part of the humerus is the corpus humeri. The head of the humerus (Caput humeri), which carries the articular surface to the shoulder joint (Condylus humeri), is located on this part.

There are two epicondyles (bone projections) towards the center (medial) and to the side (lateral), which serve as attachment points for various muscles of the shoulder joint. The neck of the upper arm (collum anatomicum of the humerus) is connected to this humeral head. The joint capsule of the shoulder joint is anchored to this neck.

If you look at the humerus from the front, you will find two more bony humps. A groove, the sulcus intertubercularis, runs between these bone protrusions. The tendon of the long biceps head runs through this groove.

At the lateral part of the bone shaft there is a roughened surface, the so-called tuberosity deltoidea. This serves as the starting point of the deltoid muscle. The entire shaft of the humerus is divided into two areas.

Both bone edges continue towards the forearm as bone edges and then merge into the epicondylus medialis and lateralis. On the back surface of the humerus there is a groove for the radial nerve (sulcus nervus radialis), which winds around the humerus. At the connection between the humerus and the forearm bone, the humerus forms a bone roll, the trochlea humeri with the fossa coronoidea.

Medial to this is a groove for the ulnar nerve. In addition, the humerus capitulum is formed, which contains a radial fossa for the radial nerve. At the posterior surface of this transition is the olecranon fossa, which contains the olecranon of the forearm.

  • Tuberculum majus, from which the continuing Crista tuberculis majoris emerges. Towards the center lies the
  • Tuberculum minus, with the continuous Christa tuberculis minoris. These points serve as attachment points for various muscles.
  • The Facies anteromedialis and
  • The anterolateral facies.

The humeral head, also called humerus head (lat.

Caput humeri), is the end of the humerus close to the body. This bone end is spherical and lies in the glenoid cavity. Thus, the head of humerus and the glenoid cavity form the shoulder joint, a ball joint.

The head of humerus is larger than the ball socket, which gives the joint three degrees of freedom and makes it very flexible. This mobility is increased because the glenoid cavity is very flat. The surface of the head of humerus consists of a firm and thick layer of cartilage.

This form of cartilage is also called hyaline cartilage and is firmly connected to the bone tissue. This smooth surface is important for friction-free movement in the joint and serves to absorb shocks. The head of humerus is clearly separated from the rest of the humerus, the corpus humeri, and merges into the so-called colum, or neck. This transition point is particularly at risk for bone fractures.