The upper section of the arm is called the humerus. It is connected to the forearm by the joint of the elbow. The shoulder joint connects the upper arm to the shoulder girdle and thus to the trunk.
What is the upper arm?
The upper arm (called brachium in Latin) is the part of the arm closest to the torso of the body. For this reason, the upper arm is the proximal (closest to the body) part of the arm. The upper arm connects the shoulder to the shoulder girdle via the shoulder joint and thus ultimately to the trunk. The brachium is connected to the forearm via the joint of the elbow. The upper arm section contains the humerus (upper arm bone), one of the longest bones in the entire human body.
Anatomy and structure
The upper arm consists of the humerus, the upper end of which consists of a ball and socket joint. This ball and socket joint sits within the scapula and provides the connection to the shoulder. The shoulder joint represents the movable part of the connection from the trunk to the arm. It is also the most mobile joint of the entire human body. This is also noticeable in the connection that exists between the upper arm and the joint. This is because, viewed from the front, they come together at the back of the bone. It is only through this that the arm exhibits its great mobility. Another joint to which the upper arm is connected is the elbow joint. This is found at its lower end and connects the upper arm to the forearm. Unlike the shoulder and wrist joints, which can be bent, approached and extended, among other things, the elbow joint can only be bent, extended and turned over. The brachium features two main muscles: Biceps and Triceps. In addition, the upper arm has a deltoid muscle. The biceps are found on the front of the upper arm, while the triceps are on the back and the deltoid is located in the shoulder area. The muscles are each surrounded by a sheath of connective tissue (called fascia). In addition, the entire upper arm musculature is surrounded by an arm fascia (called fascia brachii). Furthermore, the upper arm is composed of two septa and a whole series of nerves and vessels. However, the upper arm is not only moved by the muscles located in the brachium, but to a large extent by muscles located in the chest, back or shoulder.
Function and tasks
The arm as a whole is the body part that presents the greatest freedom of movement in the human body. As the transition of the arm to the trunk, the upper arm performs a central connecting function. In addition, the muscles in the shoulder, chest, back and upper arm make it possible to pull the arm sideways towards or away from the body. This movement is called adduction or abduction. Furthermore, the upper arm and thus the entire arm can be lifted and rotated inward and outward through the shoulder joint. In this way, the upper arm plays a not inconsiderable part in the two important arm functions – lifting and gripping. Another important function of the arms is balancing the body, for example when walking upright. Here, too, the upper arm plays a central role: because balancing the body begins in the shoulder muscles and ends in the wrist.
Diseases and complaints
One of the most common injuries of the arm is the arm fracture. This affects the upper arm less often than the forearm. Medically, an upper arm fracture is called a subcapital humerus fracture. However, these only account for about 5 percent of all arm fractures. Clearly more common fractures affect the ulna and radius, which are located in the forearm. However, fractures are not the only injuries or conditions that can occur in the upper arm and cause discomfort and limitation: Nerves, tendons, joints, vessels, muscles and veins can also be affected by injuries or by diseases. Common causes are strong external impacts on the upper arm, such as can occur in accidents. However, incorrect or excessive strain on the upper arm can also damage the muscles, tissues and nerves of the upper arm. Due to its high mobility, complaints can quickly arise in the brachium due to pinched nerves and tendons or compressed tissue. These are usually manifested by pain and by a restriction of mobility. However, both can also occur due to inflammation of the muscle tissue, nerves or tendons.An injured or diseased upper arm is usually affected not only by pain, but also by a feeling of weakness. In addition to pain, many patients complain of reduced muscle function, making it difficult or impossible to move the upper arm. In addition, clinical pictures occur where there is only limited pain in the upper arm except for limited mobility. Injuries and diseases of the brachium, however, usually do not only refer to the upper arm, but often affect other parts of the body in their function and task due to its important task. If the nerves in the upper arm are affected, numbness can thus occur in the lower extremities of the arm, i.e., in the hands or fingers, for example.
