Anatomy of the Upper Limb Bones Quiz

The bones of the upper limb, also known as the superior appendicular skeleton, provide the essential framework for both gross and fine motor functions of the upper limb in humans. These bones can be classified into two main groups based on their anatomical relationship with the axial skeleton: the pectoral girdle and the bones of the free part of the upper limb.

The Pectoral Girdle

The pectoral girdle, also known as the shoulder girdle, is a group of bones that directly articulate with the axial skeleton and are less mobile. It is composed of the clavicle and the scapula, which connect the upper limb to the axial skeleton through the sternoclavicular joint. The acromioclavicular joint, located between the acromion process on the scapula and the clavicle, is also strengthened by strong ligaments, especially the coracoclavicular ligament, which prevents excessive lateral and medial movements.

The Bones of the Free Part of the Upper Limb

The bones of the free part of the upper limb, which do not articulate directly with the axial skeleton, are more mobile. The majority of these bones are long bones, such as the humerus, radius, and ulna, which increase in number but decrease in size from proximal to distal. The upper limb also consists of flat, short, and sesamoid bones, such as the scapula, scaphoid, and pisiform bones, respectively.

The Humerus

The longest and largest bone of the upper limb is the humerus. It is a long bone that runs from the shoulder to the elbow and connects the scapula and the lower arm (consisting of the radius and ulna). The humerus is made up of the following parts:

• Head: A rounded area of the proximal humerus that interacts with the shoulder blade (scapula) to form the shoulder joint.
• Neck: A narrow part that connects the head to the body of the humerus.
• Body or shaft: A long, middle portion of the humerus.
• Distal: The lower area of the humerus that is closest to the elbow.

The humerus has a cylindrical upper portion and a more prismatic lower portion. Its lower extremity consists of two epicondyles, two processes (trochlea and capitulum), and three fossae (radial fossa, coronoid fossa, and olecranon fossa). The true anatomical neck and the constriction below the greater and lesser tubercles of the humerus are referred to as the surgical neck due to their tendency to commonly get fractured.

The Radius and Ulna

The radius and ulna are the two bones of the lower arm. The ulna is the main distal part of the elbow joint, while the radius composes the main proximal part of the wrist joint. Both bones have an essential role in providing a wide range of movements for the upper limb.

In conclusion, the bones of the upper limb, including the pectoral girdle and the bones of the free part of the upper limb, work together to provide the skeletal framework for both gross and fine motor functions. The humerus, radius, and ulna are the main long bones that support the upper limb, while the scapula, scaphoid, and pisiform bones contribute to the overall function and stability of the upper limb.