Bones of the Upper Limb

1. Introduction
2. Scapula
3. Clavicle
4. Humerus
5. Ulna
6. Radius
7. Quiz

There are five major bones that provide structure to the upper limb:

• Scapula
• Clavicle
• Humerus
• Ulna
• Radius

Introduction

This article will discuss five key bones that provide structure to the upper limb. These bones are often formed to allow for maximum manoeuvrability, allowing for complex movements to be performed. The following will be discussed:

• Scapula
• Clavicle
• Humerus
• Ulna
• Radius

Scapula

This is a large, flat, triangular bone found posteriorly in the thorax. It articulates with the humerus and clavicle to form the shoulder girdle and allow for the movement of the shoulder joint. It is the site of attachment for many muscles and is therefore vital for normal function of the shoulder. The scapula articulates with the head of the humerus via the glenohumeral joint and articulates with the clavicle via the acromioclavicular joint.

There are three main surfaces of the scapula:

• Costal surface - region facing the ribcage
• Lateral angle - region closest to the humerus that bears the glenoid fossa
• Posterior surface - region that faces outwards

Some key bony landmarks of the scapula include:

Coracoid Process - found on the costal surface, this is a projection that lies just inferior to the clavicle. It is the site of origin for many muscles, such as the coracobrachialis and biceps brachii.

Glenoid Fossa - found on the lateral surface, it articulates with the head of the humerus to form the shoulder joint.

Supraglenoid and Infraglenoid Tubercle - regions found immediately superior and inferior the glenoid fossa respectively. These are sites of attachment for heads of muscles in the upper limb.

Spine of the Scapula - found posteriorly, it divides the posterior surface of the scapula into two regions.

Supraspinous and Infraspinous Fossae - regions found just superior and inferior to the spine of scapula respectively. They give origin to supraspinatus and infraspinatus respectively, two of the rotator cuff muscles.

Acromion - a projection/elongation of the spine of the scapula which articulates with the clavicle to form the acromioclavicular joint.

Diagram - Costal aspect of the left scapula

Creative commons source by Atlas of Human Anatomy by Professor Dr. Carl Ernest Bock, edited by Dr. Sachin Sudhakaran [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]

Diagram - Posterior aspect of the left scapula

Creative commons source by Atlas of Human Anatomy by Professor Dr. Carl Ernest Bock, edited by Dr. Sachin Sudhakaran [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]

Clavicle

Also known as the collarbone, this is a long bone which articulates with both the sternum and the acromion of the scapula. It allows for movement by forming the shoulder girdle with the scapula. It provides protection by directly shielding the neurovascular structures that sit behind it, and by transmitting shock received by the hands (ie in a fall) through the chest. 

There are a few landmarks to know:

• Medial end (sternal end) - a faceted region that articulates with the manubrium of the sternum.
• Shaft - allows for attachment of different muscles and is also the region most prone to fracture.
• Lateral end - location of a small facet which articulates with the acromion.

Diagram - Anterior aspect of the left clavicle. The highlighted region in the middle illustrates the most common fracture site. The articulating surfaces are highlighted on either side, with the acromial end on the left and the sternal end on the right

Creative commons source by Atlas of Human Anatomy by Professor Dr. Carl Ernest Bock, edited by Dr. Sachin Sudhakaran [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]