The midclavicular line is usually the vertical made through the midpoint between the sternal end of the clavicle and the acromion end of the clavicle, which in the average adult male or child is located about 0.5 cm medial to the nipple.
The clavicle is the transverse bone of the pharyngeal shoulder and has an inverted S-shaped morphology, protruding forward medially and backward laterally. The midclavicular line is simply a vertical line drawn to the horizontal at the center of the two ends of the clavicle. The midclavicular line is an artificial demarcation and is not the original anatomical structure of the human body.
The delineation of the midclavicular line helps to artificially delineate the front area of the body, which facilitates auscultation, palpation, and so on. For example, in most people, the tip of the heart is located about 0.5 cm inside the left midclavicular line, which is important for auscultation of the heart.