The platysma is a superficial muscle that overlaps the sternocleidomastoid. It is a broad sheet arising from the fascia covering the upper parts of the pectoralis major and deltoid; its fibers cross the clavicle, and proceed obliquely upward and medially along the side of the neck.
For example genetic differences, females inherit X chromosomes from their father giving them a genetic make-up of XX, while males inherit a Y chromosome from their father, thus giving them a genetic make-up of XY.
Sex refers to the biological characteristics of a person at birth, while gender relates to his or her perception of being male or female and is known as the gender role. Gender role refers to the behaviors and desires to act in certain ways that are viewed as masculine or feminine by a particular culture.