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 is biological. It includes our genetic makeup, our hormones, and our body parts, especially our sex and reproductive organs. Gender refers to society's expectations about how we should think and act as girls and boys, and women and men. It is our biological, social, and legal status as women and men. Gender identity is how we feel about and express our gender and gender roles â clothing, behavior, and personal appearance. It is a feeling that we have as early as age two or three.