Men possess external genitalia (the penis, scrotum and testes) for the production and delivery of sperm, and women possess internal genitalia (the vagina, uterus and ovaries) for the production of eggs and the development of human embryos. Most physiological differences between men and women occur due to differences in the endocrine systems during critical periods of development, such as fetal growth and puberty.
The functions of the endocrine systems in men and women lead to other physiological differences throughout life. For example, men produce a more course and visible type of hair follicle called terminal hairs on the chest, abdomen, face and back. Women, however, produce a finer hair follicle called vellus hairs in fewer areas of the body. Hormone production in the endocrine system is also partially responsible for the development and differences of pattern baldness in men and women.
Great differences are also present in the skeletal and muscular systems in men and women. Typically, men possess denser, stronger tendons, ligaments and bones than women, and men generally have more muscle mass. This leads to differences in physical strength and the metabolic processes of calorie expenditure and storage. In comparison, women typically possess a skeletal system that is less robust and more smooth in structure than that found in males.