Human eye of the size of the pupil, regulation and suppression of the hormone melatonin and entrainment of the body clock. The eye is not shaped like a perfect sphere, rather it is a fused two-piece unit, composed of the anterior segment and the posterior segment. The anterior segment is made up of the cornea, iris and lens. The cornea is transparent and more curved, and is linked to the larger posterior segment, composed of the vitreous, retina, choroid and the outer white shell called the sclera. The cornea is typically about 11.5 mm (0.3 in) in diameter, and 1/2 mm (500
Development of the human body Development of the human body Human development is the process of growth to maturity. The process begins with fertilisation, where an egg released from the ovary of a female is penetrated by a sperm cell from a male. The egg then lodges in the uterus, where an embryo and later fetus develop until birth. Further growth and development continues after birth, and includes both physical and psychological development, influenced by genetic, hormonal, environmental and other factors. This continues throughout life, through childhood, and adolescence into adulthood. Development before birth, or prenatal development () is the process in which an embryo