ovary

ovary ductless gland of the female in which the ova (female reproductive cells) are produced. In vertebrate animals the ovary also secretes the sex hormones estrogen and progesterone , which control the development of the sexual organs and the secondary sexual characteristics. The interaction between the gonadotropic hormones from the pituitary gland and the sex hormones from the ovary controls the monthly cycle in humans of ovulation and menstruation . There are two ovaries in the human, held in place on each side of the uterus by a membrane; each ovary is about the size of an almond. About 500,000 immature eggs are present in the cortex of the ovary at birth. Starting at puberty, eggs mature successively, and one breaks through the ovarian wall about every 28 days in the process known as ovulation, which continues until menopause, or cessation of reproductive functioning in the female. After its release from the ovary, the ovum passes into the oviduct (uterine or fallopian tube) and into the uterus. If the ovum is fertilized by the sperm (male reproductive cell), pregnancy ensues (see reproductive system ). In flowering plants the part of the pistil containing the ova is called the ovary; the ripened ovary is the fruit.

ovary
1. The reproductive organ in female animals in which eggs (ova) are produced. In most vertebrates there are two ovaries (in some fish the ovaries fuse together to form a single structure and in birds the left ovary only is functional). As well as eggs, they produce steroid hormones (see oestrogen; progesterone). In mammals each ovary is situated close to the opening of a fallopian tube; it contains numerous follicles in which the eggs develop and from which they are released in a regular cycle. See also Graafian follicle; menstrual cycle; oogenesis; ovulation; reproductive system.

2. The hollow base of the carpel of a flower, containing one or more ovules. After fertilization, the ovary wall develops into the fruit enclosing the seeds. In some species, the carpels are fused together to form a complex ovary.

ovary In biology, part of a multicellular animal or a flowering plant that produces egg cells (ova), the female reproductive cells; in vertebrates it also produces female sex hormones. In women, there is an ovary on each side of the uterus. Controlled by the pituitary gland, each ovary produces oestrogen and progesterone, which control the functioning of the female reproductive system. In flowering plants, the female sex cells are contained within structures called ovules inside the ovary. After fertilization, the ovules develop into seeds and the ovary develops into fruit. See also hormone; menstrual cycle