Ovary

Females carry a pair of ovaries within the abdomen. The ovary is the primary female sex organ, and during each menstrual cycle it releases one ovum. Alongside this reproductive role, the ovary also acts as an endocrine gland, secreting two groups of steroid hormones: estrogen and progesterone.

Structure and hormone sources

The ovary is made up of ovarian follicles together with stromal tissue. The two hormones come from different structures within it:

• Estrogen is chiefly made and released by the growing ovarian follicles.
• Progesterone comes mainly from the corpus luteum — the structure that forms when a follicle ruptures at ovulation and is then converted into this hormone-secreting body.

What estrogen does

Estrogens have broad actions across the female reproductive system and body:

• Stimulate the growth and activity of the female secondary sex organs.
• Support the development of the growing ovarian follicles.
• Bring about the female secondary sex characters, such as a higher pitch of voice.
• Promote development of the mammary glands.
• Regulate female sexual behaviour.

What progesterone does …