Sometimes, a small sample of tissue may be taken with small tools inserted through the vagina during a transvaginal ultrasound. In all three types of pelvic ultrasound, the transducer sends the reflected sound waves to a computer, which makes them into a picture that is shown on a video screen.
So the number of egg-containing follicles remaining in the ovary undergoes a steady decline from an average of 400,000 eggs at age eighteen to an average of 25,000 eggs by age thirty-seven. After age thirtyseven or thirty-eight, there is then a very dramatic acceleration of the monthly decline of remaining eggs.
An Egg a Day is Work. If you think laying an egg is easy, think again! Robins lay only one egg per day for good reasons. Female birds have one working ovary, unlike mammals, which have two. Ovaries are the organs where eggs are produced. A bird's ovary looks like a tiny bunch of different-sized grapes.