BSIP, S & I / SCIENCE PHOTO LIBRARY BSIP, S & I / SCIENCE PHOTO LIBRARY
Corpus luteum in ovary. Coloured ultrasound scan of a healthy human ovary after egg release (ovulation). At centre is a dark cavity from which an egg has erupted. This structure is the corpus luteum and its role after ovulation is to secrete the hormone progesterone to ready the uterus for implantation of a fertilized egg. Ultrasound uses high-frequency sound waves to create images of structures inside the body from the returning echoes.
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