Explain why having more red blood cells per cm3 of blood is an advantage to an athlete.

Haemoglobin carries oxygen, therefore, more oxygen can be transported to cells such as muscle cells. More oxygen transported to cells results in more aerobic respiration of cells such as muscle cells.

the corpus luteum secretes estrogens and progesterone. the latter hormone causes changes in the uterus that make it more suitable for implantation of the fertilized ovum and the nourishment of the embryo. if the egg is not fertilized, the corpus luteum becomes inactive after 10–14 days, and menstruation occurs.

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