When the body is dehydrated, secretion of the pituitary hormone that is abbreviated causes increased reabsorption of water from the collecting ducts?

The answer is; ADH

This pituitary hormone is called antidiuretic hormone. This hormone acts on the tubules of the nephron of the kidneys. The hormone increases the reabsorption of water from the renal fluid in the tubules hence making the urine concentrated. ADH is produced when the body is dehydrated and seeks to retain water.

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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enzyme active site and substrate specificity

enzymes bind with chemical reactants called substrates. there may be one or more substrates for each type of enzyme, depending on the particular chemical reaction. in some reactions, a single-reactant substrate is broken down into multiple products