Which of the following hormones is responsible for both contraction of the uterus and milk production in lactating women?

A. The ovaries are responsible for producing hormones such as estrogen and progesterone but do not directly produce lubrication during sexual excitement.
B. The cervix produces mucus that changes in consistency throughout the menstrual cycle but does not play a significant role in lubrication during sexual activity.
C. Skene's glands, located near the urethra, secrete fluid that is often compared to prostate fluid in males, but they do not play the primary role in vaginal lubrication during sexual excitement.
D. Bartholin's glands, located near the vaginal opening, secrete mucus that provides lubrication during sexual excitement, helping to reduce friction and enhance comfort during intercourse.

A. Calcium plays a critical role in blood clotting. It is involved in the coagulation cascade and is necessary for the activation of clotting factors that help stop bleeding.

B. Calcium is not involved in acid buffering. This function is primarily carried out by buffers such as bicarbonate in the blood.

C. While calcium does help regulate some functions of cells and tissues, it does not primarily contribute to extracellular osmotic pressure; this is more a function of proteins and other ions.

D. ATP production mainly occurs in mitochondria and is driven by the metabolism of glucose and fatty acids, not by calcium directly. Calcium does, however, play a role in cellular processes like muscle contraction.