Dogs are usually in heat for 21 days. Female dogs have a cyclic sexuality that is independent of season unlike most animals. As for the male dogs, they do not have any cycles and are always ready for intimacy like most males of any species including human beings. Female dogs have a cycle of six months on average meaning they can be in heat twice a year. The heat cycle has three distinct stages. They include: Proestrus. During this stage, one may notice some bleeding from the vulva of the dog. The bleeding can either be heavy or light.
Study what happens when there is a deficiency in the protein parathyroid hormone. This hormone is important for the proper metabolism of calcium and bone tissue in the body. The physiological role of this protein hormone in the body of humans is well known and is well understood.
A) the steroid and peptide hormones must use the same biochemical mechanisms. B) the steroid and peptide hormones must bind to the same receptor protein. C) the steroid hormones affect the synthesis of effector proteins, whereas peptide hormones activate effector proteins already present in the cell.