The endocrine system consists of a series of glands that produce regulatory chemicals, which are known as hormones. The term endocrine means that these glands lack ducts, or exit passageways. They secrete their products directly into the cellular environment. The endocrine system includes these glands: pituitary, pineal, thymus, thyroid, parathyroid, adrenal, pancreatic_islets, ovaries, and testes. We will review some, but not all, of these in our lab.

We do not cover the microscopic structure of the thymus in lab, but you are responsible for identifying the thymus in the cat. The endocrine function of the thymus involves producing several hormones that regulate the production and maturation of T-cells (T-lymphocytes).