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.

The adrenal_glands sit above each kidney (are suprarenal) in the human, but are separated from the kidneys in a cat.

The interior of the adrenal glands is divided into two regions: the cortex and the medulla.

The cortex is subdivided into layers, or zones. Each zone produces different hormones.

These zones are the

zona_glomerulosa (mineralocorticoids),

zona_fasciculata (glucocorticoids), and

zona_reticularis (gonadocorticoids).

The medulla contains specilized chromaffin_cells, which produce the catecholamine hormones, including  epinephrine and norepinephrine.