• consists of endocrine glands containing cells that produce hormones to regulate growth, development, & metabolic activites of cells
• cells must have receptors for the hormones in order to resond to them
• hormones are carried from the cells that secrete them through connective tissues or the vascular system to target cells
• there are NO ducts associated w/endocrine glands

• pituitary gland or hypophysis (B)
• thyroid gland (C)
• adrenal gland (E)
• parathyroid gland (G)
• pineal gland (F)
• cells of the diffuse endocrine system that are parts of the stomach, small intestine, & lungs

Pituitary Gland - Hypophysis

• physically attached to the hypothalamus by a stalk & physiologically attached by a special vascular network
• called the "master gland" but it's function is controlled by the hypothalamus

• adenohypophysis
• epithelial glandular tissue
• pars distalis: largest part
• five types of epithelial cells in the pars distalis secrete hormones into surrounding capillaries
• the hypothalamus controls the release of hormones from the pars distalis

• neurohypophysis
• pars nervosa: largest part
• pars nervose contains  axons that produce & secrete  two types of hormones

• two distinct regions
  • cortex
  • medulla
• cortex and medulla are histologically & functionally different and have different embryological orgins

• outer region of the adrenal gland underneath the connective tissue capsule
• it is divided into three zones containing cells that secrete three different steriod hormones

• the inner regoin of the adrenal gland underneath the cortex
• functions like the nervous system
• cells in the medulla produce catechaolamines like epineprine (adrenaline)

• located in the neck
• usually consists of two lobes
• contains thyroid follicles
• follicles have a simple epithelium consisting of follicular cells
• follicular cells surround material called colliod

• synthesize, store, process, & secrete thryroid hormones
• thryoglobulin is a form of thyroid hormone that is stored in the colliod
• thyroglobulin is unusual because it's an extracellularly stored precursor to the active thyroid hormones 

• surround the colliod and are located between the follicular cells
• synthesize and secrete calcitonin, a hormone that decreases blood calcium levels

• located on the surface of or are embedded in the thyroid gland
• usually 4 of them

• chief cells synthesize and secrete parathyroid gland hormone (PTH), a hormone that raises blood calcium levels

• shaped like a pine cone and located w/in brain
• contains pinealocytes and glial cells
• pinealocytes: major cell type & secrete melatonin
• glial cells: function as supporting cells for pinealocyte