The endocrine system consists of chemical transmitters called hormones and specialized cell clusters called glands.
The endocrine system consists of three major components: glands, hormones & Receptors.
Glands: which are specialized cell clusters or organs.
Hormones: which are chemical substances secreted by glands in response to stimulation.
Receptors: which are protein molecules that trigger specific physiologic changes in a target cell in response to hormonal stimulation.
The major glands of the endocrine system are:
• Pituitary gland
• Thyroid gland
• Parathyroid glands
• Adrenal glands
• Pineal gland
• Gonads (ovaries and testes).
The pea-sized pituitary gland, located on the inferior aspect of the brain, is called the “master gland” because it regulates many key processes. It has two lobes: the posterior lobe, which stores and releases oxytocin and antidiuretic hormone produced by the hypothalamus, and the anterior lobe, which produces at least six hormones.
• Growth hormone (GH), or somatotropin
• Thyroid-stimulating hormone (TSH), or thyrotropin
• Follicle-stimulating hormone (FSH) luteinizing hormone (LH)
The thyroid gland lies directly below the larynx, partially in front of the trachea. Its two lateral lobes — one on either side of the trachea — join with a narrow tissue bridge, called the isthmus, to give the gland its butterfly shape. The two lobes of the thyroid function as one unit to produce two hormones:
• Triiodothyronine (T3) and thyroxine (T4), collectively referred to as thyroid hormone, are the body’s major metabolic hormones.
• Calcitonin maintains the blood calcium level by inhibiting the release of calcium from bone.
Four parathyroid glands lie embedded on the posterior surface of the thyroid, one in each corner. Like the thyroid lobes, the parathyroid glands work together as a single gland, producing
Endocrine system components:
Endocrine glands secrete hormones directly into the bloodstream to regulate body function. This illustration shows the location of the major endocrine glands.
Structurally, hormones can be classified into three types: