Endocrine System
The endocrine system provides long term chemical control of the body, coordinating its functions along with the nervous system. Endocrine glands such as the hypothalamus, hypophysis, pineal, parathyroid, adrenal, pancreas, and ovaries or testes secrete chemical signals called hormones into the extracellular space. These hormones can do anything from regulate the composition of extracellular fluid, regulate metabolism, regulate contraction of smooth and cardiac muscle, help maintain homeostasis, regulate the immune system, and regulate growth. The endocrine system receives most of its food and oxygen from the aorta and most of its wastes leave through the superior vena cava. Most of its lymph is filtered in the palatine tonsil.
The hypothalamus is the control center for the endocrine system. The hypothalamus is the link between the other parts of the brain and the endocrine system. It receives messages sent by the nervous system and interprets them and releases hormones from the endocrine system.
The pituitary gland is about the size of a pea, but secretes some of the most important hormones in the body. Some of the hormones secreted by the pituitary are human growth hormone, prolactin, adrenocorticotropin, thyroid stimulating hormone, oxytocin, and follicle stimulating hormone. These hormones participate in everything from initiating growth, to causing milk production.
The pineal gland is the shape of a pine cone. It is found inside the brain and the majority of its purpose are not know yet. One of the things that is known about the pineal gland is that it secretes the hormone melatonin, which causes drowsiness.
The pancreas secretes two of the most important hormones in the body, insulin and glucagon. These two hormones regulate the level of glucose in the blood. Insulin lowers the glucose level of the blood whereas glucagon increases it. Diabetics do not produce insulin, and therefore have a hard time controlling their blood sugar levels. Many need to physically inject it into themselves so as to control the level of glucose in their blood.
The thyroid and parathyroid glands are locate on the outside of the trachea. The thyroid gland releases hormones like thyroxine, triiodothyronine, and calcitonin. These hormones regulate oxygen use, cellular metabolism, growth, and development of the body.
The parathyroid glands are attached to the rear of the thyroid gland. They are small spherical tissue masses that secrete parathyroid hormone into the body. Parathyroid hormone increases the concentration of calcium and magnesium ions in the blood, increases phosphate re-absorption, and promotes the formation of calcitrol.
The adrenal glands are paired organs. One lies on top of each kidney. The adrenal glands are separated into two parts, the adrenal cortex and the adrenal medulla. The adrenal cortex secretes mineralcorticoids, glucocorticoids, and gonadocorticoids. The mineralcorticoids affect mineral homeostasis whereas the glucocorticoids control glucose homeostasis and the gonadocorticoids makes sex hormones. The adrenal medulla secrets epinephrine and norepinepherine. Epinephrine and norepinepherine, when secreted increase blood pressure by increasing the heart rate in a time of crises.
The last organs of the endocrine system are also reproductive organs. The ovaries secrete estrogen, progesterone, relaxin, and inhibin. Estrogen and progesterone stimulate bodily functions which maintain female characteristics of the body. Relaxin causes the cervix to dilate at the end of a pregnancy. Inhibin stops the FSH when the menstrual cycle is nearing its completion.
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Muscular System Excretory System Nervous System Respiratory System
Reproductive System Endocrine System Digestive System Credits