What are the functions of pineal gland, parathyroid glands and thymus glands
pineal gland function :
The primary function of the pineal gland is to produce melatonin . Melatonin has various functions in the central nervous system , the most important of which is to help modulate sleep patterns. Melatonin production is stimulated by darkness and inhibited by light.Light sensitive nerve cells in the retina detect light and send this signal to the suprachiasmatic nucleus (SCN), synchronizing the SCN to the day-night cycle. Nerve fibers then relay the daylight information from the SCN to the paraventricular nuclei (PVN), then to the spinal cord and via the sympathetic system to superior cervical ganglia (SCG), and from there into the pineal gland.
Parathyroid gland function :
The major function of the parathyroid glands is to maintain the body's calcium and Phosphate levels within a very narrow range, so that the nervous and muscular system can function properly. The parathyroid glands do this by secreting parathyroid hormone (PTH).
Parathyroid hormone (also known as parathormone) is a small protein that takes part in the control of calcium and phosphate homeostasis , as well as bone physiology. Parathyroid hormone has effects antagonistic to those of calcitonin .
- Calcium . PTH increases blood calcium levels by directly stimulating osteoblasts and thereby indirectly stimulating osteoclasts (through RANK/RANKL mechanism) to break down bone and release calcium. PTH increases gastrointestinal calcium absorption by activating vitamin D , and promotes calcium conservation (reabsorption) by the kidneys .
- Phosphate . PTH is the major regulator of serum phosphate concentrations via actions on the kidney. It is an inhibitor of proximal tubular reabsorption of phosphorus. Through activation of vitamin D the absorption (intestinal) of Phosphate is increased.
Thymus gland function :
The thymus functions chiefly to develop T lymphocytes. Once mature, these cells leave the thymus and are transported via blood vessels to the lymph nodes and spleen. T lymphocytes are responsible for cell-mediated immunity, which is an immune response that involves the activation of certain immune cells to fight infection. T-cells contain proteins called T-cell receptors that populate the T-cell membrane and are capable of recognizing various types of antigens (substances that provoke an immune response). T lymphocytes differentiate into three major classes in the thymus. These classes are:
- Cytotoxic T cells - directly terminate antigens.
- Helper T cells - precipitate the production of antibodies by B-cells and also produce substances that activate other T-cells.
- Regulatory T cells - also called suppressor T cells, these cells suppress the response of B-cells and other T-cells to antigens.
The thymus produces hormone-like proteins that help T lymphocytes mature and differentiate. Some thymic hormones include thympoeitin, thymulin, thymosin, and thymic humoral factor (THF). Thympoeitin and thymulin induce differentiation in T-lymphocytes and enhance T-cell function. Thymosin increases immune responses. It also stimulates certain pituitary gland hormones (growth hormone, luteinizing hormone, prolactin, gonadotropin releasing hormone, and adrenocorticotropic hormone (ACTH)). Thymic humoral factor increases immune responses to viruses in particular.
The primary function of the pineal gland is to produce melatonin . Melatonin has various functions in the central nervous system , the most important of which is to help modulate sleep patterns. Melatonin production is stimulated by darkness and inhibited by light.Light sensitive nerve cells in the retina detect light and send this signal to the suprachiasmatic nucleus (SCN), synchronizing the SCN to the day-night cycle. Nerve fibers then relay the daylight information from the SCN to the paraventricular nuclei (PVN), then to the spinal cord and via the sympathetic system to superior cervical ganglia (SCG), and from there into the pineal gland.
Parathyroid gland function :
The major function of the parathyroid glands is to maintain the body's calcium and Phosphate levels within a very narrow range, so that the nervous and muscular system can function properly. The parathyroid glands do this by secreting parathyroid hormone (PTH).
Parathyroid hormone (also known as parathormone) is a small protein that takes part in the control of calcium and phosphate homeostasis , as well as bone physiology. Parathyroid hormone has effects antagonistic to those of calcitonin .
- Calcium . PTH increases blood calcium levels by directly stimulating osteoblasts and thereby indirectly stimulating osteoclasts (through RANK/RANKL mechanism) to break down bone and release calcium. PTH increases gastrointestinal calcium absorption by activating vitamin D , and promotes calcium conservation (reabsorption) by the kidneys .
- Phosphate . PTH is the major regulator of serum phosphate concentrations via actions on the kidney. It is an inhibitor of proximal tubular reabsorption of phosphorus. Through activation of vitamin D the absorption (intestinal) of Phosphate is increased.
Thymus gland function :
The thymus functions chiefly to develop T lymphocytes. Once mature, these cells leave the thymus and are transported via blood vessels to the lymph nodes and spleen. T lymphocytes are responsible for cell-mediated immunity, which is an immune response that involves the activation of certain immune cells to fight infection. T-cells contain proteins called T-cell receptors that populate the T-cell membrane and are capable of recognizing various types of antigens (substances that provoke an immune response). T lymphocytes differentiate into three major classes in the thymus. These classes are:
- Cytotoxic T cells - directly terminate antigens.
- Helper T cells - precipitate the production of antibodies by B-cells and also produce substances that activate other T-cells.
- Regulatory T cells - also called suppressor T cells, these cells suppress the response of B-cells and other T-cells to antigens.
The thymus produces hormone-like proteins that help T lymphocytes mature and differentiate. Some thymic hormones include thympoeitin, thymulin, thymosin, and thymic humoral factor (THF). Thympoeitin and thymulin induce differentiation in T-lymphocytes and enhance T-cell function. Thymosin increases immune responses. It also stimulates certain pituitary gland hormones (growth hormone, luteinizing hormone, prolactin, gonadotropin releasing hormone, and adrenocorticotropic hormone (ACTH)). Thymic humoral factor increases immune responses to viruses in particular.
