Simulation · Biology · Class 11
Two hormones hold blood calcium steady
From the lesson Parathyroid gland and thymus in Chemical Coordination and Integration. Change the values and watch what happens.
Two hormones hold blood calcium steadyBiology · Class 11
The idea behind it
NCERT §19.2.5–§19.2.6
- Humans have four parathyroid glands on the back of the thyroid, one pair in each of its two lobes.
- They secrete a peptide hormone, parathyroid hormone (PTH). How much PTH is secreted is controlled by the level of calcium ions circulating in the blood.
- PTH raises blood Ca²⁺ in three ways: it stimulates bone resorption (dissolution or demineralisation of bone), it stimulates reabsorption of Ca²⁺ by the renal tubules, and it increases Ca²⁺ absorption from digested food. PTH is therefore a hypercalcemic hormone.
- PTH and TCT together play a major part in keeping the body's calcium in balance.
- The thymus is a lobular gland between the lungs, behind the sternum, on the ventral side of the aorta. It has a major role in developing the immune system.
- It secretes peptide hormones called thymosins, which have a major role in the differentiation of T-lymphocytes, the cells that give cell-mediated immunity. Thymosins also promote antibody production, giving humoral immunity.
- The thymus degenerates in old people, so less thymosin is made and their immune responses become weak.