Download Parathyroid glands produce parathyroid hormone, which

Parathyroid glands produce parathyroid hormone, which is responsible
for specific physiological responses in the body related to calcium.
LEARNING OBJECTIVES [ edit ]
Describe how the parathyroid glands regulate calcium levels in the blood
Discuss the role of the parathyroid hormone in maintaining homeostasis
KEY POINTS [ edit ]
Parathyroid glands are responsible for the regulation the body's calcium and phosphorus levels
by producing parathyroid hormone, which helps control calcium release.
Oxyphil cells and chief cells are two main types of cells that make up parathyroid tissue; chief cells
make parathyroid hormone while the role of oxyphil cells remains unknown.
Parathyroid hormone is released into the bloodstream where it travels to target cells, binding to
a receptor found on the target cells.
Parathyroid hormones help regulate calcium levels by increasing blood calcium concentrations
when calcium ionlevels fall below normal.
TERMS [ edit ]
calcitriol
the active metabolite 1,25­dihydroxycholecalciferol of vitamin D3 that is involved in the
absorption of calcium
osteoclast
a large multinuclear cell associated with the resorption of bone
parathyroid hormone
a polypeptide hormone that is released by the chief cells of the parathyroid glands and is involved
in raising the levels of calcium ions in the blood
osteoblast
a mononucleate cell from which bone develops
Give us feedback on this content: FULL TEXT [ edit ]
Parathyroid Glands
The parathyroid glands are
small endocrine glands that produce
parathyroid hormone. Most people have
four parathyroid glands; however, the
number can vary from two to six. These
glands are located on the posterior surface
of the thyroid gland. Normally, there is a
superior gland and an inferior gland
associated with each of the thyroid's two
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lobes . Each parathyroid gland is covered by connective tissue and contains many
secretory cells that are associated with a capillary network. There are two major types of cells
that make up parathyroid tissue: oxyphil cells and chief cells, the latter of which actually
produce parathyroid hormone. The function of oxyphil cells is unknown.
Parathyroid glands
The parathyroid glands are located on the posterior of the thyroid gland. The parathyroid glands
produce parathyroid hormone (PTH) which increases blood calcium concentrations when calcium ion
levels fall below normal.
One of the parathyroid glands' most important functions is to regulate the body's calcium
and phosphorus levels. Another function of the parathyroid glands is to secrete parathyroid
hormone, which causes the release of the calcium present in bone to extracellular fluid.
Parathyroid hormone (PTH), also known as parathormone, is released directly into the
bloodstream, traveling to its target cells, which are often quite far away. It then binds to
areceptor (found either inside or on the surface of the target cells). Receptors bind a specific
hormone, resulting in a specific physiologic (normal) response of the body. Parathyroid Glands and Calcium Regulation PTH opposes the effect of thyrocalcitonin (or calcitonin), a hormone produced by the thyroid
gland that regulates calcium levels. It does this by removing calcium from its storage sites in
bones and releasing it into the bloodstream. It also signals the kidneys to reabsorb more of
this mineral, transporting it into the blood. PTH can also signal the small intestine to absorb
calcium by transporting it from the diet into the blood. Calcium is important for
metabolization to occur. Blood cannot clot without sufficient calcium. Skeletal muscles
require this mineral in order to contract. A deficiency of PTH can lead to tetany, a condition
characterized by muscle weakness due to lack of available calcium in the blood. More specifically, PTH increases blood calcium concentrations when calcium ion levels fall
below normal. First, PTH enhances reabsorption of calcium by the kidneys; it then
stimulates osteoclast activity and inhibits osteoblastactivity. Finally, PTH stimulates
synthesis and secretion ofcalcitriol by the kidneys, which enhances Ca2+ absorption by the
digestive system. PTH and calcitonin work in opposition to one another to maintain
homeostatic calcium levels in body fluids.