The Parathyroid Glands and Vitamin D

These flashcards cover key terms and concepts related to the parathyroid glands, vitamin D, and the regulation of calcium and phosphate in the body.

Parathyroid hormone (PTH)

A peptide hormone secreted by the parathyroid glands, increasing plasma free Ca²⁺.

Calcitriol (Vitamin D)

A hormone that promotes bone mineralization and increases intestinal calcium uptake.

Hypercalcemia

A condition where there is excessive calcium in the blood, inhibiting PTH secretion.

Osteoclasts

Cells that promote bone resorption by dissolving bone mineral.

Osteoblasts

Cells that promote bone formation by secreting collagen and minerals.

Hydroxyapatite

The main mineral component of bones, composed of calcium and phosphate.

Calcitonin

A peptide hormone that reduces plasma free Ca²⁺ by inhibiting osteoclast activity.

Rickets

A condition in children caused by inadequate calcitriol leading to deformed bones.

Osteomalacia

A condition in adults caused by insufficient calcitriol, resulting in weakened bones.

Calcium homeostasis

The regulation of plasma calcium levels through hormones like PTH and calcitriol.

Target tissues for PTH

Bone, kidneys, and the GI tract, where it controls calcium and phosphate levels.

Hormones affecting calcium and phosphate

Includes sex steroids, glucocorticoids, growth hormone, and thyroid hormone.

Calcium reabsorption

The process in which kidneys reabsorb calcium, influenced by PTH and calcitriol.

Phosphate balance

Regulated alongside calcium and is influenced by the same hormones.

Calcium storage in bone

Bone contains about 1000 times more calcium compared to extracellular fluid.