Question

Select all the combined effects of parathyroid hormone and calcitriol. bone resorption by osteoclasts activation of osteoclasts increase excretion of calcium by the kidneys increase absorption of calcium by the small intestine

Answer 1

Parathyroid hormone and calcitriol increase the activation of osteoclasts, enhance bone resorption, and promote the reabsorption of calcium by the kidneys, while also increasing the absorption of calcium by the small intestine.

Step-by-step explanation:

The combined effects of parathyroid hormone (PTH) and calcitriol play a critical role in maintaining calcium homeostasis in the body. Parathyroid hormone, released in response to low blood calcium levels, has several effects:

It stimulates the activation of osteoclasts, which leads to bone resorption and the release of calcium into the blood.

It promotes the reabsorption of calcium by the kidney tubules, which reduces the excretion of calcium in the urine.

It increases the activation of vitamin D into calcitriol, the active form of vitamin D, which enhances the absorption of calcium by the small intestine.

Calcitriol works to increase the absorption of calcium and phosphate from the digestive tract, complementing the actions of PTH.

Answer 2

Parathyroid hormone or PTH acts to increase serum calcium by (1) promotes resorption of calcium from bones, (2) decrease calcium excretion by increasing calcium reabsorption in the kidneys, and (3) increase calcium absorption in the intestine by activation of vitamin D. It also increases phosphate excretion hence decreasing serum phosphate levels. PTH is secreted if the organ senses that there is low serum calcium.

Calcitriol or vitamin D, on the other hand, also acts in (1) resorption of calcium from bones, (2) reabsorption of calcium in the kidneys, (3) absorption of calcium in the intestines; but calcitriol, in contrast to PTH, also increases the absorption of phosphate from the intestines and increases the reabsorption of phosphate in the kidneys.

Therefore the correct answers are both PTH and calcitriol promotes bone resorption by osteoclasts, acts in activation of osteoclasts, and increase absorption of calcium by the small intestine.