Calcium and Phosphate – Electrolyte Balance (Nursing)

00:00 So now let's look at the regulation of other electrolytes in the body including calcium and phosphate.

00:08 99% of our body's calcium is going to be found in the form of calcium phosphate salts in our bones.

00:17 Calcium balance is controlled by the parathyroid hormone and rarely deviates from normal limits.

00:26 Parathyroid hormone is going to increase our calcium levels by targeting our bones by way of osteoclasts.

00:34 Osteoclasts are going to break down our bones matrix and release the calcium and the phosphate from this breakdown to our blood.

00:44 Calcium levels are also going to be regulated in the kidneys where we can get an increase in calcium reabsorption.

00:52 This will lead to a decrease in phosphate ion reabsorption.

00:58 Also in our small intestines, parathyroid hormone can also lead to an increase in our calcium absorption.

01:06 And this is going to be indirectly through the stimulation of the kidneys to activate the vitamin D precursor, which then causes us to reabsorb or absorb more calcium in our GI tract.

01:21 So 98% of our filtered calcium is going to be reabsorbed due to parathyroid hormone.

01:29 If our extracellular fluid calcium levels are normal, then parathyroid hormone secretion is going to be inhibited.

01:38 Also, 75% of our filtered phosphates are going to be reabsorbed in the proximal convoluted tubule of the nephron.

01:47 Parathyroid hormone is going to inhibit this process.

01:52 Phosphate reabsorption can also be affected by hormones such as insulin, which increases phosphate reabsorption, and glucagon, which are going to decrease phosphate reabsorption.

02:07 So if we take a look at this or summarize this, starting with hypocalcemia, or low blood calcium levels, this is going to trigger a release of the parathyroid hormone from the parathyroid gland.

02:24 Parathyroid hormone is then going to increase osteoclast activity in our bones, which is going to cause a breakdown of the bone matrix and a release of calcium and phosphate into the blood.

02:39 Also, it will trigger the increase of calcium reabsorption and our kidneys tubules.

02:46 And in the GI tract, first we're going to increase the activation of vitamin D.

02:52 And then from there, vitamin D allows for increased calcium absorption in the small intestines.

03:00 All of these effects will then lead to an increase or return to homeostatic calcium levels in the blood.