Tubular Secretion – Urine Formation (Nursing)

00:01 Along with reabsorption.

00:03 We also have secretion.

00:06 Secretion is pretty much reabsorption in the opposite direction.

00:11 Most of your secretion is going to occur almost completely in the proximal convoluted tubule.

00:18 Substances are going to be moved from the blood in the peritubular capillaries through the tubule cells and then out into the filtrate.

00:29 These include potassium, hydrogen ion, ammonium ion create, creatinine, organic acids and bases.

00:40 Substances synthesized in the tubular cells can also be secreted for example bicarbonate that is synthesized by the tubule cells can be secreted into the filtrate.

00:53 Tubular secretion is important because it allows for the disposing of substances such as drugs or metabolites that are bound to our plasma proteins.

01:05 It also allows for the elimination of undesirable substances that were passively reabsorbed such as urea and uric acid.

01:15 Tubular secretion is also responsible for how we get rid of excess potassium.

01:21 This is due to the effects of aldosterone.

01:26 And finally tubular secretion plays an important role in how we maintain our blood pH by altering the amounts of H+ and bicarbonate that are released or secreted in our urine.

01:41 So putting it all together.

01:43 We start at the proximal convoluted tubule.

01:46 We're about 65 percent of the filtrate volume is going to be reabsorbed.

01:51 We're going to be reabsorbing water, sodium bicarbonate, and many other ions as well as organic nutrients like glucose and amino acids.

02:02 From there, we go to the descending limb of the nephron loop where here, water is going to be able to be reabsorbed by ions are impermeable and cannot move out of this area.

02:16 After this, we go to the ascending limb of the nephron loop.

02:21 Here solutes are going to be able to move in and out.

02:24 But the water is impermeable in this area as there are no aquaporins.

02:30 Following this we go to the distal convoluted tubule and the collecting ducts.

02:36 Here this portion of the Nephron is going to be under hormonal control.

02:41 Hormones include the antidiuretic hormone, which is going to be responsible for the reabsorption of water, sodium chloride, as well as urea.

02:53 The aldosterone hormone is going to be responsible for the reabsorption of sodium chloride and the secretion of potassium.

03:03 Also the parathyroid hormones are going to act in this area of the Nephron and result in the reabsorption of calcium when it is needed by the body.

03:14 This area is also very important for the maintenance of our blood pH by controlling the reabsorption and or secretion of H+ and bicarbonate and also ammonia ions.