lecture 5 Flashcards
What is tubular secretion?
Tubular secretion is the selective transfer of substances from the peritubular capillaries to the tubular fluid.
The rate of excretion is greater if the fluid is both filtered and secreted compared to fluid only being filtered.
Secretion can act as a supplemental mechanism to increase the rate of excretion of various substances from the body.
K+, H+ and various organic anions and cations are examples of substances that undergo secretion. the process of secretion determine the composition of plasma potassium and pH in that filtered fluid
Explain Tubular secretion of K+
so with the tubular secretion of potassium, although they are abundant in the body, they are mostly inside cells. remember that plasma is a part of the extracellular fluid. the conc. of potassium in the plasma is very highly regulated. conditions, where you have disturbance in potassium levels, is know as Hypokalaemia (low plasma K+) and hyperkalaemia (high plasma K+) can have serious clinical consequences, particularly for organs such as the heart. why is this the case? because changes in plasma potassium levels can have a significant impact on excitable cells such as neurons, muscle cells, cardio cells.
K+ is one of the most abundant cations in the body. Only a small amount (~2%) of K+ is in the ECF, and concentrations of K+ are tightly controlled.
Filtered K+ is almost completely reabsorbed in the proximal tubule. The secretion of K+ in the distal regions of the tubule is, therefore, a major determinant of the overall excretion of K+.
The secretion of K+ is regulated by the adrenal hormone aldosterone. the main thing that regulates the amount of potassium is being excreted in the tubules. the more secreted k+ the more k+ will be lost from the body
