Renal Tubular Reabsorption and Secretion - Ch 28 pp

The filtered fluid passing through the kidney tubules is altered by reabsorbing useful substances back into the blood and secreting waste products into the urine.

Active transport is a process that requires energy to move substances across cell membranes against their concentration gradient.

Primary active transport directly uses energy (ATP) to move a substance across a membrane.

Secondary active transport uses the energy from the movement of one substance (usually Na+) to move another substance against its gradient.

The movement of substances through the spaces between cells in a tissue.

The movement of substances through the cells themselves, passing through the cell membrane.

The force that drives the movement of ions across a membrane due to differences in electrical charge.

The force that drives the movement of a substance across a membrane from a region of high concentration to a region of low concentration.

The movement of substances from the tubular fluid back into the blood through peritubular capillaries.

A type of active transport where two or more substances move across the cell membrane. One substance moves down its electrochemical gradient, providing energy for the other substance to move against its gradient.

The maximum rate at which a substance can be actively reabsorbed from the tubular fluid.

The passive movement of water from the tubular fluid into the blood due to osmotic pressure.

The movement of chloride ions from the tubular fluid back into the blood. It can occur passively or via secondary active transport.

The fraction of plasma that is filtered at the glomerulus, expressed as a percentage.

A mechanism by which the kidneys regulate blood pressure and fluid volume. An increase in blood pressure promotes increased filtration, leading to more urine excretion, thus lowering blood pressure.

A hormone that stimulates the reabsorption of sodium and water in the collecting ducts of the kidneys, leading to an increase in blood volume and pressure.

A powerful vasoconstrictor that also stimulates aldosterone secretion, leading to increased blood pressure and sodium retention.

The movement of substances from the tubular fluid back into the blood through peritubular capillaries.

The net filtration pressure (NFP) in peritubular capillaries is determined by the difference between hydrostatic pressure (Pc) and interstitial fluid pressure (Pif), minus the difference between plasma osmotic pressure (Ωp) and interstitial fluid osmotic pressure (Ωif).

Arterial pressure is a key factor in determining peritubular capillary hydrostatic pressure, directly influencing the movement of fluids between the capillaries and the interstitium.

Renal arteriole resistance influences hydrostatic pressure in peritubular capillaries by regulating blood flow into the nephrons.

Glomerulotubular balance is the process where an increase in the filtered load of a substance in the glomerulus simultaneously increases reabsorption of that substance by the proximal tubule.

Systemic osmotic pressure is a key factor in determining osmotic pressure in peritubular capillaries, influencing the movement of water between the capillaries and the interstitium.

The proximal tubule is the first part of the renal tubule where significant reabsorption of water, electrolytes, and nutrients occurs.

The loop of Henle is a U-shaped structure in the kidney that plays a crucial role in concentrating urine by establishing a concentration gradient.

The descending limb of the loop of Henle is permeable to water, allowing water to move out of the tubule and contribute to the concentration gradient.

The thick ascending limb of the loop of Henle is impermeable to water but actively reabsorbs sodium (Na+) and chloride (Cl-) ions, contributing to the concentration gradient.

Distal tubules are responsible for fine-tuning electrolyte balance and reabsorbing essential substances, particularly in the diluting segment.

Principal cells are responsible for sodium (Na+) reabsorption and potassium (K+) secretion in the late distal tubule and cortical collecting tubule.

Intercalated cells are involved in maintaining acid-base balance by secreting either hydrogen ions (H+) or bicarbonate ions (HCO3-), depending on the body's need.

The medullary collecting ducts are the final segment of the nephron, where water permeability is regulated by antidiuretic hormone (ADH) to control urine concentration.

A hormone produced in the hypothalamus and released by the posterior pituitary gland. It promotes water reabsorption in the collecting ducts and distal tubules of the kidneys by increasing the permeability of these structures to water, thus reducing urine volume.

A hormone produced in the atria of the heart. It inhibits sodium and water reabsorption in the kidneys, reducing blood volume and blood pressure. It also inhibits renin secretion, further lowering blood pressure.

A hormone produced by the parathyroid glands. It plays a critical role in calcium homeostasis by increasing calcium reabsorption in the kidneys, promoting phosphate secretion, and indirectly increasing calcium absorption in the intestines.

A branch of the autonomic nervous system that influences kidney function through alpha adrenergic receptors. It can stimulate sodium and water reabsorption, increasing blood volume and blood pressure.

A measure of the volume of plasma cleared of a substance per unit of time. It reflects the rate at which a substance is removed from the blood by the kidneys. It can be used to estimate glomerular filtration rate (GFR) and renal blood flow.