Urinary System and Renal Physiology

Vocabulary flashcards covering the urinary system, renal physiology, glomerular filtration, tubular reabsorption, tubular secretion and hormonal regulation.

Glomerular Filtration

Fluid filtered from the blood to the glomerulus.

Glomerular Filtration Rate (GFR)

Amount of filtrate formed in all the renal corpuscles of both kidneys each minute.

Tubular Reabsorption

Returning important substances from the filtrate back to the body.

Tubular Secretion

Movement of waste materials from the body to the filtrate.

Glomerular Filtration

Formation of a protein-free filtrate (ultrafiltrate) of plasma across the glomerular membrane.

Starling Forces

The balance of hydrostatic and osmotic pressures that determine the net filtration pressure.

Blood hydrostatic pressure

Main force that “pushes” water and solutes through the filtration membrane (promotes filtration).

Capsular hydrostatic pressure

Pressure from the capsular space (opposes filtration).

Blood osmotic (oncotic) pressure

Osmotic pressure of plasma proteins “pulling” on water (opposes filtration).

Macula Densa

Columnar tubule cells in the final part of the ascending limb of the loop of Henle, which contacts the afferent arteriole.

Juxtaglomerular (JG) cells

Modified smooth muscle fibers in the wall of the afferent arteriole.

Juxtaglomerular apparatus (JGA)

The juxtaglomerular cells and macula densa.

Renal Autoregulation

Regulation of the GFR by the kidneys themselves.

Neural Regulation

Regulation of GFR by the autonomic nervous system (ANS).

Hormonal Regulation

Regulation of GFR by hormones such as angiotensin II and atrial natriuretic peptide (ANP).

Angiotensin II

Vasoconstrictor of both afferent and efferent arterioles (reduces GFR).

Atrial Natriuretic Peptide (ANP)

Causes the glomerulus to relax, increasing the surface area for filtration (increases GFR).

Filtration Membrane

It consists of the fenestrated endothelium of the glomerular capillaries, the basal lamina, and the filtration slits formed by the podocytes.

Net Filtration Pressure (NFP)

The total pressure that promotes filtration, calculated as GBHP – CHP – BCOP.

Tubular Reabsorption

The process of returning important substances from the filtrate back into the renal interstitium, then into the renal blood vessels and ultimately back into the body.

Paracellular Reabsorption

Passive process of reabsorption between adjacent tubule cells.

Transcellular Reabsorption

Reabsorption through an individual tubule cell.

Obligatory Reabsorption

Water follows solutes as they are reabsorbed, maintaining the osmotic gradient.

Facultative Reabsorption

Variable water reabsorption, adapted to specific needs, regulated by ADH and aldosterone through principal cells.

Countercurrent Multiplication

Increasing osmotic gradient is formed in the interstitial fluid of the renal medulla as a result of countercurrent flow.

Countercurrent Exchange

Passive exchange of solutes and water between the blood and interstitial fluid of the renal medulla as a result of countercurrent flow.

Tubular Secretion

The movement of substances from the capillaries which surround the nephron into the filtrate. It occurs by active transport.

Renin

Enzyme secreted by the cells of the JGA in response to low blood volume and blood pressure, or sympathetic NS activity.

Aldosterone

Stimulates the principal cells in the collecting ducts to reabsorb more Na+ and Cl– and secrete more K+.