Salt and Water Balance and Nitrogen Excretion

Flashcards covering key vocabulary related to salt and water balance, nitrogen excretion, and excretory systems.

Osmolarity

Number of moles of osmotically active solutes per liter of solvent.

Excretory organs

Control osmolarity and composition of extracellular fluids by excretion of excess solutes, conserving valuable solutes, and eliminating toxic waste products.

Urine

The output of the excretory system, produced through filtration, secretion, and reabsorption.

Osmoconformers

Marine invertebrates that equilibrate their osmolarity with that of seawater.

Osmoregulators

Animals that maintain an osmolarity different from their environment; can be hypotonic or hypertonic.

Nitrogenous wastes

Toxic byproducts of protein and nucleic acid metabolism that must be eliminated.

Ammonia (NH3)

A common, toxic nitrogenous waste excreted by many aquatic animals, requiring continuous excretion or conversion.

Ureotelic animals

Animals that excrete nitrogen as urea, which is water-soluble but can result in water loss.

Uricotelic animals

Animals that excrete nitrogen as uric acid, which is insoluble in water and allows for water conservation.

Protonephridia

Excretory system in freshwater flatworms; consists of tubules and flame cells for filtration and waste removal.

Metanephridia

Excretory system in annelids; filters blood into the coelom and reabsorbs water and molecules.

Malpighian tubules

Excretory system in insects; tubules transport uric acid and ions into the gut for elimination.

Nephron

The main functional unit of the vertebrate kidney, responsible for secretion and reabsorption to produce urine.

Glomerulus

A ball of capillaries in the nephron where blood is filtered to produce renal filtrate.

Tubular reabsorption

The process in the renal tubule where specific ions, nutrients, and water are reabsorbed from the glomerular filtrate.

Tubular secretion

The process where tubule cells transport substances to be excreted into the glomerular filtrate.

Loop of Henle

A structure in the nephron that descends into the medulla and is involved in the countercurrent multiplier mechanism.

Vasa recta

Peritubular capillaries parallel to the loops of Henle and the collecting duct, preserving the concentration gradient in the renal medulla.

Aquaporins

membrane proteins that form water channels to allow for varying water permeability.

Renal failure

Results in salt and water retention, urea retention (uremic poisoning), and decreasing pH (acidosis).

Antidiuretic hormone (ADH)

Stimulates collecting duct cells to insert aquaporins and increase permeability to water.