The Urinary System and Water Physiology

Vocabulary flashcards covering the anatomy and function of the nephron, kidney physiology, and comparative osmoregulation in marine, freshwater, and terrestrial vertebrates.

Osmoregulation

The physiological processes that maintain salt and water balance, preventing an organism from drying out, flooding, or becoming too salty or not salty enough.

Nephron

The tubular functional unit of the kidney, present in hundreds to millions per kidney, that filters blood and produces urine.

Glomerulus

A bundle of leaky capillaries in the nephron that filters blood to produce ultrafiltrate containing blood components except cells and large molecules.

Bowman's Capsule

The sac-like structure in the nephron that receives ultrafiltrate immediately after it is produced by the glomerulus.

Proximal Tubule

The main site in the nephron for the reabsorption of important substances such as nutrients.

Descending limb

The segment of the Loop of Henle that serves as the main site for water reabsorption.

Ascending limb

The segment of the Loop of Henle responsible for the active removal of excess ions.

Distal tubule

The region of the nephron that serves as the main site for the secretion of waste substances.

Collecting ducts

Tubes that collect modified filtrate (urine) into larger conduits, direct them to the urinary tract for excretion, and control urine concentration.

Dialysis

The artificial filtering of the blood required for several hours a day by individuals suffering from kidney failure.

Osmoconformers

Organisms, such as hagfish, that do not regulate their internal salt and water content and instead conform to their environment.

Chondrichthyes (osmoregulation)

Cartilaginous fish that maintain an osmotic pressure as high as their environment by retaining high levels of urea in their body fluids.

Chloride cells

Specialized cells in the gills that actively pump excess salt out in marine bony fish or actively pump salt inward in freshwater fish and amphibians.

Stenohalime

Organisms that cannot tolerate a wide range of salinity and can live only where environmental salinity remains constant.

Euryhaline

Organisms that can tolerate a wide range of salinity and are capable of moving between saltwater and freshwater environments.

Diadromous

Fish that migrate between fresh and salt water, undergoing progressive changes in their physiology.

Catafemous

A life cycle pattern, exemplified by the Atlantic eel, where individuals spend most of their adult life in fresh water but migrate to reproduce and spawn in salt water.

Anadromous

A life cycle pattern, exemplified by most salmon, where individuals spend most of their adult life in salt water but migrate to spawn and reproduce in fresh water.

Poikilothermy

A physiological characteristic in certain terrestrial vertebrates that minimizes evaporative water loss due to having little need to eliminate excess body heat.