Osmoregulation & Excretory System Flashcards

Flashcards covering osmoregulation types, nitrogenous waste comparisons, aquatic and land animal adaptations, nephron anatomy, invertebrate systems, and hormonal regulation of the excretory system.

Nitrogenous wastes

Nitrogen-containing molecules generated by the body that are toxic if they accumulate; the excretory system gets rid of them.

Osmoregulation

The process of maintaining water-solute balance within an organism.

Ammonia

The most toxic nitrogenous waste produced by aquatic animals; it is not converted and simply diffuses from the body into surrounding $H_2O$.

Urea

A nitrogenous waste produced by land animals by converting ammonia; it is less toxic than ammonia, can accumulate more, and requires less $H_2O$ to wash out of the body.

Uric acid

The least toxic nitrogenous waste, produced by reptiles and birds; it can accumulate the most and requires the least $H_2O$ for excretion, exiting as a paste.

Osmoregulator

An organism that maintains a stable internal solute and $H_2O$ concentration even if environmental conditions change, though this process requires energy.

Osmoconformer

An organism whose internal solute and $H_2O$ concentrations conform to the environment to save energy; they are limited to living within specific tolerance ranges.

Iso-osmotic

A state where the cell’s solute concentration is equal to the water’s solute concentration.

Hypoosmotic

A solution or tissue that has a lower solute concentration compared to another solution, such as the tissues of saltwater fish relative to seawater.

Hyperosmotic

A solution or tissue that has a higher solute concentration compared to another solution, such as the tissues of freshwater fish relative to fresh water.

Filtration

The non-selective process in the nephron where everything not too big to cross the capillary membrane enters the tubule.

Reabsorption

The process where substances the body still needs diffuse or are pumped from the nephron filtrate back into the blood capillaries.

Secretion

The process where unneeded waste is moved from the blood capillaries across the nephron membrane into the filtrate.

Excretion

The final step where filtrate (waste and $H_2O$) leaves the body as urine.

Nephron

The functional unit of the vertebrate kidney.

Cortical nephrons

Nephrons with short loops of Henle that may barely dip into the medulla; they are found in all vertebrates and cannot make concentrated urine.

Juxtamedullary nephrons

Nephrons with long loops of Henle that dip deep into the renal medulla, allowing birds and mammals to produce concentrated urine.

Glomerulus

A cluster of leaky capillaries in the nephron that filters blood.

Bowman’s capsule

The part of the nephron that collects the filtrate from the glomerulus.

Proximal tubule

A section of the nephron featuring microvilli on its epithelium to increase surface area for reabsorption and secretion.

Descending loop of Henle

The portion of the nephron responsible for the reabsorption of $H_2O$ via osmosis.

Ascending loop of Henle

The portion of the nephron where $NaCl$ is reabsorbed; its thick part is impermeable to $H_2O$.

Collecting duct

A tube that drains multiple nephrons and reabsorbs $NaCl$, $H_2O$, and some urea; its permeability to $H_2O$ is adjustable.

Protonephridia

An invertebrate excretory system, found in flatworms, where cilia at the tube entrance draw in interstitial fluid for reabsorption and secretion.

Metanephridia

The excretory system of earthworms consisting of a tube surrounded by a capillary network for reabsorption, secretion, and excretion.

Malpighian tubules

The excretory system of insects that stems off the digestive tract; material from hemolymph enters the tubules and is excreted with feces.

Renin

An enzyme released by the kidneys into the blood in response to low blood pressure or volume, triggering the RAAS pathway.

Angiotensin II

A protein produced via the RAAS pathway that acts as a vasoconstrictor to increase blood pressure and triggers the release of aldosterone.

Aldosterone

A hormone that causes increased $NaCl$ reabsorption from the nephron, leading to $H_2O$ reabsorption via osmosis to increase blood pressure and volume.

ANF (Atrial Natriuretic Factor)

A hormone released by heart muscle cells in response to high blood pressure that inhibits RAAS to decrease $NaCl$ and $H_2O$ reabsorption.

ADH (Antidiuretic Hormone)

A neurohormone that increases solute concentration in body fluids by making the nephron collecting ducts and distal tubules more permeable to $H_2O$.

Aquaporins

Membrane channels that help $H_2O$ cross the cell membrane; their installation in the collecting duct is triggered by ADH.