Card Set Information
among the most important wastes are what?
nitrogenous breakdown products of proteins and nucleic acids
what do some animals convert ammonia (NH3) to prior to excretion?
less toxic compounds
animals that excrete nitrogenous wastes as ammonia need a lot of what?
They release ammonia across the whole body surface or through gills
The liver of mammals and most adult amphibians converts ammonia to less toxic what?
the circulatory system carries urea to where? from there it is excreted
to the kidneys
excretion of urea requires what?
Conversion of ammonia to urea is energetically expensive; excretion of urea requires less water than ammonia
Insects, land snails, and many reptiles, including birds, mainly excrete what?
uric acid is largely what in water and can be secreted as a what with little water loss
Uric acid is more energetically expensive to produce than what?
The kinds of nitrogenous wastes excreted depend on what?
an animal’s evolutionary history and habitat
The amount of nitrogenous waste is coupled to the animal’s what?
Excretory systems regulate solute movement between what and what?
internal fluids and the external environment
Most excretory systems produce urine by refining a what?
filtrate derived from body fluids
what are the key functions of most excretory systems?
what is filtration?
pressure-filtering of body fluids
what is reabsorption
reclaiming valuable solutes
what is secretion?
adding toxins and other solutes from the body fluids to the filtrate
what is excretion?
removing the filtrate from the system
what is a protonephridium? (flatworm excretion)
a network of dead-end tubules connected to external openings
what is a flame bulb? function? (flatworm excretion)
The smallest branches of the network (protonephridium) are capped by a cellular unit
These tubules excrete a dilute fluid and function in osmoregulation
earthworms have what?
Each segment of an earthworm has a pair of open-ended metanephridia
metanephridia consist of what?
consist of tubules that collect coelomic fluid and produce dilute urine for excretion
Malpighian tubules do what?
In insects and other terrestrial arthropods, Malpighian tubules remove nitrogenous wastes from hemolymph and function in osmoregulation
Insects produce a relatively dry waste matter, an important adaptation to terrestrial life
The mammalian excretory system centers on what?
where is the principle site of water balance and salt regulation in mammals?
in the kidneys
each kidney is supplied with blood by a what and is drained by a what?
a renal artery
Urine exits each kidney through a duct called the what?
both ureters drain into a common what and urine is expelled through a what?
what is a nephron?
the functional unit of the vertebrate kidney, consists of a single long tubule and a ball of capillaries called the glomerulus
what is the Bowman's capsule?
Bowman’s capsule surrounds and receives filtrate from the glomerulus
Filtration occurs as blood pressure forces fluid from the what in the glomerulus into the what of Bowman’s capsule (glomerular capsule)
Filtration of small molecules is what?
Filtration of small molecules is nonselective
The filtrate contains what 6 things?
salts, glucose, amino acids, vitamins, nitrogenous wastes, and other small molecules
From Bowman’s capsule, the filtrate passes through three regions of the nephron
the proximal tubule,
the loop of Henle (ansa nephroni),
and the distal tubule
Fluid from several nephrons flows into a what duct, all of which lead to the what, which is drained by the ureter
Cortical nephrons are confined to the what?
juxtamedullary nephrons have what?
loops of Henle that descend into the renal medulla
what takes place in the proximal tubule?
reabsorption of ions, water and nutrients
molecules are transported actively and passively from the what into the interstitial fluid and then the capillaries?
some toxic materials are secreted into the filtrate and the filtrate volume decreases
aquaporin proteins do what? (descending limb of the loop of henle)
form channels to allow reabsorption of water to continue
the movement in aquaporin proteins is driven by the high what of the interstitial fluid, which is what to the filtrate?
the filtrate becomes increasingly concentrated
what does the distal tubule regulate?
k+ and NaCl concentrations of body fluids
the controlled movement of ions contributes to pH regulation
the collecting duct carries what through the medulla to where?
to the renal pelvis
what happens in the collecting duct?
water is lost as well as some salt and urea and the filtrate becomes more concentrated
urine is what to body fluids
nephron collecting duct