excretory system (exam 3) Flashcards
carbon waste from sugar breakdown (by animals) is removed by
breathing
nongaseous waste must be removed by
excretory system
osmoregulation
controlling internal water and solute concentrations
osmolarity
total solute concentration
where does nitrogen waste come from?
breaking amino acids or nucleic acids down for energy
nitrogenous wastes must be eliminated in…
a solution (by peeing it out)
most efficient method of eliminating nitrogen and why?
ammonia; since no conversion is needed
(very toxic and must be highly diluted to be safe)
urea must be converted from
from ammonia, requiring energy
urea gets rid of __ nitrogens per one molecule. and it is not toxic, so…
2; requires less water to excrete
urea is used in
mammals, amphibians, sharks, and some bony fish
uric acid requires more/less energy than urea to convert?
more
uric acid eliminates __ nitrogen per uric acid molecule
4
uric acid is..
-not toxic
-not very soluble
-requires very little to excrete
excretion basics: 1. filtration
internal pressure pushes water and small solutes into an internal tube
- called the filtrate
-almost everything is thrown away
excretion basics: 2. reabsorption
water and useful solutes are moved back into the body from the tube
excretion basics: 3. secretion
additional wastes are actively transported into filtrate
excretion basics: 4. excretion
filtrate is excreted from the body as urine
creating filtrate
-large ball of capillaries called the glomerulus is surrounded by glomerular capsule (beginning of tubule)
in the filtrate, epithelial cells are
selectively permeable
-allows: water, ions, small solutes
-does not allow: blood, blood proteins
filtrate flow steps
o Proximal tubule
o Descending limb of nephron loop
o Ascending limb of nephron loop
o Distal tubule
o Collecting duct
ways to eliminating nitrogen:
ammonia, urea, or uric acid
ammonia is excreted by what ?
most aquatic animals and most bony fish
excretory systems are all based on
tubes
excretory basics: order
filtration, reabsorption, secretion, excretion
- proximal tubule: is the beginning of
reabsorption
- proximal tubule: ____ is actively transported out of the tubule, resulting in…
Na+ is actively transported out of tubule
(Cl- passively follows Na+ and water passively follows NaCl)
- proximal tubule: unwanted molecules are actively secreted into tubule, such as
drug metabolites; toxins, H+
- descending nephron loop: ____ reabsorption
water
- descending nephron loop: important for
water reabsorption
- descending nephron loop: epithelial cells have many
aquaporin channels (passive water transport) that are impermeable to salt and other solutes
- descending nephron loop: the filtrate loses water down the entire length of the loop, …
becoming increasingly concentrated
- ascending nephron loop: important for
ion reabsorption
- ascending nephron loop: epithelium has many ion channels that are completely impermeable to
water
- ascending nephron loop: where are the passive and active NaCl transports?
- Passive NaCl transport near bottom
of tubule
-Active NaCl transport near top of tubule
- ascending nephron loop: filtrate becomes….
less concentrated as ions leave
- distal tubule
-active NaCl reabsorption
-active K+ secretion
-controls levels in the body (crucial for proper nerve function)
- collecting duct: important for..
reabsorption of water and ions via diffusion
- collecting duct: controls
body osmotic balance (makes urine more or less concentrated AND changes if aquaporins are in ducts)
- collecting duct: not enough internal water…
water is then reabsorbed from duct
- collecting duct: too much internal water…
water is NOT reabsorbed from duct
the collecting duct sends urine…
to bladder for excretion
nephron loop creates osmolarity gradient in
medulla
collecting duct uses ___ to ___ reabsorb water
gradient; passively
length of nephron loop determines ability to
concentrate urine
