osmoregulation and excretion Flashcards
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what is excretion
elimination of cellular metabolic waste
what is the goal of excretion
removal of toxic by products and for osmoregulation
what are the products of protein and nucleic acid metabolism
nitrogenous waste (toxic)
what are 3 nitrogenous waste products from most to least toxic
ammonia / ammonotelic
urea / ureotelic
uric acid / uricotelic
what animals secrete ammonia
aquatic invertebrates and teleosts
what animals secrete urea
mammals, amphibians, cartilagous fish
what animals secrete uric acid
birds, insects and reptiles
how is ammonia secreted
as gas and mainly excreted passively across gill membrane
some can also be exchanged across gill membrane with sodium-potassium pump
what are the results of ammonia accumulation
nervous system toxicity
what animals use high amounts of ammonia beneficially and how is it used
some shrimp and squid use it in their coelomic cavities to control buoyancy
3 adaptations for urea retention
very low urine flow rates,
active reabsorption by kidney,
urea tolerance
where is urea synthesised and excreted
synthesised in liver
excreted via kidneys
name a specific animal that excretes uric acid and why
kangaroo rat - to conserve water
why do birds and reptiles secrete uric acid
prevents toxicity in eggs
what type of feedback system manages urine production
negative feedback system
what are the 2 portions of the kidney
medulla (central) and cortex
what is the kidney made up of
nephrons
what happens at the glomerulus
filters small solutes from blood
how does filtration work within the Bowans capsule
arteriole blood pressure forces water, salts, urea and other solutes out into the space within the Bowmans capsule
what happens in the descending loop of Henle
aquaproins allow water to pass from the filtrate into the interstitial fluid
water permeable, ion impermeable
what happens in the ascending loop of Henle
Na+ and Cl- are reabsorbed from filtrate into interstitial fluid
water impermeable, ion permeable
what is the role of the distal tube
selectively secrett and absorb ions to maintain blood pH and electrolyte balance
what is the osmolarity of the kidney and how does it change towards the medulla
cortex is iso-osmotic with blood
gets more salty as you move through the medulla
where in the kidney is the loop of Henle found
descending down into the medulla
what type of exchange is occuring in the loop of Henle
countercurrent exchange
what is the role of antidiuretic hormone
increase permeability by adding aquaporins to the distal tubule and collecting duct
reduce blood flow to body’s extremities
what does the juxtaglomerular apparatus (JGA) secrete
rennin
what 2 hormones in the renin-angiotensin system increase Na+ and water reabsorption
angiotensin and aldosterone
how do you calculate pH
pH = log(1/[H+])
what is the pH of pure water at 37C
6.81
what is the pH of mammalian blood at 37C
7.4
3 mechanisms for pH regulation
cellular buffering,
respiration,
renal excretion
what 2 molecules can be used in pH regulation in the kidney
H+ and HCO3-
are smaller or larger animals able to produce more concentrated urine
smaller
what is the difference in kidney structure found in animals who need to conserve water
longer loop of Henle
thin cortex and large thick medulla
what do insects excrete
uric acid
what special strcuture has developed in insects for excretion
malpighian tubules
what are malpighian tubules
closed projections which move around freely in the animal, constantly exposed to fresh medium
what is the role of malpighian tubules
reabsorb salts, water and waste from haemolymph via active transport
how are the malpighian tubules emptied
movement of animal empties tubules into hind gut for excretion
detail steps that are carried out by the malpighian tubule
active transport of Na+, K+ and H+ into lumen
creates electrochemical gradient driving secondary transport of water and small solutes via osmosis
what occurs in the insect gut
active ion transport (Na+ / K+ ATPase) back into haemolymph
water and solutes recycles
how is uric acid excreted in insects
crystals in the faeces
