urinary system in exotics Flashcards

1
Q

what is the form of nitrogenous waste in aquatic organisms

A

ammonia

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2
Q

mammals and terrestrial amphibians excrete nitrogenous waste in the form of

A

urea

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3
Q

birds and reptiles excrete nitrogenous waste in the form of

A

uric acid

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4
Q

what is uric acid

A
  • made in the liver
  • highly insoluble
  • good for water conservation, can be stored in eggs without becoming toxic to fetus
  • secreted via tubular secretion (reptilian type nephrons
  • amount excreted independent of urine flow rate, tubular water reabsorption and hydration state
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5
Q

what is gout in birds and reptiles

A

hyperuricemia (in joints or visceral)
- renal disease in which they cannot excrete uric acid
- can be due to very high dietary protein, dehydration (urates produced but cant be flushed) or nephrotoxic drugs (damage to renal tubules)

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6
Q

what are urates

A

white to yellow colloidal suspension
precipitate:
- uric acid
- protein
- Na
- K

uric acid crystals precipitate because there is no osmotic pressure (wont draw water out with it

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7
Q

what is the renal portal system and what animals have one

A
  • in reptiles, birds, amphibians and most fish
  • has both cranial and caudal portal veins
  • blood goes to kidney from heart and again from legs
  • protects against ichemic necrosis (when GFR reduced
  • portal system ensures blood flow to tubules
  • does not supply the glomerulus
  • default is closed under ACh control. Limbs -> renal portal veins -> kidney -> caudal VC
  • open under adrenaline control and diverts to mammalian system: blood from limbs goes straight to caudal VC
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8
Q

what are some clinical implications of the renal portal system

A
  • drug pharmacokinetics -> nephrotoxic drugs injected into hind limbs go straight to kidney, or secreted from tubules and peed out.
  • caudal mesenteric vein contributes to renal portal system. alimentary tract disease affects kidneys. toxins from the gut go straight to kidney
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9
Q

what structure is missing from fish and reptile nephrons

A

loop of henle
no urine concentrating ability

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10
Q

discuss avian nephrons

A
  • 70-90% are reptile type (no loop of henle, cortex only)
  • 10-30% mammalian type which have loop of henle spanning cortex and medulla
  • limited urine concentration
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11
Q

discuss avian osmoregulation in terms of hehydration

A
  • decrease GFR and urine flow rate
  • under action of arginine vasotocin (rather than ADH)
  • stimulated by increase in plasma osmolarity
  • constriction ogf afferent arteriole and perfusion maintained by renal portal system
  • controls tubular water permeability
  • urine goes into urodeum and is reabsorbed into colon and caeca
  • sodium linked water reabsorption (sodium goes out, followed by Cl then water)
  • decreased with stress polyuria
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12
Q

how do reptiles respond to dehydration

A
  • similar to birds (arginine vasotocin action)
  • reabsorption of water by reverse peristalsis: urodeum, urine into rectum/colon
  • high tolerance for severe dehydration and high salt load
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13
Q

is urinalysis useful for testing kidney function in reptiles? why or why not

A

no
urine undergoes a lot of modification after kidneys, excretion not same as what comes out of kidneys.
in cloaca, colon and bladder, lots of modification to ions, water, proteins, Na and K and urates

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14
Q

what is the morphology and location of avian kidneys

A
  • paired retroperitoneal (large)
  • caudal edge borders lungs (caudal synsacrum)
  • close association with lumbar and sacral plexus
  • spinal nerves run through kidney parenchyma
  • near abdominal air sac diverticulum
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15
Q

inflammation or neoplasia in the kidney of a bird can led to …….. why

A

lameness/paralysis
because spinal nerves run through kidney parenchyma

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16
Q

lizard kidneys

A
  • caudal aspect of kidneys fused in many species (horseshoe)
  • renal portal system
  • may or may not have a urinary bladder
17
Q

kidneys in snakes

A
  • right kidney cranial to left
  • 25-30 lobules
  • no bladder, urine stored in distal colon or flared ends of each ureter
18
Q

chelonian renal anatomy

A
  • kidneys in caudal coelom
  • bladder: single central structure +/- paired accessory bladders (important in hibernation)
  • bladder osmotically permeable (can reabsorb water) (important for hibernation)
  • in aquatic turtles a bouyancy aid and resorbs Na
19
Q

microscopic renal anatomy in reptiles

A
  • no pelvis, pyramids, cortex, medulla
  • a few thousand nephrons
  • lower GFR than mammals
  • poorly developed glomeruli, few capillaries
  • no loop of henle (cant concentrate urine)
20
Q

what are salt glands

A
  • some birds and reptiles have them, marine and desert animals only
  • for when salt consumption > renal clearance
  • excretion of salt without water loss
  • hyperplasia/hypertrophy with high salt exposure
  • countercurrent exchange
  • modified nasal/lacrima/salivary glands (located eye, nose or tongue)
  • excreted by burrowing, sneezing, tongue protrusion
  • dries to white poweder
21
Q

fish renal anatomy

A
  • single kidney length of coelom
  • divisions: cranial = endocrine and hematopoietic, caudal = filtration
  • size and number of glomeruli varies
  • +/- renal portal veins
  • no loop of henle = hypo-osmotic urine
  • water movement by osmosis over skin and gills
  • nitrogenous waste = ammonia via urine or gills
22
Q

explain osmoregulation in freshwater fish

A
  • ion loss/water gain
  • fish more salty than water, suck in water
  • kidney excretes water (high GFR)
  • gills responsible for active NaCl uptake and excretion of ammonia
  • dietary intake of NaCl
23
Q

explain osmoregulation in marine fish

A
  • water more salty than fish
  • lose water across gills and skin
  • drink seawater to replace (angiotensin 2)
  • gills excrete NaCl and ammonia
  • kidneys small or have no glomeruli and remove excess divalent ions (Mg)
24
Q

compare osmoregulation in fish

A
25
Q

which kind of fish (salt or fresh) is at most risk of gaining water from their surroundings

A

freshwater

26
Q

what type of fish (fresh or salt) has the higher GFR

A

freshwater

27
Q

in which fish (salt of fresh) are the glomeruli small/absent

A

salt

28
Q

which fish produces the most dilute urine

A

fresh

29
Q

which fish (salt or fresh) drinks the most water

A

salt

30
Q

amphibian renal anatomy and physiology

A
  • urine: kidney -> ducts -> cloaca -> urinary bladder
  • renal portal veins but not in caecilians
  • caecilians = one kidney full length of coelom
  • caudates and anurans paired posterior retroperitoneal kidneys
  • cloacal bladder not true bladder (outpouching or diverticulum of cloacal wall, no direct connection with excretory ducts, opening closed by sphincter mm.
  • nitrogenous waste type depends on lifestage and environment (aquatic = ammonia, terrestrial = urea or uric acid)
  • hypo-osmotic urine
  • aquatic amphibians skins extremely permeable to water and prone to evaporative losses. kidney must excrete excess water
  • terrestrial amphibians important water conservation. evaporative loss. urinary blader stores water and can reabsorb. decrease their GFR with reduced water. most excrete urea
31
Q

what is the clinical relevence of aquatic species and their renal phys

A
  • skin is important for fluid balance and respiration
  • diseases/damage can be catastrophic for health
  • very sensitive! (environmental contaminats, cant scrub for sx, minimise handling, wear gloves, water quality very important
  • can administer fluids/meds through water