Renal Portal System (39) - End E4 Flashcards
Dr. Seddon
Describe the urinary bladder in sauria (lizards)
most are well-developed
none in bearded dragons or most monitors
spiny lizards - only in neonates
What types of reptiles do not have urinary bladders?
snakes
crocodilians
Besides lizards, which reptiles do have urinary bladders?
turtles
rhyncocephalia
Many birds and reptiles have no bladder. What is used instead?
water reclamation in the cloaca
Some reptiles use the bladder as _____
water and/or salt storage
What is the form of nitrogenous waste in birds and reptiles?
uric acid
Nitrogenous wastes either binds with sodium ([species]) to become [acidic/alkaline] or potassium ([species]) to become [acidic/alkaline]
sodium: carnivores, acidic
potassium: herbivores, alkaline
Regarding nitrogenous wastes, _____ are excreted as a semisolid white paste
ions
What types of nephrons do birds have?
mammalian
reptilian
Which nephron contains no loop of henle?
reptilian - which makes loop diuretics like furosemide less effective
What in reptiles and some birds is synthesized in the kidney instead of the liver?
vitamin C
T/F: Birds lack a urinary bladder
TRUE
Describe differences in reptile kidneys amongst groups
T/F: Reptile kidneys are more complex than mammals and birds
FALSE - direct blood from the caudal extremities either through or around kidneys, variable
Trace filtration through kidneys (general pathway that can be applied to most reptiles)
always taking caudal blood —> goes through kidneys —> vena cava —> go back through heart
What do reptiles lack kidney structure-wise?
no pelvis or pyramids
not divided into a medulla and cortex
few short nephrons compared to other taxa - couple thousand
What are the sexual differences in the renal systems?
females (and male turtles): columnar mucous-secreting cells
males: non-breeding - flat mucosal cells
» breeding: growth and sexual secretions (amino acids, phosphatase, etc)
Where are sex cell kidney types located?
after distal tubule
What are reptile differences from mammals and birds?
reptiles: lack loop of henle, no hypertonic urine
can only add water via proximal tubule or cloaca
need other ways to prevent water loss
What is a way reptiles and marine birds prevent water loss?
salt glands
Salt glands are a _____ gland
all-or-nothing
What is the physiology of the salt gland? It gets blood supply from _____
works efficiently dealing with concentrated salt loads
ophthalmic artery
What should you consider when anesthetizing a reptile or marine bird?
most general anesthesia blocks function of this gland
Describe blood shunting in some birds and reptiles
blood can be diverted around the kidneys
birds: adrenaline causes valve to open, and Ach to close
In birds, acetylcholine causes the value to [open/close]
close
Explain drug interactions with blood shunting
certain drugs can increase or decrease blood flow through this alternative route
Explain how drugs change reptile glomeruli number
arginine vasotocin: DECREASE glomeruli
prolactin: INCREASE
What does arginine vasotocin do?
constricts the afferent glomerular arterioles, causing filtration to decrease or even stop
- tubules collapse
- lack of blood flow increases risk of ischemic necrosis
- renal portal blood continues to perfuse the tubule cells to reduce risk
Keep in mind that treating sick or dehydrated reptiles with drugs may increase _____
half-life of the drug (is longer in the system)
What is the clinical importance of injecting drugs in reptiles?
caudal injections quickly pass through the kidneys (liver) - caudal blood supply is to the kidneys
sites of drug eliminations
Where should you inject for sedation in a reptile?
front limb
hindlimb not as affected with sedation
Why are hind limbs less effective to inject?
because it is filtered faster (due to relative location near kidneys)
higher possibility of first-order elimination
Regarding type of clearance, drugs eliminated via [glomerular filtration/tubular secretion] is more affected than [glomerular filtration/tubular secretion]
more affected: tubular secretion
[Cranial/Caudal] injections are better because they are more consistent, less work, and fewer considerations
Cranial
What is autotomy?
reflexive self-amputation that ruptures nerves, blood, and muscles usually to act as a decoy
most commonly associated with lizards
In lizard tail autotomy, the tail breaks along ______. It regenerates as a ______
fracture planes
hollow cone of cartilage
