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URI > Exotics > Flashcards

Exotics Flashcards

1
Q

What are the different forms of nitrogenous waste organisms can produce?

A
  • Uric acid
  • Urea
  • Ammonia
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2
Q

What organisms are ammonotelic?

A

Aquatic

- Fish, aquatic amphibians

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3
Q

What organisms are ureotelic?

A

Mammals, terrestrial amphibians

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4
Q

What organisms are uricotelic?

A

Birds, reptiles

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5
Q

What are the advantages and disadvantages of ammonotelic excretion?

A
  • Requires a lot of water (not a problem as are aquatic)

- Little energy required to produce ammonia

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6
Q

What are the advantages and disadvantages of ureotelic excretion?

A
  • Moderate amount of water required for excretion

- Moderate amount of energy required to produce urea

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7
Q

What are the advantages and disadvantages of uricotelic excretion?

A
  • Very little water required for excretion
  • High amount of energy needed for produciton
  • Very stable, can be stored within eggs without damage to the embryo
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8
Q

Describe uric acid as an excretion molecule

A
  • Made in liver
  • Tubular secretion from repitilian type nephrons
  • Independent of urine flow rate
  • Rate of uric acid clearance approx 8-16x GFR
  • Independent of tubular water reabsorption
  • Independent of hydration state
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9
Q

What is unusual about excretion in reptiles?

A
  • Uric acid complexed with protein and Na+ (carnivorous diet) or K+ (herbivorous)
  • High levels of protein in urine
  • Are able to reabsorb protein from urine
  • Passes from urodeum to rectum by reverse peristalsis in order to do this
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10
Q

What happens to uric acid in reptiles following reabsorption in the bladder?

A
  • Actively secreted into proximal tubules

- Needs K+ for this

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11
Q

What happens to urate secretion in reptiles if blood pH drops?

A
  • Increases

- H+ ions secreted into bladder (if present) and uric acid precipitates

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12
Q

What are reptiles prone to in situations of severe dehydration?

A
  • Gout in kidneys

- Not enough water to flush things out

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13
Q

Describe the fish renal anatomy

A
  • Single kidney length of coelom
  • Retroperitoneal
  • May be separate or joined, but cranial and caudal divisions
  • Cranial: endocrine and haematopoietic
  • Caudal: filtration (nephrons)
  • May or may not have renal portal veins (supply renal tubules then back to heart, no supply to glomerulus)
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14
Q

Describe the nephrons found in fish

A
  • No glomeruli in some species
  • Freshwater: many (larger) glomeruli
  • No LoH
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15
Q

How is the ammonia removed from the fish’s body?

A
  • Urine

- Gills (most excretion from the gills)

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16
Q

Describe osmoregulation in freshwater fish

A
  • Higher conc. ions in fish than out, so water moves in by osmosis
  • Ions out of fish
  • Both of these through gills (and skin)
  • Kidney excretes water
  • Gills active NaCl uptake, excrete ammonia
  • Dietary intake of NaCl
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17
Q

Describe the excretion of water by freshwater fish

A
  • Kidney
  • High GFR
  • Most segments of kidney reabsorb vitamins and minerals
  • Distal tubules also reabsorb ions
  • Dilute urine produced
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18
Q

Describe osmoregulation in marine fish

A
  • Conc. ions higher outside than inside
  • Water out of fish by osmosis, ions in
  • Lose water across gills and skin
  • Drink seawater to replace lost water (angiotensin II)
  • Gills excrete NaCL and ammonia
  • Kidneys remove excess divalent ions (Mg2+), only small/no glomeruli
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19
Q

Describe urinary tract anatomy of amphibians

A
  • Kidney -> ducts -> cloaca -> urinary (cloacal) bladder
  • Cloacal bladder is outpuching/diverticulum of cloacal wal (no connection to excretory ducts)
  • Cloacal opening controlled by sphincter muscle
  • Have renal portal veins (not caecilians)
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20
Q

Describe the kidneys of caecelians

A
  • One kidney

- Full length of coelom

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21
Q

Describe the kidneys of caudates and anurans

A
  • Paired
  • Posterior kidneys
  • Retroperitoneal
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22
Q

Compare the excretion methods of aquatic vs terrestrial amphibians

A
  • Aquatic excrete ammonia (also larval stage)
  • Terrestrial excrete urea or uric acid
  • Some adults may be flexible depending on water availability
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23
Q

Outline osmoregulation in aquatic amphibians

A
  • Skin water permeable
  • Passive absorption of water
  • Kidney excretes excess water
  • Excretion of ammonia through gills/skin
24
Q

Outline osmoregulation in terrestrial amphibians

A
  • Water conservation important
  • Evaporative loss
  • Urinary bladder to store water (or reabsorb)
  • Controlled by arginine vasotocin (AVT)
  • Aquaporins
  • Decrease GFR with reduced water
  • Excrete urea (can store until water is available to facilitate excretion)
25
Q

What are the similarities between aquatic and terrestrial amphibian excretion?

A
  • High GFR
  • Filter coelomic and/or vascular fluid
  • Hypo-osmotic urine
  • urinary bladder stores urine after formation
26
Q

Describe avian renal anatomy

A
  • Paired kidneys (large)
  • From caudal edge of lungs to ccaudal synsacrum
  • 3 divisons of kidney (cranial, middle caudal)
  • Renal lobules with cortex and medullary cones
  • Reptilian and mammalian type nephrons
  • Limited urine concentration
27
Q

What are reptile type nephrons in the avian kidneys?

A
  • No LoH
  • cortex only
  • Short
  • Cannot concentrate urine
  • Make up 70-90%
28
Q

What are mammalian type nephrons in the avian kidneys?

A
  • LoH present
  • From cortex to medulla
  • Longer
  • Concentration of urine takes place here
29
Q

What is the significance of the lumbar and sacral plexi in relation to the kidneys?

A
  • Closely associated

- Renomegaly can increase pressure on nerve plexi, leading to non-weight bearing lameness

30
Q

Describe the elimination of uric acid in birds

A
  • White/light yellow colloidal suspension
  • Precipitate: uric acid, Na+/K+, protein
  • Uric acid crysta precipitate has no osmotic pressure, no water drawn with it for elimination
  • Eliminated as urates suspended within spheres complexed with protein (or K+ if herbivorous) and sodium
  • Small volume of water needed
  • Mixed with faecal material
31
Q

Describe the urinary anatomy of lizards

A
  • Caudal aspect of kidneys fused in many species

- +/- urinary bladder

32
Q

Describe the urinary anatomy of snakes

A
  • Right kidney cranial to left
  • 25-30 lobes
  • No bladder
33
Q

How is urine stored in snakes?

A
  • No bladder

- Stored in distal colon or flared ends of each ureter

34
Q

Describe the urinary bladder in chelonians

A
  • Kidneys in caudal coelom

- Bladder is single central structure +/- paired accessory bladders

35
Q

What is unusual about the bladder of chelonians?

A
  • Is osmotically permeable
  • Can reabsorb wateer
  • In aquatic turtles acts as buoyancy aid and reabsorbs Na+
36
Q

Describe reptile microscopic renal anatomy

A
  • No pelvis, pyramids, cortex, or medulla
  • A few thousand nephrons
  • Poorly developed glomeruli
  • Few capilaries
  • No LoH
37
Q

What is the sexual segment in squamates?

A
  • Males
  • Between distal tubule and collecting duct
  • Enlarges dramatically in breeding season
  • Cells go from cuboidal to columnar
38
Q

What occurs in the sexual segment?

A
  • Cells go from cuboidal to columnar
  • Large eosinophilic granules secreted into lumen
  • Function largely unknwon, may be to separate urine and semen, or formation of copulatory plug
39
Q

What are some additional functions of the kidney in reptiles?

A
  • Conversion of 25-hydroxycholecalciferol to active vit D3

- Vitamin C synthesis

40
Q

What is an additional function of the kidney in birds?

A

Conversion of 25-hydroxycholecalciferol to active vit D3

41
Q

Describe gout formation

A
  • Hyperuricaemia
  • Can be caused by renal disease, high protein diet, dehydration, nephrotoxic drugs, damage to renal tubules
  • Uric acid deposited in soft tissues (often kidney furthering problem)
42
Q

What is the avian renal portal system?

A
  • Second afferent lood supply from pelvic limbs to renal parenchyma
  • Cranial and caudal portal veins
  • Opened or closed by renal portal valve
  • Does not supply glomerulus
  • External iliac from hind limbs, valve at common iliac
43
Q

Compare the open vs closed renal portal valve

A
  • Closed: limbs to renal porta veins, kidney (Ach), normal conditions
  • Open: limbs to caudal vena cava (adrenaline), valve smooth muscle relaxation so can bypass kidney
44
Q

Discuss drug pharmacokinetics with respect to the renal portal system in birds

A
  • Nephrotoxic drugs straight to kidney, more damage

- Tubular secretion: if drug can be eliminated by tubular secretion, will never reach rest of body

45
Q

Describe the caudal mesenteric vein with respect to the renal portal system in birds

A
  • Contributes to renal portal system
  • Alimentary tract disease taken to kidney
  • Toxins from gut (e.g. heavy metals) straight to kidney
46
Q

Describe the renal portal system of reptiles

A
  • Similar to birds
  • Renal portal vein
  • Bypasses glomerulus, perfuses renal tubules
  • Can be valved similar to birds
47
Q

List the osmoregulatory mechanisms used by birds in dehydration

A
  • Decrease GFR
  • Arginine vasotocin release (controls tubular water permeability)
  • Sodium linked water reabsorption in the colon and ceca
48
Q

Describe sodium linked water reabsorption in the colon and ceca

A
  • In times of dehydration, urine refluxed to urodeum from proctodeum
  • Then into colon and ceca
  • Active transport of sodium into blood, chloride and water follow by diffusion
  • Does not occur in times of stress (leading to polyuria)
  • Produces concentrated uric acid, dry mixture with faeces
49
Q

Describe reptilian responses to dehydration

A
  • Afferent arteriole constriction (arginine vasotocin stimulates this)
  • Glomerulus closes, tubule collapses
  • GFR decreases
  • Decreased excretion of nitrogenous waste and sodium
  • Renal portal blood perfuses tubules
50
Q

How are reptiles adapted to conserve water?

A
  • Few nephrons
  • Lower GFR
  • Uric acid
  • Cease GFR in times of stress
  • Salt gland for excess Na+/K+ excretion
51
Q

Where is the salt gland in reptiles and birds?

A
  • Supraorbital gland
  • Drains into nostrils
  • Or above palate
52
Q

In what birds is the salt gland found and why?

A
  • Aquatic: high consumption of salt water

- Desert: need to conserve water so actively excrete salt

53
Q

What is the function of the salt gland?

A

Removal of exess salt, when salt consumption exceeds the ability of the kdiney to remove it

54
Q

How is salt removed by teh salt glands in birds?

A
  • Countercurrent blood flow, paired gland, ots of lobes, each lobe has a duct and each duct has lots of capillaries
  • Increased solute concentration in blood
  • Water out of cells, increase ECF vol
  • Increase blood plasma solute conc and ECFV leads to salt gland secretion
55
Q

Describe the salt glands of reptiles

A
  • Similar to birds
  • Actively excrete Na+ and K+
  • Near eye or nasal passages
  • High plasma osmotic concentration stimulates this
  • Sneeze excess salts
    (looks like powder around nostrils once dried)
  • Sea turtles have modified tear glands
56
Q

What are the 3 components of avian excreta?

A
  • Urate (white)
  • Faeces (brown)
  • Urine (clear)

URI (15 decks)

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