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Vertebrate Physiology > Excretory System > Flashcards

Excretory System Flashcards

1
Q

What are the functions of the excretory system?

A
  • maintain proper internal levels inorganic solutes
  • maintain proper plasma and water volume
  • removal of waste
  • maintain osmotic balance
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2
Q

What are the functions of the excretory system?

A
  • maintain proper internal levels inorganic solutes
  • maintain proper plasma and water volume
  • removal of waste
  • maintain osmotic balance
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3
Q

What are nitrogenous wastes the result of?

A

metabolism of proteins and nucleic acids

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4
Q

What does the choice of primary nitrogenous waste correlate with?

A

water availability

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5
Q

Name and describe the nitrogenous waste from most toxic to least.

A
  • Ammonia: MOST toxic; expelled by most aquatic animals that breathe water (ammonotely); can’t be broken down so it gets diluted to a non-toxic concentration.
  • Urea: expelled by most terrestrial animals (humans included) [ureotely], more expensive metabolically but is less toxic than ammonia.
  • Uric Acid: expelled by insects, reptiles, & birds (uricotely); most expensive metabolically, highly insoluble, highly non-toxic; makes water conservation for animals (semi-solid form).
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6
Q

Explain the process of transport epithelia.

A

There is a Na+/K+ ATPase pump on the basolateral (top) side of the membrane, making the Na+ concentration inside the cell lower (because pumps Na+ out of cell and K+ into). Na+ then enters the apical (bottom) side by diffusing through ENaC (epithethial Na channel). Cl- wants to counteract the outside charge (attracted to Na+), so it goes through CIC or CFTR channels and changes the gradient produced by the Na+ efflux. This increases the extracellular solute concentration, which attracts water (osmosis, low solute concentration to high to dilute) across basolateral membrane. This occurs on the PCT.

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7
Q

What is filtration?

A

water and small solutes can pass through a barrier, while cells and larger molecules remain behind (comes from the blood and goes into another area)

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8
Q

What is secretion?

A

transport epithelia move specific solutes into tubule for lumen secretion

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9
Q

What is reabsorption?

A

transport epithelia move specific solutes and water back into the body from the lumen

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10
Q

What is osmoconcentration?

A

water is removed from lumen, laving solutes behind, producing more concentrated excretory fluid (hyper osmotic)–> goal to concentrate urine and reabsorb water to avoid dehydration

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11
Q

What are the parts of the excretory system?

A
  • kidneys: urine forming organ, have 2 one on each side of vertebral column (houses renal pelvis where kidney stones develop)
  • ureters: tube like things that urine drains into from the kidneys (have 2)
  • urinary bladder (or hindgut in reptiles and birds) ureters empty urine here
  • urethra: bladder empties urine into and urine goes out through
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12
Q

What are the regions of the kidney?

A
  • renal cortex (outer portion)
  • renal medulla (inner- divided into renal pyramids in larger mammals)
  • renal pelvis (drainage area in the center of the kidneys, collects urine and releases it–where kidney stones occur)
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13
Q

What is a nephron and how many are in the human body?

A

smallest functional unit of the kidney we have ~1 million

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14
Q

afferent arteriole

A

supplies each nephron by bringing dirty blood in, made of smooth muscle

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15
Q

glomerulus

A

ball-like knot of capillaries in renal cortex, site of filtration of blood, its twisted to increase SA

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16
Q

efferent arteriole

A

exits the glomerulus and carries semi-clean blood

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17
Q

pertitubular capillaries

A

surrounds tubules, puppies renal tissue with blood and exchanges materials with tubular fluid

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18
Q

Bowman’s (glomerular) capsule

A

site of glomerular filtration

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19
Q

proximal (convoluted) tubule

A

PCT, involved in tubular reabsorption and secretion

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20
Q

loop of Henle

A

part of osmoconcentration, descending limb (plunges into medulla), ascending limb (returns to the cortex)

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21
Q

distal (convoluted) tubule

A

DCT, involved in reabsorption/secretion and osmoconcentration

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22
Q

collecting duct

A

involved in osmoconcentration, empties into renal pelvis

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23
Q

juxtaglomerular apparatus

A

JGA, sensor in osmoregulation and blood pressure regulation, on DCT near glomerulus, wants to dictate what the afferent arteriole does

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24
Q

Describe elasmobranch urinary systems.

A
  • isosmotic or hyper osmotic relative to seawater
  • fish itself is hyper osmotic, lots of solute–water wants to go into, blocks Na+
  • retain urea and trimethylamine oxide (TMAO)–breaks down, gives off fishy smell, uses compound to bring water in
  • hindgut excretes hypertonic fluid high in salt
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25
Q

Describe marine bony fish urinary systems.

A
  • hyposmotic (not much solute, drink salt water)
  • drink salt water to reverse water loss through gills
  • gills actively transport salt outward and excrete nitrogenous wastes
  • kidneys remove divalent ions
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26
Q

Describe fw bony fish urinary systems.

A
  • hyperosmotic (will drink water in and it dilutes urine)
  • takes water in through gills and mouth
  • excretes a large volume of highly diluted urine
  • gills take in salt and excrete ammonia and ammonium
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27
Q

Describe urinary systems of amphibians.

A
  • kidneys maintain constant ECF
  • metanephric nephrons: (excrete water and reabsorbs ions, it can also exert urea–checks and balances system)
  • urinary bladder: serves as a temporary water reservoir in case of dehydration
  • arginine vasotocin (AVT): triggers water uptake through aquaporins in bladder wall (similar to our vasopressin/ADH)
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28
Q

Describe urinary systems of reptiles.

A
  • nephrons resemble aquatic vertebrates
  • ureters carry urine in liquid/semi-solid form into cloaca (all waste out at same time, excretory & digestive)
  • NO loop of Henle
  • primary nitrogenous waste: uric acid (no need to dilute it)
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29
Q

What can the cloaca and lower intestine do in reptiles?

A

reabsorb water

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30
Q

What do the nasal salt glands in reptiles do?

A

secrete highly salty fluid

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31
Q

Describe avian (bird) urinary systems.

A
  • resemble reptiles
  • some mammalian-type nephrons WITH loop of henle
  • uric acid crystals are covered with proteins to form rate balls (can easily pass)
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32
Q

What do marine birds have that are different from non-marine ones?

A

nasal salt glands near the eyes

  • contain blind end tubules lined with active salt secreting cells
  • excrete excess salt out of nasal passages
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33
Q

Explain the difference between cortical and juxtaglomerular nephrons.

A
  • cortical: glomeruli in outer cortex, short loops of henle that dip only into outer medulla (humans mainly have)
  • juxtaglomerular: glomeruli in inner cortex near medulla, long loops of helm plunge into inner medulla (more time to reabsorb good stuff, birds and desert animals-need to reabsorb more water); peritubular capillaries form hairpin vascular loops (vasa recta)
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34
Q

What are the 3 layers of the molecular sieve for filtration?

A

1) glomerular capillary wall: consists of a singly layer of flattened endothelial cells, perforated with pores (too small for proteins to pass)
2) basement membrane: gelatinous layer composed of collagen and glycoproteins (further limit protein movement)
3) inner layer of Bowman’s capsule: consists of podocytes with filtration slits

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35
Q

filtration is a…… process

A

exclusively extracellular and its VERY selective

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36
Q

What are the driving forces of glomerular filtration?

A
  • glomerular capillary blood pressure
  • plasma colloid osmotic pressure
  • Bowman’s capsule hydrostatic pressure
  • net filtration
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37
Q

glomerular capillary blood pressure

A

is higher than capillary blood pressure elsewhere (ex 50mmHg), major determinant of filtration

  • afferent arteriole is larger in diameter than efferent to bring more blood into glomerulus
  • FAVORS filtration
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38
Q

plasma colloid osmotic pressure

A

protein remains in blood, it increases osmotic pressure (ex: 30mmHg) ; wants things to move-impedes filtration to go back in
-OPPPOSES filtration

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39
Q

Bowman’s capsule hydrostatic pressure

A

pressure exerted by tubular gland (ex: 15 mmHg)

-OPPOSES filtration

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40
Q

net filtration

A

net= glomerular cap. pressure–(colloid + Bowmans)
= 55mmHg – (30mmHg + 15mmHg)
= + 10 mmHg (FAVORS filtration)

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41
Q

What is the glomerular filtration rate?

A

GFR, amount of pressure in glomerulus dictates GFR
-depends on net filtration, SA, permeability of glomerular membrane, and hydrostatic pressure

GFR= filtration coefficient x net filtration pressure

42
Q

What happens when a person has long term high blood pressure and it goes undiagnosed?

A

higher pressure, enlarges pores and allows proteins and RBC to get into the urine, can cause kidney failure

43
Q

If resistance in the afferent arteriole is increased, what will happen to blood flow and GFR?

A

blood flow will decrease to glomerulus, thus decreasing GFR

44
Q

What is autoregulation and what are two types of it?

A

intrinsic control, doesn’t care what’s happening to the rest of the body, just wants to maintain its workload, no more, no less–> prevents unintentional shifts in GFR
-myogenic mechanisms and tubuglomerular feedbacks

45
Q

myogenic mechanism

A

smooth muscle contracts when afferent is stretched–> increase in blood pressure, increase blood through glomerulus, causes afferent to stretch and constricts on blood, decreases GFR back to normal by lowering the pressure

46
Q

tubuglomerular feedback

A

juxtaglomerular apparatus (DCT) there are granular cells with macula densa that sense when Na+/water content changes

  • too high, PCT didn’t absorb efficiently, macula densa will release adenosine/ATP to constrict afferent arteriole, decreasing GFR
  • too low, macula densa will release nitric oxide (NO) to dilate afferent arteriole, increasing GFR
47
Q

What does an increase in sympathetic activity do to GFR?

A

contributes to long-term maintenance of blood pressure by restoring plasma volume

  • constricts afferent arteriole, lowering GFR, decreasing urine output
  • extrinsic control, doesn’t care about what happens at kidneys, only cares about the rest of the body
48
Q

What happens if sympathetic activity is maintained for too long?

A

increases BP, increases toxins, won’t produce as much urine and urine that is produced will be super concentrated, can cause kidney stones and kidney failrue

49
Q

What happens when arterial blood pressure increases?

A

increases blood flow in afferent, increases glomerular pressure and net filtration, thus increasing GFR

50
Q

What happens when the afferent arteriole is constricted?

A

blood flow decreases, the glomerular pressure and net filtration decreases, thus decreasing GFR

51
Q

What happens when the afferent arteriole is dilated?

A

blood flow increases, glomerular pressure and net filtration increases, thus increasing GFR

52
Q

What happens when the efferent arteriole is constricted?

A

increases GFR, and decreases blood exit

53
Q

What happens when the afferent and efferent arterioles are constricted?

A

GFR stays the same, goes back to norm

54
Q

What happens in the short term when arterial blood pressure decreases? In the long term?

A

short term, heart wants to fix it

long term, kidneys take a while to correct it (~7 days)

55
Q

mammalian tubular reabsorption…..

A

is HIGHLY selective

56
Q

mammals reabsorb …. of filtered salt and water and …… of filtered glucose and amino acids

A

99% of filtered salt and water

100% of filtered glucose and amino acids

57
Q

Where does the reabsorption of most substances occur?

A

at the proximal convoluted tubule (PCT)– 2/3!

58
Q

80% of kidney’s total energy requirement is used for…?

A

Na+ transport

59
Q

Is Na+ reabsorption passive or active?

A

active (ATP) in most sections of tubule, but passive (rest) in some

60
Q

What percentages of Na+ reabsorption do the PCT, loop of henle, and DCT contain?

A
  • PCT, 67% of filtered Na+
  • loop of henle (ascending) 25%
  • DCT, 8%
61
Q

The active step of Na+ reabsorption involves……?

A

Na+/ATPase pump in basolateral membrane

62
Q

The passive part of Na+ reabsorption involves….?

A

transport of Na+ across apical membrane

63
Q

What occurs in the descending loop of henle?

A
  • fluid entering loop is isotonic
  • water reabsorption=permeable to water, drawn out into interstitial space and quickly goes into vasa recta as to not dilute interstitial
  • becomes more solute concentrated as go down because not permeable to Na+
  • hypotonic to environment
64
Q

What occurs in the ascending loop of henle?

A
  • salt (NaCl) actively pumped into interstitial space
  • walls not permeable to water, osmosis doesn’t occur
  • highly solute concentrated interstitial space at bottom
  • hypertonic to environment
65
Q

What is the countercurrent multiplier system?

A
  • water is not actively pumped out of tubes, will not cross if it is isotonic to ECF
  • structure of loop allows for concentration gradient to be set up for osmosis of water
  • ascending limb, sets up gradient
66
Q

What is countercurrent multiplication?

A

positive feedback created between 2 portions of loop of henle
-more sodium ascending limb removes, the saltier the fluid entering will be (more Na+ out, more water it can retain)

67
Q

What is the vasa recta?

A
  • specialized blood vessels around the loop of henle with ascending/descending portions
  • increased salt concentration at beginning of ascending region, pulls in water, removed from interstitial space
  • keeps Na+ concentration in interstitial high=hypertonic
68
Q

Explain the collecting duct and ADH>

A
  • last step in urine formation
  • influenced by hypertonicity of interstitial space, water will leave via osmosis if able
  • permeability to water depends on number of aquaporin channels in cells of collecting duct (determined by ADH)
69
Q

What happens in dehydration?

A

ADH secretion is high and water is reabsorbed from the collecting duct

70
Q

What happens in over hydration?

A

ADH secretion is low and water is not reabsorbed

71
Q

What happens to ADH when one drinks alcohol?

A

alcohol is a diuretic and it blocks the production of ADH, meaning no aquaporins are present, no water is reabsorbed (dehydration) because water goes into the urine

72
Q

How does the reabsorption of water occur?

A

passively reabsorbed by osmosis

  • ascending limb of loop impermeable to water
  • reabsorption from DCT and collecting duct is subject to hormonal control
  • water passes through aquaporin channels (AQPs)
73
Q

What are the types of aquaporin channels?

A
  • AQP1- channels in PCT are ALWAYS open

- AQP2- changes in DCT and collecting duct are regulated by vasopressin (ADH)

74
Q

How much of glucose and amino acids are reabsorbed?

A

100%

-VITALLY IMPORTANT and reflects nutritional value

75
Q

Describe the secondary active transport of glucose/amino acids?

A
  • symporter in apical membrane simultaneously transports Na+ down its concentration gradient and a specific organic molecule (glucose) up its gradient from the lumen into tubular cell (glucose follows Na+)
  • basolateral Na+/K+ pump indirectly drives cotransport system
76
Q

Once inside the cell, the organic molecule is transported into ECF by….?

A

facilitated diffusion

77
Q

All actively reabsorbed substances exhibit a ……… ?

A

tubular maximum (Tm)

78
Q

Plasma membrane carriers exhibit….?

A

saturation

79
Q

How does glucose reabsorption occur in diabetes mellitus?

A

plasma glucose is increased (hyperglycemia), glucose is filtered into Bowman’s capsule at same concentration as plasma–> when filtered, glucose load exceeds tubular maximum for glucose reabsorption and the excess spills over into the urine

80
Q

What is a diagnosis of diabetes mellitus?

A

glucose in the urine (both types)

81
Q

What is the only waste product to be reabsorbed?

A

urea, passively as the filtrate is progressively concentrated by reabsorption of water from proximal tube
-40% of filtered is reabsorbed, adds in water reabsorption at loop of henle and collecting duct

82
Q

How does urea recycling contribute to medullary hypertonicity?

A
  • top and middle portions of the collecting duct are impermeable to urea
  • urea concentration in collecting duct increases as water is reabsorbed
  • lowest section of collecting duct is PERMEABLE to urea, so urea diffuses out, increasing the solute concentration of medulla
  • some urea is recycled into loop of henle
83
Q

Regulation of plasma …… is important for blood pressure regulation.

A

Na+

84
Q

What does RAAS stand for?

A

Renin-angiotensin-aldosterone-system

85
Q

What signals the secretion of Renin?

A
  • granular cells of JGA, secrete renin into blood in response to a fall in Na+, ECF volume, or blood pressure
  • granular cells secrete renin in response to fall in pressure in afferent
  • macula densa cells respond to fall in DCT salt and stimulates renin secretion
  • baroreceptor reflex triggers increase sympathetic activity, stimulates renin secretion
86
Q

How does renin convert angiotensinogen?

A

renin catalyzes conversion of angiotensin, cleaves it and converts it to Ang I (active but not the best), angiotensin converting enzyme then reacts with Ang I and converts it to Ang II (major bioactive player in the body)

87
Q

What is responsible for the primary secretion of aldosterone in the adrenal cortex?

A

Ang II

88
Q

What are the effects of aldosterone?

A
  • increase in Na+ reabsorption by DCT and collecting duct
  • stimulates secretion of vasopressin (ADH) and promotes water retention by kidneys
  • potent constrictor of systemic arterioles, directly increasing BP
89
Q

What effects does Ang II have on the body?

A
  • goes to brain and triggers thirst and salt hunger
  • increases sympathetic activity, increasing HR
  • Na+ reabsorbs, K+ excreted, water retention
  • aldosterone secretion
  • vasoconstriction of arterioles, increases BP
  • ADH secretion increases (renal collecting duct reabsorption)
90
Q

What is initiated when blood pressure drops?

A

hormone cascade, brings bp up because targets multiple systems (RAAS)

91
Q

Natriuretic peptides do what to RAAS?

A

oppose it

92
Q

atrial natriuretic peptide (ANP)

A

secreted by atrial cardiac muscle cells
-inhibts Na+ reabsorption in DCT and collecting duct (decreases)
-inhibits secretion of renin, aldosterone, vasopressin (ADH) (decreases)
-decreases cardiac output and inhibits sympathetic activity
OPPOSITE OF ALDOSTERONE

93
Q

What do diuretics do?

A
  • used clinically to control BP and relieve edema

- increase urine volume, decrease blood volume, and interstitial fluid volume

94
Q

What are loop diuretics?

A

most powerful, inhibits Na+ transport out of the loop of henle

  • used for extreme hypertension
  • example: Lasix
  • can inhibit up to 25% of water reabsorption, blocks countercurrent multiplier system
95
Q

What are thiazide diuretics?

A

inhibits Na+ transport in DCT

  • used for slight hypertension
  • can inhibit up to 8% of water reabsorption
96
Q

Pharmaceutically speaking, why are diuretics not prescribed more than ACE inhibitors or Ang II drugs?

A
  • actually safer than the two because it doesn’t affect multiple systems
  • make one urinate more because increases urine volume, not prescribed as much because of patient in compliance, people don’t want to pee all the time
97
Q

What is the bladder wall made up of?

A

smooth muscle lined with transitional epithelium

98
Q

What makes the bladder wall impermeable?

A

umbrella cells joined with tight junctions

99
Q

Can the bladder accommodate large fluctuations in volume?

A

YES

100
Q

What is the bladder opening guarded by and what are they made of?

A
  • internal urethral sphincter (smooth muscle- we don’t control it, ANS and parasympathetic do)
  • external urethral sphincter (skeletal muscle-we control dilation/contraction of this)
101
Q

Describe micturition.

A

Urination

  • stretch receptors in bladder wall stimulated by distended bladder
  • stimulates parasym. neurons that originate in lower spinal cord
  • bladder wall contracts due to parasym. stimulation, mechanically pulling internal urethral sphincter open
  • external urethral sphincter opens and urine is expelled through urethra

-condensed version: bladder contracts due to parasym. activity by stretch receptors in bladder wall, pressure increases, pushed out external sphincter (we control)

Vertebrate Physiology (1 decks)

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