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ASCI2120 Exam 4 > The Urinary System > Flashcards

The Urinary System Flashcards

1
Q

What is the organization of the urinary system?

A

Two kidneys
Two ureters
One urinary bladder
One urethra

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2
Q

What do the kidneys do?

A

make urine and carry out other vital functions

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3
Q

What do the ureters do?

A

carry urine to the urinary bladder

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4
Q

What does the urinary bladder do?

A

collects, stores, and releases urine

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5
Q

What does the urethra do?

A

empties urine from the body

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6
Q

What are the six functions of the urinary system?

A
  1. Eliminating organic waste products, such as urea, uric acid, creatine, and ammonia
  2. Regulating blood volume and pressure by: adjusting the volume of water lost and releasing erythropoietin and renin
  3. regulating plasma concentrations of ions;
  4. helping stabilize blood pH: by controlling loss of hydrogen ions and bicarbonate ions in urine
  5. conserving nutrients
  6. assisting the liver in detoxifying poisons
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7
Q

What does the renal lobe of the kidny consist of?

A
  • renal pyramid
  • overlying area of renal cortex
  • adjacent tissues of renal columns
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8
Q

What is the order that urine production goes in?

A

urine from renal papilla -> minor calyx -> major calyx -> renal pelvis -> ureter

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9
Q

Compare the anatomy of kidneys between domestic animals

A
  • cattle do not have a distinct renal pelvis
  • human, cattle, and pig have multipyramidal or multilobar kidneys
  • cat, dog, and horse have unipyramidal or unilobar kidneys
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10
Q

How much cardiac output do kidneys receive?

A

20-25%

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11
Q

How many ml of blood flow per minute do kidneys receive in humans?

A

1200 ml

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12
Q

What are the nephrons of the kidney?

A

the collecting system and functional unit

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13
Q

What do nephrons consist of?

A
  • renal corpuscle
  • renal tubule
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14
Q

What are the parts of the renal tubule?

A
  • proximal convoluted tubule (PCT)
  • the Loop of Henle
  • distal convoluted tubule (DCT)
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15
Q

Describe the renal corpuscle

A

spherical structure consisting of:

  • Bowman’s capsule: forms the outer wall of the renal corpuscle and encapsulates the glomerular capillaries
  • glomerulus: capillary network
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16
Q

Describe the parts of the Bowman’s capsule

A
  • Parietal epithelium: a simple squamous epithelium, forms the outer wall. Continuous with visceral epithelium
  • Visceral epithelium: covers glomerular capillaries
  • Capsular space: separates the parietal and visceral epithelia
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17
Q

Describe the parts of the visceral epithelium

A
  • consists of large cells (podocytes) with complex processes or “feet” (pedicels) that wrap around specialized lamina densa of glomerular capillaries
  • Filtration slits: narrow gaps between adjacent pedicels
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18
Q

Describe the glomerulus

A
  • consists of 50 intertwining capillaries
  • are fenestrated capillaries
  • blood delivered via afferent arteriole
  • blood leaves in efferent arteriole: flows into peritubular capillaries which drain into small venules
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19
Q

Describe the proximal convoluted tubule (PCT) of the renal tubule

A
  • first part nearest to Bowman’s capsule
  • Loop of Henle which consists of:
    a descending limb
    a sharp turn
    an ascending limb
    each limb contains a thick segments and a thin segment
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20
Q

Describe the distal convoluted tubule (DCT) of the renal tubule

A

convoluted tubule beyond the Loop of Henle

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21
Q

Describe collecting ducts

A

recieve fluid from many nephrons

each collecting duct:
- begins in cortex
- descends into medulla
- carries fluid to papillary duct that drains into a minor calyx

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22
Q

What are cortical nephrons?

A
  • 85% of all nephrons
  • located mostly within cortex
  • Loop of Henle is short
  • peritubular capillaries surround entire renal tubule
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23
Q

Describe juxtamedullary nephrons

A
  • long loops of Henle deep into medulla
  • peritubular capillaries connect to vasa recta
24
Q

What is the goal of urine production?

A

to maintain homeostasis by regulating volume and composition of blood and including excretion of metabolic waste products

25
Q

What are the three organic waste products?

A

Urea: the most abundant organic waste and produced during the breakdown of amino acids

Creatinine: generated in skeletal muscle tissue by breaking down the high-energy compound, creatine phosphate

Uric acid: formed by recycling of nitrogenous bases from RNA molecules

26
Q

What is the pathway or urine formation?

A

renal papilla -> minor calyx -> major calyx -> renal pelvis -> ureter -> urethra

27
Q

What are the three processes of urine formation?

A

Filtration: blood pressure forces water and small solutes across membrane into capsular space

Reabsorption: movement of molecules selectively out of the tubule and itno the peritubular blood

Secretion: movement of waste molecules out of peritubular blood and into the tubule for excretion

28
Q

Describe the filtration membrane

A
  • capillary endothelium: fenestrated, 60-100 nm diameter
  • lamina densa
  • filtration slits: the finest filters of all: 6-9 nm diater
29
Q

Describe filtration

A

hydrostatic pressure forces water and small solute through membrane pores:
- metabolic wastes and excess ions
- glucose, free fatty acids, amino acids, vitamins

30
Q

Describe filtration pressures:

A

glomerular filtration is governed by the balance between:
- glomerular hydrostatic pressure (GHP): blood pressure ~ 45-55 mm Hg
-Capsular hydrostatic pressure (CsHP): opposes GHP ~ 15 mm Hg
- Blood colloid osmotic pressure (BCOP): osmotic pressure resulting from presence of suspended proteins ~ 25 mm Hg

Net hydrostatic pressure (NHP): GHP - CsHP = ~ 35 mm Hg

Filtration Pressure (FP): NHP - BCOP = ~ 10 mm Hg

31
Q

What is Glomerular Filtration Rate (GFR)?

A

is the amount of filtrate produced in the kidneys each minute
- ~125 ml per min in humans (~10% of fluid delivered to the kidneys)
- 50 gallons (180L)/day, ~70 times the total plasma volume
- 99% is reabsorbed

Any factor that alters the filtration pressure will change the GFR
- are very sensitive to changes in blood pressure
- if blood pressure at the glomeruli drops by 20%, kidney filtration will cease

32
Q

Describe the autoregulation (intrinsic) of the GFR

A

Maintains GFR despite changes in local blood pressures and blood flow

Reduce renal blood pressure triggers:
- dilation of afferent arteriole
- dilation of glomerular capillaries
- constriction of efferent arterioles

Rise in renal blood pressure:
- constricts afferent arterioles
- decreases glomerular blood flow

33
Q

What is the net effect of increased sympathetic activity?

A

moderate decrease in GFR

34
Q

Describe reabsorption and secretion

A
  • second step in urine formation
  • glomerular filtration produces a filtrate with a composition similar to blood plasma but with few, if any, plasma proteins

reabsorption: recovers useful materials from filtrate

secretion: ejects waste products, toxins, and other undesirable solutes

35
Q

How does reabsorption and secretion work?

A

occur in every segment of nephron
- except renal corpuscle

by different mechanisms: passive and active transport

relative importance changes from segment to segment

reabsorbed materials enter peritubular fluid: and diffuse into peritubular capillaries and vasa recta

36
Q

Describe reabsorption and secretion in the proximal convoluted tubule:

A

reabsorb:
- 60-70% of the volume of filtrate
- 99-100% of glucose, amino acids, and other organic nutrients
- 60-70% Na+, K+, and HCO3

secrete:
- H+, NH4+, creatinine, drugs, and toxins

37
Q

Describe reabsorption in the Loop of Henle

A

Reabsorbs about 1/2 of water, and 2/3 of sodium and chloride ions remaining in tubular fluid by the process of countercurrent multiplication

Two parallel segments of Loop of henle have very different permeability characteristics:
- thin descending limb: permeable to water; impermeable to solutes
- thick ascending limb: impermeable to water, active solute transport

38
Q

Describe countercurrent multiplication and concentration of urine

A

positive feedback loop:
- pumping out of Na+ and Cl- from the thick ascending limb elevates the osmotic concentration in the peritubular fluid around the thin descending limb
- the result is an osmotic flow of water out of the thin descending limb
- the arrival of the highly concentrated solution in the thick ascending limb accelerates the transport of Na+ and Cl- into the peritubular fluid

39
Q

Describe tubular secretion and solute reabsorption at the distal convoluted tubule

A

only 15-20% of initial filtrate volume reaches DCT

arriving tubular fluid no longer resemble blood plasma

reabsorption of water (~5%):
- under ADH stimulation

reabsorption of Na+:
- under aldosterone stimulation

Secretion of H+, NH4+, creatinine, drugs and toxins

40
Q

Describe reabsorption and secretion along the collecting system

A

the collecting ducts receive tubular fluid from many nephrons

along the concentration gradient in the medulla

reabsorption of water (~9%)
- under ADH stimulation

reabsorption of Na+
- under aldosterone stimulation

secretion of H+ or HCO3- to control body fluid of pH

41
Q

Describe the relevance of kidney and urinary stones:

A

when the concentration of some substances (e.g. calcium, oxalate, magnesium-ammonium-phosphate etc.) gets so high under certain conditions, the participate to form kidney stones (nephrolithiasis) or urinary tract stones (urolithiasis)

quite common in dogs, cats, and ruminants

42
Q

Describe the control of urine volume

A

urine volume and osmotic concentration are regulated by controlling water reabsorption

obligatory water reabsorption:
- water absorption in the proximal convoluted tubule and the descending limb of the loop of Henle
- can not be adjusted; recovers ~85% od filtrate

facultative water reabsorption:
- the amount of water reabsorbed along the distal convoluted tubule and the collecting system
- can be precisely controlled, because these segments are relatively impermeable to water except in the presence of ADH

43
Q

What hormones control urine volume?

A
  • AHD
  • Aldosterone
  • Atrial natriuretic hormones (ANH)
44
Q

How does ADH participate in the control of urine volume?

A
  • controls the permeability of the distal convoluted tubule and collecting system to water by increasing special water channels in the apical cell membranes
45
Q

How does aldosterone participate in the control of urine volume?

A
  • controls sodium ion pumps along most of the distal convoluted tubule and the proximal portion of the collecting system
  • raise the sodium concentration of blood and thus promoting reabsorption of water
46
Q

How does atrial natriuretic hormones (ANH) participate in the control of urine volume?

A
  • promotes loss of sodium via urine
  • opposes aldosterone
  • cause the kidney to reabsorb less water and thereby produce more urine
47
Q

What is the relevance of diabetes insipidus?

A
  • deficient release of ADH or reduced responsiveness of the kidney to AHD
  • intense thirst and heavy urination (>20 L/day in humans)
48
Q

What does the vasa recta do?

A
  • to return solutes and water reabsorbed in medulla:
  • to general circulation without disrupting the concentration gradient
49
Q

What is the normal average pH of arterial blood?

A

7.4

50
Q

What is acidemia?

A
  • when the pH of plasma falls below 7.35
  • the physiological state that results is acidosis
51
Q

What is alkalemia?

A
  • when the pH of plasma rises above 7.45
  • the physiological state that results is called alkalosis
52
Q

What range of pH can animals not survive in?

A

animals can not survive long with an ECF pH below 6.8 or above 7.7

53
Q

What does an animal body do to control the pH?

A

the buffer systems:
- the carbonic acid-bicarbonate buffer system: CO2 + H2O <-> H2CO3 <-> H+ + HCO3-
- phosphate buffer system: H2PO4- <-> H+ + HPO42-
- protein buffer system

respiratory compensation: affecting the carbonic acid-bicarbonate buffer system by pulmonary ventilation

renal compensation: the kidneys excrete alkaline or acid urine as needed

54
Q

Describe respiratory and renal compensation in regulating pH

A
  • in renal compensation, the kidneys vary their rates of H+ secretion and HCO3- reabsorption, depending on the pH of the ECF
55
Q

What is the micturition reflex?

A

stretch receptors in bladder -> afferent fibers -> sacral spinal cord
- efferent fibers -> stimulates detrusor muscle (smooth muscle) contraction
- interneuron -> cerebral cortex -> inhibits the micturition reflex or voluntary relaxation of external urethral sphincter (skeletal muscle)

ASCI2120 Exam 4 (5 decks)

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