Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physiology > Chapter 12 (Urinary System) > Flashcards

Chapter 12 (Urinary System) Flashcards

1
Q

10 Main Kidney Functions

A
  1. Maintain H2O, salt, and electrolyte balance in the body by urinary output.
    eg. maintain a surplus and deficit for ECF constituents
  2. Maintains the proper osmolarity of body fluids, primarily through regulating H2O balances (prevents the disruption in osmosis)
  3. Regulates and maintains the quantity and concentration of most ECF ions, Na+, Cl-, K+, HCO3-, Ca2+, Mg+, SO4- and PO4
    eg. minor changes in ecf K+ lead to fatal cardiac arrest or dysfunction
  4. Maintains proper plasma volume to regulate long-term blood pressure, through kidney’s ability to maintain salt and water balance.
  5. Helps maintain proper acid-base balance in the body; through adjusting urinary output of H+ and HCO3-.
  6. Excretion of the end products (wastes) of bodily metabolisms (urea, uric acid and creatinine)
  7. Excreting many foreign compounds (drugs, pesticides, food additives)
  8. Produces erythropoietin to regulate RBC production.
  9. Produces renin (kidney enzyme) that triggers RAAS, important in salt conservation by the kidneys.
  10. Converting vitamin D into its active form (absorb calcium)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Structure of Kidneys

A
  1. Ureter
  2. Renal pelvis
  3. Renal pyramid
  4. Renal cortex
    - Houses the nephron. Filtration, reabsorption, and secretion.
  5. Renal medulla
  6. Renal artery
  7. Renal vein
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

The Nephron Basics

A
  • Functional unit of the kidney
  • Smallest unit
  • 1 million/kidney
  • The arrangement of nephrons separate the cortex and medulla.
  • Cortical nephrons: 80% of nephrons. Lies in the outer layer of the cortex
  • Juxtamedullary Nephrons: lies in the inner layer of the cortex. Performs most of the urine concentration
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Vascular Component of the Nephron

A

Afferent arteriole: carries blood to the glomerulus
Glomerulus: a tuft of capillaries that filters protein free plasma into the tubular component
Efferent arteriole: carries blood from the glomerulus
Peritubular capillaries: supplies the renal tissues; involved in exchanges with the fluid in the tubular lumen

  • Water and solutes are filtered through the glomerulus as blood passes through it.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Tubular Component of the Nephron

A

Bowman’s capsule: collects the glomerular filtrate
Proximal tubule: uncontrolled reabsorption and secretion fo selected substances occur here
Loop of Henle of long-looped nephrons: establishes an osmotic gradient in the renal medulla that is important in the kidney’s ability to produce urine of varying concentration
Distal tubule and collectng duct: variable, controlled reabsorption of Na+ and H2O, and secretion of K+ and H+ occurs here; fluid leaving the collecting duct is urine, which enters the renal pelvis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Juxtaglomerular Apparatus

A
  • Produces substances involved in the control of kidney function
  • Both vascular and tubular
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

3 Renal Processes

A
  1. Glomerular filtration: non discriminant filtration of a protein free plasma from the glomerulus into the Bowman’s capsule.
    - Influenced by changes in the filtration coefficient
    - The kidneys receive 20-25% of the cardiac output.
  2. Tubular reabsorption: selective movement of filtered substances from the tubular lumen into the peritubular capillaries
    - The tubules have a high absorptive capacity for substances needed by the body and little or no capacity for substances of no value. (Dependent on the body’s needs)
  3. Tubular secretion: selective movement of non filtered substances from the peritubular capillaries into the tubular lumen (kidney tubules)
    - Involves transepithelial transport but steps are reversed.
    - Tubular secretion provides a second route of entry into the tubule for selected substances
    - Includes H+, K+, organic anions and cations
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Layers of the Glomerulus Membrane

A

In order to be filtered, a substance must pass through:

  1. The pores between the fenestrations within the endothelial cells of the glomerular capillary
  2. An acellular basement membrane
  3. The filtration slits between the foot processes of the podocytes in the inner layer of the bowman’s capsule
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Glomerular Capillary Blood Pressure

A
  • Pressure exerted on the glomerular capillaries depends on
    1. Contraction of the heart
    2. Resistance to blood flow offered by afferent and efferent arterioles
    3. Size of diameter of the efferent arterioles
    55mm Hg
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Plasma-colloid Osmotic Pressure

A
  • Caused by unequal distribution f plasma proteins across glomerular membrane (by osmosis)
  • Opposes filtration
    30 mm Hg
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Bowman’s Capsule Hydrostatic Pressure

A
  • Pressure exerted by fluid in the initial part of the tubule
  • Tends to push fluid out of the Bowman’s capsule
  • Opposes filtration
  • 15 mm Hg
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Glomerular Filtration Rate (GFR)

A
  • Difference between force favouring filtration and forces opposing filtration
  • 10 mm Hg
  • About 20% of plasma is filtered each day.
  • for 180 L of glomerular filtrate, 125ml/min (male)
  • for 165 L of glomerular filtrate, 115ml/min (female)
  • When drinking more H2O, the GFR would increase.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Controlled Adjustment in the GFR

A
  • When plasma colloid-osmotic pressure and BC’s hydrostatic pressure are constant, the glomerular capillary goes up, the net filtration pressure increases and the GFR increases.
  • If resistance increases in the afferent arteriole, there is less blood flow into the glomerulus which leads to a lower blood pressure and lower net filtration.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Mechanisms that Regulate GFR

A
  • Glomerular capillary blood pressure can be controlled to adjust GFR to suit the body’s needs.
    1. Autoregulation: prevents spontaneous changes in GFR
  • Myogenic mechanism
  • Tubuloglomerular feedback (TGF)
    2. Extrinsic sympathetic NS: regulates long-term blood pressure regulation
  • Baroreceptor reflex
    Both directed towards adjusting glomerular blood flow by:
    a. regulating caliber/diameter
    b. resistance in the afferent arterioles.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Intra-renal Mechanisms of Autoregulation

A
  1. Myogenic
    - Relates to the properties of arteriolar vasculature smooth muscles - stretches automatically
    - If afferent arteriole smooth muscle constricts, there is decreased blood flow to the glomerulus and there’s a decreased GFR
  2. Tubuloglomerular Feedback (TGF) mechanism
    - Juxtaglomerular apparatus: smooth muscles cells within wall off afferent arteriole.
    - The arteriole contains granular cells.
    - Specialized tubular cells in juxtaglomerular region contain macula densa cells. These cells detect changes in the rate at which fluid past the tubules. If there’s an increase in fluid passing through, there is a release of vasoactive chemicals from teh macula densa.
    - ATP is converted into ADP that acts on the adjacent arterioles to constrict.
    - This reduces the blood flow to the glomerulus, which returns the GFR back to normal.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Juxtaglomerular Apparatus

A

Tubuloglomerular mechanisms initiated by the tubules to help each nephron regulate the rate of filtration through its own glomerulus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Factors that affect the GFR

A
  1. Sympathetic nervous system
  2. Baroreceptors
  3. Filtration coefficient
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Baroreceptor Reflex Influence on the CFR

A

Short term:

  1. Decreased arterial blood pressure
  2. Detection by aortic arch and carotid sinus baroreceptors
  3. Increase sympathetic activity and generalized arteriolar vasodilation.
    - This causes increased cardiac output, and increased peripheral resistance. Causes increased arterial blood pressure (short term)

Long term:

  1. Decreased arterial blood pressure
  2. Detection by aortic arch and carotid sinus baroreceptors
  3. Increase sympathetic activity and generalized arteriolar vasodilation.
  4. Afferent arteriolar vasoconstriction
  5. Decreased GFR
  6. Decreased urine volume
  7. Increased conservation of fluid and salt
    - This causes increased arterial blood pressure (long-term)
19
Q

Filtration Coefficient

A

The rate of glomerular filtration depends on:
1. The filtration coefficient
2. Net filtration pressure
KF is subjected to change under physiological control. This depends on:
1. Surface area
2. Permeability of the glomerular membrane

20
Q

Podocytes

A

Podocytes are cells in the Bowman’s capsule in the kidneys that wrap around capillaries of the glomerulus.

  • Contraction and relaxation of podocytes with foot processes, increase or decrease the number of filtration slits in the inner membrane
  • The number of slits determine the permeability; more the slits open, the greater the permeability.
  • Contractile activity of the podocytes, in turn, affect permeability and the KF (filtration coefficient) appears to be under physiological control.
21
Q

Transepithelial Transport

A
  • Involves the transfer of substances from kidney/renal tubular lumen into peritubular capillaries
  • Highly selective and variable process
    1. The luminal cell membrane
    2. The cytosol
    3. The basolateral cell membrane
    4. The interstitial fluid
    5. The capillary wall
22
Q

Transport of Material Across the Tubules

A
  1. Passive
    - no energy
    - follows the concentration gradient
  2. Active
    - ATP used as an energy source
    - substances move against the electrochemical gradient
    eg. glucose, amino acids, Na., K, Cl, electrolytes and Po4.
23
Q

Water Reabsorption in the Proximal Tubule

A
  • out of 125 ml/min of plasma filtered, only 124 ml/min plasma is reabsorbed, only 1% becomes a part of the urine
  • regulated by vasopressin/ADH
24
Q

Na+ Reabsorption

A
  1. an active Na+, K- ATPase pump in the basolateral membrane is essential for Na+ reabsorption
  2. Of the total energy spent by th kidneys, 80% is used for Na+ transport
  3. Na+ is not reabsorbed int he descending limb of the loop of Henle
  4. Water follows reabsorbed Na+ by osmosis. Directly affects blood volume and pressure.

Area of Reabsorption

  1. Proximal tubule: 67%
    - Plays role in reabsorbing glucose, amino acids, H2O, Cl-, and urea
  2. Ascending limb of LOH: 25%
    - Plays critical role in kidneys’ ability to produce urine of varying concentrations
  3. Distal and collecting tubules: 8%
    - Variable and subject to hormonal control; plays role in regulating ECF volume
25
Q

Glucose and Amino Acids Reabsorption

A
  • are reabsorbed back into the blood by energy and Na+
  • dependent mechanism in the proximal tubules
  • use secondary active transport by using co-transport carrier molecule within the proximal tubules
  • co-transport molecules simultaneously transports glucose and amino acids from lumen to blood and vice-versa
26
Q

Filtered load of glucose

A
  • Quantity of any substance filtered/min is the filtered load
  • The normal plasma concentration of glucose is 100mg/100ml of plasma
  • Glucose is freely filterable at the glomerulus, it’s concentration is same in both plasma and BC.
  • With 125 of plasma being filtered each minute, 125mg of glucose passes into the Bowman’s capsule every minutes.
  • Filtered load of substance = plasma concentration x GFR
    100/100 x 125 = 125
  • at a constant GFR, the filtered load of glucose is directly proportional to the plasma glucose concentration
27
Q

Tubular Maximum for Glucose

A
  • 375 mg/min
  • If more glucose is absorbed than filtered, and exceeds 375 mg/100 ml, it will end up in the urine.
  • TM occurs when the maximum reabsorption rate is reached and when all carriers of a substance are occupied/saturated
28
Q

Passive Reabsorption of Urea at the End of the Proximal Tubule

A
  • Reabsorption of Na in the proximal tubules increases the amount of water reabsorbed.
  • This redes the original filtrate from 125ml/min to only 44ml/mind at the end of the proximal tubule.
  • Na and H2O creates a concentration gradient for urea to passively diffuse from the tubular lumen into the peritubular capillary plasma
  • An elevated urea level is one of the first chemical characteristics to be identified in the plasma of a patient with severe renal failure.
29
Q

Roles of H+, K+, and Organic Ions

A

H+
- Important in regulating acid-base balance
- Secreted in proximal, distal and collecting tubules
K+
- Keeps plasma K+ concentration at appropriate levels to maintain normal membrane excitability in muscles and nerves
- Secreted only in the distal and collecting tubules under the control of aldosterone
Organic ions
- Accomplishes more efficient elimination of foreign organic compounds from the body
- Secreted only in the proximal tubule

30
Q

Reabsorption in the Proximal Tubule

A
  • 67% of filtered Na+ actively reabsorbs, not subject to control, Cl- follows passively
  • All filtered glucose and amino acids reabsorbed by secondary active transport are not subject to control.
  • Variable amounts of filtered PO34- and other electrolytes reabsorbed are subject to control.
  • 65% of filtered H2O is osmotically reabsorbed. Not subject to control
  • 50% of filtered urea passively reabsorbed, not subject to control.
  • Almost all of filtered K+ reabsorbed is not subject to control
31
Q

Secretion in the Proximal Tubule

A
  • Variable H+ secretion depending on acid-base status of the body
  • Organic ion secretion. Not subject to control.
32
Q

Reabsorption of the Distal Tubule and Collecting Duct

A
  • Variable Na+ reabsorption, controlled by aldosterone. Cl- follows passively.
  • Variable H20 reabsorption, controlled by vasopressin
33
Q

Secretion of the Distal Tubule and Collecting Duct

A
  • Variable H+ secretion, depending on the acid-base status of the body
  • Variable K+ secretion, controlled by aldosterone
34
Q

Plasma Clearnace

A
  • Useful substances are conserved by reabsorption so that they don’t appear into the urine
  • Plasma clearance is the volume of plasma cleared of a particular substance/min or the volume of the plasma completely cleared off that substance by kidney/min
  • By excreting substances in the urine, kidneys clear the plasma of these substances

Plasma clearance = urine concentration of substance x urine flow rate ml/min.

35
Q

Diuretics

A
  1. ANP
  2. Alcohol
  3. Coffee
36
Q

Concentrations

A

Isotonic: equal substrate - water ratio
Hypotonic: too much water - too little substrate
Hypertonic: too little water - too much substrate

37
Q

Countercurrent Multiplication

A
  • The countercurrent multiplication mechanism is established by medullary vertical osmotic gradient
  • The passive exchange of solutes and H2O between the two limbs of the loop of Henle.
  • There is a countercurrent flow produced by the close proximity of the two limbs

Ascending Limb:

  • Actively transports NaCl out of the tubular lumen into the surrounding interstitial fluid.
  • Impermeable to water. Osmosis does not occur

Descending limb:
- Highly permeable to water but does not extrude sodium for reabsorption.

38
Q

Mechanism of Action of Vasopressin

A
  • Vasopressin controlled variable water reabsorption occurs in the final tubular segments
  • 65% of the water reabsorption is obligatory the proximal tubule.
  • In the distal tubule and collecting duct it is variable. Based on the secretion of ADH.

Steps:

  1. Blood-borne vasopressin binds with receptor sites on the basolateral membrane of a distal or collecting tubule cell.
  2. This binding activates the cyclic AMP second-messenger system within the cell
  3. Cyclic AMP increases the opposite luminal membrane’s permeability to H2O by prompting the insertion of water channels in this membrane. The membrane is impermeable to water in the absence of vasopressin.
  4. Water enters the tubular cell from the tubular lumen through the inserted water channels and enters the blood (reabsorbed). Water exits the cell through a different water channel permanently positioned at the basolateral border.
39
Q

Effect of ADH on Distal Tubules and Collecting Tubules

A

Posterior pituitary - vasopressin/adh - blood - kidney- H2O

  • Negative Feedback
40
Q

Functions of Renin-Angiotensin-Aldosterone System

A
  1. Aldosterone increases reabsorption Na+ in the distal and collecting tubules
  2. Promotes salt retention and resultant H20 retention. This leads to the elevation of arterial blood pressure.
  3. Angiotensin-II a potent arteriole constrictor. I increases blood pressure and peripheral resistance.
  4. Stimulates thirst and vasopressin release.
41
Q

Nervous Control of Micturition

A

The bladder wall consists of smooth muscles lined by endothelium. This expands to accommodate a large volume of the urine. The highly folded bladder wall can flatten out during filing.
- The bladder is guarded by two sphincters - internal and external urethral sphincters.

42
Q

Micturition Reflex

A

Reflex Control

  1. Bladder fills
  2. Stretch Receptors
  3. Parasympathetic nerve
  4. Bladder contracts
  5. Internal urethral sphincter mechanically opens when the bladder contracts
    5a. External urethral sphincter opens when motor neuron is inhibited

Voluntary Control:
1. Cerebral Cortex
2. Motor neuron to external spinchter
3. External urethral sphincter opens when motor neuron is inhibited
or
4. External urethral sphincter remains closed when the motor neuron is stimulated. - no urination.

43
Q

What to know

A

Know name and sequence of trans epithelial transport
Know the amount of sodium reabsorbed from the proximal tubule, loop of henle and distal/collecting tubules
Know the filtered load of glucose
What is the tubular maxium 375 mg
If you consume 600, subtract 375 to find out how much glucose will be excreted in the urine
Plasma clearance

Physiology (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions