Renal Exam 5 Flashcards

1
Q

Anatomy of the Kidney: Functional portion, functional unit, nephron

A

Functional portion: Parenchyma
Functional unit: nephron
Nephron: renal corpuscle and renal tubules

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2
Q

Kidneys: Maintenance of homeostasis

A

Blood ionic composition: Na, K, Ca, Cl, HPO4
Blood pH: Excretion of H+
Blood Volume: Conservation or elimination of water
Blood Osmolarity: Regulating loss of water and solutes in urine

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3
Q

Kidneys: Removal of substances from blood

A

Metabolic waste and chemicals: urea (aa), creatinine (creatine phosphate in muscle), bilirubin (hemoglobin)
Drugs and metabolites

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4
Q

Kidneys: Regulation of processes

A

Hormone production: Calcitriol (activate Vit D) and Erythropoietin
Blood Pressure: renin release
Blood Glucose Levels: Gluconeogenesis (Gln)

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5
Q

Functional portion of kidneys contains two distinct regions

A

Renal cortex (superficial area)
Renal medulla (inner portion)

they constitute the parenchyma or functional portion

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6
Q

Nephrons: location and used for

A

Located in both cortex and medulla
Used for filtration of blood & reabsorption & secretion of materials

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7
Q

Nephrons: parts and functional units

A

Parts: renal corpuscle and renal tubule
Functional Units because they: form urine, remove waste from blood, regulate water and electrolyte concentrations

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8
Q

Nephron: Renal Corpuscle

A

Renal corpuscle is the filtration unit
Composed of: glomerulus, glomerular or Bowman’s capsule

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9
Q

Renal Tubule sections

A

1: Proximal Convoluted tubule
2: Loop of Henle
3: Distal Convoluted Tubule
Collecting Tubule often is not considered as part of the nephron

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10
Q

Types of Nephrons

A

Two types based on anatomical location
-Cortical nephrons
-Juxtamedullary nephrons

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11
Q

Cortical Nephrons

A

Corpuscles located closer to surface of the kidney (renal capsule)
SHORT nephron loops: extend only to outer region of renal medulla
80% of nephrons (near top of cortex)

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12
Q

Juxtamedullary Nephrons

A

Corpuscles in the cortex but close to renal medulla
Nephron loops extend deep into the renal medulla
20% of nephrons
Important for regulating water

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13
Q

Arterial and Venous blood supply to the kidney

A

Arterial flow brings blood into the kidney:
-Renal Artery
-Transports O2 blood from heart and aorta to kidney for filtration

Venous flow takes blood out of the kidneys:
-Renal Vein
-Transports filtered and deoxygenated blood from the kidney to the posterior vena cava and then the heart

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14
Q

Arterial blood supply to the kidneys

A

-Kidney receives blood via renal artery (1)
-Renal artery divides into segmental arteries (2)
-Segmental arteries branch (3)
— enter the parenchyma and pass through renal columns as interlobar arteries

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15
Q

Blood flow from renal column to the renal cortex as follows in the kidney:

A

-Interlobar arteries arch at the base of the pyramids (between medulla and cortex) forming arcuate arteries

-Arcuate arteries divide producing interlobular arteries

-Interlobular arteries enter the renal cortex and branch off to form afferent arterioles, which supply the nephron

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16
Q

Blood supply to the Glomerulus: Efferent arteriole, afferent arteriole

A

Afferent arteriole:
-Transports arterial blood to the glomerulus for filtration
-Divides into glomerular capillaries
-Has larger diameter than efferent arteriole
-Passes blood to the efferent arteriole

Efferent arteriole:
-It carries blood out of the glomerulus
-efferent arteriole give rise to capillaries that surround renal tubule

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17
Q

Blood Supply of Renal Tubule of Cortical Nephrons

A

-Peritubular capillaries originate from efferent arteriole
-Capillaries are low-pressure, porous and adapted for absorption
-They surround the tubules mainly in the renal cortex and the short loop of Henley in the medulla
-They empty into interlobular veins

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18
Q

Blood Supply of Renal Tubule in Juxtamedullary Nephrons

A

Efferent arteriole originates the vasa recta capillaries

Vasa recta is deep down into the medulla
-parallels the Loop of Henle in juxtamedullary nephrons
-they carry blood at a slow rate
-helps to concentrate the filtrate

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19
Q

Renal Venous System

A

-Takes blood out of the kidneys
-From the nephron blood enters the interlobular veins
-Blood drains through the arcuate veins
-From arcuate veins blood enters the interlobar veins between the pyramids
-Blood leaves the kidney through a single renal vein

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20
Q

Renal blood supply pathway:

A

Renal Artery
Interlobar artery
Arcuate artery
Interlobular artery
Afferent arteriole
Glomerulus
Efferent arteriole
Interlobular vein
Arcuate vein
Interlobar vein
Renal vein

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21
Q

Processes of Urine Formation: Reabsorption, Filtration, Secretion

A

-selective process
-right amount of substances, H2O, electrolytes, glucose enter blood
-waste products and substances in excess are not reabsorbed

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22
Q

Processes of Urine Formation: Filtration

A

-Water and solutes from blood
-Based on size

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23
Q

Processes of Urine Formation: Secretion

A

-Removes substances that must be eliminated from the blood
-Lower plasma concentration of undesirable materials

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24
Q

Glomerular Filtration: occurs where, what moves accross capillaries, where does it move

A

Occurs: in the renal corpuscle

Move freely across glomerular capillaries: Inorganic ions, low molecular weight solutes, and water

From the glomerular capsule, the filtrate moves into the renal tubule

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25
Q

Glomerular Filtration: what are the filtered substances

A

Commonly filtered substances:
Ions such as Na, K, Cl, HCO3

Natural organic such as glucose and urea

Amino Acids, vitamins, and small proteins are also filtered

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26
Q

Components of Renal Corpuscle: Glomerulus and Glomerular (Bowman’s) capsule

A

Glomerulus:
site for blood filtration
semi-permeable capillary network - caused by afferent capillaries
filtrate -> product of glomerulus

Glomerular (Bowman’s) capsule:
Epithelial cup or sac surrounding capillaries
Transfer filtrate from glomerulus to Proximal Convoluted Tubule (PCT)

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27
Q

Histology of Bownman’s Capsule: Parietal Layer and Visceral Layer

A

Parietal Layer:
Outer wall of glomerular capsule
Squamous epithelial cells

Visceral Layer:
Covers glomerulus
Podocytes -> modified squamous cells, component of glomerular filtration barrier

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28
Q

Components of Podocytes

A

Primary process -> cell surface extensions from cell body
Secondary -> fingerlike extensions aka pedicels

(hand -> fingers (gaps in fingers that water can seep through)

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29
Q

Filtration Membrane or Barrier of Renal: filtration, barrier

A

Filtration of water and small solutes

Effective barrier for most plasma proteins, blood cells, and platelets

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30
Q

Filtration Membrane: Components (layers)

A

Podocytes: (outside)
form filtraition slits

Basement Membrane or Basal Lamina:
glycoprotein matrix
collagen and proteoglycans
located between endothelium and podocytes

Endothelial Cells: (inside)
have fenestrations, leaky

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31
Q

Filtration Process forces

A

Outside: forces opposing filtration
Inside: (in blood) force favoring filtration

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32
Q

Force Favoring Filtration

A

Glomerular blood hydrostatic pressure (GBHP)
-Blood pressure in the glomerular capillaries
-Generally is high -> efferent arterioles are smaller than afferent arterioles

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33
Q

Forces Opposing Filtration

A

Capsular Hydrostatic Pressure (CHP)
-Pressure exerted by fluid already in the capsular space and renal tubules

Blood colloid osmotic pressure (BCOP) -> Due to the presence of proteins in plasma

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34
Q

Net Filtration Pressure (NFP)

A

Glomerular Blood Hydrostatic Pressure (55 mmHg)
Capsular Hydrostatic Pressure (11 mmHg)
Blood Colloid Osmotic Pressure (30 mmHg)
55mg - 15 mmHg - 30 mmHg = 10 mmHg
*filtration ceases when the glomerular blood pressure is 45 mmHg

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35
Q

Control of Glomerular Filtration Rate

A

-GFR is the volume of fluid filtered from the glomerulus into Bowman’s space per unit time
-GFR can change, but subject to physiological regulation
-Neuronal and hormonal mechanisms are important to maintain a nearly constant glomerular filtration rate
-Regulation of the afferent and/or efferent arterioles adjust blood flow in and out of the glomerulus changing the net GF pressure

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36
Q

Decreased GFR

A

-Construction of the afferent arterioles
-Decreases the hydrostatic pressure in glomerular capillaries
(smaller AA in front)

-Dilation of efferent arterioles
-Decreases the hydrostatic pressure in glomerular capillaries
(dilate EA in back)

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37
Q

Increased GFR

A

-Constriction of the efferent arterioles
-Increase the hydrostatic pressure in glomerular capillaries
(Constrict EA in back)

-Dilation of the afferent arterioles
-Increase the hydrostatic pressure in the glomerular capillaries
(dilate AA in front)

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38
Q

Myogenic Mechanism: muscle cells, blood flow

A

-involves smooth muscle cells in walls of afferent arterioles and prevents increased pressure in the glomerulus
-adjusts blood flow by adjusting the diameter of arterioles
-rapid regulation (works in seconds)
-sympathetic system produces a similar effect

39
Q

Myogenic Mechanism: Blood Pressure and contraction of smooth muscle

A

Increased Systemic Blood Pressure
-Increased renal blood flow
-Stretching of arterioles
-protects glomerular capillary from sudden changes in blood pressure w/in seconds
Increased GFR

Contraction of muscle in walls of afferent arterioles (narrows lumen)
-Decrease renal blood flow
-Decrease blood volume
-Decrease glomerular blood pressure
Decreased GFR

40
Q

Tubular Reabsorption

A

-Polarized epithelial cells — Apical and basolateral membrane
-Different proteins in each membrane
-Reabsorption removes useful solutes from the filtrate and returns them to blood
-Secretion removes solutes from the blood into filtrate

41
Q

Characteristics of the Proximal Convoluted Tubule (PCT)

A

-Originates at the glomerular Bowman’s capsule
-Connects with the loop of Henle
-Lies within the cortex
-Involved in the reabsorption of most of useful solutes and water
-Site for secretion
—Elimination of drugs, waste, and hydrogen ions

42
Q

Tubular Reabsorption: Paracellular reabsorption, transcellular reabsorption

A

Paracellular reabsorption:
Passive process that occurs between adjacent tubule cells through tight junctions

Transcellular reabsorption:
-Movement through an individual cell
-Mediated by channels, transporters, or pumps
-Can be active, passive, or facilitated

43
Q

Function of Sodium/Potassium ATPase in Basolateral Membrane of PCT: Function and Expression

A

Function:
Ensures one-way process to move substances from apical to basolateral membrane (across cells)

Expression:
-Most abundant cation in filtrate -> cotransport substanses
-Pump is present in basolateral membrane use ATP to move ions
— decreases intracellular Na+ -> maintains a Na+ gradient

44
Q

PCT Reabsorption

A

PCT is most active section of the tubule for reabsorption
-Transport of most solutes is facilitated by Na+ concentration gradient established by sodium pump

Secretion of H+ also occurs in the PCT

45
Q

Amino Acids, glucose and sodium are reabsorbed by ____ ______ -> transport requires _____

A

Active transport, ATP***

46
Q

What is needed for glucose reabsorption in PCT (3 things)

A

In apical membrane
-Na+ glucose symporter

In basolateral membrane
-Na+/K+ - ATPase
-Glucose transporter

47
Q

Glucose Reabsorption in PCT

A

Active transport of glucose
-Symporter transports Na+ and glucose into cell
-Na+ is actively transported out of PCT cells by Na/K pump
-Glucose diffuses into the interstitium via facilitated diffusion using glucose transporter

48
Q

Glucose is _____ absorbed in PCT

A

100%

49
Q

What are the two things that are reabsorbed in PCT

A

Glucose and Bicarbonate

50
Q

What is needed for Bicarbonate Reabsorption in PCT

A

Apical Membrane:
Na+/H+ exchanger or antiporter

Basolateral Membrane:
HCO3- transporter
Na+/K+ ATPase pump

51
Q

What are the two steps in bicarbonate reabsorption in PCT

A

1: Formation of H2CO3 and then CO2 in the lumen of the tubule
2: Resynthesize bicarbonate in PCT cells, diffusion of bicarbonate into blood vessels

52
Q

Step 1 Bicarbonate Reabsorption: Na+-H+ antiporter

A

Na+-H+ Antiporter:
H+ secretion into the tubular fluid -> pH maintenance
Secreted H+ keeps the antiporter running
Carries Na+ inside the cell down its concentration gradient

53
Q

Step 1 Bicarbonate Reabsorption: Formation of carbonic acid

A

H+ secretion into the tubule lumen by Na+-H+ antiporter
HCO3- in the filtrate reacts with H+ to form H2CO3
Luminal carbonic acid anhydrase (CA) catalyses the reaction

54
Q

Step 1 Bicarbonate Reabsorption: Formation of CO2

A

Dissociation of H2CO3
CO2 diffuses into the PCT
In cells, CO2 also comes form metabolism

55
Q

Step 2 Bicarbonate Reabsorption: Formation of HCO3- in PTC cells

A

Hydration of CO2 - carbonic anhydrase (enzyme)
Hydrolysis of H2CO3 forms HCO3- -> H+ production

56
Q

Step 2 Bicarbonate Reabsorption: Bicarbonate Diffusion

A

HCO3- leaves the cells by facilitated transport
Diffuses into the capillaries
Na+ is transported out of the cells by Na+/K+ ATPase

(One HCO3- is absorbed for every secreted H+, active process)

57
Q

Passive Reabsorption of Ions, Cations, and Urea in PCT

A

Cl- is in high concentration in filtrate
—Cl- diffusion makes interstital fluid more negative
—Promotes diffusion of cations

Passive Diffusion of Cl-, K+, Ca2+, Mg2+ and urea into capillaries

Creation of osmotic gradient promotes reabsorption of water

58
Q

Water Reabsorption in PCT

A

Osmosis
-Water will move through the cell into the capillaries following reabsorption of solutes
-Obligatory water reabsorption by cellular or paracellular passive diffusion

59
Q

Loop of Henle: Basics

A

-Connects proximal and distal convoluted tubules
-Extends into the medulla
-Has three portions with specific characteristics -> separate functional units
-Creates an hypertonic gradient in the renal medulla

60
Q

What are the three sections of the Loop of Henle

A

Descending loop*
Ascending thick limb*
Ascending thin limb

61
Q

Reabsorption in the Loop of Henle

A

Lumen -> LOH cell -> interstitial tissue -> blood
H2O, NaCl, K+, Bicarbonate, Ca2+, Mg2+

62
Q

LOH opposing flow, countercurrent, what is important for water reaborption

A

-Opposing flows are called countercurrent flow
-Countercurrent system creates a hyperosmotic or concentrated -medullary interstitial fluid -> gradient formed
-Hyperosmotic fluid in medulla is important for water reabsorption in DCT and collecting tubules

63
Q

Properties of The Descending Limb

A

Highly permeable to water:
High expression of water channels (aquaporins)
Water moves out by osmosis
—Reabsorption of water from filtrate while concentrating the urine

Impermeable to NaCl:
It does not participate in active solute reabsorption or active transport

64
Q

Properties of Thick Ascending Loop

A

Impermeable to Water:
Little or not water is reabsorbed

Permeable to ions:
Na+ and Cl- move out down their concentration gradient
Reabsorption of Na+ from the filtrate by active transport
Presence of Na+/K+/2Cl- symporter on the apical membrane
—Thick loop has high symporter expression

65
Q

Thin ascending loop has ____ expression of the symporter

A

Low -> low reabsorption than the thick ascending loop

66
Q

Mechanism of Na+/K+/2Cl- symporter in Loop of Henle

A

Na+ and Cl- reabsorption
—Causes build up Na+ and Cl- in renal medulla forming a gradient

K+ rate limiting substrate
K+ recycles by the apical K+ channels -> maintain transporter activity

Movement of K+ and Cl- promotes reabsorption of cations via the paracellular route

67
Q

Formation of the Osmotic Gradient in the Renal Medulla

A

-Starts with active transport of Na+ and Cl- from ascending limb into interstitial fluid

-Interstitial fluid surrounding the descending loop becomes more concentrated than tubular fluid

-Higher concentration makes H2O move to interstitial fluid by osmosis from descending limb

-Fluid in the descending limb becomes hypertonic

-Length of LOH, the difference in concentration is multiply as the the fluid goes deeper into the medulla

68
Q

Fluid Concentration in the LOH

A

1: Filtrate enters and is isomotic to blood plasma and inter fluid
2: Water moves out concentrating filtrate
3: Filtrate reaches highest concentration at loop bends
4: Na+ & Cl- pumped out of filtrate (increases interstitial fluid osmol)
5: Filtrate most dilute as it leaves loop

69
Q

Role of Vasa Recta in the Osmotic Gradient

A

-Is a countercurrent exchanger
-Loop run parallel to LOH
-Maintains gradient set by LOH
—Solutes and water passively exchanged between blood of vasa recta and interstitial fluid of renal medulla
-Supplies renal medulla with O2 and nutrients while preserving osmotic gradient

70
Q

Descending Limb of Vasa Recta

A

Blood picks up NaCl
Releases some H2O
Gradual increase of plasma osmolarity

71
Q

Ascending Limb of Vasa Recta

A

Blood picks up H2O
-Permits passive H2O reabsorption
-Returns H2O to body
NaCl diffuses out of blood into medulla
-maintain hypertonic medulla
Gradual decrease of plasma osmolarity

72
Q

Urea recycling and osmotic gradient in medulla

A

-Helps increase solute concentration and osmolarity in the medulla
-Urea active absorption in collecting tubule under influence of ADH
-Enhances concentration gradient in interstitial fluid in medalla

73
Q

Distal Convoluted Tubule and Collecting Duct: final adjustments of tubular fluid and volume

A

Final adjustments in the composition of tubular fluid
-osmotic concentration is adjusted through active transport

Final adjustments in volume
-Exposure to ADH determines final urine concentration

74
Q

Early Distal Convoluted Tubule

A

Lumen -> DCT cell -> interstitial tissue -> blood
NaCl, bicarbonate, calcium, H2O

Secreted: H+,K+,NH4+, and drugs

75
Q

NaCl reabsorption in Early DCT

A

Active transport of Na+ and Cl-

Apical Membrane:
Na+/Cl- symporter
K+ leaves for lumen

Basolateral Membrane:
Na+/K+ ATPase pump
Cl- leaves for blood

76
Q

Ca2+ reabsorption in Early DCT

A

Active transport of calcium in DCT
PTH (thyroid) promotes reabsorption of Ca2+ (Apical Membrane)
Ca2+ reabsorbed passively in the PCT and Loop of Henle

77
Q

Late Distal Convoluted Tubule and Collecting Duct: Principal and intercalated cells reabsorption & secretion

A

Principal Cells:
Reabsorption of Na+, Cl-, H2O
Secretion of K+

Intercalated Cells:
Reabsorption of K+
Reabsorption of HCO3-
Secretion of H+

78
Q

Potassium Secretion in Late DCT

A

K+ secretion adjusts to dietary intake
Na+/K+ ATPase creates K+ gradient
K+ leakage channels in apical and basolateral membranes

79
Q

Collecting Tubule: final composition, hormone regulation

A

Regulates final composition of urine
-Na+, Cl-, H2O reabsorption
-Secretion of K+ and urea

Hormonal regulation of salt and water balance
-Angiotensin 2, ADH, aldosterone, natriuretic peptide

80
Q

DCT and collecting tubule are impermeable to _______

A

Water
(Hormones regulate the water permeability)

81
Q

Principal Cells in CT

A

Na+ reabsorption and K+ secretion regulated by aldosterone
-Aldosterone regulate body water content by regulating Na+ content

Water reabsorption regulated by vasopressin
-ADH regulates osmolarity by altering water reabsorption

82
Q

Aldosterone Effect

A

Modifies membrane permeability to Na+ and K+
-Causes upregulation of Na+ channels, Na+/K+ ATPase and K+ channels

83
Q

Obligatory Water Reabsorption

A

Water movement that cannot be prevented
By osmosis -> PCT and LOH
Usually recovers 85% of filtrate volume

84
Q

Facultative Water Reabsorption

A

-Controls volume of water reabsorbed along DCT & collecting tubule
-15% of filtrate volume
-Segments semi-impermeable to water -> need hormone regulation
-Final fixes in volume & osmotic concentration of tubular fluid

85
Q

Vasopressin Effect

A

ADH increases variable (facultative) H2O reabsorption
Tubules are impermeable to H2O without ADH
ADH activates the insertion of H2O channels in apical membrane

86
Q

Absence of ADH

A

H2O is not reabsorbed back into blood
H2O remains in renal tubule giving large urine volume
(clear pee)

87
Q

Presence of ADH

A

Increased H2O channels at the membrane
H2O moves into interstitial fluid and then capillaries
Low urine volume (dark pee)

88
Q

What is the urine drainage system

A

Papillary duct in renal pyramid -> minor calyx -> major calyx -> renal pelvis -> ureter -> urinary bladder

89
Q

Acid-Base Balance: regulating H+: Buffer system, exhalation of CO2, kidney excretion of H+

A

Buffer System:
-phosphate and ammonia

Exhalation of CO2:
-↑ rate & depth of breathing reduce H2CO2

Kidney excretion of H+ or basic ions in urine:
-Secretion of H+ in PCT and collecting tubule
-Intercalated cells of the collecting tubule*

90
Q

Kidney Excretion of H+: in PCT and collecting tubule

A

-Only way to eliminate acid load
-Change in rates of H+ and HCO3- secretion or reabsorption by kidneys in response to changes in plasma pH
-In PCT, Na+/H+ antiporters secrete H+ as they reabsorb Na+
-In collecting tubule intercalated cells secrete H+ using proton pump*

91
Q

Intercalated cells in collecting tubule: Type A and Type B cells

A

Type A:
Secrete H+
-H+-ATPase and H+/K+ exchanger on APICAL MEMBRANE
Reabsorb HCO3-
-Cl-/HCO3- exchanger BASOLATERAL MEMBRANE

Type B:
Reabsorb H+ basolateral membrane
Secrete bicarbonate apical membrane

92
Q

Activation of Type A cells: Acidosis

A

Acidosis -> blood and other body tissues are too acidic
H+ is secreted and HCO3- is reabsorbed

93
Q

Activation of Type B cells: Alkalosis

A

Alkalosis -> blood is too alkaline
H+ absorbed and HCO3- secreted

94
Q

Buffering of H+ in Urine

A

NH3 -> NH4+
formation of phosphoric acid