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AUBF > Renal AnaPhy > Flashcards

Renal AnaPhy Flashcards

1
Q

functional units of the kidney

A

Nephron

  • approx. 1-1.5M each kidney
  • has 2 types (cortical; juxtamedullary)
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2
Q

describe cortical nephron

A
  • make up approx. 85% of nephrons
  • location: renal cortex
  • functions:
      • removal of waste products
      • reabsorption of nutrients
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3
Q

type of nephron responsible for urine concentration

A

Juxtamedullary nephron

- has longer loops of Henle (extending deep into the renal medulla)

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4
Q

renal functions

A

a. renal blood flow
b. glomerular filtration
c. tubular reabsorption
d. tubular secretion

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5
Q

___________ supplies blood to the kidney

A

Renal Artery

- human kidneys receive approx. 25% of blood pumped through the heart

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6
Q

renal blood flow

A

aorta -> renal artery -> segmental artery -> interlobar artery -> arcuate artery -> cortical radiate artery -> afferent arteriole -> glomerular capillaries
-> efferent arteriole -> peritubular capillaries -> cortical radiate vein -> arcuate vein -> interlobar vein -> renal vein -> inferior VC

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7
Q

T/F:

blood enter the nephron through the efferent arteriole, then through the glomerulus, and into the afferent arteriole

A

FALSE

- blood enters through the Afferent arteriole, through the glomerulus, and into the Efferent arteriole

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8
Q

before returning to the renal vein, blood from the efferent arteriole enters the _____________ & ______________

A

a. Peritubular capillaries
- surround the PCT & DCT
- functions:
- - reabsorption of essential substances from the fluid (PCT)
- - final adjustment of urine composition (DCT)

b. Vasa recta
- adjacent to the ascending & descending loops of Henle
- function: major exchanges of water & salts between blood & medullary interstitium to maintain osmotic gradient

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9
Q

define osmotic gradient

A

salt concentration

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10
Q

total renal blood flow in an average body size

A
  • approx. 1200mL/min.

Total renal plasma flow
- 600-700mL/min.

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11
Q

T/F:

normal values for renal blood flow & renal function tests depend on body size

A

TRUE

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12
Q

non-selective, passive filter of plasma substances with mol. wts. less than 70,000

A

Glomerulus

  • with a “capillary tuft” (coil of approx. 8 capillary lobes)
  • location: within the Bowman’s capsule
  • forms the beginning of the renal tubules
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13
Q

factors that influence the actual (glomerular) filtration process

A

a. cellular structure of capillary walls & Bowman’s capsule
b. hydrostatic & oncotic pressures
c. feedback mechanisms of the RAAS

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14
Q

cell layers in which plasma filtrate must pass through

A

a. capillary wall membrane
b. basement membrane (“basal lamina”)
c. visceral epithelium of Bowman’s capsule

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15
Q

differential features of the endothelial cells of the capillary wall

A

a. fenestrated

b. contains pores that increase capillary permeability but do not allow the passage of large molecules & blood cells

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16
Q

these are formed by the intertwining foot processes of the podocytes (inner layer of Bowman’s capsule)

A

Filtration slits

- further restriction of large molecules occurs as filtrate passes through basal lamina & its thin membranes

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17
Q

which among the afferent and efferent arterioles are small/large?

A

a. afferent arteriole = larger size

b. efferent arteriole = smaller

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18
Q

pressure that enhances filtration

A

Hydrostatic pressure

  • result from the size of efferent arteriole & glomerular capillaries
  • necessary to overcome the opposition of pressures from:
      • fluid within Bowman’s capsule
      • oncotic pressure of unfiltered plasma proteins in the glomerular capillaries
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19
Q

what stimulates the autoregulatory mechanism within the juxtaglomerular apparatus?

A

Increasing/decreasing the size of afferent arteriole

- the mechanism maintains glomerular BP at a relatively constant rate, regardless of fluctuations in systemic BP

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20
Q

effect of afferent arteriole dilation & efferent arteriole constriction (when BP DROPS)

A
  • marked decrease in blood flowing through the kidneys is prevented –> increase in blood level of toxic waste products prevented
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21
Q

effect of afferent arteriole constriction (when BP INCREASES)

A

overfiltration or damage to the glomerulus is prevented

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22
Q

meaning of RAAS

A

Renin-Angiotensin-Aldosterone System

  • controls the regulation of blood flow to & within the glomerulus
  • responds to changes in BP & plasma sodium content monitored by the juxtaglomerular apparatus
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23
Q

juxtaglomerular apparatus

A

juxtaglomerular cells (afferent arteriole) + macula densa (DCT)

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24
Q

T/F:

low plasma sodium content increases water retention within the circulatory system

A

FALSE
- low plasma sodium content DECREASES water retention

  • this results in a decreased overall blood volume & subsequent decrease in BP
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25
Q

__________ senses changes in plasma sodium content & BP

A 
Macula densa (DCT)
- triggers the start of a cascade of reactions in the RAAS
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26
Q

define renin

A
  • enzyme produced by the juxtaglomerular cells

- reacts with angiotensinogen

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27
Q

T/F:

angiotensinogen is an active enzyme

A

FALSE

  • angiotensinogen is a chemically inactive precursor of angiotensin
  • a blood-borne substrate; reacts with renin to produce angiotensin I (inert)
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28
Q

what converts angiotensin I to its active form?

A

Angiotensin converting enzyme (ACE)

- as AG I passes through the lungs it is converted to the active form, angiotensin II

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29
Q

how does angiotensin II correct renal blood flow?

A

a. causes afferent arteriole vasodilation & efferent arteriole constriction
b. stimulates reabsorption of sodium in PCT
c. triggers the release of aldosterone (adrenal cortex) & ADH (hypothalamus)

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30
Q

sodium-retaining hormone

A

aldosterone

  • secreted by the adrenal cortex
  • stimulates sodium reabsorption (DCT)
31
Q

T/F:

as systemic BP &plasma sodium increase, the secretion of renin decreases

A

TRUE

- actions of angiotensin II produce a constant pressure within the nephron

32
Q

how much is filtered by the glomerulus every minute?

A

approx. 120mL of water-containing LMW substances

33
Q

glomerular filtrate content vs. plasma content

A
  • glomerular filtrate has no plasma protein, protein-bound substance, and cells
34
Q

specific gravity of glomerular filtrate

A
  1. 010

- glomerular filtrate = ultrafiltrate of plasma

35
Q

when the plasma filtrate enters the ________, nephrons begin reabsorbing essential substances & water

A

Proximal convoluted tubule
- reabsorbed through cellular transport mechanisms (active & passive transport)

  • PCT = REABSORPTION
36
Q

for this to occur, the substance to be reabsorbed must combine with a carrier protein

A

Active transport

  • carrier proteins are contained in the membranes of the renal tubular cells
  • the electrochemical energy created by the substance + protein interaction transfers the substance across the cell membranes & back to the bloodstream
  • responsible for the reabsorption of:
      • glucose, amino acids, salts (PCT)
      • chloride (asc. LOH)
      • sodium (DCT)
37
Q

movement of molecules across a membrane as a result of differences in their concentration/electrical potential on opposite sides of the membrane (gradients)

A

Passive transport

38
Q

ADH

A

Antidiuretic hormone

  • aka “vasopressin”
  • stimulates water reabsorption (Collecting duct)
39
Q

passive reabsorption of water

A

takes place in all parts of the nephron EXCEPT asc. LOH (walls are impermeable to water)

40
Q

passive reabsorption of urea

A

PCT & asc. LOH

41
Q

passive reabsorption of sodium

A
  • accompanies the active transport of chloride in asc. LOH
42
Q

T/F:

similar to passive transport, active transport is influenced by the concentration of the substance being transported

A

TRUE

43
Q

effect of abnormally high level of substance reabsorbed

A

Filtrate concentration exceeds maximal reabsorptive capacity of the tubules –> substance begins appearing in the urine
- occurs when the plasma concentration of a substance (normally completely reabsorbed) reaches an abnormally high level

44
Q

renal threshold

A

Plasma concentration at which active transport stops

- renal threshold of glucose = 160-180mg/dL

45
Q

glucose appearing in the urine of a person with a normal blood glucose level is an indication of..

A

Tubular damage

- not DM

46
Q

active transport of more than __________ of the filtered sodium out of the PCT is accompanied by passive reabsorption of an equal amount of water

A

2/3

47
Q

where does renal concentration begin?

A

Loops of Henle (asc. & desc.)
- where filtrate is exposed to the high osmotic gradient of the renal medulla

  • desc. LOH = water removed by osmosis
  • asc. LOH = sodium & chloride reabsorbed
48
Q

countercurrent mechanism

A
  • selective reabsorption process that serves to maintain the osmotic gradient of the medulla
  • maintenance of osmotic gradient is essential for the final concentration of filtrate when it reaches the collecting duct
49
Q

Countercurrent Mechanism:

excessive reabsorption of water as the filtrate passes through the highly concentrated medulla is prevented by..

A

walls of the asc. LOH

- impermeable to water

50
Q

Countercurrent Mechanism T/F:

sodium & chloride leaving the filtrate prevent dilution of the medullary interstitium by the water reabsorbed

A

TRUE

51
Q

final concentration of the filtrate through the reabsorption of water begins in the __________ & continues in the collecting duct

A

(late) DCT

52
Q

T/F:

reabsorption depends on the osmotic gradient in the medulla only

A

FALSE
- reabsorption depends on the osmotic gradient in the medulla AND ADH

  • ADH controls the permeability of the walls of the DCT & collecting duct to water
53
Q

effect of high level ADH

A

Increased permeability to water

- results in increased reabsorption of water & low-volume concentrated urine

54
Q

effect of low level of ADH

A

Walls impermeable to water

- results in a large volume of dilute urine

55
Q

the final determinant of urine volume & concentration

A

Chemical balance in the body

  • aldosterone production = controlled by the body’s sodium concentration
  • ADH production = determined by the body’s state of hydration
56
Q

__ body hydration = ↓ADH = ↑ urine volume

A

↑

57
Q

__ body hydration = ↑ADH = ↓ urine volume

A

↓

58
Q

MORSE:
1 - in tubular reabsorption, substances are retained in the glomerular filtrate

2 - in tubular secretion, substances are passed from the blood in the peritubular capillaries to the tubular filtrate

A

1 - FALSE
- in tubular reabsorption, substances are REMOVED from the glomerular filtrate & RETURNED TO THE BLOOD

2- TRUE

59
Q

major functions of tubular secretion

A

a. elimination of waste products not filtered by the glomerulus
b. regulation of acid-base balance in the body (through H+ secretion)

60
Q

why can foreign substances (e.g. medications) not be filtered by the GLOMERULUS?

A

since they are bound to plasma proteins

  • when protein-bound substances enter the PERITUBULAR CAPILLARIES, they dissociate from the carrier proteins (they develop a stronger affinity for tubular cells), hence their transport into the filtrate by the tubular cells
61
Q

major site of removal of nonfiltered substances

A

PCT

62
Q

normal blood pH

A
  1. 4

- to maintain, blood must buffer & eliminate excess acid formed by dietary intake & metabolism

63
Q

bicarbonate

A

HCO3^-

  • readily filtered by glomerulus
  • must be returned to the blood to maintain proper pH
  • buffering capacity of blood depends on it
64
Q

this prevents the filtered bicarbonate from being excreted in the urine

A

(secretion of) H+

  • by renal tubular cells; occurs in PCT
  • causes the return of HCO3^- to the plasma
  • provides for almost 100% reabsorption of filtered HCO3^-
65
Q

T/F:

the actual excretion of excess H+ does not depend on tubular secretion

A

FALSE

  • excretion depends on tubular secretion
  • because of their small mol. size H+ are readily filtered & reabsorbed
66
Q

primary methods of H+ excretion

A

a. H+ + phosphate ion
(HPO4^-)
- secreted H+ combines with filtered phosphate ion instead of bicarbonate
- excreted rather than reabsorbed

b. H+ + ammonia (NH3)
- ammonia is produced & secreted by the cells of DCT & by the breakdown of glutamine in PCT
- ammonia reacts with H+ to form ammonium ion (NH4^-)
- ammonium is excreted in the urine

67
Q

acidosis

A

Metabolic, renal tubular

  • inability to produce an acid urine
  • result of any disruption in secretory functions
68
Q

urinary excretion rate

A 
UER = FR - RR + SR; where:
UER = urinary excretion rate
FR = filtration rate
RR = reabsorption rate
SR = secretion rate
69
Q

T/F:

glomerular capillaries are under high pressure compared to glomerular capsule

A

TRUE

- CAPILLARIES = HIGH PRESSURE

70
Q

renal handling (4 hypothetical substances)

A

a. filtration only
b. filtration, partial reabsorption
c. filtration, complete reabsorption
d. filtration, secretion

71
Q

excretion rate = filtration rate

A

Filtration only

  • substance is freely filtered; not reabsorbed nor secreted
  • ex. CREA goes directly to urine
72
Q

excretion rate = filtration rate - reabsorption rate

A

Filtration, partial reabsorption

  • urinary excretion is less than rate of excretion
  • ex. electrolytes
73
Q

all filtered substances are reabsorbed

A

Filtration, complete reabsorption

  • occurs for some nutritional substances in the blood, conserved in body fluids (unless kidneys are damaged)
  • ex. glucose, amino acids
74
Q

excretion rate = filtration rate + tubular secretion rate

A

Filtration, secretion

  • substances freely filtered; additional quantities are secreted from peritubular capillaries to the tubules
  • ex. organic acids, bases are rapidly cleared from the blood & excreted in large amounts

AUBF (9 decks)

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