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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
__________ senses changes in plasma sodium content & BP
``` Macula densa (DCT) - triggers the start of a cascade of reactions in the RAAS ```
26
define renin
- enzyme produced by the juxtaglomerular cells | - reacts with angiotensinogen
27
T/F: | angiotensinogen is an active enzyme
FALSE - angiotensinogen is a chemically inactive precursor of angiotensin - a blood-borne substrate; reacts with renin to produce angiotensin I (inert)
28
what converts angiotensin I to its active form?
Angiotensin converting enzyme (ACE) | - as AG I passes through the lungs it is converted to the active form, angiotensin II
29
how does angiotensin II correct renal blood flow?
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)
30
sodium-retaining hormone
aldosterone - secreted by the adrenal cortex - stimulates sodium reabsorption (DCT)
31
T/F: | as systemic BP &plasma sodium increase, the secretion of renin decreases
TRUE | - actions of angiotensin II produce a constant pressure within the nephron
32
how much is filtered by the glomerulus every minute?
approx. 120mL of water-containing LMW substances
33
glomerular filtrate content vs. plasma content
- glomerular filtrate has no plasma protein, protein-bound substance, and cells
34
specific gravity of glomerular filtrate
1. 010 | - glomerular filtrate = ultrafiltrate of plasma
35
when the plasma filtrate enters the ________, nephrons begin reabsorbing essential substances & water
Proximal convoluted tubule - reabsorbed through cellular transport mechanisms (active & passive transport) * PCT = REABSORPTION
36
for this to occur, the substance to be reabsorbed must combine with a carrier protein
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
movement of molecules across a membrane as a result of differences in their concentration/electrical potential on opposite sides of the membrane (gradients)
Passive transport
38
ADH
Antidiuretic hormone - aka "vasopressin" - stimulates water reabsorption (Collecting duct)
39
passive reabsorption of water
takes place in all parts of the nephron EXCEPT asc. LOH (walls are impermeable to water)
40
passive reabsorption of urea
PCT & asc. LOH
41
passive reabsorption of sodium
- accompanies the active transport of chloride in asc. LOH
42
T/F: | similar to passive transport, active transport is influenced by the concentration of the substance being transported
TRUE
43
effect of abnormally high level of substance reabsorbed
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
renal threshold
Plasma concentration at which active transport stops | - renal threshold of glucose = 160-180mg/dL
45
glucose appearing in the urine of a person with a normal blood glucose level is an indication of..
Tubular damage | - not DM
46
active transport of more than __________ of the filtered sodium out of the PCT is accompanied by passive reabsorption of an equal amount of water
2/3
47
where does renal concentration begin?
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
countercurrent mechanism
- 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
Countercurrent Mechanism: excessive reabsorption of water as the filtrate passes through the highly concentrated medulla is prevented by..
walls of the asc. LOH | - impermeable to water
50
Countercurrent Mechanism T/F: sodium & chloride leaving the filtrate prevent dilution of the medullary interstitium by the water reabsorbed
TRUE
51
final concentration of the filtrate through the reabsorption of water begins in the __________ & continues in the collecting duct
(late) DCT
52
T/F: | reabsorption depends on the osmotic gradient in the medulla only
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
effect of high level ADH
Increased permeability to water | - results in increased reabsorption of water & low-volume concentrated urine
54
effect of low level of ADH
Walls impermeable to water | - results in a large volume of dilute urine
55
the final determinant of urine volume & concentration
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
__ body hydration = ↓ADH = ↑ urine volume
↑
57
__ body hydration = ↑ADH = ↓ urine volume
↓
58
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
1 - FALSE - in tubular reabsorption, substances are REMOVED from the glomerular filtrate & RETURNED TO THE BLOOD 2- TRUE
59
major functions of tubular secretion
a. elimination of waste products not filtered by the glomerulus b. regulation of acid-base balance in the body (through H+ secretion)
60
why can foreign substances (e.g. medications) not be filtered by the GLOMERULUS?
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
major site of removal of nonfiltered substances
PCT
62
normal blood pH
7. 4 | - to maintain, blood must buffer & eliminate excess acid formed by dietary intake & metabolism
63
bicarbonate
HCO3^- - readily filtered by glomerulus - must be returned to the blood to maintain proper pH - buffering capacity of blood depends on it
64
this prevents the filtered bicarbonate from being excreted in the urine
(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
T/F: | the actual excretion of excess H+ does not depend on tubular secretion
FALSE - excretion depends on tubular secretion - because of their small mol. size H+ are readily filtered & reabsorbed
66
primary methods of H+ excretion
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
acidosis
Metabolic, renal tubular - inability to produce an acid urine - result of any disruption in secretory functions
68
urinary excretion rate
``` UER = FR - RR + SR; where: UER = urinary excretion rate FR = filtration rate RR = reabsorption rate SR = secretion rate ```
69
T/F: | glomerular capillaries are under high pressure compared to glomerular capsule
TRUE | - CAPILLARIES = HIGH PRESSURE
70
renal handling (4 hypothetical substances)
a. filtration only b. filtration, partial reabsorption c. filtration, complete reabsorption d. filtration, secretion
71
excretion rate = filtration rate
Filtration only - substance is freely filtered; not reabsorbed nor secreted - ex. CREA goes directly to urine
72
excretion rate = filtration rate - reabsorption rate
Filtration, partial reabsorption - urinary excretion is less than rate of excretion - ex. electrolytes
73
all filtered substances are reabsorbed
Filtration, complete reabsorption - occurs for some nutritional substances in the blood, conserved in body fluids (unless kidneys are damaged) - ex. glucose, amino acids
74
excretion rate = filtration rate + tubular secretion rate
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

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