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AP2 B4 > Loop of Henle/DCT > Flashcards

Loop of Henle/DCT Flashcards

1
Q

In the entire LOH, unlike the PCT, solute and water reabsorption are ___ regulated

A

independently

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2
Q

mostly water reabsorption and solute secretion (concentrates the filtrate)

A

Descending limb (of LOH)

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3
Q

no water reabsorption, but reabsorption of solutes occurs (dilutes the filtrate)

A

ascending limb (of LOH)

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4
Q

This region is passively permeable to water and solutes

A

Descending Limb LoH

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5
Q

Solute reabsorption occurring simultaneously in the ascending limb creates a ___ concentration (osmolarity) in the interstitial fluid

A

higher

More solutes and less water causes the “first” concentration of filtrate inside the tubule (hyperosmotic) (from descending limb)

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6
Q

Increased interstitial fluid osmolarity forces the descending limb to attempt to find equilibrium (in the descending LOH), causing water ___ and solute ___ to occur in the descending limb

A

reabsorption

secretion

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7
Q

Urea, Na+, and Cl- are ___ into tubule

in the descending LOH

A

secreted

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8
Q

This region is passively permeable to small solutes, but impermeable to water (no water reabsorption occurs here)

Because of this, as solutes move out of tubule (reabsorbed), water is left inside the tubule

This creates the “first” dilution of filtrate inside the tubule (hypoosmotic)

A

Ascending Limb LoH

thin portion

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9
Q

Active reabsorption (movement out of tubule) of Na+, K+, Cl- occurs here, but this region is still impermeable to water

This means that as filtrate moves up the ascending limb, it dilutes even more

A

Ascending Limb LoH

thick portion

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10
Q

Reabsorbs 10-15% of filtered water that is left

A

Early portion of the DCT

reabsorbs sodium and chloride as well

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11
Q

By the time filtrate reaches this portion, 90-95% of filtered solutes/water have been reabsorbed and returned to interstitium/bloodstream

A

Late portion of the DCT

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12
Q

Specialized cells found intermixed in the DCT and throughout the collecting ducts

A

Principal cells

Intercalated cells

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13
Q

In the DCT and collecting ducts, the amount of reabsorption of solutes/water is dependent on feedback from the body in general… hormones, osmorecptors?

A

Hormonal (ADH, Aldosterone, Atrial Natriuretic Peptide)

Osmoreceptors throughout the body (ex: body requires more sodium than what’s already been reabsorbed)

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14
Q

DCT is similar to PCT in that Na+ reabsorption occurs via ___ transport

A

active

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15
Q

In DCT/Collecting ducts though, the cells are relatively still impermeable to water, so water does not follow Na+ via osmosis BUT…

A

when the need arises, there is a mechanism that gets activated in these cells that allows them to be able to selectively reabsorb water

(Anti-Diuretic Hormone (ADH) causes principal cells in the DCT and collecting ducts to become permeable to water)

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16
Q

ADH targets principal cells in the

A

DCT and collecting ducts

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17
Q

ADH triggers these cells to generate ___ in the apical membrane of the cells lining the tubule

A

aquaporin-2 channels

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18
Q

The more ADH that is present, the more aquaporin-2 channels will be _____

A

generated

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19
Q

In general, in the presence of ADH, we produce a small quantity of ____ urine

A

highly concentrated

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20
Q

in the presence of ADH, when more water is reabsorbed, it creates an ___ imbalance when it gets to the distal collecting duct

This forces some of the urea to be reabsorbed in order to correct the interstitial fluid imbalance

A

osmotic

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21
Q

The addition of ___ in the interstitial fluid from the collecting duct assists in increasing the high osmolarity in the interstitial fluid

(ADH effects)

A

urea

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22
Q

This helps to keep the osmotic gradient constantly moving

The urea that is reabsorbed at the distal collecting ducts migrates through interstitial fluid and gets secreted in the descending limb of the loop of Henle (Urea recycling)

A

ADH

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23
Q

When ADH is at it maximal secretion…

A

Body can produce as little as 400-500mL of very concentrated urine each day

The rest is returned to the interstitium/blood stream instead of being urinated out

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24
Q

When blood pressure/volume stabilizes, ADH levels decline causing …

A

The aquaporin-2 molecules to be removed from principal cells

Normal volume of normal to dilute urine produced

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25
Q

Aquaporin-2 molecules are only effective in the presence of ADH whereas aquaporin-1 molecules are independently functioning in the ___

A

PCT/LOH

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26
Q

Under the influence of aldosterone, principal cells cause the following:

A

Sodium reabsorption (usually brings water with it)

Potassium secretion

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27
Q

What causes aldosterone to be released?

A

Hyperkalemia

Presence of angiotensin II
This occurs when the renin-angiotensin-aldosterone system is stimulated by low blood volume or pressure

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28
Q

Two types of intercalated cells in this region (DCT)

A

Type A

Type B

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29
Q

Intercalated Cells Type A

cause?

A

Causes secretion of hydrogen (H+) ions
Causes reabsorption of bicarb
Causes reabsorption of potassium (K+)

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30
Q

Causes secretion of hydrogen (H+) ions
Causes reabsorption of bicarb
Causes reabsorption of potassium (K+)

A

Intercalated Cells Type A

cause?

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31
Q

Intercalated Cells Type B

cause?

A

Causes reabsorption of hydrogen (H+) ions
Causes secretion of bicarb
Causes secretion of potassium (K+)

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32
Q

Causes reabsorption of hydrogen (H+) ions
Causes secretion of bicarb
Causes secretion of potassium (K+)

A

Intercalated Cells Type B

cause?

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33
Q

When atrial cells are stretched because of increased blood pressure or volume, they release ___

A

ANP

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34
Q

When ANP is stimulated, it has direct actions on the cells located in the ___

A

DCT and the Collecting Ducts

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35
Q

Inhibits the reabsorption of sodium and water

If this is inhibited, it means more water (fluid volume) is left in filtrate to be eventually excreted (via urination)
This causes a reduction in blood volume/pressure

A

Atrial Natriuretic Peptide

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36
Q

Also inhibits the renin-angiotensin-aldosterone system

This further reduces reabsorption of various solutes and water

A

Atrial Natriuretic Peptide

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37
Q

Activated in response to low renal vascular flow/pressure

Example: Low blood pressure

A

Renin-Angiotensin-Aldosterone System

38
Q

System activated when blood volume/pressure is too low, no longer stretching the walls of the afferent arteriole

A

Renin-Angiotensin-Aldosterone System

39
Q

This causes the juxtaglomerular cells to secrete the hormone/enzyme renin into the blood stream

At the same time, angiotensinogen is released by hepatocytes into the blood

A

Renin-Angiotensin-Aldosterone System

Renin finds angiotensinogen and cleaves off a 10-amino acid peptide
This converts angiotensinogen to angiotensin-1

40
Q

Angiotensin I continues to course through the blood until it reaches the lungs. What happens?

A

Here, angiotensin-I is converted to angiotensin-II by lung endothelial angiotensin converting enzyme (ACE)
Angiotensin II is the active form of the hormone

41
Q

Angiotensin II affects renal physiology in three ways:

A

1.Decreases GFR by causing vasoconstriction of afferent arteriole
2. Enhances Na+, Cl- and water reabsorption in the PCT
3. Stimulates the adrenal cortex to release aldosterone
Aldosterone stimulates the principal cells in the collecting ducts to reabsorb more Na+ and Cl- and secrete more K+
With increased reabsorption of Na+ and Cl-, more water is reabsorbed which causes INCREASED blood volume and blood pressure

42
Q

Even though fluid intake can vary widely, the total volume of fluid in the body remains relatively ___, largely in part to the kidneys

A

stable

43
Q

Body fluid volume homeostasis largely dependent on rate of water ___ in urine

A

excretion

44
Q

The regulation of plasma ____ and volume are the responsibility of the Loop of Henle, the DCT, and the collecting ducts

A

osmolarity

45
Q 
Concentrating urine (initially)
Permeable to water mostly, therefore concentrating the filtrate
A

Descending limb of LOH

46
Q 
Diluting urine (initially)
Impermeable to water, therefore diluting the filtrate
A

Thick ascending limb of LOH

47
Q

Where final dilution/concentration occurs

Where the majority of ADH has its action

A

DCT + Collecting Ducts

48
Q

Dilution/Concentration in the DCT and the collecting ducts is controlled by the presence or absence of ADH

A

In absence of ADH
Urine is diluted
In presence of ADH
Urine is concentrated

49
Q

Urine volume?

A

1-2 liters

50
Q

Urine color?

A

yellow or amber, varies with urine concentration and diet (beets, medications [pyridium], kidney stones can cause blood in urine)

51
Q

Urine turbidity?

A

transparent when voided, becomes cloudy with time

52
Q

Urine odor?

A

mildly aromatic, becomes ammonia-like with time

Bacteria turning urea back into ammonia

53
Q

Urine pH?

A

ranges from 4.6-8.0, average is 6.0, varies with diet, high protein increases acidity, vegetarian increases alkalinity

54
Q

Urine specific gravity?

A

density (ratio of weight of solutes vs water) usually 1.001-1.035 (the higher the solutes the higher the value)

55
Q

Solutes account for 5% of urine (electrolytes, solutes derived from cellular metabolism, exogenous substances like drugs)

A 
Urea (from breakdown of proteins)
Creatinine (from breakdown of creatine phosphate in muscle)
Uric Acid (breakdown of nucleic acids)
Urobilinogen (breakdown of hemoglobin)
Small amount of fatty acids, pigments, enzymes, and hormones
56
Q

This urea results from the catabolism and deamination of amino acids (proteins) in the liver
Urea can be reabsorbed from filtrate to help create/maintain an osmotic gradient in the kidneys
When GFR reduces severely (as in renal disease), BUN increases

A

Blood Urea Nitrogen (BUN)- measures urea (uremia)

57
Q

Two blood tests can provide kidney function information

A

Blood Urea Nitrogen (BUN)- measures urea (uremia)

Plasma creatinine- catabolism of creatine phosphate in skeletal muscle

58
Q

catabolism of creatine phosphate in skeletal muscle

Normally remains steady as the rate of creatinine excretion in urine equals its discharge from muscle

There is NO use for creatinine in the body, so we should excrete much, if not all of it in the urine

A

Plasma creatinine

59
Q

The volume of plasma (mL) that can be completely cleared of a substance per unit time (min)

A

Renal Plasma Clearance

60
Q

plant polysaccharide, easily passes through the filter and is excreted in urine 100%

Great measure of true GFR

A

Inulin

Great method but inulin is not produced in the body so this test is difficult to do

61
Q

As creatinine is filtered, not reabsorbed, its clearance is a good estimate of GFR

A

Creatinine Clearance

At times, can overestimate GFR by 10-20%

62
Q

Collecting ducts –-papilla - papillary ducts - minor calyces – major calyces – renal pelvis – ureters – urinary bladder – urethra

A

urine transport

63
Q

Urine transport by peristalsis (___ to ___) aided by hydrostatic pressure and gravity

A

renal pelvis

urinary bladder

64
Q

Ureters are ___

A

retroperitoneal

65
Q

Ureters pass ___ into posterior/inferior aspect of bladder

A

obliquely

66
Q

When the bladder fills with urine, it pulls the bladder down which closes these valves so no “backflow” occurs

A

Called the anti-reflux mechanism

67
Q

Three layers (superficial to deep) of ureter

A

Adventitia
Muscularis
Mucosa

68
Q

anchors ureters to surrounding tissues, contains blood vessels, nerves, lymphatic vessels

A

Adventitia

69
Q

(peristalsis)-outer circular, inner longitudinal smooth muscle

A

Muscularis

70
Q

transitional epithelium with goblet cells that secrete mucous (to protect mucosa from acidity)

A

Mucosa

71
Q 
posterior to pubic symphysis
anterior to rectum in males
anterior to vagina in females
inferior to uterus in females
held in place by peritoneal folds
A

Urinary Bladder

72
Q

Three layers make up the urinary bladder wall

A

Serosa
Adventitia
Muscularis (Detrusor muscle)
Mucosa

73
Q

covers superior surface, visceral peritoneum

A

Serosa:

74
Q

covers posterior and inferior surfaces, continuous with the ureters

A

Adventitia

75
Q

Three layers
Inner longitudinal
Middle circular
Outer longitudinal

A

Muscularis (Detrusor muscle)

76
Q

When the detrusor is relaxed, it allows for ___

A

filling

77
Q

When the detrusor is ___, it forces urine into the urethra

A

contracted

78
Q

Rugae

Trigone

A

Mucosa ( uroepithelium)

79
Q

allows bladder to expand when it is filling

Transitional epithelium – shape of these epithelial cells changes with the degree of stretch placed on them

A

Rugae

80
Q

smooth, triangular area in bladder floor

ureteral openings in posterior corners

internal urethral orifice in anterior corner

!!!

A

Trigone

81
Q

Circular smooth muscle (extension of the detrusor muscle) near internal urethral orifice

Involuntary (controlled by parasympathetic nervous system)

Is just above the prostate in males

A

Internal urethral sphincter (inferior aspect of bladder)

82
Q 
Skeletal muscle (composed of deep perineal muscles/pelvic floor) 
Voluntary

Sits just below the prostate (in males)

Is at the opening of the external urethral orifice (in females)

A

External urethral sphincter

83
Q

Prostatic
Membranous
Spongy

A

Male Urethra

84
Q

circular smooth muscle forms internal urethral sphincter

male urethra

A

Prostatic

85
Q

shortest region passing through urogenital diaphragm, circular skeletal muscle forms external urethral sphincter

A

Membranous

86
Q

longest region passing through penis

contains bulbourethral (Cowper’s gland)

A

Spongy

87
Q

delivers alkaline fluid to help neutralize acidity of urethra

A

Bulbourethral (Cowper’s gland)

88
Q

Short tube that conveys urine from bladder to exterior

A

Female Urethra

89
Q

Parasympathetic reflex initiates the mechanism for urination which causes

A

micturition = urination

90
Q

___ contractions of the detrusor muscle

(micturition)

Internal urethral sphincter to open

This causes urine to move from the bladder into the urethra

This causes the sensation that we perceive as our body telling us we need to urinate soon. But voluntary contraction prevents this.

A

Involuntary

91
Q

____ relaxation of this external sphincter allows the flow of urine to occur

A

Voluntary

92
Q

Effects of aging on kidneys?

A

Kidney shrinkage

Renal bloodflow/GFR decreases

Increased incidence of calculi/inflammation/UTIs

Retention (BPH/prostate cancer/hematuria/dysuria)

AP2 B4 (3 decks)

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