B5: Cell Bio Exam 2 Practice Q's

simple cuboidal epithelium

What type of epithelium lines the proximal convoluted tubule (PCT)?

simple cuboidal epithelium with a thick/tall microvilli brush border, glycocalyx

What is the histology of the proximal convoluted tubule (PCT)?

short sparse microvilli

What is the histology of the distal convoluted tubule (PCT)?

HCO3-, H2O, Na+, Cl- (bicarb, water, sodium, chloride), amino acids, and glucose

Which substances are reabsorbed in the proximal convoluted tubule (PCT)?

Hint: most things!

Hint hint: All Brackish Water has Salt and Sugar

creatinine, urea, H+

Which substances are secreted in the proximal convoluted tubule (PCT)?

Bowman’s capsule & thin descending loop of Henle

Which structures of the nephron are made of simple squamous epithelium?

both convoluted tubules (proximal and distal) & thick ascending loop of Henle

Which structures of the nephron are made of simple cuboidal epithelium?

Bowman’s capsule, proximal convoluted tubule, thin descending loop of Henle

Which structures of the nephron are permeable to water?

thick ascending loop of Henle and distal convoluted tubule

Which structures of the nephron are impermeable to water?

hint: if you thicc and far away, you getting no water

Na/K/ATPase, ENaC

aldosterone stimulates _____ and ______ on principal cells in the basolateral collecting duct

principal, basolateral

aldosterone stimulates Na/K/ATPase and ENaC on ______ cells in the ______ collecting duct

H+, Cl-

alpha intercalated cells of the collecting duct are responsible for secretion of:

HCO3-

beta intercalated cells of the collecting duct are responsible for secretion of:

HCO3-, K+

alpha intercalated cells of the collecting duct are responsible for reabsorption of:

H+

beta intercalated cells of the collecting duct are responsible for reabsorption of:

ENaC

potassium sparing diuretics block ______ in the apical collecting duct, leading to decreased Na+ resorption, H2O follows

apical

potassium sparing diuretics block ENaC in the _____ collecting duct

potassium sparing diuretics

amiloride and triamterene (and spironolactone!) are classified as:

ADH/vasopressin

_________ cause an increase in water resorption by acting on aquaporins on the basolateral membrane

basolateral

ADH/vasopressin cause an increase in water resorption by acting on aquaporins on the _______ membrane

reabsorption

_______ occurs from the lumen into the interstitium

transcellular

_____ reabsorption occurs via passive and active transport

paracellular

_____ reabsorption occurs via passive transport

hint: P & P

transcellular, paracellular

Water follows high solute concentration using ______ (AQP4) and _____ transport

reabsorbed, secreted

GFR may not be accurately reflected in the excreted urine if the substance is ______ or _______

inulin

What is the gold standard for measuring GFR, as clearance of this substance is equal to GFR?

it is freely filtered and neither reasorbed nor secreted

Why is inulin the gold standard for measuring GFR?

secreted into the renal tubules

If excretion of a substance is greater than amount filtered, it is being:

absorbed back into blood

If excretion of a substance is less than the amount filtered, it is being:

transporter-mediated diffusion

Glucose uses ________-________ ________ for filtration → as glucose increases, approaches transporter saturation causing increased excretion of glucose

increased excretion of glucose

Glucose uses transporter-mediated diffusion for filtration → as glucose increases, it approaches transporter saturation causing:

filtered

ID purple

glucose transport graph

What is this graph representing?

excreted

ID dark blue

renal threshold

ID light blue

reabsorbed

ID red

splay

ID yellow

normal

ID green

Tmax

_____ is the transport maximum of glucose, aka the maximum rate of glucose reabsorption as plasma glucose increases, at 375 mg/min

hyperglycemia

in ________, glucose exceeds the Tmax, therefore the remaining glucose that cannot be reabsorbed is excreted instead

glucosuria

In _______, the amount of glucose present in the urine depends on the reabsorption rate

1. PCT

2. Thin descending LOH

3. Bowman’s capsule

4. DCT

5. Thick ascending LOH

rank the parts of the nephron from most permeable to water to least permeable to water.

transport saturation graph

ID graph

reabsorption

What does this curve represent?

greatest rate of glucose filtration

ID E

lowest glucose concentration where it starts appearing in the urine

ID C

lowest plasma glucose level where you are reabsorbing at Tmax

ID D

it is constant

What happens to the rate of glucose reabsorption as you move from D to E?

increases

What happens to the rate of glucose excretion as you move from D to E?

increases

What happens to the rate of glucose filtration as you move from A to B?

increases

What happens to the rate of glucose reabsorption as you move from A to B?

proximal convoluted tubule

Where is 65-80% of Na and H2O reabsorbed in the nephron?

thin descending LOH

Where is NO Na reabsorbed in the nephron because it is impermeable to Na?

thick ascending LOH

Where is 10-20% Na reabsorbed in the nephron?

distal convoluted tubule

Where is 5-10% Na reabsorbed in the nephron?

paracellular flux

In pulmonary edema, disruption of ________ _____ causes leakage of fluid/proteins into interstitial space → exacerbates edema

transcellular flux

In pulmonary edema, paracellular flux disruption plays a bigger role than ______ ___ disruption, destroying the gradient

endothelial damage

In pulmonary edema, Kf increases due to _______ ______ causing fluid/protein leakage → exacerbates edema

transcytosis, caveolae-mediated

Increased ______ and ________-_______ transport, causing fluid/protein leakage → exacerbates edema

furosemide

blocks NKCC on apical thick ascending LOH → can cause hypokalemia

hydrochlorothiazide

blocks Na/Cl symporter in DCT → can cause hyponatremia, hypokalemia, hypochlorhydria (the hypo-trio)

Acetazolamide

Carbonic anhydrase inhibitor in PCT → can cause hyponatremia, low bicarb, hypochlorhydria

ARBs

block AngII in apical PCT → cause decreased apical Na/H exchange

nephritic syndrome

inflammation of the glomerulus

-PSGN, IgA nephropathy

1. Hematuria (gross blood in urine)

2. Azotemia (increased waste in blood)

3. Casts (RBC’s in urine sediment)

3 symptoms of nephritic syndrome

nephrotic syndrome

derangement in glomerular capillary walls leading to increased permeability

-minmal change disease, FSGS, membranous nephropathy

1. Massive proteinuria (>3.5mg)

2. Hypoalbuminemia

3. Hyperlipidemia

3 symptoms of nephrotic syndrome

net filtration (+)

what happens in the afferent arteriole end of the glomerular capillary?

net reabsorption

what happens in the efferent arteriole end of the glomerular capillary?

autoregulation

First line of defense against MAP spikes = ________ for MAP within that range

60-140mmHg MAP

autoregulatory range

myogenic response

-CONSTRICTION ONLY

↑ arterial pressure → ↑ flow → vascular smooth muscle contraction → maintains normal flow

metabolic response

CONSTRICT AND DILATE – Tubuloglomerular Feedback

↑ flow/osmolarity = ↑ GFR leads to ATP released by macula densa → inhibition of RAAS → decreased GFR, increased Na excretion

↓ flow/osmolarity = ↓ GFR → NO & prostaglandins released by macula densa → stimulation of RAAS → increased GFR, decreased Na excretion

vasoconstriction in afferent arteriole

↓ RBF

↓ RPF

↓ GFR

-SNS activation, NSAIDs

vasodilation in afferent arteriole

↑ RBF

↑ RPF

↑ GFR

-CA or alpha-1 blockade

vasoconstriction in efferent arteriole

↓ RBF

↑ RPF

no change (or ↑) GFR

-RAAS activation (Ang II)

vasodilation in efferent arteriole

↑ RBF

↓ RPF

no change (or ↓) GFR

-ACEis and ARBs

norepinephrine, epinephrine, endothelin

these substances affect afferent vasoconstriction

eNOS, prostaglandins

these substances affect afferent vasodilation

𝑁𝐹𝑃 = 𝐾_f (𝑃_c −𝑃_b −𝜋_c)

net filtration pressure

𝐽_v =𝐾_f[(𝑃_c−𝑃_i)−𝜎(𝜋_c −𝜋_i)]

fluid flux

-if 𝐽_v positive → filtration/flux out of capillary

-if 𝐽_v negative → reabsorption/flux into capillary

filtration coefficient

𝐾_f = 𝐿_p ∗ 𝑆𝐴

-Lp = hydraulic conductivity

-SA = surface area

junctional integrity, ionic permissivity, tissue integrity, podocyte health/number

what factors affect hydraulic conductivity (Lp)?

diameter of capillaries, radius of filtration slits, disease (loss of tissue)

What factors affect surface area (SA)?

large size (heavy molecular weight) and negative charge

What factors reduce relative filterability?

(renal) clearance

𝐶𝑥 = ([U]_x • V) / [P_x] mL/min

Cx = clearance, [U] = urine concentration, V = urine volume/time, Px = plasma concentration

clearance

the rate at which a specific substance is removed and excreted in the urine

-used to measure GFR
-Inulin is GOLD STANDARD for measuring
-Creatinine is most commonly used clinically, tends to overestimate GFR by 10-20%

kidney

Only ______ extracts para-aminohippurate (PAH), so [RA]PAH = [RV]_PAH in other organs

glomerular filtration rate

𝐺𝐹𝑅 = ([U]_inulin • V) / [P]_inulin

renal plasma flow in other organs

RPF = [U]_PAH • V / [P]_PAH

renal plasma flow in kidney

RPF = ([U]_PAH • V) / ([RA]_PAH - [RV]_PAH)

filtration fraction

FF = GFR / RPF

inulin

filtration mechanics: filtration only

𝐹𝑖𝑙𝑡𝑒𝑟𝑒𝑑 𝐿𝑜𝑎𝑑 = 𝐺𝐹𝑅 (𝑚𝑙/𝑚𝑖𝑛) ∗ [𝑃]_x (𝑚𝐸𝑞/𝑚𝐿)

𝐸𝑥𝑐𝑟𝑒𝑡𝑖𝑜𝑛 𝑅𝑎𝑡𝑒 → 𝐶_x = 𝑈_x ∗ 𝑉

𝑅𝑒𝑠𝑜𝑟𝑝𝑡𝑖𝑜𝑛 𝑜𝑟 𝑆𝑒𝑐𝑟𝑒𝑡𝑖𝑜𝑛 = (𝐺𝐹𝑅 ∗ 𝑃_x)−(𝑈_x ∗𝑉)

Na, K, Cl

filtration mechanics: filtration & partial reabsorption

𝐹𝑖𝑙𝑡𝑒𝑟𝑒𝑑 𝐿𝑜𝑎𝑑 = 𝐺𝐹𝑅 (𝑚𝑙/𝑚𝑖𝑛) ∗ [𝑃]_x (𝑚𝐸𝑞/𝑚𝐿)

𝐸𝑥𝑐𝑟𝑒𝑡𝑖𝑜𝑛 𝑅𝑎𝑡𝑒 → 𝐶_x = 𝑈_x ∗ 𝑉

𝑅𝑒𝑠𝑜𝑟𝑝𝑡𝑖𝑜𝑛 𝑜𝑟 𝑆𝑒𝑐𝑟𝑒𝑡𝑖𝑜𝑛 = (𝐺𝐹𝑅 ∗ 𝑃_x)−(𝑈_x ∗𝑉)

glucose, bicarb

filtration mechanics: filtration & complete reabsorption

𝐹𝑖𝑙𝑡𝑒𝑟𝑒𝑑 𝐿𝑜𝑎𝑑 = 𝐺𝐹𝑅 (𝑚𝑙/𝑚𝑖𝑛) ∗ [𝑃]_x (𝑚𝐸𝑞/𝑚𝐿)

𝐸𝑥𝑐𝑟𝑒𝑡𝑖𝑜𝑛 𝑅𝑎𝑡𝑒 → 𝐶_x = 𝑈_x ∗ 𝑉

𝑅𝑒𝑠𝑜𝑟𝑝𝑡𝑖𝑜𝑛 𝑜𝑟 𝑆𝑒𝑐𝑟𝑒𝑡𝑖𝑜𝑛 = (𝐺𝐹𝑅 ∗ 𝑃_x)−(𝑈_x ∗𝑉)

creatinine

filtration mechanics: filtration and secretion

𝐹𝑖𝑙𝑡𝑒𝑟𝑒𝑑 𝐿𝑜𝑎𝑑 = 𝐺𝐹𝑅 (𝑚𝑙/𝑚𝑖𝑛) ∗ [𝑃]_x (𝑚𝐸𝑞/𝑚𝐿)

𝐸𝑥𝑐𝑟𝑒𝑡𝑖𝑜𝑛 𝑅𝑎𝑡𝑒 → 𝐶_x = 𝑈_x ∗ 𝑉

𝑅𝑒𝑠𝑜𝑟𝑝𝑡𝑖𝑜𝑛 𝑜𝑟 𝑆𝑒𝑐𝑟𝑒𝑡𝑖𝑜𝑛 = (𝐺𝐹𝑅 ∗ 𝑃_x)−(𝑈_x ∗𝑉)

renal plasma flow

𝑅𝑃𝐹 = ([U]_PAH • V) / ([RA]_PAH - [RV]_PAH)

or

𝑅𝑃𝐹 = [U]_PAH • V / [P]_PAH

renal blood flow

𝑅𝐵𝐹 = 𝑅𝑃𝐹 / (1−𝐻𝑐𝑡)

capillary

ID C

fenestrated endothelium

ID F