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125 Cards in this Set

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  • Back
What is the normal osmolarity of ECF?
285 mosm/l.
What regulates the extracellular concentration of NaCl?
The kidney.
What is the exctracellular concentration of Na+?
142 mosm/l.
What is extracellular concentration of Cl-?
102 mosm/l.
What is the normal pH in ECF?
7.4
The kidney regulates the rate at which H+ and HCO3- are excreted in urine. That is the mechanisms for regulation of what?
Regulation of pH.
What is the normal concentration of HCO3- in ECF?
25 mmol/l.
Name five kidney functions.
1. Maintenance of water and salt balance;
2. Contribution to pH regulation;
3. Excretion of nitrogenous waste products;
4. Conservation and regulation of essential substances;
5. Hormone secretion.
In two different occasions:
dehidration, urine output 0.3 ml/min and concentr. is about 1200 mosm/l
and
Overhidration, urine output of 15 ml/min of concentr. about 80 mosm/l,
what would be the difference between the blood osmolarity?
The blood osmolarity would be the same, 285 mosm/l.
Label the diagram.
Fill in labels.
Put in labels.
How many percent of reabsorption of glomerular filtrate is happening in the kidneys?
99%.
What is the normal value for glomerular filtration rate of a healthy adult?
120 ml/min.
Which cells lay the walls of the proximal convoluted tubule?
Cuboidal epithelial cells with microvilli.
Which three parts make juxta-glomerular apparatus?
JG cells, macula densa, mesangium.
What blood vessels surround the proximal convoluted tubule?
Peritubular capillary bed.
Which blood vessels surround the loop of Henle?
Vasa recta.
What does the rate of filtration of a given substance depends on?
Molecular weight, shape and electrical charge.
The glomerulus works as a filtration barrier, which three layers a substance has to cross to get through?
Capillary endothelium, bacement membrane, glomerular epithelium.
The podocyte foot processes are part of which epithelium in the glomerulus?
They are part of glomerular epithelium.
The fenestrations are the part of which epithelium in the glomerulus?
Part of Capillary endothelium.
Name four Starling's forces that are involved in glomerular filtration.
Two hydrostatic pressures (in glom.capillaries and in Bowman's capsule) and two colloid osmotic pressures (in glom.capillaries and in Bowman's capsule).
State the equation for calculation the GFR.
GFR = KS [(Pgc - Pt) - (πgc-πt)] where
K - permiability of glomerular barrier
S - surface area available for filtration
KS - filtration coefficient
Pgc - hydrostatic pressure of in Glomerular capillaries
Pt - hydrostatic pressure in Bowman's tubule
πgc - colloid osmotic pressure in Glomerular capillaries
πt - colloid osmotic pressure in Bowman's tubule
What is nephrotic syndrome?
Nephrotic syndrome is a nonspecific disorder in which the kidneys are damaged, causing them to leak large amounts of protein from the blood into the urine.
What can lead to decrease in GFR?
Decrease in a surface area of glomerular membrane (e.g. when one kidney is removed);
Decrease in Pgc (e.g. when systemic blood pressure falls or blood is deverted from the kidney);
Increase in Pt (e.g. if there is a blockage in renal tubules, like kidney stone).
What can lead to increase in GFR?
Change in permeability of glomerular membrane (e.g. nephrotic syndrome);
Decrease in colloid osmotic pressure in glomerular capillaries (e.g. in nephrotic syndrome, liver disease);
Increase in colloid osmotic pressure in tubular fluid (in nephrotic syndrome).
What is the glomerulus membrane selective for?
Plasma proteins and cells.
Where does the energy for glomerular filtration come from?
From the beating of the heart, the kidney does not spend any energy on that. It is a passive process.
In what occasion reabsorption starts to happen in glomerulus?
It never happens, only filtration.
What is autoregulation in kidneys?
Autoregulation is the relative independence, from systemic blood pressure, of glomerular filtration rate and renal blood flow over the physiological range of mean arterial pressure (c.80-180 mmHg).
What is the formula of rate of filtration of a substance through the glomerulus?
ROF = GFR x Px
Px - concentration of a substance in plasma.
What is the formula for the rate of excretion of a substance?
ROE = V x Ux
V - urine output
Ux - concentration of a substance in urine.
What is the equation for the GFR using the inulin or creatinine concentrations?
GFR = (Ux x V)/Px
Ux - urinary concentration of a substance
V - urine output
Px - convcentration of a substance in plasma.
What are the criterion for a substance that can be used for measuring GFR?
It must:
be freely filtered;
no tubular transport (no excretion or reabsorption);
Be non-toxic;
be easily measured;
not metabolised by kidney;
not stored by kidney;
not change GFR.
Why is it said that using creatinine to measure the GFR is not accurate?
Because there is a small excretion happening in the kidney, so there is a slight overestimation.
What factors of the blood in the peritubular and vasa recta capillaries favour reabsorption of fluid into the capillary blood?
Blood in the peritubular capillaries or the vasa recta has:
- Low hydrostatic pressure
- High oncotic pressure
High haemotocrit and thus high viscosity which results in sluggish blood flow.
What is renal clearance?
A clearance of a substance is a rate at which the substance is cleared from the blood. (ml/min) In other words, clearance is a volume of plasma cleared of a substance per unit time.
State the formula for the clearance of a substance.
Clearance = (Ux x V)/Px
Ux - urine concentration of a substance
V - urine output
Px - plasma concentration of a substance.
When does the GFR equal clearance rate?
When there is no tubular transport of a substance (e.g. for inulin).
When does the excretion rate equals the filtration rate?
When there is no tubular transport of a substance (e.g. for inulin).
Which substances have following processes in the kidney:
Excretion rate < filtration rate;
Clearance < GFR?
Glucose, Na+, amino acids. There is net reabsorption of these substances.
Which substances have net secretion in the kidney?
Drugs, H+, PAH.
Paracellular reabsorption happens through the cells or between the cells?
Between the cells.
What is the longest segment of a nephron?
Proximal tubule.
Which part of a nephron does 60-70% of reabsorption happen?
In proximal tubule.
Which hormones influence the reabsorption in the proximal tubule?
No hormones are involved, no hormonal control.
Which part of nephron the reabsorption is isosmotic?
In the proximal tubule.
Name several substances that are 100% reabsorbed in the kidney?
Glucose, amino acids, vitamin C.
What is transport maximum?
A limit for the amount of substance that can be transported per unit time.
Why is the reabsorption in PCT isosmotic?
Because it reabsorbs about 67% Na+ and 67% water filtered.
Which substances are reabsorbed by PCT in help of contransport.
The cotransport mechanisms in the luminal membrane of PCT are Na+ - glucose, Na+ - amino acid, Na+ - phosphate, Na+ - lactate, Na+ - citrate. So Na+ moves down its electrochemical gradient, other substances move against theirs.
Which is the only countertransport mechanism in the luminal membrane of PCT?
NA+ - H+ exchange.
Explain NA+ - H+ exchange mechanisms in laminal membrane of PCT?
Countertransport. Na+ moves into the cell of PCT and H+ moves out. In the lumen H+ binds to HCO3-, converting it to CO2 and water, which then move from lumen into the cell. In the cell, the back process happens and they are converted back to H+ and HCO3-. Here, HCO3- is reabsorbed into the blood by facilitated diffusion, adn H+ repeats the cycle.
Which part of the kidney is responsible for most of the energy comsumption?
PCT, because many movements of a substances across the proximal tubule wall are driven by the active reabsorption of Na+.
Which substances are reabsorbed in PCT? (9)
Na+, Cl-, water, amino acids, lactate, glucose, HCO3-, phosphate, citrate.
What is the osmolarity of the tubular fluid entering the loop of Henle?
300 mosm/l, so it is isosmotic to plasma.
What is the osmolarity of the tubular fluid leaving the loop of Henle?
100 mosm/l, so it is more dilute than in the beginning of the LOH.
Excreted urine is isotonic/hypertonic/hypotonic to plasma?
It is hypertonic - more concentrated than plasma, 1200 mosm/l.
What is the relationship between the length of LOH and concentration of urine excreted? Why?
The longer are LOH, the more concentrated is urine. Because longer loops create larger osmotic gradient.
What is the difference in osmolarity between cortex and papilla in the kidney?
In the cortex the osmolarity is 300 mosm/l, and in the papilla it is 1200 mosm/l.
What is the result of countercurrent multiplication?
Osmotic gradient in the meddulla.
Which part of the LOH is working in reabsorption of Na?
The thick ascending limb.
Which part of LOH is impermiable to water?
The thick ascending limb.
Which type of transport is used for Na reabsorption in thick ascending limb of LOH?
Na+-K+-2Cl- cotransport, active transport.
What are the functions of vasa recta?
- Providing oxygen and nutrients for renal medulla
- Remove CO2 and other metabolic waste generated by cells in the renal medulla
- Reabsorb ab.20% of glomerular filtrate from fluid in the LOH
-Reabsorb variable amount of salt and water from the fluid in the collecting ducts.
Which two processes contribute in the establishment of corticopapillary osmotic gradient?
Urea recycling and countercurrent multiplication.
What is the affect of ADH in the cortical and outer medullary collecting ducts?
Increase water permeability.
Does ADH increase urea permiability?
No.
What causes the urea concentration of tubular fluid to increase in cortical and outer medullary collecting duct?
The differential effect of ADH on water and urea. ADH increases water permeability, but not ureas.
In inner medullary collecting duct what is the effect of ADH?
It affects the permeability to water and urea.
What is the difference of effect of ADH in inner medullary collecting duct and cortical, outer medullary collecting duct? And why is it important?
In cortical and outer medullary collecting duct ADH effects only permeability to water, but in inner medullary collecting duct it afects permeability to water AND urea.
It is important because it creates large concentration gradient for urea, so in inner medullary collecting duct urea defused down its concentration gradient and is recycled.
Name 3 components of the collecting ducts of nephron.
- Distal convoluted tubule
- Cortical portion of collecting duct
- Medullary portion of collecting duct.
How many percent of glomerular filtrate does collecting duct receive?
Less than 20%.
Which part of nephrone is responsible for adjustments in K+ excretion?
Distal tubule and collecting ducts. It reabsorbs or excretes K+ to keep it in balance.
Which cells in distal nephron (distal tubule and collecting ducts) is responsible for K+ secretion?
Principal cells.
Which cells in distal nephron (distal tubule and collecting ducts) is responsible for K+ reabsorption?
Intercalated cells.
Where and how is most of K+ reabsorbed?
80% of K+ reabsorption occurs before the distal tubule via a paracellular route and NA+K+2Cl- cotransport.
Is cortical and medullary collecting ducts permeable to urea and water?
No. Only in presence of ADH, and it also depends on the section of collecting ducts.
If there would be no ADH present in the kidney what would be rate of urine production and osmolarity?
About 23 L/day and it would be dilute - 60 mosm/l.
What whould be the urine excretion rate and its osmolarity with the maximal presence of ADH?
400 ml and 1200 mosm/l.
What is the normal urite excretion rate and its osmolarity?
1.4 l and 300-800 mosm/l.
What is the other name for ADH?
Vasopressin.
Which two hormones are involved in endocrine control in the distal nephron?
Vasopressin and aldosterone.
What effect does aldosterone has in distal nephron?
It increases:
- Na reabsorption
- Water reabsorption
- Cl reabsorption
- K secretion
- H excretion
- Na/K ATPase
- Na channels.
Which two processes are regulated in the kidney in order to maintain body acid base balance?
H+ excretion and HCO3- reabsorption.
Which gland secretes anti-diuretic hormone?
Posterior pituitary gland.
What are the differences in alveolar ventilation in different parts of the lung?
Alveolar ventilation is lowest in apex of the lung and highest in the base of the lung.
Na+ movement is directly regulated by which hormone?
Aldesterone.
What secretes aldosterone?
Adrenal gland.
ECF osmolarity is established by regulating what?
Body water, not salt!
Present distribution of body water in man by body fluid compartments. In liters per every compartment (5).
Total body water (45L):
Intracellular (30L) and
extracellular (15L): Plasma (3L) and Interstitial fluid (12L).
What are three actions of ADH on the renal tubule?
1. Increase in water permeability (reabsorption) of the principal cells of the late distal tubule and collecting ducts;
2. Increases activity of Na+K+2Cl- cotransporter of the thick ascending limb;
3. Increases urea permeability in the inner medullary collecting ducts (recycling).
What is the name of the water channels that are activated by ADH?
Aquaporins.
Where are aquaporins situated?
In the principal cells of the late distal tubule and collecting duct.
What happens in case of increased osmolarity of the ECF?
High osmolarity is detected by osmoreceptors in hypothalamus, and leads to increased frequency of nerve impulsesalong hypothalamo-hypophysial tracts. That causes secretion of ADH from hypothalamo-hypophyseal nerve terminal. ADH acts on the kidney to reabsorb water.
Sensation of thirst is induced by which two mechanisms?
- Stimulation of hypothalamic osmoreceptors (via raised plasma osmolarity);
- hypovolaemia (low blood volume) detected by cardiovascular stretch receptors.
What is Diabetes insipidus?
Diabetes insipidus is a condition in which the kidneys are unable to conserve water.
There are two types of Diabetes insipidus. Name them and tell what is the cause.
DI caused by a lack of secretion of ADH is called central diabetes insipidus. When DI is caused by a failure of the kidneys to respond to ADH, the condition is called nephrogenic diabetes insipidus.
What is the name of increased and decreased blood volume?
Increased: hypervolaemia;
decreased: hypovolaemia.
What does hypovolaemia lead to?
Leads to reduced blood pressure and reduced tissue perfusion.
What does hypervolaemia lead to?
To increased blood pressure and strain on heart.
Which parts of the nephrone reabsorption of Na Does not occur?
In glomerulus.
What is Addison's disease?
Low levels of aldosterone, that leads to hypovolaemia and hypotension.
What is Conn's disease?
High levels of aldosterone, what leads to hypervolaemia and hypertension.
How is aldosterone helping body to regulate blood potassium?
Increased K in the blood --> Increased release of aldosterone from adrenal cortex --> Increased exchange of Na and K in distal nephron --> Increased excretion of K.
Name three factors regulating the release of renin/angiotensin.
1. Drop in renal arterial pressure detected by stretch receptors in walls of afferent arteriole.
2. Increase in renal sympathetic activity, which increases when blood pressure falls.
3. Drop in Na at macula densa, if GFR is reduced.
Name three factors regulating release of aldosterone.
1. Renin/angiotensin in the blood.
2. Decr.in Na and incr.in K in adrenal cortical blood.
3. Drop in ECF volume detected by volume reeceptors in atria and great veins.
What is ANPH?
Atrial natriuretic peptide/hormone.
Where and why is ANPH released?
In atria and great veins in response to stretch.
What effect does ANP have on kidney?
It is vasodilator - increases GFR;
It reduces Na reabsorption from collecting ducts --> natriuresis and diuresis.
Which hormone reduces Na reabsorption in distal nephron?
ANP.
Which hormone closes Na channels in membrane of principal cells?
ANP.
What does reduced reabsorption of Na in distal nephron lead to?
To reduced Cl and water reabsorption and increased urine output, decreased blood volume, decreased blood pressure.
What does release of ANP lead to?
To reduced Na, therefore Cl and water reabsorption in the kidney and increased urine output, decreased blood volume, decreased blood pressure.
What does vitamin D deficiency lead to?
- Richets (deformed bones in children)
- Osteomalacia (weak bones in adults).
Describe juxtaglomerular apparatus.
The juxtaglomerular apparatus is a microscopic structure in the kidney, which regulates the function of each nephron. It is found between the vascular pole of the renal corpuscle and the returning distal convoluted tubule of the same nephron. This location is critical to its function in regulating renal blood flow and glomerular filtration rate.
The three cellular components of the apparatus are the
- macula densa,
- extraglomerular mesangial cells,
- juxtaglomerular cells (juxtaglomerular cells are not granular cells but are granulated as they release Renin).
What are three capillary beds that perfuse the nephron?
- Glomerular capillaries
- Vasa recta
- Peritubular capillaries.
Dexcribe effects of hormones: Aldosterone, Angiotensin, ADH, ANP.
Aldosterone:
A hormone produced by the adrenal glands that stimulates the reabsorption of Na+ by the distal convoluted tubules, causing water to follow (because of osmosis).
Angiotensin:
A plasma protein in the blood, activated by renin, that causes constriction of arterioles and stimulates the adrenal glands to produce aldosterone (though always in the blood, only the active form, angiotensis II, acts as a hormone).
Antidiuretic hormone (ADH):
A hormone that increases the permeability of the distal convoluted tubules and the collecting ducts to water, so that more is reabsorbed, in the event that the osmolarity of the blood is too high (normally signifying excessive water loss). ADH also induces thirst.
Atrial natriuretic peptide:
A hormone released by the walls of the heart's atrium in response to increased blood volume and pressure which inhibits the release of renin and aldosterone.
What is cortical nephron?
A nephron whose loop of Henle does not extend past the cortex.
What is juxtamedullary nephron?
A nephron whose loop of Henle extends past the cortex and well into the medulla.
What is the other name for cortical nephron?
Sub-capsular nephron.
Which organisms can have cortical nephrons?
Animals without the need for reabsorbption, like freshwater fish.
Mention different factors that affect GFR (7).
1. changes in glomerular hydrostatic pressure;
2. Changes in Bowman's capsule hydrostatic pressure;
3. Changes in glomerular colloid osmotic pressure;
4. REnal vasodilators;
5.Functioning kidney mass;
6.Changes in Filtering surface area;
7. changes in permeability of glomerular membrane.
What is renal clearance?
Renal clearance is a measurement that allows one to analyze the activity of the kidney. The definition for clearance is the volume of plasma from which a substance is completely removed by the kidney in a given amount of time (usually a minute).
Numerically: Clearancce of a substance = urine concentration of a substance x urine flow rate / plasma concentration of a substance.