Renal Flashcards
What are 3 hormones produced by the kidneys?
Renin, EPO and calcitrol
How many nephrons are found in the body in total?
around 2.5 million.
How much blood is filtered out from the glomerular arterioles?
around 20%
Which fibres alter the blood flow to the glomeruli?
Sympathetic fibres
How many nephrons are juxtamedullary?
Between 15-25%
What is the importance of juxtamedullary nephrons?
They have very long loops of henle and collecting ducts allowing them to concentrate urine more than other types of nephrons.
What do efferent arterioles recombine into?
The peritubular capillaries.
What do the peritubular capillaries become when they are closely linked to the collecting duct and loop of henle?
The vasa recta
Where does the majority of reabsorption take place?
The PCT.
What does the PCT reabsorb?
Ions, Water and organic nutrients
What does the PCT secrete?
Metabolites and other drugs such as xenobiotics.
Name a renal tracer and explain its importance.
Para-aminohippurate is a renal tracer. It cannot be reabsorped by the nephorn once filtered so its concentration in urine is a useful indicator of GFR
How much plasma do the glomeruli filter per minute?
125ml/min which is around 180l/day
Which forces help to push solute out of afferent capillaries and what is it greater than?
Hydrostatic forces is greater than oncotic pressure.
What is the net filtration pressure across the glomeruli?
10mmHg
What components form the GFR co-efficient?
The slit surface area and barrier permeability.
Which hormones can influence afferent arteriole resistance and flow to glomeruli?
Catecholamines and angiotensin 2
What is the range of kidney autoregulation of GFR?
130-60mmHg
What happens to 50% of the urea which is filtered by glomeruli?
It is reabsorbed.
What substances are reabsorped by channel or carrier proteins?
Glucose, amino acids, phosphates and organic ions.
What is a normal value of ECF [Na+]?
142mmol
How much sodium is reabsorbed in the PCT?
65-75%
Is Na+/K+ transport affected by transport maximum?
No.
WHere are the hydrogen ions that are excreted in urine formed?
They are formed in the tubular lumen epithelium
What does the inability to reabsorb everything mean for urine concentration?
It means that there will be a minimum amount of effective osmoles still in the urine, which draws water into the urine. This means that there is a maximum attainable concentration for urine.
What happens to metabolites which are too large or charged to pass the glomerular barrier?
They are secreted into the PCT by unspecific carriers.
What is the primary intracellular cation?
K.
What is a normal ECF [K+]?
4mmol
What concentration might be classed as hyperkalaemia?
> 5.5mol
What concentration might be considered hypokalaemia?
<3mmol
What does hypokalaemia mean for cells?
They are hyperpolarised so struggle to reach threshold for action potential propagation.
Name another tracer molecule.
inulin.
What is renal clearance?
A measure of how well the kidneys are excreting substances.
What is average plasma mOsm/l?
~285mOsml/l
What is reabsorbed in the descending loop of henle?
Water, no ions
What is reabsorbed in the ascending loop?
Ions, no water.
What can alter ADH secretions?
Stress, pain and emotion
What is neurogenic diabetes insipidus?
Deficiency of ADH production.
What is nephrogenic diabetes insipidus?
Nephrogenic ADH insensitivity
A moderate decrease in ECF is detected by which receptors?
Atrial receptors
When do all baroreceptors detect a change in ECF volume?
When the change is very significant.
Where is angiotensin secreted from?
The liver.
Where is renin secreted from?
The kidneys.
What does renin do?
Converts angiotensin to angiotensin 1
Which enzyme converts angiotensin 1 to angiotensin 2?
Angiotensin converting enzyme (ACE)
What is special about ACE?
It is an ectoenzyme meaning it is bound to a membrane
What effect does ANG II have on the adrenal cortex?
Stimulates it to secrete aldosterone and initiate vasoconstriction.
How does ANG II decrease heart rate?
By acting on the medullary cardiovascular centre
What effect does aldosterone have on sodium and water reabsorption?
It stimulates the DCT to reabsorb more sodium and water to increase the blood pressure.
Which cells in the DCT are directly stimulated by aldosterone?
P-cells
When is atrial natiuretic peptide secreted?
When the atria are hyperdistended.
What does 2 main roles does ANP have?
To inhibit aldosterone and increase GFR
Why does ANP perform these roles?
To decrease the amount of sodium and therefore water that is being reabsorbed. This will result in reduced ECF volume and blood pressure.
What is a normal pH range?
7.35-7.45
What is a normal PCO2?
40mmHg or 5.33kPa
What is a normal [HCO3-] concentration?
24mM
What can cause metabolic acidosis?
Diabetic ketoacidosis.
What can prolonged vomiting cause in terms of acid/base disorders?
metabolic alkalosis
Acute respiratory acidosis may be cause by?
Breathing 7% CO2
What acid/base disorder might emphysema cause?
Chronic respiratory acidosis.
Prolonged time in high altitude might cause which acid/base disorder?
Chronic respiratory alkalosis.
What might be a cause of acute respiratory alkalosis?
Hyperventilation.
What is the first step in determing the acid/base disorder?
Is the pH high or low?
What is the second step in determing the acid base disorder?
Whether it is metabolic or respiratory.
How can you determine whether the acid/base disorder is metabolic or respiratory?
If it is respiratory then PCO2 is likely to be affected.
If it is metabolic then PCO2 is likely to be unaffected.
What is the 3rd step in determining acid/base disorder?
Whether or not it is chronic or acute.
How can you determine whether an acid/base disturbance is chronic or acute?
If the [HCO3-] has signficantly moved from a normal level then it is likely to be chronic, if not, then it is likely to be acute.
If the acid/base disturbance is caused by a change in [HCO3-] is the cause likelt to be respiratory or metabolic?
Metabolic.
When might renal compensation for an acid/base disorder occur?
When the cause if the disturbance is respiratory.
What is respiratory compensation in response to?
A renal/metabolic issue causing an acid/base disturbance.
