Renal Physiology 1 & 2 Flashcards
What are the major functions of the kidney? (6)
Endocrine functions
Metabolic functions: gluconeogenesis
pH regulation
Salt/ion homeostasis
Excretion of medication
Body water balance
The resting membrane potential is based on the what of cells?
K+ gradient inside and outside of cells - very important for neurons and cardiomyocytes (heart and brain function)
This is kidney disease/failure.
Hyperkalemia
This is a commonly used anaesthetic that is excreted by the kidneys after metabolism in the liver due to its fat soluble nature.
Lidocaine
This is a common painkiller excreted directly by the kidneys due to its high water solubility.
Aspirin
What’s the difference between lipophilic drugs and hydrophilic drugs? (in terms of excretion)
Lipophilic drugs need to be metabolised in the liver then filtered in the kidney.
Hydrophilic drugs can be directly filtered in the kidney and excreted in urine.
True or false. Total body water hardly remains constant.
False. It remains relatively constant, it must to maintain kidney function.
True or false. Urine output may be adjusted to ensure total body water is balanced.
True
How does the kidney regulate pH?
By reabsorbing and secreting bicarbonate and hydrogen ions.
Remember: even in the GI tract, when it comes to secretion of bicarbonate and hydrogen ions, it always boils down to pH regulation function.
True or false. Males have more body water than females.
True
What are the proportions of ECF (plasma + interstitial fluid) and ICF in the body?
2/3 ICF
1/3 ECF (1/5 plasma, 4/5 interstitial fluid)
This is defined as the total number of solute molecules in solution.
Osmolarity
This is defined as having the same amount of solute molecules per litre - same osmolarity.
Isosmotic
This is when there are less solute molecules per litre and there is a decrease in osmolarity (more water).
Hyposmotic
This is when there are more solute molecules per litre and there is an increase in osmolarity (less water).
Hyperosmotic
This occurs in the renal corpuscle. It is the process of moving plasma from the glomerular capillaries into the glomerular capsule.
Filtration
True or false. Water and solutes are filtered at a constant rate at the renal corpuscle.
True.
This is the process of moving solutes from the peritubular capillaries into the tubular fluid. It removes additional substances like waste products from the blood so that they’re excreted in the urine. (eg., metabolites, medications and toxins)
Secretion
Where does the secretion of metabolites, medication and toxins occur in the nephron?
Proximal tubule
This is the process of moving solutes from the tubular fluid into the peritubular capillaries. It returns useful substances to the blood so that they are not excreted in the urine.
Reabsorption
This is where the bulk reabsorption of ions, water and nutrients occur. (2 locations)
Proximal tubule and nephron loop
This is where the fine-tuning reabsorption of ions and water occurs. (2 locations)
Distal tubule (fine tuning of Na+ only) and collecting duct (fine tuning of Na+ and water)
What are the 2 types of forces that drive glomerular filtration?
Hydrostatic pressures and colloid osmotic pressures
This is the pressure due to the volume of fluid. It pushes the fluid away.
Hydrostatic pressure
This is the pressure due to protein. It pulls fluid towards.
Colloid osmotic pressure
True or false. Positive pressures pull from capillaries to capsule and negative pressures pull from capsule to capillaries.
True
This is the amount of plasma filtered in the kidneys.
Filtration fraction
This is the amount of plasma filtered by the kidneys per unit of time.
Glomerular filtration rate
True or false. The GFR is loosely regulated and can differ from person to person.
False.
If you think about it, GFR is the amount of plasma filtered per time so it must be regulated tightly to ensure balance/homeostasis in the process.
This is the amount of a particular substance/solute filtered per unit of time.
Filtered load
This is the volume of plasma that is cleared of a substance by the kidneys per unit of time.
Renal clearance
True or false. The filtered load can quantify how a substance is handled by the kidneys.
False. Renal clearance can quantify how a substance is handled by the kidneys.
Filtered load is how much substance/solute is filtered per time.
The renal clearance of creatinine is proportional to the ?
GFR => volume of plasma filtered per minute.
Why?
Because ALL the creatinine and insulin in the plasma is filtered.
The renal clearance of PAH (medication) is proportional to the?
RPF => volume of plasma flowing through kidneys per minute
Why?
Because ALL of the PAH in the plasma is filtered and cleared; all in blood is excreted in urine.
The renal clearance of glucose is proportional to ?
0 because no plasma is cleared of glucose. Glucose is fully reabsorbed in the proximal tubule.
The renal clearance of sodium is proportional to ?
Very small amount of plasma per minute.
So almost all sodium will be reabsorbed except for a little bit (which will also be excreted in the urine)
What 2 main substances are used to estimate GFR using renal clearance?
Inulin and creatinine
If plasma creatinine concentration was increasing what does this mean?
Kidney is not functioning properly because creatinine is not being filtered and excreted.
This is where the secretion of metabolites, medications, and toxins occurs
Proximal tubule
The kidney releases this when it detects that blood oxygen levels are low.
EPO (erythropoietin)
What does EPO do to increase blood oxygen levels?
Stimulates the bone marrow to produce more red blood cells
What are the 2 main sources of acid in the body?
1) acids coming from metabolism of food and drink
2) carbon dioxide from metabolism
Blood pH is controlled by what organs? How?
1) lungs - via inhalation of CO2
2) kidneys - via reabsorption and secretion of bicarbonate (HCO3-) and acid (H+)
How much body water do males and females have?
Females: 55%
Males: 60%
Males have more body water than females. Females usually need more fat to survive.
Filtration of plasma occurs where?
Glomerulus
What are the 4 forces which influence filtration?
1) Glomerular hydrostatic pressure (blood pressure)
2) Blood colloid osmotic pressure
3) Capsular hydrostatic pressure
4) Capsular colloid osmotic pressure
What is the equation for calculating filtration fraction?
Filtration fraction is the amount of plasma filtered in the kidneys.
FF = GFR/RPF
What is the equation for Filtered load?
Filtered load is the amount of substance/solute filtered in the kidneys.
FL = GFR x solute plasma concentration
What is the equation for renal clearance?
Renal clearance is how much of plasma is being cleared of a specific substance per unit time.
RC = ([urine] x vol. of urine) / [plasma]
