Main functions of kidney and nephron processes Flashcards
Why do we need kidneys?
We need kidneys to control what is in our blood and how much blood we have
Kidneys remove waste products, drugs/medications and toxins from the blood so that they don’t build up and cause harm
Kidneys maintain a homeostasis of water, ions and pH - by controlling water and sodium
What are the endocrine functions of kidney?
Kidneys able to sense amount of oxygen in blood, if low they release EPO which stimulates bone marrow to make more RBC
If you have kidney/renal failure the kidneys cannot make enough EPO hence anaemia occurs - don’t have enough haemoglobin as don’t carry the right amount of oxygen in the blood
What is the metabolic function of kidney?
Gluconeogenesis- kidneys can make glucose from lactate during fasting or when body is under stress
What is the pH regulation function of kidney?
pH of blood is controlled very tightly, needs to fall between 7.35-7.45 for body to function correctly
Controlled by getting rid of anything we have too much of (acid or base) in the urine, pH range of urine is 4.6-8.0
Acids come from metabolism and from carbon dioxide
pH of blood controlled by lungs (exhalation of CO2) and kidneys (reabsorption and secretion of bicarbonate and H+)
What is the salt/ion homeostasis function of the kidney?
Potassium concentration vital for many processes - resting membrane potential and AP in neurons and cardiomyocytes
Kidneys secrete potassium to maintain potassium balance, if your kidneys don’t function properly too much can lead to hyperkalemia (death)
What is the excretion of medication function of the kidney?
Medication needs to be removed so that when you need to take another dose the concentration doesn’t build up
Hydrophilic drugs - excreted directly by kidneys due to high water solubility e.g. aspirin
Lipophilic drugs (dissolve in lipids) - travel around body attached to proteins, excreted by kidneys after metabolism in liver e.g. lidocaine
Medications are filtered and secreted then excreted in the urine
What is the body water balance function of the kidneys?
Total body water remains relatively constant, amount of water taken in needs to be the same as amount of water taken out. Urine output is adjusted to maintain balance
What are the volumes and composition of the human body?
Total body water (TBW) in males is 60%, in females 55%
Extracellular fluid (ECF) makes up 1/3 (33%) of TBW
Intracellular fluid (ICF) makes 2/3 (67%) of TBW
Plasma makes up 1/5 (20%) of ECF
Interstitial fluid makes up 4/5 (80%) of ECF
When will the volume of fluid in body water change?
Volume of fluid in body water can change due to how much water there is in body and the osmolality of the body water compartments
More plasma = increase in BP, less plasma = decrease BP
More water in our cells, increase in ICF = swell of cells
Less water in our cells, decrease in ICF = shrinking of cells
What are the three states of body fluid volume?
Isosmotic = same amount of solute molecules per litre, same osmolarity
Hyposmotic = increase in water, less solute, decrease in ECF/plasma osmolarity
Hyperosmotic = decrease in water, more solutes, increase in ECF/plasma osmolarity
What happens when there is a loss or gain of water?
Loss of water: water loss from ECF, ECF osmolarity increases, water moves from ICF -> ECF until the osmolarity of each is balanced, loss of water from both ECF and ICF, cells shrink
Gain of water: water gain to ECF, ECF osmolarity decreases, water moves from ECF -> ICF until osmolarity of each is balanced, gain of water to both ECF and ICF, cells swell
What happens when there is a loss or gain of isosmotic fluid?
Loss of isosmotic fluid: loss of water and ions from ECF, osmolarity of ECF and ICF are the same, no net water movement, decrease in ECF volume only
Gain of isosmotic fluid: gain of water and ions into ECF, osmolarity of ECF and ICF are the same, no net water movement, increase in ECF volume only
What is filtration in the kidneys?
Filtration occurs in renal corpuscle/glomerulus. Movement of plasma from the glomerular capillaries into glomerular capsule
Most substances are freely-filtered except for large proteins and substances bound to proteins. Water and solutes filtered at a constant rate creating a plasma like filtrate of the blood
What is secretion in the kidneys?
Secretion is when substances move from peritubular capillaries (blood) into the tubular fluid (nephron). Removes additional substances/waste products from the blood by secreting them into the tubular fluid so they are excreted in urine
Proximal tubule is where the secretion of metabolites, medications and toxins occurs
What is reabsorption in the kidneys?
Reabsorption is when something from within the nephron is brought back into the blood, returns only useful substances (so they aren’t excreted in the urine)
In the proximal tubule there is bulk reabsorption of ions, water and nutrients. In the nephron loop there is bulk reabsorption of ions and water. In the distal tubule and collecting duct fine-tuning reabsorption (by hormone) of ions and water occurs
