Lecture 30 Flashcards
What are the major functions of the kidney?
Endocrine, metabolic, pH, water, salt/ion, reabsorption and excretion
What are the endocrine functions?
EPO, VD → Calcitriol, Renin secretion
What is EPO?
Erythropoietin, a hormone secreted by the kidney to stimulate the bone marrow to produce RBCs
What is chronic kidney/renal failure?
Kidneys cannot make enough EPO leading to reduced RBC production and potential for anaemia (low blood O2 levels)
What is the metabolic function?
Gluconeogenesis - synthesis of new glucose from lactate
When does glucogenesis occur?
While fasting or when the body is under stress
What is pH?
A measure of how acidic or alkaline a solution is
pH = - log [H+]
More H+ means…?
lower pH, more acidic
Fewer H+ means…?
Higher pH, more basic
What is the normal pH range for the blood?
7.35-7.45
What is the normal pH range for the urine?
4.6-8
What are the main sources of acid in the body?
Acids coming from metabolism, food and drink as a direct source of H+ and carbon dioxide from metabolism
What is the pH of the blood controlled by?
The lungs and kidneys
Why are there two systems controlling blood pH?
If one fails, the other can compensate
How do the lungs control blood pH?
Exhalation of carbon dioxide
How do the kidneys control blood pH?
Through reabsorption and secretion of bicarbonate and H+
Why is water homeostasis important?
ECF osmolarity and blood pressure
What can be adjusted to maintain water balance within the body?
Urine output
Why is salt/ion homeostasis important?
[Na+], [K+] and blood pressure
Why is [K+] so important?
All cells resting membrane potential is based on the K+ gradient and neurons & cardiomyocytes rely on K+ for action potentials, rhythm generation in pacemaker cells, contractility and signalling
What happens if you suffer from a kidney disease or failure?
Kidneys cannot secrete enough K+ leading to a build-up in the blood (hyperkalemia) which can cause arrhythmias and death
What nutrients are reabsorbed?
Amino acids and glucose
What medication are excreted?
All e.g. asprin and lignocaine
What toxin is excreted?
All e.g. urea
What metabolite is excreted?
Uric acid
What is lidocaine?
A lipophilic medicine used for local anaesthetic
How are lipophilic medicines excreted?
Via the kidneys AFTER metabolism in the liver
What is asprin?
A hydrophilic medicine used as a pain killer
How are hydrophilic medicines excreted?
Directly via the kidneys
How much of TBW is extracellular fluid?
1/3
How much of TBW is intracellular fluid?
2/3
How much of ECF is plamsa?
1/5
How much of ECF is interstitial fluid?
4/5
How can the volume of fluid in the body water compartments change?
Based on how much water there is in the body and the osmolarity of the body water compartments
What does a change in plasma water content cause?
A proportional change in blood pressure
What does an increase in ICF water content cause?
Swelling of cells
What does a decrease in ICF water content cause?
Shrinking of cells
What is osmolatiry?
The total number of solute molecules in a solution
What is isosmotic?
The same amount of solute molecules, same osmolarity
What is hyposmotic?
Increase water, less solute molecules, decrease in ECF osmolarity
What is hyperosmotic?
Decrease in water, more solute molecules, increase in ECF osmolarity
Where do ingested fluids travel first?
To the extracellular fluid
What does the addition of isosmotic fluid in the body cause?
A change in ONLY the ECF
What are the basic functions of the nephron?
Filtration, secretion and reabsorption
Where does filtration occur?
In the renal corpuscle
What does filtration do?
Creates a plasma-like filtrate of the blood
What movement occurs during filtration?
Plasma from glomerular capillaries to glomerular capsule
Blood → Nephron
What can be filtered?
Most substances are free filtered except large proteins and RBCs
Where does secretion occur?
In the proximal convoluted tubule
What does secretion do?
Removes additional substances from the blood and adds them to the tubular fluid
Blood → nephron
What additional substances are added to the tubular fluid?
Metabolites, mediations and toxins
Where does reabsorption occur?
The PCT, nephron loop and DCT
What does reabsorption do?
Returns useful substances to the blood by removing them from the peritubular fluid
Nephron → blood
What major function occurs in the glomerulus?
Filtration
What major functions occur in the PCT?
Secretion, bulk reabsorption (ions, H2O & glucose)
What major function occurs in the nephron loop?
Bulk reabsorption (ions & H2O)
What major function occurs in the DCT and collecting duct?
Fine-tuning reabsorption (ions and H2O)
How do you determine the amount of a substance excreted in the urine?
Amount filtered + amount secreted - amount reabsorbed
What happens to glucose in the nephron?
Freely filtered, not secreted and fully reabsorbed in PCT (none in urine)
What happens to sodium in the nephron?
Freely filtered, not secreted and almost fully reabsorbed (small amount in urine)
What happens to mediation and toxins in the nephron?
Free filtered, rest entirely secreted, none reabsorbed so ALL in urine
What happens to creatinine and insulin in the nephron?
Freely filtered, not secreted or absorbed so all filtered is in urine, rest remains in blood
