L118: Kidney 3 Flashcards
The primary function of the kidneys is to filter blood however, what else do they regulate?
- Fluid and electrolytes: blood volume ~ blood pressure;
- Acid-base blood balance;
- Calcium and vitamin D metabolism;
- Erythropoietin.
What is the series of events upon excess fluid levels?
- Excess fluid;
- Elevated blood volume;
- Elevated blood pressure;
- Large volume of dilute urine;
- Reduced blood pressure.
What is the series of events upon reduced fluid levels?
- Reduced fluid;
- Reduced blood volume;
- Reduced blood pressure;
- Small volume of conc. urine;
- Elevated BP.
What is glomerular filtration rate (GFR)?
The rate at which blood is filtered through the glomerulus into the Bowman’s capsule
What are the three main factors that influence GFR?
- Hydrostatic pressure;
- Osmotic pressure;
- Blood pressure.
What is the main driver of hydrostatic pressure in the glomerulus?
The afferent arteriole is larger than the efferent arteriole
How do the kidneys estimate GFR?
Blood pressure
If blood pressure increases, and the kidneys are unable to adjust (CKD) the GFR, GFR will…
increase
An increase in GFR leads to…
less time to reabsorb sodium and more sodium entering the DCT
What is the juxta-glomerulus apparatus (JGA) and what is its purpose?
- Connects the glomerulus with the DCT;
- Measures the [Na+] of the filtrate;
- Adjusts the diameter of the afferent arteriole.
What is the macula densa?
- A component of the JGA;
- An area of closely packed specialised cells;
- Detect the [Na+].
What are juxtaglomerular cells?
- A component of the JGA;
- Modified smooth muscle cells around the afferent arteriole (some on efferent);
- Synthesise, store and secrete the enzyme, renin;
- Adjust the diameter of the arterioles.
How do macula densa cells respond to an increase in blood pressure and why?
- Increased BP;
- Increased glomerular hydrostatic pressure;
- Increasder GFR;
- Increased Na+ in filtrate;
- Detected by macula densa;
- Macula densa release adenosine.
What does the release of adenosine from macula densa cells cause?
- Paracrine signal to juxtaglomerular cells;
- Juxtaglomerular cells constrict afferent arteriole;
- Tubular-glomerular feedback.
How does the constriction of the afferent arteriole lead to restored homeostasis?
- Reduces glomerular hydrostatic pressure (less blood can flow in);
- Reduced GFR;
- Homeostasis restored.