Renal Physiology Flashcards
What makes up the renal corpuscle?
Glomerulus (tuft of capillaries) and bowman’s capsule
What feeds the glomerulus
Afferent arteriole
What drains the glomerulus
Efferent arteriole
What can pass through the glomerular basement membrane?
Positively charged molecules eg Sodium
What is the histology of the glomerules?
Fenestrated endothelial capillaries
What are the two layers of the Bowmans Capsule
Visceral Layer (podocytes)
Parietal layer
What connects the podocytes
Nephrin
What do mesangial cells do
Phagocytosis any molecules stuck in slit diaphragm
What do mesangial cells do
Phagocytosis any molecules stuck in slit diaphragm
What do juxtaglomerular cells do?
Baroreceptors that sense change in blood pressure and secrete renin in response
What is the glomelular filtration rate?
The amount of plasma volume being filtered by the glomerulus into the bowmans capsule per minute
What is the sum of the net filtration pressure
Pressures forcing in - pressures forcing out
What is glomerular hydrostatic pressure?
The pressure pushing the plasma components out of the capillary and into bowmans space
What is colloid osmotic pressure
Exerted by albumin to keep the plasma in the blood
What is capsular hydrostatic pressure
Backpressure built up by bowmans capsule
What is tubular secretion
Moving substances from the blood into the PCT
What is tubular reabsorption
Moving substances from the PCT into the blood
What kind of transport is the sodium glucose transporter?
Secondary active transport
What is 100% reabsorbed from the kidney tubules into the blood
Glucose
Amino Acids
Lactate
What is an antiporter
Transporter that moves two molecules in two different directions
What junctions are in the PCT
Tight junctions
what is paracellular transport
When substances move between cells eg Cl, Ca, Mg, K
What are the two components of the Loop of Henle
Descending and ascending limb
What happens to osmolarity as you go down the loop of henle
It gets larger so hypertonic
What does the Na/K/Cl transporter do
Transport these substances from the lumen of the filtrate to the tubule cell of the ascending limb
Why does osmolarity increase going down the loop of henle
Na/K/Cl transporter in the ascending limb pushing out these molecules to make it saltier and water follows
What are aqua porin 1 channels
Channels that are always open in the descending limb of the loop of henle allowing water to exit to follow salt in the interstitium
What is the counter current multiplier mechanism
As the ascending limb gets rid of salt this creates a gradient for water to follow too
What is the ascending limb impermeable to
Water
What is the descending limb impermeable to
Salt
At the end of the descending limb what is the solution
Hypertonic
What is the purpose of the counter current exchanger?
To prevent the rapid removal of NaCl from the medullary interstitium to maintain a gradient. This enables the kidney to produce different concentrations of urine depending on how much circulating ADH is present.
What happens in the early distal tubule
5% out 10% of the remaining sodium is pumped out via the sodium and chloride symporter and reabsorbed
What happens when you have low blood calcium
Parathyroid gland secretes PTH to eventually produce protein kinase A and phosphorylates calcium channel to reabsorb calcium to filtrate in early DCT
What causes aldosterone to be produced?
Hyperkalemia/ hyponatremia and angiotensin II
Where does ADH act
DCT
What does aldosterone do
Increased sodium reabsorption and potassium ion secretion
Where is urea excreted
collecting duct and reabsorbed by ascending limb
What do type A intercalated cells do
Actively secrete H into lumen and reabsorb bicarb against conc gradient allowing for H secretion in response to acidosis, then combine with phosphate or ammonia to prevent reabsorption
What do type B intercalated B cells do
Secrete HCO3 and reabsorb H in response to alkolosis
What is the affect of NSAIDs on the kidney
NSAIDs inhibit Cox 1 and Cox 2 needed for prostaglandin synthesis. Prostaglandins cause dilatation of renal afferent arteriole to maintain GFR without this there is there is vasoconstriction of the afferent arteriole and subsequent decrease in GFR.
Where are macula densa cells found and what is their action
Final part of ascending loop of henle and sense changes in NaCl conc.
An increase in blood pressure increases the GFR, which increases the sodium chloride delivery to the nephron and is detected by the macula densa. In return, the macula densa cells release ATP and adenosine which act locally on the afferent arteriole to constrict it and lower GFR
The macula densa cells can also release nitric oxide which acts as a vasodilator when low sodium chloride levels are detected.
They also have the ability to increase renin production from the juxtaglomerular cells when this occurs.
Where does furosemide work
Thick ascending loop of henle on the Na+/K+ 2Cl - carrier
By what transport method does sodium move out of the ascending loop of henle?
Active transport
What can excess aldosterone secretion lead to
Greater H excretion from alpha cells of the collecting duct and results in alkalosis
What effect would low bp have on the efferent arteriole
Would constrict to increase hydrostatic pressure at the glomerulus and maintain pressure
What do principal cells do
Found in the collecting ducts
Respond to levels of ADH in from posterior pituitary to control urine conc and plasma osmolarity
Respond to aldosterone to increase sodium reabsorption and increase potassium and hydrogen secretion
What does prostaglandins cause
Constriction of afferent arteriole
Which layer of the glomerular filtration membrane between the glomerulus and Bowman’s capsule filters by negative charge?
The basement membrane
Describe the histology + function of the PCT
- Simple cuboidal cells with microvilli
- Absorption of water, sodium ions, chloride ions, glucose, amino acids (~65%). Secretion of certain drugs and waste products.
Describe the histology + function of the thin descending limb
-Simple squamous
- Only permeable to water. No active secretion or reabsorption of molecules.
Describe the histology + function of the thin ascending limb
- Simple squamous
-Impermeable to water. No active secretion or reabsorption of molecules.
Describe the histology + function of the thick ascending limb
- Simple cuboidal cells
- Impermeable to water. Active reabsorption of solutes, in particular sodium ions.
Describe the histology + function of the DCT
- Simple cuboidal cell
- Secretion of potassium and hydrogen ions. Active reabsorption of sodium ions and other solutes. Water permeability is variable depending on ADH (Anti-diuretic hormone).
Where do aquaporin 2 channels insert
Onto the luminal membrane of collecting ducts (between tubular lumen and collecting duct cells)
Which part of the nephron is responsible for excess dietary excretion of potassium
Principal cells of the late distal tubules and collecting duct
What is the largest fluid compartment in the body
Intracellular
