Renal Flashcards
Does filtration occur in the renal cortex or medulla?
Cortex
Which part/s of the nephron dip down into the medulla?
The loop of henle, the collecting ducts
Do the peritubular capillaries connect to the afferent or efferent arterioles?
Efferent.
Describe the vascular structure of the nephron. Include: afferent arterioles, efferent arterioles, peritubular capillaries and renal vein and artery
Renal artery supplies the afferent arterioles, which supplies blood to the glomerulus. The glomerulus contains many capillaries where filtration occurs, then the efferent arterioles take blood away from the glomerus to the PT capillaries then to the renal vein
Location of PCT vs DVT?
Proximal tubule is after the bowmans capsule, DCT is after the loop of henle.
Excretion = _____ - reabsorption + ____?
Filtration - reabsorption + secretion
Describe the movement of substances that occurs during glomerular filtration
Movement of fluid + solutes from the glomerular capillaries into the bowmans space
Describe the movement of fluid and solutes that occurs during tubular reabsorption
Moves from the tubules into the peritubular capillaries (back into the body / won’t be excreted)
Describe the movement of fluid and solutes that occurs during tubular secretion
Moves from peritubular capillaries into the tubule to be excreted
What is the main site of sodium reabsorption?
Proximal tubule
Does sodium reabsorption happen in the descending or ascending loop of henle?
Ascending
Does water reabsorption happen in the ascending or descending loop of henle?
Descending
ADH / vasopressin increases permeability at which part of the nephron?
Collecting duct and distal tubule
Explain how ADH works in dehydration.
Dehydration causes an increase in ECF osmolarity. This is detected by osmoreceptors, which signals to the posterior pituitary to release ADH as well as increasing thirst. ADH acts on the nephron to increase water reabsorption and reducing its excretion
Where is aldosterone released from
The adrenal gland
What stimulates the release of aldosterone
Angiotensin 2 and increased concentration of potassium
Action of aldosterone?
Acts on the distal tubule and collecting duct to increase sodium reabsorption (promotes the secretion and excretion of K and reabsorption of water)
Which substances are commonly secreted back into the tubule for excretion?
Uric acid, urea, drugs, H+ and HCO3-
What % of the CO do the kidneys receive?
20-25%
Why do kidneys need so much blood?
To ensure a high enough hydrostatic pressure to drive fluids and solutes across the filtration barriers
Name 2 barriers to filtration
- negatively charged basement membrane
- endothelial fenestrations
- podocytes and slit diaphragm
Name 2 factors that oppose filtration
- pressure in the filtrate / bowmans capsule
- osmotic pressure of plasma (due to proteins)
Factor that favours filtration?
Glomerular capillary pressure
What effect does an increase in GFR have on tubular flow rate?
Increases it. Causes a reduction in reabsorption, leading to the loss of important solutes
Consequence of a slow GFR?
Increases reabsorption since the tubular flow rate is so slow. Leads to waste not being excreted
Name an example of something that would increase plasma osmotic pressure
Water loss - dehydration or diarrhoea
If the clearance of a drug is less than the clearance of creatinine (125), what does this indicate?
It is being reabsorbed
If the clearance of a substance = 125, what does this indicate?
Not being reabsorbed or secreted. If more than 125, it is being secreted
Where are macula densa cells found?
In the distal tubule
Explain what juxtaglomerular cells are
Smooth muscle cells in the afferent arterioles that secrete renin
Which cells detect NACL Levels in the distal tubule and respond by changing release of renin?
Macular densa cells
Name 2 Intrinsic factors for bp regulation
Myogenic mechanism and tubuloglomerular mechanism
Name 2 extrinsic factors for BP regulation
Hormonal and neural (SNS activity)
Which cells are responsible for the secretion of renin? And where are these cells located?
The juxtaglomerular cells in the afferent arterioles
Other than low blood pressure, what else can stimulate the release of renin? (3 answers)
Low sodium concentration detected by macular densa cells in the distal tubule, decreased blood volume and increased beta sympathetic activity
Force that favours filtration?
Glomerular capillary pressure
2 forces that oppose filtration
Plasma-colloid osmotic pressure (oncotic)
Bowmans capsule hydrostatic pressure
