Dr. Houston (Renal)-Exam 5 Flashcards
- What is the most superior layer around the kidney?
- What is superior to the medulla?
- What is around the glomerua?
- What vessels go away and towards the glomerus?
- Super. layer: Renal Capsule
- Cortex is superuor to medulla
- Bowman’s capusle is around the glomerus
- Towards the glom=afferent artery
- away the glom=efferent artery
What is the difference between cortical and JM nephrons?
JM nephrons are longer and more in the inner medulla. This area is salty therefore better at pulling in water
* See more dry area animals with more JM nephrons
What is the pathway of nephron out to the urethra?
Papillary duct (end of collecting duct)-> papilla-> minor calyx-> major calyx-> renal pelvis-> ureter-> bladder-> urethra
What is the blood supply of JM nephron vs cortical nephron?
- JM: Vasa recta (around loop of henle)
- Cortical: Peritubular capillaries (aroung prox and distal tubules)
Explain the breakout of the arteries and veins of the kidney
* What do you change in order to affect flow?
Explain the breakout of the arteries and veins of the kidney
* What do you change in order to affect flow?
Urine formation involves what three basic processes?
- Glomerular filtration
- Tubular reabsorption
- Tubular secretion
What is the excreted formula?
Excreted=filtered-Reabsorbed+secreted
What area of the nephron reaborbs about 65% of glomerular filtrate? What does it remove?
PCT reabsorbs about 65% of glomerular filtrate, removes some substances from blood, and secretes them into tubular fluid for disposal in urine
Proximal Convoluted Tubule
* What type of reabsorption?
* What is absorbed there? (3)
- Nonregulated reabsorption
- 70% of Na+ and H2O are absorbed here
- All glucose is absorbed here
Proximal Convoluted Tubule
* What are the characterisitics?
- Many microvilli (increase SA to allow mvt)
- Many mitochondria (lots of active transporters so need mitochondria for ATP)
- “Leaky” tight junctions (allow mvt)
Loop of Henle (juxtamedullary nephrons only)
* What does it create?
* Critical in what?
- Creates an osmotic gradient in the renal medulla
- Critical in water conservation
Distal Tubule and Collecting Duct
* More what than proximal tubule?
* What is there less of?
* What type of junctions?
* What hormone receptors are there?
- More regulated than proximal tubule
- Smaller and fewer microvilli
- Less mitochondria
- “Tight” tight junctions
- Hormone receptors: ADH (insertion of aquaporin channels) , aldosterone (na reabsorption and K secretion), etc.
Glomerular Filtration Rate (GFR)->(volume of plasma filtered per unit time)
* What is the rate?
* How much volume is filtered?
* How much urine is made daily?
- Average GFR = 125 ml/min
- 180 L filtered daily
- Only 1.5 L urine made daily
- Most filtered fluid is reabsorbed
Glomerular Filtration Rate
* What impacts GFR?
Changes in MAP could impact GFR by changing Glomeular Capillary Pressure (PGC)
Long lol
What are all the different forces on the glomerus?
- Hydrostatic Pressure in Glomerular Capillaries (PGC 55 out): This is the blood pressure within the glomerular capillaries, pushing water and solutes out of the blood into Bowman’s capsule. The value is 55 mm Hg, directed outward.
- Colloid Osmotic Pressure in Glomerular Capillaries (COP 30 in): This pressure is due to plasma proteins in the blood that draw water back into the glomerulus from Bowman’s capsule. The value is 30 mm Hg, directed inward.
- Capsular Hydrostatic Pressure (CP 15 in): This is the pressure exerted by the fluid already in Bowman’s capsule, which opposes further filtration. The value is 15 mm Hg, directed inward.
- Colloid Osmotic Pressure in Bowman’s Capsule (COP 0 out): Typically, there are no proteins in Bowman’s capsule to exert this pressure, hence it is zero.
- Net Filtration Pressure (NFP 10 out): This is the net pressure driving the filtration process. It is calculated by subtracting the inward pressures (COP in and CP in) from the outward pressures (PGC out and COP out). Here, NFP is 10 mm Hg, directed outward, indicating the overall force favoring filtration.
What range does GFR does not change? Why?
Between 80 – 180 mmHg, GFR does not change much with changes in MAP because of intrinsic regulatory mechanisms
GFR controlled by what?
adjusting glomerular blood pressure from moment to moment
GFR is influenced by what three homeostatic mechanisms?
Renal Autoregulation
* What is it?
* Enables the kidney to do what?
- The ability of the nephrons to adjust their own blood flow and GFR without external (nervous or hormonal) control
- Enables kidney to maintain a relatively stable GFR in spite of changes in systemic blood pressure
Renal Autoregulation
* What are the two methods of autoregulation?
- myogenic mechanism
- tubuloglomerular feedback
Renal Autoregulation-myogenic mechanism
* Based on what?
Based on the tendency of smooth muscle to contract when stretched
Renal Autoregulation-myogenic mechanism
* What happens if the arterial blood pressure increases?
- Afferent arteriole is stretched
- Afferent arteriole constricts and prevents blood flow into the glomerulus from changing
Renal Autoregulation-myogenic mechanism
* What happens when arterial blood pressure decreases?
- Afferent arteriole relaxes
- Afferent arteriole dilates and allows blood to flow more easily into glomerulus, so that flow rate remains similar and filtration remains stable
Increase the pressure
What are the macula densa cells, mesangial cells and granular cells?
-
Macula densa cells (chemoreceptors): monitor the composition of the fluid (NaCl) in the tubule lumen-> located in DCT
* Increase NaCl=increase filtration=increase pressure - Mesangial cells: transmit information from macula densa cells to the granular cells (SM of afferent arteriole)
- Granular cells: modified vascular smooth muscle cell; synthesize and release renin
Glomerulus receives feedback on the status of what?
downstream tubular fluid and adjusts filtration rate accordingly
Tubuloglomerular feedback
* What happens when the GFR is too high?
If GFR too high (increased fluid [NaCL]):
* Macula densa detects increased filtrate [NaCl], secretes ATP
* Granular cells respond by constricting afferent arterioles
* Constriction reduces blood flow which corrects GFR
Tubuloglomerular feedback
* What happens if GFR is too low?
- Granular cells also contain granules of renin, which they secrete in response to drop in blood pressure (mechanoreceptors)
- Participate in the renin-angiotensin-aldosterone system that works to control blood volume and pressure
Extrinsic Control of GFR
* When MAP is outside the range of 80-180mmHg, what is needed?
* What is the most important homeostatic variable?
- When MAP is outside the range of 80-180 mmHg, nervous system intervention is necessary
- Recall, MAP is the most important homeostatic variable we need to control
Explain the extrinsic control of GFR when you have hemorrhage/sweating
Sympathetic Control
* Sympathetic nervous system and adrenal epinephrine causes what?
constrict the afferent arterioles in strenuous exercise or acute conditions like circulatory shock
What are the effects of sympathetic nervous system?(3)
- Reduces GFR and urine output
- Redirects blood from the kidneys to the heart, brain, and skeletal muscles
- GFR may be as low as a few milliliters per minute
Hormonal Control
* What is the RAAS pathway/
(Renin)->Angiotensinogen->Angiotensin I->Angiotensin II->(Aldosterone)
What are the four effects of angiotensin 2
Control of Water Loss
* How concentrated the urine becomes depends on what?
on body’s state of hydration
Control of Water Loss
* What is the difference between state of normal hydration and state of state of dehydration?
- What is the mulitplier?
- What is the countercurrent?
- Multiplier: continually recaptures salt and returns it to extracellular fluid of medulla which multiplies the osmolarity of adrenal medulla
- Countercurrent: because of fluid flowing in opposite directions in adjacent tubules of nephron loop
Explain how the the nephron acts as a deep medulla?
What is the result of countercurrent multiplier?
What is the normal pH range?
Respiratory acidosis and alkalosis are caused by what?
altered levels of PaCO2
What are the causes of respiratory acidosis?
What are the causes of respiratory alkalosis?
What is metabolic acidosis?
Metabolic acidosis is a condition in which tissue and blood pH is abnormally low due to an increase in nonvolatile acids.
What are the causes metabolic acidosis?
What are the causes of metabolic alkalosis?
What is uncompensated, partially compensated, fully compensated, anion gap?
- Uncompensated: The body has not made any changes to counteract the pH disturbance
- Partially compensated: The body has made changes to counteract the pH disturbance, but the disturbance is still not corrected.
- Fully compensated: The body has made changes to counteract and correct the pH disturbance.
- The anion gap is a useful concept, especially when trying to determine the possible cause of metabolic acidosis.
