Kaplan Prep - Renal System (Kidneys) - problem set 3 Flashcards
For urine formation to occur what three processes must take place?
For urine formation to occur, three processes must take place:
filtration,
reabsorption
and secretion.
In urine formation, where does the processes of filtration take place?
In the glomerulus (in the renal corpuscle)
In urine formation, where do the processes of reabsorption, and secretion occur?
Reabsorption and secretion occur in the tubular section
What structures are part of the tubular section of the kidney?
Proximal Convoluted Tubule, Loop of Henle, Distal Convoluted Tubule, Collecting Ducts
What TYPE of filtration takes place in the glomerulus?
Filtration in the glomerulus is mechanical filtration.
What is another way of saying “mechanical filtration”?
filtration by size
Does “mechanical filtration” require ATP?
No
Why can’t the red blood cells pass through the very porous capillary membrane?
They are too big
Approximately how many nanometers (nm) is an RBC?
~600 nm
Approximately how many nanometers (nm) is Albumin?
~7 nm
Approximately how many nonometers (nm) is glucose?
~0.6 nm
What is Albumin?
The most abundant blood plasma protein. It is produced by the liver. One of it’s functions is maintaining colloid osmotic pressure (COP), helping keep fluid from leaking into tissue.
How is filtration regulated in the glomerulus?
by regulating PRESSURE and VARYING the pressure
What are the two TYPES of pressure acting in the glomerulus?
FLUID pressure and Blood Colloid Osmotic Pressure (COP)
What another name for Fluid Pressure (FP)?
Hydrostatic Pressure (HP)
What is the normal (constant) range of COP pressure?
25 mmHg - 32 mmHg
What does GFR stand for?
Glomerular Filtration Rate
What is the average GFR?
~ 120 - 125 milliliters per minute
What are the three controls over how fast “Glomerular Filtration Rate” happens?
- Auto regulation
- Nervous System (Sympathetic)
- Hormonal
About how many times a day is the blood filtered by the kidneys?
The kidneys filter the entire plasma volume about 60 times each day
What volume of filtrate is produced by the kidneys per day?
About 47 gallons of glomerular filtrate is produced
How much urine is produced per day?
About 0.5 gallon of urine is produced.
What materials are prevented from moving through the filtration that occurs in the glomerulus and why?
The capillary pores prevent passage of blood cells and blood proteins which maintains the osmotic pressure of glomerular blood.
The glomerular filtration rate (GFR) is very high at 180 L/day. What 3 factors make this high filtration rate possible?
The high glomerular filtration rate (GFR) is due to (1) the huge surface area of glomerular capillaries, (2) the large membrane permeability and (3) the high filtration pressure.
Why must the glomerular filtration rate (GFR), which is very high at 180/day, be maintained?
The GFR must be maintained to allow adequate reabsorption of water and other needed substances from the filtrate and filtration of wastes since if flow is very rapid, needed substances cannot be adequately reabsorbed and if flow is too slow nearly all of it is reabsorbed, including most of the wastes that are normally disposed of.
What system causes renal autoregulation (in the context of renal flow regulation)?
Renal autoregulation is caused by the kidney
What system causes nervous system control(in the context of renal flow regulation)?
sympathetic nervous system
What system causes nervous system control(in the context of renal flow regulation)?
sympathetic nervous system
What cells kick off the RAAS system hormonal control? (to affect regulation of renal flow)?
the juxtaglomerular cells of the kidney produce and release renin.
Explain why tubular reabsorption must take place
Reabsorption is necessary otherwise the entire plasma would be drained away as urine within an hour.
Explain how substances like glucose and Na+ ion are reabsorbed (during tubular reabsorption)
Substances like glucose and Na+ ion move by diffusion into tubule cells, then are actively carried into the interstitial space and then move passively into the peritubular capillaries.
How are substances like water absorbed (during tubular reabsorption)?
Water moves passively into the peritubular capillaries by osmosis because of the difference in osmotic pressure established by the movement of Na+ ions
Where does the greatest amount of renal tubular reabsorption occur
The greatest amount of renal tubular reabsorption occurs in the proximal convoluted tubule cells.
How much water and Na+ ion are absorbed in the proximal convoluted tubule?
About 65% of the Na+ and 65% of the water are absorbed there.
Describe the reabsorption characteristics of the descending and ascending limbs of the loop of Henle.
NaCl can leave the ascending limb but not the descending limb and water can leave the descending limb but not the ascending limb.
How much water and Na+ ion are absorbed in the loop of Henle?
In the loop of Henle, another 25% of the Na+ and 15% of the water are reabsorbed.
Describe how ADH works
Antidiuretic hormone (ADH), secreted by the posterior pituitary, causes the collecting ducts to reabsorb more water.
Describe how Aldosterone works
Aldosterone increases the Na+ reabsorption by the distal convoluted tubules and collecting ducts and at the same time causes increased water reabsorption.
How much water and Na+ ion are absorbed in the distal convoluted tubule and collecting ducts?
Hormonally regulated reabsorption in the distal convoluted tubule or the collecting ducts can reclaim nearly all water and Na+ ion.
Why is tubular secretion necessary?
Tubular secretion is necessary to remove certain substances.
What is an example of a type of ion that the system might have an excessive amount of that might need to be secreteted?
excessive potassium ions
How might it be that certain substances that are actually unwanted and need to be excreted ended up getting reabsorbed in the first place?
they might have gotten reabsorbed through passive passive processes
What are two examples of substances that might need to be secreted by tubular secretion in order to control blood pH?
HCO3- and H+
What is an example of a type of drug that might need to be removed using tubular secretion?
penicillin
When tubular secretion is occurring where are the substances moving TO?
the substances are being moved (secreted) into the filtrate.
When tubular secretion is occuring, where are the substances moving FROM?
moving from the blood of the peritubular capill
aries
What system causes hormonal control?
the endocrine system
