* actually, this is one of my post in our medic's group, tmd.. juz wanna share in this blog because i as a muslim medical student really want to relate my studying with how amazing the creation of Allah. and this is one of the article that relates it, maybe.. but, only medical student will understand this, sorry eh.. :P
Bismillah.. nak share skit di pagi hari.. cer teka, sy nak share apa?
Physio bab 28..
just want to practice my english writing here, so, sorry for the broken2 one.. and most of these are my own sentences, so if it differs from textbook, just correct it in comment and take the textbook's one..
mostly, this chapter is about concentration and dilution of urine.
one of the topic that made me love studying this system, look at how amazing the God creation is..
why we have to dilute and concentrate urine?
as we want to maintain our plasma osmolarity at about 300 mOsm/L,
- we have to dilute our urine when we drink too much water, such as in competition of drinking water
- we have to concentrate our urine when we don't have water to drink such as lost in desert maybe.
So, you want to know how the body regulate the plasma osmolarity? But we have to know the term and the fact first:
max urine concentration: 1200-1400 mOsm/L
this mean that when we drink little of water, our body can concentrate up to 1200 mOsm/L
min urine concentration: 50-70 mOsm/L
this is the most dilute urine we can produce
obligatory solute excretion: 600 mOsm/day
this means that our body MUST excrete 600 mOsm every day, it composed of salt, urea etc. so the minimum volume of water NEEDED to excrete this obligate amount, we call it:
obligatory urine volume: the min urine volume in which the excreted solute can be dissolved and excreted. to calculate it:
obligatory solute excretion / max urine concentration
First, i want to tell difference between healthy and people with chronic renal failure.
Obligatory urine volume depends on the maximum concentrating ability of kidney,
So, healthy people can concentrate 1200mOsm/L, so every day at least he must urinate:
600 / 1200 = 0.5 L/day
However, patient with kidney failure lost the ability to concentrate urine, he can concentrate only 300 mOsml/L which is equal to plasma osmolarity itself, so just calculate how much min volume he must urinate every day:
600/300= 2 L/day , so by now, you know how renal failure patient get oligouria.
Just want to make you think how cactus and desert's animals can conserve water? Try to think before you get the answer..
It's because they can concentrate their waste product up to very high concentration, maybe they can just use water produced by metabolism in other to excrete their waste product..
There's some interesting story about how shipwrecked people can die out of dehydration, find this in Guyton.
Now, let see at very complex mechanism how renal can concentrate and dilute urine. Doc said that it is easy to dilute urine but difficult to concentrate it, no wonder la our difference with renal failure ptn also on concentrating it, right?
Mechanism to dilute urine:
First, we look at every segment's reabsorption and osmolarity:
proximal tubule: reabsorption of water and solute = isoosmotic (300 mOsm/L)
descending loop of henle: reabsorption of water but no active pump of Na = increase osmolarity
ascending loop of henle: no reabsorption of water because water impermeability, but powerful active transport of Na outside the tubule= osmolarity decrease
early distal tubule: still no reabsorption of water, water become more and more dilute
late distal tubule: water reabsorption depends on ADH
cortical collecting tubule: water reabsorption depends on ADH
medullary collecting tubule: still water reabsorption depends on ADH
so, how to DILUTE urine, just decrease the ADH, so less or no water reabsorbed at distal part and collecting tubule.
so, now what about concentrating it? just incrase ADH, so that water will be reabsorbed more? not as simple as that..
Ok, lets see the overview how we can concentrate water..
Concentrating water need :
1. HIGH ADH
2. MEDULLARY HYPEROSMOLAR INTERSTITIUM
Why we need both of that?
ADH is needed in other to make pore at tubule, make water become permeable ( can check this out on prev chapter )
Medullary hyperosmolar interstitium needed in other to create gradient between tubule and interstitium, so that water can move from tubule to more hyperosmotic area which is medullary interstitium and next to blood vessel.
Just imagine, if the osmoalarity between two area is equal, there will no net movement of water right even with ADH..
So, lets see the MOST complicated part in this lecture is HOW RENALS CREATE AND MAINTAIN HYPEROSMOLAR INTERSTITIUM:
Creating it:
1. countercurrent multiplier system
2. urea recycling
Maintaining it:
1. vasa recta countercurrent exchanger system
Ok, lets see one by one this very important mechanism:
COUNTERCURRENT MULTIPLIER SYSTEM: just check out this video in other to understand it..
http://www.colorado.edu/intphys/Class/IPHY3430-200/countercurrent_ct.swf
UREA RECYCLING: just hear the explanation here..
http://www.wiley.com/college/jenkins/0470227583/animations/ur3a/screen_2_3.swf
In the begining, i myself really wonder why we need to recycling urea again and again and just excrete about 20% of it as urine,, because urea is just a waste product right?? but after i read and think about it, urea contribute about 50 % of hyperosmolarity at medullary interstitium.. how great the role of urea recycling here right at concentrating urine..
Just want to stress here doctor's point in class on how ADH mediate the urea recycling:
1. ADH will reabsorbed water, and this will concentrate the urea inside tubule.. and allowing it to passively diffuse
2. ADH activate urea transporter 3
VASA RECTA COUNTERCURRENT EXCHANGER:
ok, just take a look at this picture:
Just want to share how doc najeeb explain this thing.
How vasa recta can carry this function on maintaining the hyperosmolarity:
1. Because of the blood flow is low.. just imagine, if we want to clear a dirty place we will use a pipe and try to increase its velocity but press on the tip.. just like this blood vessel, if the blood flow is high it will wash out all the solute and destry the osmolarity in the interstitium.. but just remember, the tubule still need nutrient and oxygen supplier, so Allah created this vasa recta that has low blood flow..
2. And Allah also created its shape as loops to enable the exchange to occur..
Just imagine, if a greedy but dumb thief entered a house. As he entered he took all the materials he can look at.
Just imagine how big his bag was and how full his hands were as he reached the room which contains much more precious things, jewels and so on.
As he went out of the house, he found nothing more in his hand as he released one by one things because it was so many heavy things..
hehe, even this story is not logical but just accept it..
Same goes to the exchanger, as the blood enter the solute will diffuse into the blood vessel, but when the conc gradient in vasa recta increase it will release back the sodium as it move up the vessel..
now, say alhamdulillah for this wonderful creation of your body.. just imagine is the vasa recta created just straight, no loop.. :')
just want to share these great creation of Allah.. lets open our eyes, look at Allah's creation inside our body..
satu hari bersembang dgn bbrp kawan..
A: eh, apa subjek yg ko suka ye?
B: Aku suka patho, sbb dia mcm praktikal skit.. belajar tntg penyakit ptn kte nanti.. tak suka anat, byk kene hafal, susah pulak tu..
A: Eh, anat la best.. sebab lg byk kita discover pasal body kita ni dan lg byk keajaiban2 Allah yg kte temui dalam penciptaan manusia ni..
B: *sentap*
thanks to this really amazing friend that reminded me to seek Allah in studying medicine..
5 days to go.. study with ehsan.. study as if you have to teach other people, will make you study the details with good understanding..
Bismillah.. nak share skit di pagi hari.. cer teka, sy nak share apa?
Physio bab 28..
just want to practice my english writing here, so, sorry for the broken2 one.. and most of these are my own sentences, so if it differs from textbook, just correct it in comment and take the textbook's one..
mostly, this chapter is about concentration and dilution of urine.
one of the topic that made me love studying this system, look at how amazing the God creation is..
why we have to dilute and concentrate urine?
as we want to maintain our plasma osmolarity at about 300 mOsm/L,
- we have to dilute our urine when we drink too much water, such as in competition of drinking water
- we have to concentrate our urine when we don't have water to drink such as lost in desert maybe.
So, you want to know how the body regulate the plasma osmolarity? But we have to know the term and the fact first:
max urine concentration: 1200-1400 mOsm/L
this mean that when we drink little of water, our body can concentrate up to 1200 mOsm/L
min urine concentration: 50-70 mOsm/L
this is the most dilute urine we can produce
obligatory solute excretion: 600 mOsm/day
this means that our body MUST excrete 600 mOsm every day, it composed of salt, urea etc. so the minimum volume of water NEEDED to excrete this obligate amount, we call it:
obligatory urine volume: the min urine volume in which the excreted solute can be dissolved and excreted. to calculate it:
obligatory solute excretion / max urine concentration
First, i want to tell difference between healthy and people with chronic renal failure.
Obligatory urine volume depends on the maximum concentrating ability of kidney,
So, healthy people can concentrate 1200mOsm/L, so every day at least he must urinate:
600 / 1200 = 0.5 L/day
However, patient with kidney failure lost the ability to concentrate urine, he can concentrate only 300 mOsml/L which is equal to plasma osmolarity itself, so just calculate how much min volume he must urinate every day:
600/300= 2 L/day , so by now, you know how renal failure patient get oligouria.
Just want to make you think how cactus and desert's animals can conserve water? Try to think before you get the answer..
It's because they can concentrate their waste product up to very high concentration, maybe they can just use water produced by metabolism in other to excrete their waste product..
There's some interesting story about how shipwrecked people can die out of dehydration, find this in Guyton.
Now, let see at very complex mechanism how renal can concentrate and dilute urine. Doc said that it is easy to dilute urine but difficult to concentrate it, no wonder la our difference with renal failure ptn also on concentrating it, right?
Mechanism to dilute urine:
First, we look at every segment's reabsorption and osmolarity:
proximal tubule: reabsorption of water and solute = isoosmotic (300 mOsm/L)
descending loop of henle: reabsorption of water but no active pump of Na = increase osmolarity
ascending loop of henle: no reabsorption of water because water impermeability, but powerful active transport of Na outside the tubule= osmolarity decrease
early distal tubule: still no reabsorption of water, water become more and more dilute
late distal tubule: water reabsorption depends on ADH
cortical collecting tubule: water reabsorption depends on ADH
medullary collecting tubule: still water reabsorption depends on ADH
so, how to DILUTE urine, just decrease the ADH, so less or no water reabsorbed at distal part and collecting tubule.
so, now what about concentrating it? just incrase ADH, so that water will be reabsorbed more? not as simple as that..
Ok, lets see the overview how we can concentrate water..
Concentrating water need :
1. HIGH ADH
2. MEDULLARY HYPEROSMOLAR INTERSTITIUM
Why we need both of that?
ADH is needed in other to make pore at tubule, make water become permeable ( can check this out on prev chapter )
Medullary hyperosmolar interstitium needed in other to create gradient between tubule and interstitium, so that water can move from tubule to more hyperosmotic area which is medullary interstitium and next to blood vessel.
Just imagine, if the osmoalarity between two area is equal, there will no net movement of water right even with ADH..
So, lets see the MOST complicated part in this lecture is HOW RENALS CREATE AND MAINTAIN HYPEROSMOLAR INTERSTITIUM:
Creating it:
1. countercurrent multiplier system
2. urea recycling
Maintaining it:
1. vasa recta countercurrent exchanger system
Ok, lets see one by one this very important mechanism:
COUNTERCURRENT MULTIPLIER SYSTEM: just check out this video in other to understand it..
http://www.colorado.edu/intphys/Class/IPHY3430-200/countercurrent_ct.swf
UREA RECYCLING: just hear the explanation here..
http://www.wiley.com/college/jenkins/0470227583/animations/ur3a/screen_2_3.swf
In the begining, i myself really wonder why we need to recycling urea again and again and just excrete about 20% of it as urine,, because urea is just a waste product right?? but after i read and think about it, urea contribute about 50 % of hyperosmolarity at medullary interstitium.. how great the role of urea recycling here right at concentrating urine..
Just want to stress here doctor's point in class on how ADH mediate the urea recycling:
1. ADH will reabsorbed water, and this will concentrate the urea inside tubule.. and allowing it to passively diffuse
2. ADH activate urea transporter 3
VASA RECTA COUNTERCURRENT EXCHANGER:
ok, just take a look at this picture:
Just want to share how doc najeeb explain this thing.
How vasa recta can carry this function on maintaining the hyperosmolarity:
1. Because of the blood flow is low.. just imagine, if we want to clear a dirty place we will use a pipe and try to increase its velocity but press on the tip.. just like this blood vessel, if the blood flow is high it will wash out all the solute and destry the osmolarity in the interstitium.. but just remember, the tubule still need nutrient and oxygen supplier, so Allah created this vasa recta that has low blood flow..
2. And Allah also created its shape as loops to enable the exchange to occur..
Just imagine, if a greedy but dumb thief entered a house. As he entered he took all the materials he can look at.
Just imagine how big his bag was and how full his hands were as he reached the room which contains much more precious things, jewels and so on.
As he went out of the house, he found nothing more in his hand as he released one by one things because it was so many heavy things..
hehe, even this story is not logical but just accept it..
Same goes to the exchanger, as the blood enter the solute will diffuse into the blood vessel, but when the conc gradient in vasa recta increase it will release back the sodium as it move up the vessel..
now, say alhamdulillah for this wonderful creation of your body.. just imagine is the vasa recta created just straight, no loop.. :')
just want to share these great creation of Allah.. lets open our eyes, look at Allah's creation inside our body..
" We have indeed created man in the best of moulds,"
At-Tin [95:4]
At-Tin [95:4]
satu hari bersembang dgn bbrp kawan..
A: eh, apa subjek yg ko suka ye?
B: Aku suka patho, sbb dia mcm praktikal skit.. belajar tntg penyakit ptn kte nanti.. tak suka anat, byk kene hafal, susah pulak tu..
A: Eh, anat la best.. sebab lg byk kita discover pasal body kita ni dan lg byk keajaiban2 Allah yg kte temui dalam penciptaan manusia ni..
B: *sentap*
thanks to this really amazing friend that reminded me to seek Allah in studying medicine..
5 days to go.. study with ehsan.. study as if you have to teach other people, will make you study the details with good understanding..
No comments:
Post a Comment