Anatomy & Physiology Urinary System

Hi and welcome back to www.educator.com.0000

This is the lesson on the urinary system.0002

The function of the urinary system is not just as simple as making urine and getting rid of it.0006

That is the primary function, it is the removal of metabolic waste that is really what urine contains.0011

Solid waste of course would be in the fecal matter which is part of the digestive system in terms of getting rid of it.0017

But here is all about filtering blood and getting rid of metabolic waste out of your bodily fluids.0023

In addition to that you have the regulation of blood volume and blood pressure.0029

Your kidneys actually secrete hormones in response to how much blood is flowing through them.0034

The pressure and lack of fluid or too much fluid and that has an effect on your blood pressure and blood volume.0040

It also regulates plasma concentrations of various electrolytes various minerals like sodium and potassium, chloride etc.0048

Because it is going to get rid of more of those or less of those through urine depending on how much you have.0056

It also helps to stabilize blood PH.0063

In addition getting to rid of stuff like sodium or hang onto it, hanging onto H+ or getting rid of H+ these hydrogen ions that has an effect on PH.0066

In addition bicarbonate ions which has an effect on the alkaline levels.0078

If you know about PH hanging onto this would actually make the blood slightly more acidic.0084

Getting rid of this would make the blood slightly more basic.0091

The normal PH for blood in the human body is 7.4 on the PH scale that is slightly basic.0094

It also conserves valuable nutrients.0101

You want to hang on to certain things in your bloodstream and not get rid of them and that comes down to kidney function.0104

We look at the different organs and tissues in the urinary system, there are 4 main players.0110

Here is a little drawing of it.0117

You got the kidneys of course they look like kidney beans.0118

This is the left kidney.0121

This is the right kidney.0122

The left kidney is ever so slightly higher.0123

The right kidney is a little bit lower because of the liver can hang down over it.0126

You know it is normal to be born with 2 kidneys.0131

There are the ureters which are these tubes that take recently made urine out of the kidneys0135

to a temporary storage spot known as the urinary bladder.0142

Just calling it the bladder is not sufficient in anatomy because there is also the gallbladder.0145

You want to specify that this is the urinary bladder.0150

And then the urethra is that tube that takes urine out of the body.0154

It is longer in males and shorter in females.0160

I will discuss that more later.0164

When we look at the kidneys, these amazing organs that actually make urine.0167

You do have two kidneys on either side of the spine between the thoracic vertebrae at the bottom of the thoracic curvature0174

so number 12 where your last ridge are found and down to about the third lumbar vertebra0183

which means that their only partially covered by a rib cage.0190

Just the top portion has some ribs going just posterior to it.0195

Your kidneys are very much a posterior organ.0201

There is this term kidney shots when someone hits you right back there right at the rib cage0205

and that kind of impact can damage kidneys.0210

It happens in combat sports often.0213

The left kidney is slightly superior or higher on to the right one.0215

They are held in place by surrounding connective tissue and that surrounding connective tissue includes the peritoneum.0220

It is a nice wrapping around abdominal organs that keeps them in place.0229

There is other neighboring organs that help keep them in place.0235

The reddish brown, the reddishness of course because of the high blood flow.0241

There is a lot of blood going to your kidneys every second of the day.0245

They are about 10 cm long, 5 ½ cm wide and about 3 cm thick with a mass of 150 g each.0249

Here are the major parts and let us label these.0256

The renal cortex you see that right here.0260

As with the adrenal glands or any other organ that has the term cortex that means the superficial outer part of it.0265

The renal cortex you are going to see a lot going on in the next few slides in terms of how the filtration process gets started.0272

The renal medulla that is a bit deeper just like with the adrenal medulla.0279

You can see these little areas that kind of a triangular that is really where most of the medulla is going on0290

and those are called renal pyramids because they do look pure, middle, triangular.0299

Here is a renal pyramid.0306

Those makeup most of that medullary layering the kidneys.0310

And this is of course in a cross section.0317

A frontal or coronal section through kidney from the outside you would not see the pyramids.0319

Seeing the medulla you have to cut it.0326

Then you have these two areas the major and minor calyx.0330

Once you have development of urine it comes out of the medullary area into where called minor calyx.0337

All of the minor calyx lead to major calyx.0344

These are the major calyx here and then it goes into was called the renal pelvis.0349

The renal pelvis we used yellow for the calyx.0355

Here is the calyx and then the renal pelvis is this collecting area in here.0361

The hilum is that exit region of the kidney through which the renal pelvis empties into the ureters.0374

Renal pelvis is actually at the medial side of the kidneys because the kidneys point towards each other0385

and renal pelvis feed into the ureters which of course then go into the bladder.0393

Blood flow to kidneys in a healthy individual over 1 liter of blood flows through kidneys each minute of your life.0399

That is incredible to think about because the average person has about 5 liters of blood in their body or 10 pints.0411

It is amazing to think that 20% of that is constantly just there every minute.0417

It is going through your kidneys.0426

They are doing an amazing job of filtering blood.0428

They receive blood through renal arteries.0431

The term renal always applies to the kidneys.0433

Here are these different parts here.0436

The segmental arteries are right here.0439

The segmental arteries actually branch off the major renal artery into the kidney.0444

The interlobar arteries they actually end up going into each little lobe.0451

All of these are interlobar arteries which branch off of the little segmental arteries here.0472

The arcuit arteries finally take blood branching off the interlobar all the way up to the more superficial cortex regions.0479

Here and here and so on.0494

You are going to see those arcuit arteries.0498

Finally those branch off into these tiny little capillary bundles you can call them afferent arterials that lead to the capillary bundles0500

because arterioles branch of arteries slightly smaller and they lead to capillaries.0513

Afferent arterials because they are going to these little filtering regions in the kidney.0519

Those all these up here is afferent arterials get super tiny to the microscopic and the form little capillary bundles called glomerulus.0524

You are going to hear more about those on the next two slides.0534

The afferent arterials those are all in here in the cortex of the kidney.0537

They branch off into millions of little bundles of capillaries.0543

Blood leaves through the renal veins so you have this blue little tube here.0548

The renal veins take blood out of the kidney.0553

The blood that has not been filtered out to make urine and of course blood flows is going to be regulated by nerves that are called renal nerves.0556

Nephrons these are the little filtering units of the kidney.0565

This is where all the action happens.0572

They are microscopic tubular structures in the cortex of the kidneys.0573

This is where they begin that do the filtering of blood and production of urine.0577

Here is a model of what it looks like.0582

Because it is a three dimensional space some of the precise arrangement of where these tubes are kind of crisscrossing can vary0584

and you are going to see that represented in future slides in this lesson0592

where sometimes this little tubule is actually slightly off to the side over here.0593

The name is still the same based on the order in which fluid is moving through there.0600

1.25 million nephrons per kidney.0607

It is amazing to think about that you are going to have 2 ½ million total microscopic little amazing filters getting the job done.0611

First off is the glomerulus.0620

The glomerulus is this little bundle here.0622

It is a bundle of capillaries and they go into this little capsule and then you have certain items, water, ions, etc.0627

Moving across into the capsular space which then leads to these little tubes or tubules.0636

The bowman's capsule, I am going to label glomerulus that is I am going to checkmark there because that is in red.0642

The bowman's capsule named after Dr. Bowman I presume is this right here.0649

Together you can call them together the glomerulus and the capsule around it a renal corpus school.0659

I did not actually write that that but this thing here that little box that is describing the interaction between those two renal corpus school.0666

The bowman’s capsule that leads into this here.0675

That is known as the proximal convoluted tubule.0679

It is twisty and turny proximal to where this began and then later will be more distant.0682

Proximal convoluted tubule or PCT is right here.0690

It leads to the loop of henle.0700

Henle is another scientist I presume.0705

That is what is going on here.0710

This is the loop of henle.0711

There are 2 parts, there is the descending limb of the loop and the ascending limb going back up.0713

The distal convoluted tubule or the DCT is a little more distant and here it is.0720

And eventually we will get to some other parts.0732

This is the collecting tube which has some ducts that is leading to what is called a papillary duct.0735

And of course that is going to lead deeper and deeper in the kidney and by the time you get down here it is urine.0743

That urine collects from all these millions of different nephrons together going out the ureters to the bladder.0749

You are going to hear more about that in a few slides.0756

How do stuff get filtered out of the glomerulus?0760

Glomerulus is a bunch of capillaries.0767

I did not label it the last time so I will tell you here.0770

This is the afferent capillary going in here and to what we call the glomerulus and this would be the afferent one.0773

Just like with nerves going to the brain, out of the brain, afferent neurons and efferent neurons is the same idea here afferent to efferent.0781

They are fenestrated.0790

If you watch the blood vessel lessons previously a fenestra that means window.0793

So instead of solute microscopic particles having to go through the barriers of these capillary wall cells,0798

they do not just go through a little the borders of the cells.0809

They are actually in each cell or little holes essentially.0814

The fenestrated capillaries make it very easy for stuff to quickly pass through that small enough to fit through.0818

Blood pressure forces water because that is smaller and small solutes across the membrane through the fenestrated capillaries0825

and into the capsular space the bowman's capsule here.0832

Some important nutrients like glucose, fatty acids, amino acids and vitamins can also pass through.0837

You do not want to let go of all those things because specially if you are low on them at that moment0844

you need these things in your bloodstream to supply these nutrients to your cells.0848

There is a way to get that stuff back in your bloodstream which we will cover a little bit later.0853

It has to do with them being reabsorbed into the proximal convoluted tubule.0859

The proximal convoluted tubule.0865

Right after we leave the glomerulus and a mixture of water solutes0868

and maybe some of those slightly larger organic compounds are coming through here.0874

Here we are now in the proximal convoluted tubule or PCT it is the first segment of these renal tubular system.0878

And it is lined with simple cuboidal epithelium.0885

If you remember back to the tissues lessons we went over what simple cuboidal epithelium looks like0890

if you were to take a cross section of the PCT you would see kind of cube looking, one cell layer thick cells.0896

They have their own little nucleus.0910

Here is that rounded cuboidal epithelium and this would be called the lumen or the space within this tube.0914

Reabsorption of nutrients happens here.0923

What was meant by that is you have water and solutes coming through here and that is eventually going to be urine.0927

At this point as you go through this tube you can actually suck out because of osmosis and diffusion.0934

Some of the nutrients ions, water, and plasma, proteins that happen to come in there that you want hang onto.0942

As you go through the PCT you are going to have the release of these items into the paratubular fluid.0948

Fluid that is around here.0956

Speaking of which if you look at a highly detailed version of this diagram you would see your venus blood or0959

just capillaries in general that are not part of the glomerular complex just coming around these tubes.0967

You can get that stuff back into your bloodstream once it is exited this tubule.0975

That is good.0981

You do not want to let go of the ions that your low on or plasma proteins that are important to have.0982

Once you have some of the reabsorption occurring through this PCT.0987

You are going to end up in the loop of Henle.0994

And this is actually under exaggerated.0995

It should be much longer.0999

Some of these loops go very deep into the medulla of the kidney.1000

It is found in the medulla area of the kidneys.1006

And like I have mentioned before here is the descending limb and ascending limb of the loop of henle.1008

What is going on here?1014

You actually have active transport occurring in this section.1015

Earlier I have mention how diffusion or osmosis would drive reabsorption here, that is a passive process but active transport can occur here.1020

You are going to pump out some sodium and chloride ions which is going to move water out of the tubule1028

and start to make urine more concentrated.1033

You do not want to let go of too much water in your urine.1036

Water moving out of that loop helps concentrate the tubular fluid as the fluid moves through here.1039

The distal convoluted tubule or DCT which is here and here in kind of this salmon pinkish color.1046

It differs from the PCT that was kind of this purplish because of a small diameter, smaller than the PCT, and lack of micro villi.1058

You actually would find some micro villi associated with that cuboidal epithelial layer.1067

What does the DCT do?1075

It is important for three basic processes.1077

It will actively secrete ions, acids, drugs, and toxins.1079

So your kidneys are actually helping out with getting rid of drugs and toxins.1083

The liver of course plays a big part in that too.1089

Your kidneys are going to help with this and that is great.1091

Selective reabsorption of sodium and calcium ions based on your needs.1095

Depending on your calcium sodium levels in your blood that is going to determine how selected that absorption is.1099

It selectively absorbs water.1105

It is just finalizing what is going to become urine and how much stuff you are going to let go of and how much stuff you are going to hang onto.1107

Finally it is the collecting system.1114

We have talked about this renal corpus school the glomerulus and the bowman’s capsule.1117

Here is that PCT in the loop of Henle, the DCT and then you finally get to what is called the collecting system.1124

There is some final filtration that happens here.1133

Secretion, reabsorption I am going to talk more about what these terms specifically mean on the next slide.1135

Concentrated urine passes through the collecting duct, this purple region which merges into papillary ducts.1141

The papillary ducts get all the different collections, urine collected from the different nephrons in this region.1151

And finally empty it into what is called the minor calyx which I mentioned before.1158

The minor calyx lead to these major calyx is these kind of hallways that lead urine into the renal pelvis.1163

And finely out into the ureters.1171

Summary of urine formations.1175

There are three terms that you need to keep in mind.1178

Three basic processes and the first one is filtration.1180

Filtration that is mainly what is going on with the glomerulus, that collection of capillaries and the bowman's capsule.1183

Blood pressure forces water and some other solutes into the bowman's capsule to start it off.1193

That is the initial filtration from out of your blood then reabsorption.1199

Reabsorption is getting the stuff that you want to hang onto out of that tube so it does escape through your urine.1204

Water and solute are moved from the tubule or the PC T, etc. And going to the paratubular fluid outside of those tubes.1213

Important fluids are reabsorbed into the blood through active transport and osmosis.1224

As blood leaves the kidney that stuff is not going to escape through urine and secretion.1228

Solutes are transported from the paratubular fluid back into the tubule.1236

It is the final chance to get stuff that you do want to get rid of out of that paratubular fluid where stuff is reabsorbed1242

and can go back into the distal part of the tubule then into the collecting system.1251

This is necessary to do because filtration alone is not enough to get unwanted wastes out of the plasma.1259

If we did not have the secretory ability the amount of waste you will get rid of every time1266

you urinate would not be sufficient to maintain homeostasis.1271

Urine is about 95% water sometimes it is 93%, sometimes it is 97%.1274

This is an average for most of the time.1281

What is the other 5% what else is in it?1283

Here are some main players that are going to be found in urine.1287

Urea it is very abundant in terms of how concentrated is urine versus the other things.1290

It comes from the breakdown of amino acids.1296

That is happening constantly in the body.1299

It is a way to get that waste out and amino acids are the building blocks of proteins.1300

A lot of protein stuff going on in terms of decomposition of proteins in your body.1306

You need to remake proteins they do not last forever.1311

Creatinine comes from the breakdown of creatine phosphate which is from the muscles.1314

And if you watch the muscular lessons, you learn about how creatine phosphate can aid with remaking ATP quickly in muscles which is important.1320

Uric acid formed from a cycling of nitrogenous bases of RNA.1328

You are making RNA in your cells constantly throughout life.1332

On so uric acid is going to be from this RNA waste.1336

And what makes urine yellow?1341

Urobilin is a term also some people refer to as urochrome.1344

Urochrome literally means color of urine.1348

Urobilin is a byproduct of the breakdown of bilirubin.1351

That also influences the color of fecal matter but the reason why urine is yellow is when bilirubin is broken down1356

and this comes from the breakdown of red blood cells from heme groups in RBC's.1366

That by itself is yellowish and so it makes up enough of urine to give that yellow color.1371

Sometimes urine is a bit more clear and that typically means the specific concentration of water is as much higher.1377

If water is clear that means you are super hydrated.1383

You have so much water relative to other times that you are getting rid of that water.1387

You have taken so much water when you do not need that much or if your urine is clear that could mean you are drunk1395

because you will learn this in future lesson if you look at the alcohol lesson.1401

The ADH or anti diuretic hormone, that ability to hang on to water in the kidneys is definitely damaged by alcohol intoxication.1405

And the amazing thing about urine is even though some people find it disgusting there is nothing1417

that is actually harmful about in terms of bacteria.1424

It is sterile unless you have a urinary tract infection.1427

Urine itself is sterile when it comes out of the body.1431

There is no bacteria in it.1435

You may have seen survival shows or a list of things to do if you are stranded on a raft1436

in the middle of ocean or in a desert where there is no water or no moisture.1444

If you want to prolong life, one of the things you can do is drink your urine because it is a way to get those fluids back into body just let go of.1448

Eventually if you just keep doing that you are going to stop making urine because you are not introducing a new water in your body1458

but even that is disgusting to think about it can keep you alive for a little longer.1464

But if you urinate in to a bottle and you wait a while, you do not drink it right away but wait for hours.1469

In that bottle that you have just urinated in there was bacteria.1477

And your urine is warm and has nutrients bacteria are going to start eating stuff in there and dividing.1480

If you do leave the urine in the container that can introduce into a bacterial infection your body than your itself is sterile.1486

The ureters that is what is actually taking urine down into the urinary bladder.1494

On it is a pair of muscular tubes here in yellow that connect the kidneys to urine but firmly attached to the posterior wall.1500

Remember the kidneys are found in the back portion of your abdominal region.1508

The tubes are coming out of it are going to be right there.1513

3 tissue layers.1515

Similar to what we saw with digestive system stuff.1517

Inner mucosa that is actually adjacent to the lumen that is where urine is going to be.1521

Muscular layer because you do have to help move along the urine and the outer connective tissue1526

that is going to help keep these tubes anchored to the neighboring tissues and organs.1532

Peristalsis we seen that term before with moving your digestive stuff through.1537

Also through moving to the fallopian tubes ova eggs waiting for sperm.1544

Peristalsis is this wave like muscular contraction actually happens here.1550

It sweeps urine down through these tubes.1553

It is not just gravity taking them down.1556

The sweeping muscular action of peristalsis actually gets urine constantly into the bladder.1558

Your urinary bladder is hollow muscular organ that is a temporary reservoir for urine.1566

It can hold as much as 1 liter of urine.1575

Think one of those soda bottles that is 2 liters, it is a lot of urine.1580

That is when you are really have to go because just as much as 200 ml of urine 20% of that is going to initiate1584

some urinary reflex that is going to start preparing your body for urinary time.1597

The rugae, when we look inside of the urinary bladder you are going to see fold similar to what see inside of the stomach.1602

The rugae are folds as the urinary bladder expands as it holds more urine.1610

Those rugae is obvious because of the stretching mechanism of the bladder.1615

The trigone is this triangular feeding area that urine is going to be collected into and then eventually emptied into the urethra.1619

The borders though between the trigone and urethra is the internal urethral sphincter.1629

Sphincters are always a muscular kind of doorway from one part of the tubular passageway to another and in this case this is involuntary.1634

You do not have voluntary muscular control over this.1646

This is going to open up as stretching happens in the inferior parts of urinary bladder.1649

That need to urinate as the internal urinary sphincter relaxes and lets more urine out.1656

That is when you need to go.1664

The urethra is that final tube leading out of your urinary bladder and out of the body.1667

It extends from the neck of the urinary bladder and finely exits out.1674

Longer in males than in females.1679

You can see from this image here when we take into account the external genitalia of men the urethra can sometimes be1681

8 inches long because you are also including the internal parts prior to entering the penis that empties out of the bladder.1689

If you have taken a cow’s penis their urinary tract is going to be longer.1700

In females it is only about that big because once you come out of the bladder you are going hit the external genitalia of females.1707

The UTI likelihood or urinary tract infection likelihood is actually much more common in females which I will be talking about more later.1715

The external urethral sphincter is what is the final muscular doorway that is not letting urine out.1725

You have voluntary control over that.1732

It is similar to the external anal sphincter.1735

Voluntary control you can hold that to a point but once your bladder is filled up to that 1 liter max1737

and urine is creeping into the urethra that need to let it go.1747

Micturition is the technical term for urinating.1753

Micturition reflex that is going to happen as you get stretching in the bladder.1757

As your neurons stack to the bladder get sense of that stretching it is going to send signal to the brain1763

and then send signal back down onto the voluntary muscles.1770

On when you actually actively urinate.1774

Remember there is involuntary parts too.1777

As the involuntary muscles relax the need to let it go is going to happen.1779

Urinary conditions and disorders.1786

Like I mentioned ago, UTI or urinary tract infection much more common in women because it is typically a bacterial infection.1790

If you think about the urinary tract of females being as this big, the ease for bacteria or ability to take over this region happens much easier.1798

The dividing of the bacteria can quickly invade on that tube.1808

If the tube does is this long it is less likely that the bacteria are going to be able to conquer the tube and cause significant urinary tract infection.1813

It does happen in men and do not get me wrong but this is more common in women.1822

Kidney stones happen in men and women.1826

I have read that they happen slightly more in men.1830

I do not know if that is dietary differences on average but kidney stones can happen for variety of reasons.1833

It is basically a collection of hard deposits in the parts of the kidney overtime.1838

They are so hard and so large relative to the size of the tubules in the kidney that they cannot get completely through the urethra.1847

And they do get backed up.1858

You can see an image here these are actually fragments of kidney stones.1860

It is very tiny and you can see that utmost they are half mm in diameter.1863

They are very tiny but if you think about how tiny the tubules are leading urine out of the body you can see that they get stuck.1872

You need a backup they are very painful.1879

One amazing way that you can get rid of it and that does not require surgery is they have learned that if you projects sound waves1883

at the kidney you can sometimes shatter these kidney stones into tinier bits that can1890

actually be eliminated from the body which is amazing to think about.1896

The technical term is renal calculi.1900

Kidney dialysis is accompanied with renal failure.1905

Somebody's kidneys are not doing the job done of filtering the blood.1909

You will hook them up to machine that basically filters their blood for them.1913

It is as the kidneys also have a lot to do with stimulating the making of red blood cells and other cells in the bone marrow.1918

Drugs that help make red blood cells will also be introduced into the body in addition to the filtering of the blood.1927

This is a temporary solution.1936

Kidney dialysis is not cure for kidney failure.1939

And it will prolong life but the need is for a kidney transplant.1942

You can get a transplant from a donor who is deceased.1947

I have heard that is a 5% effective on average if you get a kidney from a relative who was alive you are likelihood of success1951

and prolong your life is more like 90% in terms of adding years on your life.1960

And being a successful transplant.1965

People who do get kidney transplants they need to take immune suppressing drugs because even if it is your brother1968

that is going to donate one of his kidneys or a cousin, that is not your kidney.1977

And the precise protein makeup on those kidney cells is not close enough to fool your body thinking it is your cells.1983

You actually would have to take immune suppressing drugs to calm down your immune system's response to that tissue introduction1992

and that makes a person who's received a kidney transplant slightly more susceptible to other on illnesses.1998

But it is worth in prolonging your life.2005

Glomerulonephritis, nephritis basically means like infection affecting the nephrons and has to do with the glomerulus coming into that region.2008

The amazing thing about this is the infection is not in the kidney itself but some infection in the body is now affecting the kidney negatively.2018

And the reason why that negative impact happens is with certain infections in the body2028

you are going to get a buildup of a lot of different antibodies in response to antigens.2033

Of that is part of your lymphatic systems ability to beat the illness.2037

That buildup when it gets into the glomerulus that can really affect blood flow out of the glomeruli2042

into those corpus schools and into the bowman’s capsule specifically.2051

This is an infection that is negatively impacted the filtration ability of kidney.2056

Incontinence this is the inability to fully control when you want to urinate.2063

This tends to happen more in older people as they age.2069

The muscular tone in terms of keeping your insight is not as good.2072

Also strokes and Alzheimer’s can have an impact on the ability to control urination.2079

It also can happen in pregnant women too.2086

The babies going to take up a lot of space and in that region of the abdomen.2089

It can only press on the bladder but also stretch out some of those your urethral muscles2095

makes it hard to hang on urine during pregnancy for some.2102

Thank you for watching www.educator.com.2105