- In this chapter,
we're looking at the urinary system.
Now, we're talking about the urinary system
and how the urinary system
can help with homeostasis,
but one of the main roles
of the urinary system is excretion.
Excretion: removing waste from the body
or simply excess material.
Things that you have too much of.
So, there's four main systems
that go through excretion.
We have the digestive system.
Anything that is extra
or anything that was a waste product
from the liver is removed.
Now, your digestive system is removing
both solid and liquid waste.
Respiratory system, well,
you're removing excess amounts
of carbon dioxide.
Now, it's important, your body must
have certain levels of carbon dioxide,
but too much becomes a problem.
So, your lungs can go through excretion.
Integumentary system,
well, that's your skin.
Your skin can excrete water.
Your skin regularly excretes salt.
That's why sometimes if you ever get
sweat in your eyes, it stings.
That's the salt.
If he ever get sweat in your mouth,
it tastes a little salty
due to the salt content of the water.
And of course,
we're talking about the urinary system,
so we need to make sure the urinary system
also goes through excretion.
Nitrogenous wastes, excess solutes,
waters, pretty much any liquid waste
or liquid component is removed by the urinary system.
Alright, so here we have a figure.
Let's start with the food intake.
Food and water intake all starts off
in the digestive tract.
Well, if you don't use the food,
then you have to eliminate it,
so it comes out as feces,
but some of it,
the nutrients and water, are absorbed.
They're pulled into your system,
into the circulatory system.
Well, from the circulatory system,
you'll head to the liver, one of the places,
where you try and go through
is creates metabolic products.
Unfortunately, pulling out toxins.
There's things in your food
that you wouldn't really want in your body.
Well, the liver can get rid of waste in two ways.
It can go right back into the digestive tract
or head in the circulatory system
and head out a different way.
Use your skin (mumbles) water and salt.
Your respiratory system,
getting rid of CO2, but picking up oxygen.
Now, if you notice water just popped up.
So, both the respiratory system,
not only are we getting rid of CO2,
we're also getting rid of water.
Think about it this way:
if you've ever been outside on a cool,
cool day or evening,
and you exhale through your mouth
and you see your breath in front of you,
that's showing you that there's water content
in that exhaled breath.
And the yellow parts your urinary system.
That's what we need to focus on.
The urinary system will take excess water,
excess solutes, which could be salt,
could be calcium, and any liquid waste
from the circulatory system,
filter it out, and excrete it.
Eliminating all these components
in a liquid format.
So, excretion really can occur
in many different ways,
but all of these systems
are all working together.
Alright, so let's start with the kidneys.
The kidneys, themselves,
really help to control your body's water level.
Now, they're not the only thing
to control water levels,
but they're one of the major ones,
so anything that you have excess of,
especially excess water,
is excreted.
You can think about it this way:
the more fluid you drink in a day,
the more you urinate.
It's because your body has too much water.
Now, the output varies from person to person.
Depends on environment.
Is it dry, is it
hot?
Depends on person.
Depends on what their activity levels are.
It can go anywhere from two
to 2 1/2 liters a day,
which isn't that much,
all the way up to a liter an hour
if there's a lot of fluid being consumed.
But besides the water,
you're also getting rid of nitrogenous waste.
You have nitrogen from your amino acids.
Remember amino acids
were part of protein.
So, you get rid of these nitrogenous wastes.
You can get rid of other metabolic waste.
Things along the line of sodium,
chloride, potassium, calcium,
even hydrogen.
All these different components
can be removed from your body through your urine.
So, where do you get your water from?
Well, you first off, you drink in water.
The amount of fluid you drink in a day
is usually about a thousand milliliters or a liter.
Some people drink more,
some people drink less,
but even if you think,
"Well, I drink a lot,"
look at how much water comes in the food.
There's more water, on average,
in your food than there is in the water you drink.
Well, think about it this way:
the food you eat,
is it all completely rock solid?
No, there's different textures to it,
different consistencies.
That's all based on the amount
of fluid in the food.
And then metabolic production,
this is dealing with when your body's
going through chemical processes.
Some of these chemical processes
ending up giving off water
as a by-product.
So, all said and done,
on average you're looking
at about 2,500 milliliters per day
or
2.5 liters gained per day.
Water loss?
Well, your water loss
should hopefully match your water gain,
so on average the most fluid loss
comes out of urine.
Makes sense,
but look how much you lose
from just breathing.
The simple act of breathing
allows for evaporative loss
of about 500 milliliters a day
or about half a liter.
You lose about a little through the skin
and of course, you have
to lose some through the feces.
Now, depending on the feces,
the amount changes if it's more solid, more loose.
Evaporative loss, the skin,
the more clothing you have on,
the more it keeps the fluid on the skin
or in the skin.
There are some variables here,
but on average,
ya gain 2,500, you lose
2,500 milliliters per day.
Looking at the kidneys
from an anatomical standpoint,
this could be the primary
or principal organ of a urinary system.
In total, there are four different organs
found in the urinary system.
We're gonna focus on the kidney to start with.
Now, the kidneys have a cortex.
The cortex, as you can see in the figure,
is gonna be the outside area of the kidney.
So, it's really the outer portion.
The outer coating.
But it's not just a shell,
there's actually some depth to it there.
Once you go to the inside,
you get the medulla.
Can you see those things
that almost look like triangles
or guitar picks?
Well, from there inwards,
so the whole inner area,
is the medulla.
Now, in general, cortex medulla:
cortex just means outside,
medulla means inside.
Now, the two kidneys located
more in a posterior,
more towards your back.
They're just towards the bottom of the rib cage.
The kidneys, themselves,
are fed by what's called the renal artery
and blood drains the renal vein.
Well, that renal artery's pretty important
because that's how all the blood
gets in the kidney,
that's how all the blood gets filtered.
Now, the filtration of your blood
occurs in the far right-hand side, you see,
where you have this thing called a nephron.
The nephron will allow the blood
to be filtered and then we'll change up,
absorb, reabsorb, secrete
what's in that filtrate,
what's in that fluid.
The whole point of a nephron
is to make sure
that the urine that's being released
has the proper concentration,
the proper ionic balance.
So, the nephron is going to add
and subtract ions as necessary.
Well, another organ from the urinary system
is the ureter.
The ureter is meant to take the urine
from the kidney, where it's produced,
down to the urinary bladder.
Well, the urinary bladder stores the urine.
Now, I have 600 to 1,000 milliliters.
Again, depends on the person,
depends on the size of bladder,
but everyone knows there's that point
where just the urinary bladder cannot hold
the urine anymore,
so there's a variable here.
And we have the urethra.
The urethra is what allows the urine
to carry it from the urinary bladder
out through an external orifice,
but the urethra has these two sphincters.
Sphincters are a ring of muscle
that allows to be closed or opened, relaxed.
So in this case, these sphincters
are helping to keep the urine
in the urinary bladder
or they open up and allow the urine
to travel through the urethra
out of the body.
Now, the male and female system,
there are some similarities
and some differences here.
Both males and females have kidneys.
No question there.
Both have ureters.
Both have urinary bladders.
The difference comes though,
from the size and position
of the urinary bladder and urethra.
Now, you can see in the female system here,
the urinary bladder, a lot of times,
is a little bit smaller,
more compressed,
due to the presence of the uterus.
But then the pathway from the urinary bladder
out through the urethra,
the female has a much shorter urethra.
The male has a much longer urethra.
And this urethra length
is one of the reasons why,
a lot of times, females
have a greater chance of urinary tract infections.
It's a shorter distance
and it's easier for infection
to get up a short urethra
than a longer urethra.
So, the urethra is a major difference
between male and female,
but still all four organs are present.