Transcript PRESENTATION NAME

The Urinary System
The kidneys and the balance of water
We know it’s important…
• We all understand that water is important as it
has a few main functions in the human body:
The kidney
• The kidney is the main organ responsible for
the regulation of water in the body
• However, because water retention is so
essential for the human body, there are other
systems that have either minor or major
involvement:
Maintenance of water balance
• Therefore, becuase it is an essential substance
in the body, the regulation of water levels in
the body is essential to the survival of a
human being
Losing water
• It is, however, worthwhile to note that as
important as water retention is, water loss is
necessary
• While egestion (defecation) in the
gastrointestinal tract is one method by which
we dispose of solid waste,
Urinary purpose
• Therefore, the urinary system carries out
three main purposes:
Linked to blood
• Therefore, it is important to note that the
urinary system is linked to the cardiovascular
system
• Water transport between these two systems
occur through OSMOSIS
Not just water
• Before continuing, it is also important to note
how important the role of other substances
dissolved in blood plasma is to the process of
water filtration in the kidney
• Other substances such as
Salt is a key player
• It is important to note that out of all of these, salt
is the most important accessory substance in
fluid regulation
• Mainly this refers to NaCl, but other dissolved
ions from salts such as potassium play a role
• Although consumption of excess salt has earned a
bad rep for causing health problems, it is
worthwhile to note that the opposite problem,
HYPONATREMIA can be just as harmful to the
human body
Gross anatomical structure
Gross anatomical structure
The Nephron
• The kidney is the organ – however, the
functional unit within the kidney that carries
out filtration is known as the NEPHRON
• The nephrons in the kidney are composed of:
The nephron
Blood supply
• The renal artery feeds blood into the kidney
• This blood supply provides the kidney with the
necessary blood flow for function, however,
Bowman’s capsule
Filtration
• Water from the blood plasma filters into the
glomerulus via blood pressure in the capillaries
• Remember that capillaries have FENESTRAE or small
holes in them
• As the heart beats, it produces pressure; this forces
water out of the fenestrae
Losing stuff
• So the first process of filtration results in important
substances such as water and salts being removed
from the blood plasma
• Therefore, the kidney must be able to retrieve these
substances and control their removal
A word on osmosis
• Osmosis will cause water to move towards
area of low water concentration (though
sometimes we don’t think about it this way –
since water is usually a solute)
• The easiest way to think about this is:
Overview of kidney function
• http://health.howstuffworks.com/humanbody/systems/kidney-urinary/adam200032.htm
• http://www.aboutkidshealth.ca/HowTheBody
Works/UrineFormation.aspx?articleID=10245&categoryID=
XK-nh1-04
• Check out this tutorial at home:
• http://www.aboutkidshealth.ca/En/HowTheB
odyWorks/KidneysandBladderOverview/TheKi
dneysOverview/Pages/UrineFormation.aspx
Renal tubule
• More than just a pipe, the renal tubule is lined
with cells that can move substances across
concentration gradients
• The renal tubule is divided into 4 major parts
that cross the 3 different layers of the kidney:
Some vocabulary
• Absorption/Reabsorption:
• Secretion:
The basics
• What you should notice is a net movement of water
and NaCl out of the renal tubule
• The absorption of water is facilitated by the
absorption of NaCl
• This is the idea behind electrolyte drinks: the body
is more efficient at reabsorbing water if it has salt to
help it do so!
Physiology
• The ascending loop of Henle is impervious to water – this means
that no water is lost from this loop –
• The descending limb is more permeable to water and less
permeable to salt
• Since the ascending limb doesn’t allow for water secretion and
only salt secretion, this creates a more hypotonic fluid entering
into the collecting duct –
• The collecting duct is generally impervious to water, but can
increase its permeability (hormones/drugs can change this)
• Water, NaCl and other ions move out of proximal tubule
• As water moves into descending loop of Henle into the outer
medulla, the fluid is low in solutes due to loss of ions, so
water moves out of the tube into the salty interior of the
medulla
• As the fluid in the descending loop of Henle enters the loop
of Henle in the inner medulla, the fluid is now higher in salt –
so NaCl passively moves out of the loop of Henle
• As the fluid moves up into the ascending loop of Henle, salt is
actively pumped out the tubule into the outer medulla,
helping to create the salty environment that drives water
reabsorption in the descending loop
• In the distal tubule, salt is actively pumped out allowing water
to follow it
• In the collecting duct that passes through the outer medulla,
salt is actively pumped out leaving the fluid entering the inner
medulla to be less salty – creating conditions for the last
reabsorption of water before the fluid leaves the collecting
duct and drains into the ureter for excretion
Structure
Absorbs
Secretes
Proximal tubule
Via active transport:
NaCl, nutrients such
as glucose
Via passive transport:
Bicaronate, K+, water
Via active transport:
H+
Via passive transport:
Ammonia
Descending loop of Henle
Via passive transport:
Water
Thin segment of ascending loop
of Henle in outer medulla
Via passive transport:
NaCl
Thick segment of ascending loop
of Henle in inner medulla
Via active transport:
NaCl
Distal tubule
Via active transport: Via active transport:
NaCl, bicarbonate
H+, K+
Via passive transport:
water
Collecting duct in inner medulla
Via active transport:
NaCl
Via passive transport:
Urea, water
Control
• The cells in certain parts of the renal tubule
are responsive to hormones and drugs that
can control the rate of absorption of water
and salt
Fluid regulation in a small range
• One center of fluid control is initiated by your brain
• Arteries carrying blood to your brain must pass
through your hypothalamus
• (Caffeine is a DIURETIC – does the opposite –
increases water secretion; therefore coffee = need
to pee)
HIGH WATER, LOW SALT = low osmotic pressure (low plasma-osmality)
LOW WATER, HIGH SALT = high osmotic pressure (high plasma-osmality)
Fluid regulation in a larger
range
• More serious responses are needed for rapid
changes in blood pressure
• For example, severe bleeding is a good
example of this
• Losing blood means a severe drop in blood
volume which can lead to a severe drop in
blood pressure
JGA (Juxtoglomerular
Apparatus)
• The JGA is composed of the glomerulus and the
blood vessels that feed it
• The JGA can sense changes in blood pressure
The adrenal gland
• The adrenal gland then secretes
ALDOSTERONE in response to angiotensin II
Decrease
in blood
pressure
sensed
by the
JGA