Transcript Diffusion and Osmosis in the Human Body

Diffusion and Osmosis in
the Human Body
Circulation, excretion, respiration, and
hormone production.
Homeostasis
 Defined as one of the fundamental
characteristics of all living systems
 It is the tendency of an organism to maintain
a stable, constant internal environment
 Maintained by various organ systems in the
body

An organ system is a group of organs that
works together to perform a common function
Circulatory System
 Made up of heart and various blood vessels filled with
different types of blood cells and platelets
 Flow of blood goes from right side of heart to left side
of hear in the following path…
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right atrium receives deoxygenated blood from the
superior and inferior vena cava  right ventricle
pulmonary artery lungs (capillaries in the lungs
allow for diffusion of CO2 out of blood stream and O2
into bloodstream)  pulmonary vein left atrium 
left ventricle  oxygenated blood pumped to body
from aorta to other arteries
http://www.stjosephaspirin.com/images/stjoseph/pump
blood/
Circulatory System
 Arteries are blood vessels
that flow away from the heart
and typically carry
oxygenated blood… the only
deoxygenated artery is the
pulmonary artery
 Veins are blood vessels that
flow towards the heart and
typically carry deoxygenated
blood and CO2 waste… the
only oxygenated vein is the
pulmonary vein
 Blood vessels get smaller as
they get to areas in the body
where gas exchanges must
be made (lungs, body
tissues, etc.) arteries branch
into arterioles and veins
branch into venules.
Arterioles connect to venules
through capillaries, the
thinnest of all blood vessels.
Through the walls of the
capillaries, gasses are
exchanged through the
process of diffusion.
Capillary beds have a total
surface area in each human
of about 6300 square
meters!
Flow of blood in heart and body
Respiration and Diffusion
 As you saw with your
dissections, respiration depends
heavily on both the circulatory
system and the process of
diffusion.
 The passage of air into your
lungs comes in through the
nasal cavity  trachea 
branching system of bronchial
tubes in each lung  alveoli
 The alveoli are lined with
capillaries so that O2 you
breathe in can enter the
bloodstream and CO2 waste
can leave the blood stream.
 Like most animals, your lungs
are lined with moist mucus
providing a wet environment for
gas exchange
Diffusion and Osmosis… a review
 Why does the CO2 leave the blood stream and O2
enter?... Diffusion
 Diffusion is a form of passive transport (no energy
required) in which substances flow from an area of
high concentration to an area of low concentration.
Substances such as O2 and CO2, are small enough
to pass through the walls of the capillaries.
 A specific type of diffusion is osmosis, or the
movement of water from high to low concentration
due to a change in conditions (think of the eggsperiment)
Diffusion and Osmosis
 Three types of environments can exist outside cells
to effect the internal environment
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Isotonic – concentration of solute is the same both in
and out of cell, water movement is equal
Hypertonic – concentration of solute is greater outside
the cell, water moves to the outside of cell to balance
out (possibly resulting in cell shriveling)
Hypotonic - concentration of solute is lower outside
the cell, water moves into the cell to balance out
(possibly resulting in cell explosion)
Cells in the three environments
Diffusion and osmosis in the kidney
 The main function of the
kidneys is to filter our
blood and remove
waste as urine. Both
kidneys do the same
job. Blood is taken to
the kidneys by the renal
artery and when it is
cleaned, it is returned to
the heart by the renal
vein. The urine is taken
to the bladder by the
ureters.
Diffusion and osmosis in the kidney
 The functional unit of the kidney is the nephron.
They are long coiled tubes that act as filtering units in
the kidney. Each nephron has a capsule (bowman’s
capsule) that is in direct contact with a capillary bed
known as the glomerulus. The glomerulus is the site
of filtration. The capillaries in the glomerulus drain
into more arterioles that continue to help blood get
filtered along the nephron before returning to the
renal vein. Reabsorption takes place between the
nephron tubule and the second capillary bed.
 http://www.youtube.com/watch?v=glu0dzK4dbU&feat
ure=related
Diffusion and Osmosis in the kidney
 Maintaining water balance in the kidney can be
inhibited by a diuretic, a substance that causes the
kidneys to allow excess water loss. A very common
diuretic is caffeine.
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Diuretics block the production of the hormone
vasopressin, an anti-diuretic hormone (ADH). When
the blood has a high concentration of sodium ions, the
hypothalamus and pituitary gland (both in the brain)
triggers the release of ADH which would tell the
kidneys to reabsorb more water to help rehydrate the
body. This is an example of maintaining homeostasis
with the endocrine system. The endocrine system is
made up of glands and cells that release chemical
messengers called hormones, directly into the blood
stream.
Hormones and Homeostasis
 The endocrine system helps maintain homeostasis
with positive and negative feedback.(p235)
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Negative feedback involves constantly adjusting to
correct and abnormal situation.
 Example – production of ADH returns water balance to
normal, ADH production stops
Positive feedback involves processes that must be
completed quickly and the production of some
hormone triggers the production of more
 Example – production of chemical clotting agents at
the site of a cut will trigger the production of more
clotting agents to rapidly clot and minimize blood loss