Blood and Tissue Fluid
• explain the differences between blood, tissue
fluid and lymph
• describe how tissue fluid is formed from
plasma;
Blood
• Blood is liquid held in our blood vessels
• It consists of:
• Plasma: watery fluid containing dissolved oxygen, carbon
dioxide, salt, glucose, fatty acids, amino acids, hormones and
plasma proteins (proteins made in the liver)
• Cells including red blood cells (erythrocytes) white blood cells
(leucocytes) and platelets
Tissue Fluid
• Similar to blood but does not contain most of the cells found
in blood or any plasma proteins
• Role is to transport oxygen and nutrients from the blood to
the cells and to carry carbon dioxide and other wastes back
to the blood
Task
• Using Biology 1 p77-78, explain what tissue
fluid is and how it is formed
• Complete SAQ 9 & 10 on p78
How Tissue Fluid is Formed?
• When blood is under high pressure in the
artery before it enters the capillary, some
blood fluid is pushed out of the capillaries
though tiny gaps in the capillary wall, this is
called tissue fluid.
• The pressure that the blood is under due to
the contraction of the heart is called
hydrostatic pressure (a bit like fluid pushing up
against the walls of a container)
What is in Tissue Fluid?
• Plasma with dissolved nutrients and oxygen
• The red blood cells, platelets and most of the
white blood cells remain in the blood, with
the plasma proteins. These are too large to fit
through the gaps in the capillary wall
What does tissue fluid do?
• It surrounds the body cells, so exchange of
gases and nutrients can occur across the cell
membranes (plasma membranes)
• This exchange occurs by diffusion and
facilitated diffusion
• Oxygen and nutrients (e.g. glucose) enter the
cells, carbon dioxide and other wastes (e.g.
urea) leave the cells
How does the fluid get back into the
blood?
• The tissue fluid itself has some hydrostatic
pressure and is pushed up against the capillaries
allowing it to re-enter
• The blood and the tissue fluid both contain
solutes (dissolved substances) making their water
potential more negative
• The blood’s water potential is usually more
negative so water tends to move from the tissue
fluid back into the blood by osmosis, down the
water potential gradient
Water potential: the analogy
• Imagine 3 people, all of whom have a bank account with an
overdraft (which means they can borrow money from the
bank and make their account negative)
Whom should give money to whom?
Bill (Student)
-$800
Jim (Computer Designer)
$0
Shelly (Office Worker)
-$475
Water potential: the analogy
• Imagine 3 people, all of whom have a bank account with an
overdraft (which means they can borrow money from the
bank and make their account negative)
Total = -$1275 /3
Bill (Student)
-$425
Jim (Computer Designer)
-$425
Shelly (Office Worker)
-$425
Total Hydrostatic pressure = 4.3-1.1 = 3.2kPa
Effective blood pressure
= 3.2 - 2 = 1.2kPa
Total water potential = -3.3 – (-1.3) = -2kPa
Inside capillary (arterial end) fluid moves out of
capillary as tissue fluid
Arterial
end
Tissue fluid has lower
hydrostatic pressure
High hydrostatic
pressure in capillary
Hydrostatic pressure = 4.3
Tissue fluid has higher
hydrostatic pressure
Water potential = -3.3
Hydrostatic pressure = 1.1
Lower hydrostatic
pressure in capillary
Hydrostatic pressure = 1.6
Water potential = -3.3
Water potential = -1.3
Hydrostatic pressure = 1.1
Water potential = -1.3
Venous
end
Total Hydrostatic pressure = 1.6 -1.1 = 0.5kPa
Effective blood pressure
= 0.5 - 2 = -1.5kPa
Total water potential = -3.3 – (-1.3) = -2kPa
Inside capillary (venous end) fluid moves into
capillary from tissue fluid
Movement back into the blood
stream
• At the venous (vein) end of the capillary, the
blood has lost its hydrostatic pressure. The
combined effect of the hydrostatic pressure in
the tissue fluid and the osmotic force of the
plasma proteins is sufficient to move fluid
back into the capillary.
• It carries with it any dissolved waste
substances, such as carbon dioxide, that have
left the cells
Lymph
Complete the following questions using Biology 1 p78
1.
2.
3.
4.
5.
6.
What determines the amount of fluid leaving the capillaries?
Explain why fluid flows out at the arterial end and in the venous end
What is tissue fluid?
What is lymph?
How does tissue fluid get into the lymphatic system?
What is oedema?
Feature
Blood
Cells
Tissue Fluid
Lymph
Some phagocytic
white blood cells
Proteins
Some proteins
Fats
Some transported
as lipoproteins
Some/none
More than in blood
(absorbed from
lacteals in
intestine-villi)
Glucose
80-120mg per
100ml
More/less
More/less
Amino Acids
More/less
More/less
More/less
Oxygen
More/less
More/less
More/less
Carbon dioxide
Lot/little
More/less
More/less
Feature
Blood
Tissue Fluid
Lymph
Cells
Erythrocytes,
leucocytes and
platelets
Some phagocytic
white blood cells
Lymphocytes
Proteins
Hormones and
plasma proteins
Some hormones,
proteins secreted
by body cells
Some proteins
Fats
Some transported
as lipoproteins
None
More than in blood
(absorbed from
lacteals in
intestine-villi)
Glucose
80-120mg per
100ml
Less (absorbed by
body cells)
Less
Amino Acids
More
Less (absorbed by
body cells)
Less
Oxygen
More
Less (absorbed by
body cells)
Less
Carbon dioxide
Little
More (released by
body cells
More
Carriage of Oxygen
• describe the role of haemoglobin in carrying
oxygen and carbon dioxide;
• describe and explain the significance of the
dissociation curves of adult oxyhaemoglobin
at different carbon dioxide levels (the Bohr
effect);
• explain the significance of the different
affinities of fetal haemoglobin and adult
haemoglobin for oxygen.
Task
• Using Biology 1 p80-84, produce a revision box
for each of the following:
• Haemoglobin dissociation curve
• Carbon dioxide transport in the blood
• The Bohr shift
• Fetal Haemoglobin
You are limited to one piece of A3 paper- you
will need to read the information, decide what
is important, and include it in the box,
highlighting key terms
Haemoglobin Dissociation Curve
Carbon Dioxide Transport
The Bohr Shift
Fetal Haemoglobin