Download tissue fluid

Fluids of the circulatory system
name them
• the fluid derived from blood plasma, that
surrounds the cells in a tissue
Tissue fluid
• the fluid held in the heart, arteries, veins and
capillaries Blood/plasma
• the fluid held in the lymphatic system (lymph
nodes and lacteals)
Lymph
Learning Objectives
• the formation of tissue fluid from plasma
• To include reference to
– hydrostatic pressure,
– oncotic pressure
– an explanation of the differences in the
composition of blood, tissue fluid and lymph.
Tissue fluid
• colourless fluid formed from blood plasma by
pressure filtration through capillary walls
• surrounds all the cells of the body
• Allows exchanges between the blood and cells of
eg oxygen, glucose, carbon dioxide
Tissue fluid contains:
1. Glucose
2. Amino acids
Supplies all
of these to
3. Fatty acids
the tissues
4. Salts
5. Oxygen
So what does the tissue
fluid take away?
1. Carbon dioxide
2. Other waste
products
Pressures at work
• Hydrostatic Pressure
– Pushing fluid out
– arterial end about 4.6KPa
– Venous end about 2.3KPa
• Oncotic Pressure (-3.3KPa)
– Blood proteins pulling fluid back in
• Arterial end: blood is under high
pressure (hydrostatic pressure =
4.6kPa) due to contraction of heart
muscle
• tends to push blood out of capillaries
through tiny gaps in their walls
• (red blood cells, most white blood
cells, platelets and plasma proteins
are too large to leave)
• Venous end: blood has lost hydrostatic pressur
it is now 2.3 kPa.
• Osmotic pressure -3.3kPa exceeds hydrostatic
pressure so this creates a pull which moves fluid
back into capillary
Net outflow?
1.2kPa
Net inflow?
see p183
-1.0kPa
Fluid in or out of the capillary?
• Both hydrostatic and oncotic pressure are
found in the blood vessels and in the tissues.
Their relative balance determines whether
fluid enters or leaves the capillary
• What effect could high blood pressure have on
tissue fluid formation.
Lymph
A milky liquid made up of
1. excess tissue fluid
not all tissue fluid returns to
capillaries about 10% drains
away into lymphatic system
2. fatty substances
absorbed from intestines
3. Lymphocytes
produced in lymph nodes
(swellings along lymphatic
system which filter bacteria
from lymph fluid).
phagocytes engulf and destroy
bacteria.
Human Lymphatic System
Lymphatic system is made up of one way
vessels resembling blood capillaries
Start at tissues, drain excess fluid into
larger vessels
Rejoin blood system in chest cavity
Lymphatic System
Lymphatic problems
Oedema accumulation of
tissue fluid can have
several causes.
Malnutrition
Kwashiorkor
Elephantiasis caused by
roundworm infection in the
lymph nodes
Past paper questions
Jan 2004
Jan 2002
Capillary
Capillary
HP +SP (OP)
4.3kPa +-3.3kPa= 1.0kPa
HP +SP (OP)
1.6kPa +-3.3kPa= -1.7kPa
Tissues
Tissues
HP=SP (OP)
1.1kPa + -1.3kPa = -0.2kPa
HP=SP (OP)
1.1kPa + -1.3kPa = -0.2kPa
Pulling fluid into tissues with
a force of 0.2kPa
Pulling fluid into tissues
with a force of 0.2kPa
Add this to the capillary
outward force of 1.0kPa =
1.2kPa in total
Add this to the capillary
inward pull of -1.7kPa =
-1.5kPa in total
NOTE
You may not be expected to take the hydrostatic and oncotic effect of the tissues
into account but you should be aware of it
Heart
Lymph is moved along the vessels in
three ways:
1. Hydrostatic pressure.
2. Contraction of the body muscles.
3. Valves maintain one way flow
Tasks
• Complete the comparison table for blood,
tissue fluid and lymph