Consists of blood cells in a
watery fluid called plasma
Contains many dissolved
substances such as oxygen, CO2,
salts, glucose, fatty acids, amino
acids, hormones and plasma
proteins
Tissue Fluid
Similar to blood, but does
not contain most of the
cells found in the blood
nor the plasma proteins
Transports oxygen and nutrients
from blood to cells and CO2 and
other wastes back to the blood
Formation
At the arterial end of a
capillary, the blood is under
higher pressure due to the
contraction of the heart muscle
This forces blood fluid and small
molecules out of the capillaries
through tiny gaps in the capillary
wall (pressure filtration)
Platelets, plasma proteins & red blood
cells remain in the blood, as they are too
large to be pushed out through the gaps
The tissue fluid
surrounds the
cells and
exchange of
gases and
nutrients occurs
by diffusion and
facilitated
diffusion
Tissue fluid itself has
some hydrostatic
pressure, which tends to
push the fluid back into
the capillaries
Both blood & tissue fluid
contains some solutes, giving
them a low water potential
The water potential of the tissue fluid is less
negative than that of blood, so water tends to
move back into the blood from the tissue fluid by
osmosis, DOWN the water potential gradient
At the venule end of the capillary, the
blood has lost its hydrostatic pressure so
fluid moves back into the capillary
Lymph
Liquid held within the lymphatic system
Contains same solutes as tissue
fluid, but less oxygen and fewer
nutrients (more CO2 & waste)
Contains fatty materials
that have been absorbed
from the intestines
Formation
Some tissue fluid is drained into
the lymphatic system to prevent
tissues filling up with too much fluid
Lymph vessels are
similar to capillaries
in structure. They
start in the tissues
and drain the excess
fluid into larger
vessels, which
eventually re-join the
blood system in the
subclavian veins and
the vena cava at the
thoracic duct