The tunica externia consists of mainly collagen fibres
Tunica externia
The walls are mainly made out of collagen
because blood is pumped at low pressure
Tunica media is very thin and contains some smooth muscle and elastic fibres
Tunica media
This is much less elastic due to the less in
pressure to pump blood. Unlike Arteries, the
tunica media needs to be thicker.
Lumen is large so there is less resistance to blood flow
Lumen
Blood is mainly deoxynated apart from the pulmonary vein
Cappillieries
These are only one cell thick, the lumen is just enough for the RBC to pass.
Cappillieries make sure that there is exchange
between materials between the blood and the
tissues
The wall is made out of endothelium
Blood changes to oxynated to deoxynated (except the lungs)
Arteries and Arterioles
Arteries have a much bigger tunica
externa which is made out of collagen
fibres and some elastic fibres
Contains elastic fibres because arteries pump blood away
from the heart and to the lungs at high pressures
Tunica externia
The tunica media is much more thicker
and contains smooth muscle tissue,
collagen fibres, and elastic fibres
Tunica media
The tunica intima, contains endothelium
which is a very smooth single layer of cells
Tunica intima
Blood is mainly oxynated apart from the pulmonary artery
Arteries expand during systole and relax after diasytole
Red blood cell/Erythrocytes
Red blood cells have no nucleus, they are also biconcave in shape which
makes them easier to flow through blood flow.
Red blood cells have haemoglobin which combines to oxygen to produce oxyhaemoglobin
They combine when there are areas with high concentration of oxygen and release it when there
are areas of low concentration e.g picks up oxygen in the lungs and releases it into the tissues
Function of the Erythrocytes
They have a large surface area : volume ratio which
means that the surface area is large so the RBC can
fit much more haemoglobin onto it.
They are small in size which means that they can rapidly
pick up oxgen because RBC's are close to the surface
Containing no nucleus means that there is much room for
more haemoglobin to fit onto the cell.
Tissue Fluid
Blood Plasma
Blood plasma is like tissue fluid however contains a lot more proteins, placelets, and
leucocytes(WBC)