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Maintaining a Balance
Topic 10: Structure and Function of Arteries, Capillaries and
Veins
Biology in Focus, HSC Course
DOT POINT
 Compare the structure of arteries, capillaries and veins in
relation to their function
Transport Vessels
The transport or vascular system
in mammals consists of the
heart, blood vessels and lymph
vessels, as well as the fluids
transported in them - blood and
lymph. These systems are
interrelated and it is important
to understand their interactive
functioning.
cikgurozaini.blogspot.com
Transport Vessels
Transport vessels all have some structural features in common:
They are long, hollow structures that consist of a lumen (cavity),
surrounded by a wall.
cikgurozaini.blogspot.com
Blood and Blood Vessels
-Blood is transported by
arteries away from the heart,
towards the tissues of the body.
-Blood is transported by veins
from the tissues in the body
back to the heart.
cikgurozaini.blogspot.com
Blood and Blood Vessels
Capillaries are tiny, thin-walled blood vessels in the tissues of
the body that carry blood very close to the cells, linking the
arteries and veins. Arteries branch to form arterioles (tiny
arteries) that lead directly into capillary networks in the tissues.
en.wikipedia.org
Blood and Blood Vessels
Blood flows from the capillary networks of tissues into venules
which join up to form veins so that blood can be returned to the
heart. Fluids that seep out of capillaries into the surrounding
tissues are returned to the bloodstream by the lymphatic system.
medical-dictionary.thefreedictionary.com
Lymph and Lymphatic Vessels
The lymphatic system is part of
the circulatory system made up
of a network of vessels. In the
tissues of the body, water and
dissolved substances diffuse out
of the capillaries and bathe the
tissues, as tissue fluid or
interstitial fluid. This occurs
partly as a result of blood
pressure and partly due to the
osmotic pressure of the tissues.
en.wikipedia.org
Lymph and Lymphatic Vessels
Some tissue fluid returns to the
capillaries, but a large amount
does not. Excess accumulation
of fluid in the tissues is
overcome by the presence of
tiny lymphatic vessels which
penetrate deep into the body.
The fluid is absorbed into the
lymphatic vessels and, together
with the other substances there,
and form the fluid called
lymph.
medical-dictionary.thefreedictionary.com
Lymph and Lymphatic Vessels
Lymph is a milky white fluid which contains dissolved substances,
a large number of white blood cells (called lymphocytes) and
chylomicrons. Chylomicrons are the end product of lymph
digestion which drain into the lymphatic vessels from the lacteals
in the small intestines.
en.wikipedia.org
Lymph and Lymphatic Vessels
The lymph flows in one direction – from the tissues towards the
heart. The flow is brought about partly by contractions if the
muscles of the body through which the lymph vessels pass and
partly by the pressure of the lymph accumulation in the tissues.
lymphnotes.com
Lymph and Lymphatic Vessels
The lymphatic vessels from all
regions of the body eventually
join up to form two main
lymphatic channels and, in the
regions of the shoulders, these
drain into the venous system
where the lymph fluid re-joins
the blood.
The lymphatic system therefore
provides a link between the
tissue fluids in the deeper cells
of the body and the blood
plasma.
mayoclinic.com
Lymph and Lymphatic Vessels
The lymphatic system also
plays a role in the defence of
the body. We all have lymph
nodes which are small, oval
bodies at intervals along the
course of the vessels. They are
the sites of lymphocyte
production and they also filter
out and destroy bacteria.Your
tonsils are examples of lymph
nodes.
healthcaredir.com
Lymph and Lymphatic Vessels
The interaction between the blood and lymphatic systems is
important in the transport of nutrients to and wastes from the
tissues of the body.
remedialmassageforhealth.com
Arteries, Capillaries and Veins
The function of arteries and veins is to carry blood over relatively
long distances, from one organ to another. Capillaries form
branching networks to carry blood over relatively short distances
within organs.
scientificpsychic.com
Arteries, Capillaries and Veins
Arteries, Veins and
Capillaries have similar
basic structure, but they
differ in terms of the
layers of tissues that
make up the wall of each
and the size of the lumen,
so that each vessel is
structurally modified to
best carry out its specific
transport function.
mysciencevirtualclass.blogspot.com
Arteries
The function of arteries is to carry blood away from the heart to
the various parts of the body. Since the blood is pumped out of
the heart in regular bursts under high pressure, the walls if the
arteries are thicker than those of veins, to withstand the force.
hwcrc.org
Arteries
Major arteries close to the heart have thick layers of smooth
muscle in their walls to allow them to withstand the increase in
blood pressure as blood is pumped from the heart.
cikgurozaini.blogspot.com
Arteries
The smooth muscle also
functions to adjust the diameter
of the lumen and therefore
regulates blood flow in the
arteries. When the smooth
muscle contracts, the size of the
lumen is decreased
(vasoconstriction) and this
slows down blood flow. When
the smooth muscle relaxes
(vasodilation) allows blood flow
to increase.
daniellefanfair.com
Arteries
The walls of arteries also have a large proportion of elastic fibres
in both the inner layer, surrounding the endothelium, and in the
middle layer, surrounding the smooth muscle. This increased
elasticity enables the arteries to expand (stretch) to
accommodate the increased volume of blood pumped with each
heartbeat.
cikgurozaini.blogspot.com
Arteries
When the heart relaxes, the elastic fibres allow the arteries to
recoil, returning to their original diameter, squeezing the blood
forward and propelling it along, ensuring a continuous flow in
one direction.
vetmed.vt.edu
Arteries
In certain parts of the body where large arteries are near the
surface of the skin, the expansion and recoil of the arteries can be
felt by a pulse.You are feeling the arteries response to increased
pressure with each heartbeat, followed by a decrease in pressure.
The force that blood exerts against the walls of the blood vessels
in which it is contained is called blood pressure.
en.wikipedia.org
Veins
Blood enters veins from the capillary networks of tissues, via
venuels. Structurally, veins have walls that are thinner than those
of arteries, since the blood that they receive flows in under lower
pressure. Its not pumped in.
beltina.org
Veins
The walls have very few elastic fibres as no stretch and recoil is
necessary and the smooth muscle layer is much thinner. The
lumen also has a wider diameter, for easy flow of blood.
leavingbio.net
Veins
Since blood seeps into veins and is not pumped, two mechanisms
prevent the backflow of blood. This is especially important in
veins such as those in the legs, where blood flows against the
force of gravity.
muscleandstrength.com
Veins
The first is many veins are situated between large groups of
muscles (particularly in the legs and arms) and their relatively
thin walls allow them to be easily compressed. When the muscles
in the surrounding tissue contract, the veins are compressed and
this propels the blood towards the heart.
leavingbio.net
Veins
And second, veins have valves –
small pocket-like folds of the
endothelium lining the lumen
of veins. These valves occur at
regular intervals along the
inside walls and by their action
they prevent blood from
flowing backwards.
merckmanuals.com
Veins
Valves work like one-way swing doors – they open to allow blood
to flow through in one direction (towards the heart), but the
pressure of blood trying to flow backwards causes them to swing
shut.
veincenterofvirginia.com
Capillaries
Capillaries are extremely tiny, microscopic vessels that bring the
blood into close contact with the tissues, for the exchange of
chemical substances between cells and the bloodstream. The
walls of capillaries consist of only one layer of cells – the
endothelium lining the lumen (cavity) of arteries and veins.
biology.about.com
Capillaries
Capillaries have no other layers in their walls. Diffusion is a fairly
slow, passive process and so the structure of capillaries is suited
to slowing down the flow of blood. To maximise exchange of
substances between the blood and cells of the body, capillaries
have:
 Thin walls
 A small lumen
nature.com
Capillaries
Thin walls allow for the
efficient diffusion of substances,
so that they do not have far to
travel between the blood and
body.
A small lumen (only slightly
larger than the diameter of red
blood cells) to force the red
blood cells to pass through in
single file, slowing down their
flow and increasing their
exposed surface area for gaseous
exchange.
faculty.stcc.edu
Capillaries
Capillaries form an expansive network to spread blood flow over
a large surface are so that no cells are far from the blood supply.
fineartamerica.com
Activity/Homework
Students to complete:
-10.1.2 Relating Structure to Function Activity