Blood vessels

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Circulation and Blood
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Blood vessels
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Arteries are defined as blood vessels that carry
blood away from the heart. In most cases they
are delivering oxygenated blood to the body
tissues.
This is the SYSTEMIC CIRCULATION (since it is
going to the systems)
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The pulmonary artery transports deoxygenated
blood from the heart to the lungs.
This is part of the PULMONARY CIRCUIT
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Veins are defined as blood vessels that transport
blood back to the heart.
In the systemic circuit, they transport
deoxygenated blood
In the pulmonary circuit, they transport
oxygenated blood
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Arteries and veins have structural differences as
well. The arterial wall are able to expand and
receive a quantity of blood every time the heart
pumps. Approximately 70 ml is pumped into the
aorta with each contraction of the left
ventricle. The resulting expansion of the walls
of the arteries is detected as the pulse.
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Arteries and veins have structural differences as
well. The veins are relatively thin-walled.
They do not receive any large volumes of blood or
pressures from blood flow.
Veins also contain valves to assist with the
upward movement of blood back to the heart. The
valves prevent back flow.
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The third type of blood vessels are capillaries.
These blood vessels are so tiny that they will
only allow blood cells through them one at a time.
They are also very thin-walled thus helping with
the delivery of materials to and from cells in a
process of capillary fluid exchange
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Two other types of blood vessels are often
described. They are arterioles and venules (small
arteries and small veins). All the features of
arteries and veins apply to arterioles and
venules (respectively), but on a smaller scale.
In addition, arterioles leading into a particular
organ or region are equipped with sphincter
muscles. When triggered, these can dilate or
constrict to regulate blood pressure and flow to
the intended capillary beds.
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MAJOR BLOOD VESSELS
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AORTA
This is the major blood vessel carrying
oxygenated blood out of the heart. It leaves the
left ventricle, loops over the top of the heart
creating the structure known as the aortic arch
before descending along the inside of the
backbone ( dorsal blood vessel). Branches from
this blood vessel feed all the body systems
except the lungs.
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Coronary arteries and veins
The very first branches off the aorta are the
coronary arteries. These relatively small blood
vessels can be seen on the surface of the heart.
They feed the heart muscle. The heart does not
receive its nutrients from the blood that travels
through it. The muscle tissue is too dense and
thick and the blood is travelling though it too
hard and fast. The coronary veins take the "spent
blood" back to the vena cava.
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Carotid arteries
These branches of the aortic arch take the blood
to the head (including the brain). They are
highly specialized in that they contain a number
of different types of nerve endings chemorecepto
rs that detect oxygen content, and pressure
receptors that detect blood pressure changes.
These features are essential for homeostasis. The
carotid arteries run reasonably close to the
surface, and the pulse in the carotids can
usually be easily found along the sides of the
neck.
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Jugular veins
Unlike most arteries, which are paired with veins
having a corresponding name, the jugular veins
are the match for the carotid arteries. As such,
they conduct blood out of the head region to the
anterior vena cava. The jugular veins do not
contain valves. The blood flowing through them
is under the influence of gravity. (When you
stand on your head, the blood stays in your head!)
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Subclavian arteries and veins
The subclavian arteries also branch from the
aorta (see diagram). The subclavians, as their
name suggests travel under the clavicle
(collarbone) and branch to feed the arms
(brachial artery) and the chest wall etc. An
interesting feature of the subclavian veins is
that just before they join the anterior vena cava
to return the blood to the heart, they meet up
with the major lymphatic ducts.
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Mesentaric arteries
These arteries branch off the aorta as it travels
posteriorly. They go to the intestines where they
subdivide to form the capillaries that can be
identified in the villi. In addition to feeding
the organs of the digestive system, they pick up
the newly digested nutrients and carry them away.
The mesentaric vein is reduced in structure and
function because of the hepatic portal vein.
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Hepatic portal vein
This vein transports blood rich with nutrients
directly from the intestines to the liver.
Hepatic means liverportal indicates that there
is a capillary bed on both ends of it. The liver
detoxifies blood, destroys aged red blood cells,
and regulates the glucose concentration in the
blood
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Hepatic vein
When the blood leaves the liver it returns to the
venous system. The hepatic vein carries the blood
to the posterior vena cava.
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Renal arteries and veins
The renal arteries branch off the dorsal aorta as
it passes through the lumbar region of the body.
They take blood to the kidneys while the renal
veins take blood away from the kidneys and back
to the posterior vena cava.
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Iliac arteries and veins
When the dorsal aorta gets to the pelvic region,
it branches into two iliac arteries, one goes
down each leg. The femoral artery is a major
branch of the iliac artery . The femoral artery
services the large quadriceps muscle of the
leg.
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Anterior and Posterior Vena Cava
The vena cavae collect up all the blood from the
various veins of the systemic circuit and conduct
it back into the right atrium. The anterior vena
cava services the anterior part of the body,
while the posterior services the posterior part.
Note anterior superior
posterior inferior
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Pulmonary veins and arteries
Reflecting back on the difference between
systemic and pulmonary circuits, all of the blood
vessels listed so far are part of the systemic
circuit. The pulmonary circuit is comprised of
the pulmonary trunk and arteries that take
deoxygenated blood from the right ventricle to
the lungs while the pulmonary veins take
oxygenated blood from the lungs to the left
atrium.
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For the rest Blood, Antigens and Antibodies as
well as Capillary Fluid Exchange, Fetal
Circulation and the Lymphatic System see the
handout. Once youve had a good read attempt the
Vocabulary exercise for Unit J.