Download Blood vessels - MRs. Saikali

Blood vessels
11.3
Arteries
• The blood from the heart is carried through
the body by a complex network of blood
vessels
• Arteries take blood away from the heart
• The main artery is the aorta
• Aorta branches into other major arteries,
which take blood to different limbs and organs
Arteries
• Carotid artery takes blood to the brain
• Brachial arteries take blood to the arms
• Thoracic artery take blood to the thorax and
then into the hepatic, renal and gastric
arteries for the liver, kidneys and stomach
respectively
• Iliac artery takes blood to the lower limbs
Layers of the arteries
• The arteries have three layers of tissues:
– An outer layer of connective tissues (stretches to
support blood flow)
– A middle layer of smooth muscles (regulate blood
flow by altering vascular resistance by constriction
and dilation)
– A smooth inner single layer of epithelial cells
called the endothelium
Pulse
• When blood is forced through the artery by
the contraction of the heart, the artery
expands
• The expansion can be felt as the pulse
• The artery has to be large, close to the skin
and in front of a bone
• Do mini investigation page 488
Arterioles
• The major arteries diverge into minor arteries,
and then into smaller vessels called arterioles
• Arterioles reach more deeply into the muscles
and organs of the body
• Arterioles have smooth muscle in their wall,
thus they can be controlled by the nervous
system
Arterioles
• Signals from the nerves can regulate the
diameter of the arterioles and control the
blood flow to certain parts of the body
– Vasodilation: an increase in the diameter of
arterioles that increases the blood flow to tissues
– Vasoconstriction: a decrease in the diameter of
the arterioles that decreases the blood flow to
tissues
Arterioles
• Vasoconstriction is an important feature of the
circulatory system. Without it your body will
need 200 L of blood to fill all the blood vessels
• The ability to control blood flow ensure that
the 5 L of blood we have is distributed where
it is needed
Capillaries
• Arterioles diverge into capillary beds
• Capillary beds contain 10 to 100 capillaries
that branch among the cells and tissues of the
body
• https://www.youtube.com/watch?v=Q530H1
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Capillaries
• Capillaries are narrow diameter tubes
• Can fit blood cells in a single-file lines
• Supply oxygen and nutrients to every cell
throughout the body tissues
• Carbon dioxide and other waste produced
during aerobic cellular respiration diffuse into
the tissue fluid and then into the capillaries
Fluid exchange
• High fluid concentration on the arterial side
cause water to diffuse from the blood to the
tissue fluid
• On the venous side, high concentration of
water in the tissue fluid causes water to move
from the tissue fluid to the blood
• This maintains a balance between the fluids in
the circulatory system and the tissues
Controlling blood flow
Page 489
https://www.youtube.com/watch?v=yeX0uDpPB
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Venules and veins
• The capillaries connect the arteries to the
veins
• On one side we have the arteries and
arterioles carrying oxygenated blood and
nutrients to the tissues
• On the other side the capillaries merge into
small vessels called venules that merge to
form large vessels called veins
Venules and veins
• Venules and veins carry deoxygenated blood
containing carbon dioxide and other waste
products from the tissues to the heart
• The middle layer of smooth muscle is not as
thick as the arteries
• The walls in the veins are not as elastic as the
arteries
• Blood pressure in veins are lower than in
arteries
Venules and veins
• Veins have valves to prevent the backflow of
blood
• Because veins have to work against gravity to
get blood back to the heart,
• contraction of skeletal muscle assists with the
flow of blood back to the heart
• https://www.youtube.com/watch?v=HNuPWd
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Blood pressure
• https://www.youtube.com/watch?v=qWti317
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