Download Circulatory system

Why do we need a transport
system?
• We have a small surface area to volume
ratio
• Simple diffusion throughout the body
surfaces is insufficient
• Useful substances needs to transported
through the body and unwanted
substances needs to be eliminated
What is the importance of the circulatory system?
• It transports blood throughout our body – to all parts
of our body
• Needed substances by the body such as: oxygen,
nutrients and hormones are sent to all cells in the
body
• Unwanted substances such as carbon dioxide and
nitrogenous waste products are sent to be eliminated
by the body.
What does our transport
system consist of?
• A transporting medium – the blood
• Tubes through which the medium can
travel – blood vessels
• A pump to push the medium through the
tubes – the heart
Objective: To describe the composition and components of
blood
BLOOD
what’s in
digested food
red blood cells
white blood cells
oxygen
waste (urea)
platelets
carbon dioxide
plasma
hormones
The Blood
red blood cell
platelets
white blood cell
plasma
Blood Components
Composition of Blood
• Blood is composed of three types of
cells: red blood cells, white blood cells
and platelets, floating in a liquid called
plasma.
• Plasma makes up 55% of the volume of
the blood and the cells make up the
other 45%
Blood Cells
Blood = 55% Plasma + 45%
Blood Cells
Red Blood Cells
a biconcave disc that is
round and flat without a
nucleus
contain haemoglobin, a
molecule specially designed
to hold oxygen and carry it
to cells that need it.
can change shape to an
amazing extent, without
breaking, as it squeezes
single file through the
capillaries.
Red Blood Cells (Erythrocytes)
• Formation – red bone marrow of the
pelvis, scapula, ribs, sternum etc
• Destroyed in the liver and spleen
• Functions – transport oxygen as
oxyhaemoglobin from lungs to tissues.
Transport small amounts of carbon
dioxide from tissues to lungs
How do red blood cells
transport oxygen?
• In their cytoplasm is a red pigment
called haemoglobin
• Haemoglobin has a high affinity for
oxygen
• It forms an unstable compound called
oxy-haemoglobin
• In conditions of low oxygen
concentration oxy-haemoglobin breaks
down and releases the oxygen.
Oxygen in Red Blood Cells
Did you know?
• There are about 5 ½ million red blood
cells in a cubic millimetre of blood
• A red blood cells lasts for about 4
months
• About 200 billion red blood cells are
formed and destroyed each day
• About 1% of the total red blood cells
are replaced each day.
White Blood Cells (Leucocytes)
there are many different types and
all contain a big nucleus.
the two main ones are the
phagocytes and the lymphocytes.
phagocytes ‘eat’ or engulf disease
causing bacteria in the blood at
sites of infection and the lymph
nodes
some lymphocytes fight disease by making antibodies to destroy
antigens (foreign proteins) by dissolving them.
other lymphocytes make antitoxins to break down poisons.
Platelets (Thrombocytes)
Platelets are formed in
the bone marrow of long
bones by disintegration of
certain cells .
Platelets produce
tiny fibrinogen
fibres to form a net.
This net traps other
blood cells to form a
blood clot.
Plasma
It also contains useful
things like;
• carbon dioxide
A strawcoloured
liquid that
carries the
cells and the
platelets
which help
blood clot.
• glucose
• amino acids
• proteins
• minerals
• vitamins
• hormones
• waste materials
like urea.
Objective: To describe the structure and function of blood
vessels
BLOOD VESSELS
blood from the heart gets around
the body through blood vessels
There are 3 types of blood vessels
a.
ARTERY
b.
VEIN
c.
CAPILLARY
The ARTERY
Arteries carry blood away from the heart.
the elastic fibres allow
the artery to stretch
under pressure
thick muscle and
elastic fibres
the thick muscle can
contract to push the
blood along.
Arteries
• Carries high pressure oxygenated blood
away from the heart
• Blood moves in pulses created by
ventricle contractions
• Most lie deep in the body where they
are protected
• Thick elastic walls composed of three
layers to withstand high pressures of
blood
• Arteries divide into smaller vessels
called arterioles
Structure of an artery
The CAPILLARY
Capillaries link Arteries with Veins
they exchange materials
between the blood and
other body cells.
the wall of a capillary
is only one cell thick
(endothelial cells)
The exchange of materials
between the blood and the
body can only occur through
capillaries.
The CAPILLARY
A collection of capillaries is known as a capillary bed.
arteriole
body cell
venule
capillaries
Did you know?
• The capillary network is so dense that
no living cell is far from a supply of food
and oxygen
• In the liver every cell is in direct
contact with a capillary. Why do you
think this is so?
• Some capillaries are so narrow that the
red blood cells are squeezed flat while
passing through them.
The VEIN
Veins carry blood towards from the heart.
veins have valves
which act to stop the
blood from going in
the wrong direction.
thin muscle and
elastic fibres
body muscles surround the veins
so that when they contract to
move the body, they also squeeze
the veins and push the blood along
the vessel.
Structure of Veins
Vein Valves
Varicose Veins
• This happens when the valves stop
working properly
• The blood is left in the veins instead of
flowing back to the heart
• This makes the vein swell and causes a
varicose vein
• Varicose veins show up on the legs ankle
and knees because they are furthest
from the heart
SUMMARY
copy and complete the following;
away from the heart. The walls of an artery
Arteries take blood ______
muscular walls and elastic fibres. Veins
are made up of thick _________
towards the heart and also have valves. The
carry blood ________
capillaries link arteries and veins, and have a one cell thick wall.
_________
plasma the liquid part of the
Blood is made up of four main things ______,
oxygen White Blood cells to protect
blood; Red Blood Cells to carry ______;
platelets to help blood clot.
the body from disease and _________