Transcript Circulatory system

S. MORRIS 2006
What is the circulatory system?
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The circulatory system carries blood and dissolved
substances to and from different places in the body.
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The Heart has the job of pumping these things around
the body.
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The Heart pumps blood and substances around the
body in tubes called blood vessels.
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The Heart and blood vessels together make up the
Circulatory System.
The Heart
• Very muscular, about the size of your fist
• Major portion of the heart known as
MYOCARDIUM and composed of cardiac
muscle
• A PERICARDIAL SAC covers the heart,
made from epithelial and fibrous tissue,
that contains lubricating liquid
Our circulatory system is a double circulatory system.
This means it has two parts parts.
Lungs
the right side of
the left side of
the system
the system
deals with
deals with
oxygenated
deoxygenated
blood.
blood.
Body cells
The SEPTUM separates / divides the 2 sides
How does this system work?
pulmonary vein
pulmonary artery
lungs
head & arms
aorta
main vein
Right
Left
liver
digestive system
kidneys
legs
Circulatory System
The Heart
This is a vein. It brings
blood from the body,
except the lungs.
These are arteries.
They carry blood
away from the heart.
2 atria
2 ventricles
Coronary arteries,
the hearts own
blood supply
The heart has four chambers
now lets look inside the heart
The Heart
Artery to Lungs
Vein from Head and Body
Right Atrium
valve
Right Ventricle
Artery to Head and Body
Vein from Lungs
Left Atrium
valve
Left Ventricle
The Valves
• There are 4 valves in the heart:
– 2 Atrioventricular Valves (AV Valves)
– 2 Semi-Lunar valves (SL Valves)
AV Valves
• Between the artia and ventricles
• Control the flow of blood between the
chambers, and prevent backflow
– TRICUSPID VALVE: between the right atrium
and right ventricle. It has 3 flaps.
– BICUSPID VALVE: between the left atrium
and left ventricle. It has 2 flaps.
Chordae Tendinae
• support the valves and prevent them from
inverting. They are attached to muscles in the
ventricular walls
The SL Valves
• Between the ventricles and the attached
blood vessels
• Blood flows through these valves as it
leaves the heart
• Pulmonary SL Valve: right side, right
ventricle pumps blood to lungs through the
pulmonary artery
• Aortic SL Valve: left side, left ventricle
pumps blood to body through the aorta
IMPORTANT
• Deoxygenated blood NEVER mixes with
oxygenated blood.
• Remember too that both atria contract at
the same time (simultaneously), and the
ventricles both contract at the same time
(simultaneously).
How does the Heart work?
STEP ONE
blood from the
body
blood from
the lungs
The heart beat begins when the
heart muscles relax and blood
flows into the atria.
How does the Heart work?
STEP TWO
The atria then contract and
the valves open to allow blood
into the ventricles.
How does the Heart work?
STEP THREE
The valves close to stop blood
flowing backwards.
The ventricles contract forcing
the blood to leave the heart.
At the same time, the atria are
relaxing and once again filling with
blood.
The cycle then repeats itself.
Heartbeat: the sound you hear
• LUB
– first heart sound
– Occurs when the A-V valves close due to
ventricle contraction and is known as Systole
(pressure in ventricle is higher than pressure
in the atrium)
– Louder and longer than the second heart
sound
• DUB
– Sharp and short sound
– Occurs when the S-L valves snap shut
– Known as Diastole (when the ventricles relax)
NOTE
• Systole: refers to CONTRACTION of the
heart muscle
• Diastole: refers to RELAXATION of the
heart
• Cardiac Cycle is another name for the
heartbeat, it occurs on average 70 times
per minute in an adult.
What controls the heartbeat?
• 2 ways: Intrinsic (without the brain telling
it) and Extrinsic (brain involved)
• Intrinsic: has special tissue called Nodal
Tissue (has both nerve and muscle tissue)
1. SA (sinoatrial) Node: located in the upper
back wall of the right atrium (also called the
Pacemaker of the heart)
• Initiates the heartbeat by sending a signal every
0.85 seconds to make the atria contract
2. AV (atrioventricular) Node: found at the
base of the right atrium near the septum
• When pulse from the SA node reaches
the AV node, the AV node sends out a
signal to special fibers called Purkinjie
Fibers to message the ventricles to
contract
Text page 245
• Intrinsic controls the steady beating of
your heart, Extrinsic factors can control
how fast your heat beats
• This involves Nervous Control, by a part of
your brain called the Medulla Oblongata
• This part of your brain can sped up or slow
down your heart rate depending on stimuli
it receives from the Autonomic Nervous
System (ie. Stress, oxygen levels, blood
pressure)
Blood Pressure
• Measured using a SPHYGMANOMETER
• 2 numbers:
– First number (bigger number ALWAYS) is the
highest arterial pressure reached during
ejection of blood from ventricles of the heart
(SYSTOLIC)
– Second number (lower number ALWAYS) is
the lowest arterial pressure while the
ventricles are relaxing (DIASTOLIC)
• Blood pressure decreases with distance
from the heart and as a result the velocity
of blood also decreases gradually, which
is very important because the slow
movement going into capillaries allows for
exchange of substances between blood in
capillaries and surrounding tissues.
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.
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.
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
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.
artery
body cell
vein
capillaries
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
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.
White Blood Cells
there are many different types and
all contain a big nucleus.
the two main ones are the
lymphocytes and the macrophages.
macrophages ‘eat’ and digest microorganisms .
some lymphocytes fight disease by making antibodies to destroy
invaders by dissolving them.
other lymphocytes make antitoxins to break down poisons.
Platelets
Platelets are bits of cell
broken off larger 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.
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 _________