Transcript Human Circulatory System

Human Circulatory System
Heart and Blood Vessels
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Contents
In single celled organisms
In small multicellular
organisms
Circulatory system
Types of Circulatory System
The Human Circulatory
System
Blood vessels
Exchange of materials
Portal blood system
The Heart
Valves in heart
Systole & Diastole
Heartbeat
Blood Pressure
Healthy Circulatory System
The Lymphatic System
Blood and Lymph vessels –
diagram
Lymph System Composition
The Lymph System
Lymph nodes
Functions of the Lymph
System
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In single celled organisms
• All cells need to take in various nutrients e.g.
oxygen
• All cells need to get rid of waste products e.g.
carbon dioxide
• Single celled organisms e.g. Amoeba, achieve
this by diffusion
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Exchange of materials in Amoeba
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In small multicellular organisms
• Small multicellular organisms e.g. flatworms
have bodies only a few cells thick
• They too can exchange materials with their
environment by diffusion
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Exchange of materials in a flatworm
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Circulatory system
• Larger multicellular animals need a
circulatory system
as the distance from the body surface to
the centre is too great for diffusion
A circulatory system consists of: 1. A fluid called blood
2. A pump called a heart
3. Tubes or vessels to carry the blood to the
cells of the body
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Types of Circulatory System
Two types
1. Open Circulatory System
2. Closed Circulatory System
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Open Circulatory System
• Blood not always found in blood vessels
• Heart pumps blood into open ended
vessels and into body cavity
• Body cells bathed in blood – exchange of
materials takes place
• Blood passes back into blood vessels and
back to heart
This type of circulatory system is found in
insects
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Open circulatory system
Go to Slide 58
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Closed Circulatory System
• Blood remains in blood vessels
• Exchange of materials possible – smallest
blood vessels have thin walls
• Materials diffuse from the blood into the
tissue fluid and then into the body cells
• All cells are surrounded or bathed in a fluid
called tissue fluid (E.C.F.) – a medium for
the exchange of materials
Found in earthworms and vertebrates – a
more efficient system
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Closed Circulatory System
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The Human Circulatory System
Humans have a double circulatory system i.e.
blood is pumped from the heart to the lungs
and back to the heart
This is pulmonary circulation
and from the heart to the body and back to the
heart
This is systemic circulation
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Double
circulation in
humans
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Separate systems
• Heart divided by a muscular wall into left and right
sides
• Right side pumps deoxygenated blood to the lungs
(pulmonary)
• Left side pumps oxygenated blood to the body
(systemic)
Advantage of double circulatory system is adequate
blood pressure ensured for both systems.
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Blood vessels
Three types
• Arteries
• Veins
• Capillaries
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Arteries
• Thick-walled
• Small lumen (central cavity)
• Carry blood away from the heart
• Blood under pressure from heart
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T.S. Artery and Vein
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Veins
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•
•
•
•
•
Thinner walls than arteries
Larger lumen
Have valves – for what?
Carry blood to the heart
Less pressure – not under influence of heart
Contraction of body muscles squeeze veins
and push blood back to heart
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Branching network
• Arteries branch into smaller arterioles
• Arterioles branch into capillaries
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Capillaries
• Are the smallest blood vessels
• Are thin-walled – one cell thick
• Lie close to nearly every cell in the body –
ensuring efficient exchange of material
• Allow exchange of substances between blood
and body cells
• Reunite to form venules and veins which
returns blood to the heart
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Exchange of materials
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The structure of the blood vessels
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Differences between arteries, veins
& capillaries
Artery
Structure
Function
Blood
flow
Vein
Capillary
Thick, three-layered wall Thin, three-layered wall Wall only one cell
of muscle & elastin
of muscle & elastin
thick
Narrow lumen
Large lumen
Extremely narrow
lumen
No valves
Valves present
No valves
Carry blood away from
heart
Rapid under pressure
from heart
Carry blood to heart
Allows exchange of
materials between …
Sluggish under low
pressure
Pressure reducing
Blood flows in pulses
Blood flows steadily
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Portal blood system
(1/3)
The pulmonary and systemic circulatory systems
begin and end in the heart.
Pulmonary System (refer to a diagram)
Heart  Pulmonary Artery  Arterioles 
Capillaries in lungs  Venules  Pulmonary
Vein  Heart
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Portal blood system
(2/3)
Systemic System
Heart  Aorta  Arterioles  Capillaries in
body organs  Venules  Veins  Heart
The Portal System begins and ends in
capillaries e.g. hepatic portal system
Capillaries (in stomach & intestines) 
Venules  Hepatic Portal Vein  Venules
 Capillaries (in the liver)
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Portal blood system
(3/3)
Usually blood flows
Artery  capillary  vein
The portal system is an exception to this
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The human
circulatory system
showing the portal
system
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The Heart
• Hollow muscular organ
• Slightly to the left of the sternum
• Above the diaphragm
• Size of clenched fist – 300g
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Cardiac muscle
• Surrounded by fluid filled chamber (friction
free movement) and protective sac =
pericardium
• Heart wall made of cardiac muscle
• Contracts without nervous stimulation
• Will not fatigue
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Cardiac Blood Supply
Consists of the coronary blood vessels i.e.
• Coronary arteries bringing nutrients to the
cardiac tissue from the aorta, and
• Coronary veins carry deoxygenated blood back
to the right atrium
• Emerging from the heart are the aorta, vena
cava, pulmonary arteries and veins.
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External view of human heart
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Internal structure of heart
• Four chambers – 2 upper & 2 lower
• Two upper atria – thin walled
• Two lower ventricles – thick walled and larger
than atria
• Divided vertically into left and right by wall –
septum
• Blood does not flow through the septum
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Diagram of internal heart structure
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Questions
1. Describe the direction of blood flow through
the heart.
2. Why is the wall of the left ventricle thicker
than that of the right ventricle?
3. Why are atrial walls thinner than ventricle
walls?
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Valves in heart
Found at the exits of each chamber
Four chambers  four valves
Function: to prevent a back flow of blood
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Operation of valves in the heart
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How to draw the heart
(1/6)
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How to draw the heart
(2/6)
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How to draw the heart
(3/6)
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How to draw the heart
(4/6)
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How to draw the heart
(5/6)
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How to draw the heart
(6/6)
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Systole & Diastole
systole: contraction phase of cardiac cycle
during which the chambers discharge the
blood.
diastole: relaxation phase of cardiac cycle during
which the chambers fill with blood.
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Heartbeat
(1/2)
Pacemaker (S-A node) located in right atrium
sends out wave of impulses to muscles of
both atria causing atria to contract.
This is Atrial systole.
The impulses are picked up by the atrioventricular node (A-V node)
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Heartbeat
(2/2)
and transmitted to the ventricles via the
Purkinje fibres - causing the ventricles to
contract.
This is Ventricular systole.
While the atria are contracting and emptying
(atrial systole) the ventricles are relaxing
and filling with blood (ventricular diastole)
and vice versa
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Heartbeat – diagram
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Heartbeat sound
The lupp-dup sound, heard through a
stethoscope, is caused by the closing of the
valves of the heart
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The Pulse
When the ventricles contract blood is forced
through the aorta and into the arteries.
This causes the arterial walls to expand and
contract rhythmically.
This is the pulse and can be felt where an artery
is near the body surface e.g. wrist, temple,
neck.
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Blood Pressure
Is caused by the pumping action of the heart.
Needs to be reasonable high to keep the blood
moving.
Highest pressure is where the blood is forced
into the aorta by contraction of the left
ventricle = systolic pressure
Lowest pressure is when the ventricles relax =
diastolic pressure
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Taking blood pressure
Use a B.P. machine = sphygmomanometer
Measures pressure required to stop the blood
flow in artery of upper arm
Contraction and relaxation pressures recorded
Expressed as a fraction
Systolic pressure
Diastolic pressure
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Blood pressure readings
e.g. healthy young adults B.P. = 110/75 mmHg
Hypertension = abnormally high blood pressure
i.e. > 140/90 mmHg
Hypotension = abnormally low blood pressure.
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Healthy Circulatory System
Effects of
Exercise,
Diet and
Smoking
on the circulatory system
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Exercise
When we exercise the heart beats faster.
Makes the heart muscle stronger and
more efficient at pumping blood
Improves the oxygen supply to the cardiac
muscle and
Reduces blood pressure
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Diet
Too much cholesterol from animal fats can build
up on the inner walls of the arteries
and reduces the rate of flow of the blood
e.g. a blockage in the cardiac artery prevents
blood and oxygen getting to the cardiac
muscle and will cause a heart attack
Eating fewer fatty meats and fatty dairy
products can reduce the risk of heart disease
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Smoking
Major cause of heart disease
Tobacco smoke contains nicotine and carbon
monoxide (CO)
Nicotine increases blood pressure
CO interferes with the transport of oxygen to
the body cells
High levels cause hardening of the arteries
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The Lymphatic System
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The lymphatic system
Forms part of the transport system
and the immune system
Collects excess tissue fluid (see slide 10) and
transports it back to the bloodstream
Tissue fluid = similar to blood plasma but
without the plasma proteins.
When tissue fluid enters the lymph system it is
called lymph.
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Blood and Lymph vessels
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Lymph System Composition
Composed of:
a fluid
= lymph, and
a system of tubes
= lymph vessels
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Lymph
A fluid containing:
lymphocytes (white blood cells)
proteins and
fats
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Lymph vessels
1.
2.
3.
4.
Similar to veins – thin walled
Form a one way system
Have valves – function = ?
No heart – no pumping – lymph moves by
contraction of body muscles
5. Empty lymph back into bloodstream at
subclavian veins
Volume of circulating fluid in body remains
fairly constant
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The Lymph System
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Lymph nodes
Small rounded structures found along the
lymph vessels
produce antibodies - destroy invading
pathogens and
produce and store lymphocytes (white blood
cells)
Lymph nodes filter the lymph as it flows
through trapping and destroying bacteria
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Functions of Lymph System
1. Return excess ECF to blood system maintain balance of fluids in body =
HOMEOSTASIS.
2. Absorb and transport fatty acids and
glycerol from intestines - lacteals.
3. Produce lymphocytes.
4. Produce antibodies.
5. Remove and destroy bacteria.
6. Transport hormones.
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END
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