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Circulatory system
The Circulatory System
The bodily system consisting of the
heart, blood vessels, and blood that
circulates/transports blood the body,
delivers throughout nutrients and
other essential materials to cells, and
removes waste products.
Circulatory Systems:
External Environment
Exchange Surface
Oxygen
nutrients
C
I
R
C
U
L
A
T
O
R
Y
Heat….. Hormones
Antibodies, blood
cells etc
Carbon
Dioxide
Nitrogen
waste
SYSTEM
Cells
ALL CIRCULATORY SYSTEMS HAVE:
• a circulatory fluid of some sort
• vessels in which circulatory fluid moves at
some point
• a mechanisms for moving the circulatory fluid
Open
Closed
Circulatory Systems
Open Circulatory Systems
• Circulatory fluid is not totally
confined within vessels
• A pump provided force to push
fluids around
• The circulatory fluid simply
flows over internal organs,
delivering requirements and
picking up waste products
• e.g. insects
Closed circulatory systems
• Circulatory fluid moves
entirely within closed vessels
(arteries, veins and capillaries)
• The movement of this fluid is
controlled with a pump (the
heart).
• All vertebrates and some
invertebrates have a closed
circulatory system. eg.
Mammals, frogs, earth worm
Comparing Circulatory Systems of
different animals
Circulation in Mammals
(and birds)
Double circulation
Fish
Single circulation
The Circulatory System
Blood
The fluid or liquid tissue that is
pumped through the body by the
heart and contains plasma, blood cells
(red and white), and platelets.
Blood
It is maintained at body
temperature of 37 C.
Adults have approx 5-6 litres of
blood.
55%Plasma
45% Cells
Blood
Functions:
Nutrient transport
Waste transport
Hormone transport
Control of body
temp
Protection from
infection
Clotting
Blood cells
RED BLOOD CELLS (erythrocytes)
Structure
Mature rbc:
• Formed in the bone marrow
• Shape: biconcave disk
• No nucleus or mitochondria
• Haemoglobin molecule
• (protein containing iron) a part of
structure
• Red in appearance
• Size: ~8µm
• live for: ~120days
Erythrocytes
Function
• carries most oxygen around the body
• carries some carbon dioxide
Red Blood Cells stained and viewed
with the light microscope
Related Disease
Anaemia: low red blood cells count or low
haemoglobin
Possible Causes:
• excessive blood loss,
• deficiency of key vitamins and/or minerals,
• bone marrow cancer
Blood cells
White BLOOD CELLS (Leukocytes)
Different types with different functions
General role: Immunity: defending body against
pathogens and foreign material
• Some engulf and destroy damaged or infected
cells
• Some produce antibodies
Structural features: Large distinct nucleus
Size: b/w 7-21 micrometers(microns)
About 1% of blood in a healthy person
Blood cells
Blood Clotting
•
•
•
Platelets and fibrinogen (a protein) form a blood clot
These form when a blood vessels is damaged
Role: to minimize blood loss and reduce entry of pathogens
PLASMA
• straw coloured fluid
• suspends other blood components
• transports nutrients, hormones and most
carbon dioxide
• suspends rbc and wbc
• carries materials to stabilise pH and osmotic
pressure
• carries blood clotting materials and
antibodies and distributes heat
Take a piece of plasticine.
Make a red blood cell, a
white blood cell and a
platelet.
Try and make them to
scale in relation to each
other and think about the
shape of each of the cells.
The Human Circulatory System
The heart has four
separate chambers.
The two upper chambers
are called the atria and the
lower two chambers are
called the ventricles.
The ventricles are thicker
walled than the atria
because they pump blood
greater distances.
The Heart
Put your hand on your heart.
• Did you place your hand on the left side of
your chest? Many people do, but the heart is
actually located almost in the center of the
chest, between the lungs. It's tipped slightly
so that a part of it sticks out and taps against
the left side of the chest, which is what makes
it seem as though it is located there.
Position of heart in thoracic cavity
Human Heart
• Made of cardiac muscle cells
• 2 sides divided by wall of muscle=septum
• It is a double pump with 4 Chambers: 2 Types
Atria (upper chambers)
– Thin walled
– Receive Blood
– Move blood into ventricles below
Ventricles (lower chambers)
– Thick Walled
– Eject Blood
Valves: Regulate DIRECTION of blood flow
The work of the heart
• Give a tennis ball a good, hard squeeze.
• You're using about the same amount of force
your heart uses to pump blood out to the
body.
• Even at rest, the muscles of the heart work
hard—twice as hard as the leg muscles of a
person sprinting
The Heart
Right Pulmonary
Aorta
Artery
Superior Vena
Cava
Left
atrium
Semi-lunar valves
Aortic valve
Pulmonary valve
Bicuspid
valve
Right atrium
Tricuspid
valve
Inferior
Vena Cava Tendons
(Chordae
Papillary Tendineae)
Right
Muscle
Left
Pulmonary
Artery
Pulmonary
veins
ventricle
Left
ventricle
septum
apex
Mammalian Circulatory
System



Double pump
Double circulation
2 separate paths


Lungs (pulmonary)
Body (systemic)
Blood flow in the heart
1.
2.
3.
4.
5.
6.
Oxygen-poor blood (shown in blue)
flows from the body into the right
atrium.
Blood flows through the right atrium
into the right ventricle.
The right ventricle pumps the blood to
the lungs, where the blood releases
waste gases and picks up oxygen.
The newly oxygen-rich blood (shown in
red) returns to the heart and enters the
left atrium.
Blood flows through the left atrium into
the left ventricle.
The left ventricle pumps the oxygen-rich
blood to all parts of the body.
Comparing Ventricles
http://www.pediatricheartsurgery.com/DiagnosticCategoriesAll.htm
Our Pump: Heart
Supplying Heart Tissue With Blood
CORONARY BLOOD VESSELS
Coronary Arteries
Blood vessels
• Blood vessels are classified as
organs.
• Blood circulates in a series of
different kinds of blood vessels as
it circulates round the body.
• Each kind of vessel is adapted to
its function.
Comparing Blood Vessels
• The aorta, the largest artery in
the body, is almost the diameter
of a garden hose.
• Capillaries, on the other hand,
are so small that it takes ten of
them to equal the thickness of a
human hair.
Comparing arteries and veins
Arteries and veins have the same layers of tissues in
their walls, but the proportions of these layers
differ.
Lining the core of each is a thin layer of
endothelium, and covering each is a sheath of
connective tissue, but an artery has thick
intermediate layers of elastic and muscular fibre
while in the vein these are less developed.
The thicker arterial wall helps the arteries withstand
and absorb the pressure waves which begin in the
heart and are transmitted by the blood.
Arteries and arterioles
Function is to carry blood from the heart to
the tissues
Thick walls with smooth elastic layers to
resist high pressure and muscle layer to aid
pumping
Small lumen
No valves (except in heart)
Blood at high pressure
Blood usually oxygenated (except in
pulmonary artery)
Veins and Venules
Function is to carry blood from tissues to
the heart
Thin walls, mainly collagen, since blood at
low pressure
Large lumen to reduce resistance to flow.
Many valves to prevent back-flow
Blood at low pressure
Blood usually deoxygenated (except in
pulmonary vein)
Blood flow through a vein
Capillaries
Function is to allow exchange of materials
between the blood and the tissues
Very thin, permeable walls, only one cell
thick to allow exchange of materials
Very small lumen. Blood cells must distort
to pass through.
No valves
Blood pressure falls in capillaries.
Blood changes from oxygenated to
deoxygenated (except in lungs)
Capillaries
The capillaries are actually only one epithelial cell thick.
They are so thin that blood cells can only pass through
them in single file.
The exchange of oxygen and carbon dioxide takes place
through the thin capillary wall.
The red blood cells inside the capillary release their oxygen
which passes through the wall and into the surrounding
tissue.
The tissue releases its waste products, like carbon dioxide,
which passes through the wall and into the red blood cells.
Fluid movement across capillaries
Capillaries are where fluids, gasses, nutrients,
and wastes are exchanged between the blood
and body tissues by diffusion.
Capillary walls contain small pores that allow
certain substances to pass into and out of the
blood vessel.
99% of fluid leaving the arteriole end of the
capillary RE-ENTERS at the venous end
Blood Vessels Summarised
Arteries
Veins
High in O2 content
Low in O2 content
Low in CO2 content
High in CO2 content
Thick muscular walls – elastic nature of
arteries propels blood along
Thin walls
High pressure tubes
Low pressure tubes – BP in veins in
almost zero.
Flow is pulsating & rapid – force
provided by heart
Flow is constant & slower
No valves are present
One way valves prevent backflow of
blood
Carry blood away from heart
Blood is moved back to heart by
pressure on the wall of the vein exerted
by contraction of skeletal muscle
The Lymphatic System
The lymphatic system is a series of
vessels throughout the body that drain
fluid from tissues.
Bacteria and other microbes are picked
up in the lymphatic fluid and trapped
inside lymph nodes, where they can be
attacked and destroyed by white blood
cells.
The Lymphatic System
The lymphatic system is a network of tubes
throughout the body that drains fluid (called
lymph) from tissues and empties it back into the
bloodstream.
The main roles of the lymphatic system include
managing the fluid levels in the body, filtering
out bacteria, and housing types of white blood
cells.
Lymph is filtered through the spleen and lymph
nodes before being emptied into the blood.
Lymphatic System
Picks up fluid that has
leaked from blood
vessels and returns it to
blood
Houses white blood cells
involved in immunity
Picks up triglycerides
from intestines (lacteals)
Blood Tissue Fluid and Lymph
Cardiac Cycle
• Diastole (dilation)
– Blood enter atria and ventricles
• Systole (contraction)
– Brief contraction of atria
(completes filling of Ventricles)
– Ventricles contract
• AV valves close (LUB)
• SL valves open
• Heart is relaxed:
• SL valves close (DUB)
• AV valves open
Blood Pressure
A force exerted by circulating blood on the
walls of blood vessels, and is one of the
principal vital signs. During each heart beat,
BP varies between a maximum (systolic) and
a minimum (diastolic) pressure:
Systolic – Pressure on arterial wall during
contraction of left ventricle
Diastolic – Pressure on arterial wall during
relaxation
Blood Pressure
Normal: Systolic 120 +/- 10mm Hg
Diastolic 80 +/- 10mm Hg
High:
140/90 mm Hg
Low:
100/60 mm Hg
Heart Rate
• Can be monitored by counting the heart beats
directly
• If can be more easily be determined by
measuring how many arterial palpitations
occur per minute
• Carotid Pulse (neck)
• Radial Pulse (wrist)
• Others
Take your resting
heart rate for 15
seconds and x 4.
What is your Heart Rate?
• List Factors that may affect heart rate
• Briefly state why each would effect heart rate
Heart Beat
• Your heart beats about 100,000 times in one
day
• That’s about 35 million times in a year.
• During an average lifetime, the human heart
will beat more than 2.5 billion times
Pulse Rates
• A normal healthy adult (at rest): 60 to 100 BPM (average
is 72BPM for an adult)
• During sleep: can drop to as low as 40 BPM
• During strenuous exercise: can rise as high as 150–200
BPM
• Well-conditioned athletes may have a healthy pulse rate
lower than 60 BPM.
• The resting heart rate for an infant is usually close to an
adult's pulse rate during strenuous exercise (average 110
BPM for an infant).
Heart Rates of different mammals
Can you explain this?
Mouse
Human
500 beats/min
70 beats/min
Elephant
28 beats/min
Heart Rates for
Various Mammals
(beats/minute)
Whale 20
Horse 45
Human 70
Cat 150
Hamster 330
Shrew 600
Cardiac Output (Q)
The amount of blood pumped by the heart each minute.
Therefore it is the product of heart rate and stroke volume.
Q = HR x SV
Heart rate (HR)= number of beats per minute
Stroke volume (SV) = amount of blood ejected in each beat
Blood flow during exercise
During exercise, blood flow increases to the heart and
skeletal muscle.
Amazing Heart Facts
It takes 20 seconds for blood to circulate the entire body. Oxygenated
blood leaves the aorta about 1 mile an hour.
The power output of the heart ranges from 1-5 watts per minute.
Which is the equivalent to the usage of a 60 watt bulb. It has been said
that enough energy is produced a day to drive a truck 20 miles.
“Ventricle” means “little belly” in Latin where as “Atrium” is Latin for
“entrance hall”.
Red blood cells live for up to 4 months and make approximately
250,000 round trips around the body before returning to the bone
marrow, where they were born, to die. Between 2.5 and 3 million red
blood cells (erythrocytes) are lost and replaced every second.
Amazing Heart Facts
Human blood is colourless, it is the haemoglobin that makes it
red.
Due to the heart having its own electrical impulse, it will
continue to beat even when removed from the body as long as it
has an adequate supply of oxygen.
On average, the human body has about 5 litres of blood
continually traveling through it by way of the circulatory system.
A kitchen tap would need to be turned on all the way for at least
45 years to equal the amount of blood pumped by the heart in
an average lifetime
Hold up your hand and make a fist. If you're a child,
your heart is about the same size as your fist, and if
you're an adult, it's about the same size as two fists
It pumps 8000 litres of blood around the body each
day.
Now imagine your fist holding a hand held pump and
you have 8000 cartons of milk lined up in front and you
are required to pump all that milk in a day!
The largest artery in the body is the aorta because it is
closest to the heart and so has to cope with the most
amount of force from the heart