TRANSPORT
IN ANIMALS
THE CIRCULATORY SYSTEM
The human circulatory system consists of a network of
arteries, veins, and capillaries, with the heart pumping
blood through it.
The Circulatory System is responsible for transporting
materials throughout the entire body.
It transports nutrients, water, and oxygen to your
billions of body cells and carries away wastes such as
carbon dioxide that body cells produce.
It is an amazing highway that travels through your entire body
connecting all your body cells.
The Circulatory System
The circulatory system is a system of blood vessels with a
pump and valves to ensure one-way flow of blood
Circulation in Different Animals:-
Fish have a two-chambered
heart and a single circulation
This means that for every one
circuit of the body, the blood
passes through the heart once
Double circulation
Mammals have a four-chambered heart and a double
circulation
This means that for every one circuit of the body, the
blood passes through the heart twice
The right side of the heart receives deoxygenated blood
from the body and pumps it to the lungs (the pulmonary
circulation)
The left side of the heart receives oxygenated blood from
the lungs and pumps it to the body (the systemic
circulation)
Blood travelling through the small capillaries in the lungs loses a lot of pressure that was
given to it by the pumping of the heart, meaning it cannot travel as fast
By returning the blood to the heart after going through the lungs its pressure can be raised
again before sending it to the body, meaning cells can be supplied with the oxygen and
glucose they need for respiration faster and more frequently
HEART
The Heart- A hollow muscular organ located in the chest cavity that pumps the
blood through the circulatory system by rhythmic contraction and dilation.
The heart consists of four chambers.
It is the size of our fist. The human heart has a mass of around 300g and is
roughly the size of a closed fist
It is protected in the chest cavity by the pericardium, a tough and fibrous sac
The right side of the heart receives deoxygenated blood from the body and
pumps it to the lungs
The left side of the heart receives oxygenated blood from the lungs and pumps it
to the body
Blood is pumped towards the heart in veins and away from the heart in arteries
The two sides of the heart are separated by a muscle wall called the septum
The heart is made of muscle tissue which are supplied with blood by the
coronary arteries
POSITION OF HEART
The back surface of the heart lies near
the vertebral column, and the front
surface sits behind the sternum and rib
cartilages.
The largest part of the heart is usually
slightly offset to the left side of the
chest (though occasionally it may be
offset to the right) and is felt to be on the
left because the left heart is stronger
and larger,
Your heart is located between your lungs in the middle of your
chest, behind and slightly to the left of your breastbone
(sternum).
HEART- STRUCTURE
FOUR CHAMBERS OF HEART
The heart is divided into four chambers. The two top
chambers are atria and the bottom two chambers
are ventricles
The left and right sides of the heart are separated by a
wall of muscular tissue, called the septum. The portion
of the septum which separates the left and right atria is
called the interatrial septum, while the portion of the
septum which separates the left and right ventricles is
called the interventricular septum
The septum is very important for ensuring blood
doesn’t mix between the left and right sides of the
heart
The ventricles have thicker muscle walls than the atria as they are pumping blood
out of the heart and so need to generate a higher pressure
The left ventricle has a thicker muscle wall than the right ventricle as it has to
pump blood at high pressure around the entire body, whereas the right ventricle is
pumping blood at lower pressure to the lungs
The septum separates the two sides of the heart and so prevents mixing of
oxygenated and deoxygenated blood
Can you label the chambers AND
valves of heart?
VALVES IN THE HEART
The basic function of all valves is to prevent blood
flowing backwards
There are two sets of valves in the heart:
The atrioventricular valves separate the atria from the
ventricles
The valve in the right side of the heart is called the
TRICUSPID and the valve in the left side is called the
BICUSPID
These valves are pushed open when the atria contract
but when the ventricles contract they are pushed shut
to prevent blood flowing back into the atria
The semilunar valves are found in the two blood
arteries that come out of the top of the heart
They are unusual in that they are the only two arteries
in the body that contain valves
These valves open when the ventricles contract so
blood squeezes past them out of the heart, but then
shut to avoid blood flowing back into the heart
Pathway of Blood through the Heart
Deoxygenated blood coming from the body flows into the right atrium via the vena
cava
Once the right atrium has filled with blood the heart gives a little beat and the blood
is pushed through the tricuspid (atrioventricular) valve into the right ventricle
The walls of the ventricle contract and the blood is pushed into the pulmonary
artery through the semilunar valve which prevents blood flowing backwards into
the heart
The blood travels to the lungs and moves through the capillaries past the alveoli
where gas exchange takes place (this is why there has to be low pressure on this
side of the heart – blood is going directly to capillaries which would burst under
higher pressure)
Oxygen-rich blood returns to the left atrium via the pulmonary vein
It passes through the bicuspid (atrioventricular) valve into the left ventricle
The thicker muscle walls of the ventricle contract strongly to push the blood
forcefully into the aorta and all the way around the body
The semilunar valve in the aorta prevents the blood flowing back down into the
heart
Blood vessels
Arteries
Carry blood at high pressure away from the heart
Carry oxygenated blood (other than the pulmonary artery)
Have thick muscular walls containing elastic fibres
Have a narrow lumen
Speed of flow is fast
Veins
Carry blood at low pressure towards the heart
Carry deoxygenated blood (other than the pulmonary vein)
Have thin walls
Have a large lumen
Contain valves
Speed of flow is slow
Capillaries
Carry blood at low pressure within tissues
Carry both oxygenated and deoxygenated
blood
Have walls that are one cell thick
Have ‘leaky’ walls
Speed of flow is slow
How Structure of Blood Vessels is
Adapted to their Function
Arteries
Have thick muscular walls containing elastic fibres to withstand high pressure of
blood and maintain the blood pressure as it recoils after the blood has passed
through
Have a narrow lumen to maintain high pressure
Veins
Have a large lumen as blood pressure is low
Contain valves to prevent the backflow of blood as it is under low pressure
Capillaries
Have walls that are one cell thick so that substances can easily diffuse in and out
of them
Have ‘leaky’ walls so that blood plasma can leak out and form tissue fluid
surrounding cells
Arterioles & Venules
As arteries divide more as they get further away from the heart, they get
narrower
The narrow vessels that connect arteries to capillaries are called arterioles
Veins also get narrower the further away they are from the heart
The narrow vessels that connect capillaries to veins are called venules
Shunt Vessels
Sometimes the cardiovascular system needs to
redistribute the blood to specific areas of the body
For example:
During exercise, more of it goes to the working
muscles and less of it goes to other body organs such
as the digestive system
When we are hot, more blood flows through the
surface of the skin and when we are cold less blood
flows through the surface of the skin
This redirection of blood flow is caused by the use of a
vascular shunt vessel
The shunt vessels can open or close to control the
amount of blood flowing to a specific area
A shunt vessel in the skin when we are cold A shunt vessel in the skin when we are hot
Naming the blood vessels
SYSTOLE AND DIASTOLE
Exercise & Heart Rate
Heart activity can be monitored by
using an ECG, measuring pulse rate or
listening to the sounds of valves closing
using a stethoscope
Heart rate (and pulse rate) is measured
in beats per minute (bpm)
To investigate the effects of exercise
on heart rate, record the pulse rate at
rest for a minute
Immediately after they do some
exercise, record the pulse rate every
minute until it returns to the resting
rate
This experiment will show that during
exercise the heart rate increases and
may take several minutes to return to
normal
Why does Heart Rate Increase during
Exercise?
So that sufficient blood is taken to the working muscles to provide them with
enough nutrients and oxygen for increased respiration
An increase in heart rate also allows for waste products to be removed at a
faster rate
Following exercise, the heart continues to beat faster for a while to ensure
that all excess waste products are removed from muscle cells
It is also likely that muscle cells have been respiring anaerobically during
exercise and so have built up an oxygen debt
This needs to be ‘repaid’ following exercise and so the heart continues to
beat faster to ensure that extra oxygen is still being delivered to muscle
cells
The extra oxygen is used to break down the lactic acid that has been built up
in cells as a result of anaerobic respiration
Coronary Heart Disease
The heart is made of muscle cells that need their own
supply of blood to deliver oxygen, glucose and other
nutrients and remove carbon dioxide and other waste
products
The blood is supplied by the coronary arteries
If a coronary artery becomes partially or completely
blocked by fatty deposits called ‘plaques’ (mainly formed
from cholesterol), the arteries are not as elastic as they
should be and therefore cannot stretch to accommodate
the blood which is being forced through them - leading to
coronary heart disease
Partial blockage of the coronary arteries creates a
restricted blood flow to the cardiac muscle cells and
results in severe chest pains called angina
Complete blockage means cells in that area of the heart
will not be able to respire and can no longer contract,
leading to a heart attack
Preventing & Treating CHD
Quit smoking
Reduce animal fats
in diet and eat
more fruits and
vegetables - this
will reduce
cholesterol levels
in the blood and
help with weight
loss if overweight
Exercise regularly -
again, this will help
with weight loss,
decrease blood
pressure and
cholesterol levels
and help reduce
stress
Treatment of coronary heart disease
Aspirin can be taken daily to reduce the risk of blood clots forming in arteries
Surgical treatments include:
Angioplasty
A narrow catheter (tube) is threaded through the groin up to the blocked
vessel
A tiny balloon inserted into the catheter is pushed up to the blocked vessel
and then inflated
This flattens the plaque against the wall of the artery, clearing the
blockage
To keep the artery clear, a stent (piece of metal / plastic mesh) is also
inserted which pushes against the wall of the artery
Sometimes the stent is coated with a drug that slowly releases medication
to prevent further build-up of plaque
Coronary bypass surgery
A piece of blood vessel is taken from the patient’s leg, arm, or chest and used to create a
new passage for the flow of blood to the cardiac muscle, bypassing the blocked area
The number of bypass grafts gives rise to the name of the surgery, so a ‘triple heart
bypass’ would mean three new bypass grafts being attached
Components 0f blood
Types of WBC
White blood cells are part of the body’s immune
system, defending against infection by pathogenic
microorganisms
There are two main types, phagocytes and lymphocytes
Phagocytes
Carry out phagocytosis by engulfing and digesting pathogens
Phagocytes have a sensitive cell surface membrane that can detect chemicals
produced by pathogenic cells
Once they encounter the pathogenic cell, they will engulf it and release digestive
enzymes to digest it
They can be easily recognised under the microscope by their multi-lobed nucleus
and their granular cytoplasm
Lymphocytes
Produce antibodies to destroy pathogenic cells and antitoxins to neutralise
toxins released by pathogens
They can easily be recognised under the microscope by their large round
nucleus which takes up nearly the whole cell and their clear, non-granular
cytoplasm
Functions of the Parts of the Blood
Plasma is important for the transport of carbon dioxide,
digested food (nutrients), urea, mineral ions, hormones
and heat energy
Red blood cells transport oxygen around the body from
the lungs to cells which require it for aerobic respiration
They carry the oxygen in the form of oxyhaemoglobin
White blood cells defend the body against infection by
pathogens by carrying out phagocytosis and antibody
production
Platelets are involved in helping the blood to clot
Platelets are fragments of cells which are
involved in blood clotting and forming scabs
where skin has been cut or punctured
Blood clotting prevents continued / significant
blood loss from wounds
Scab formation seals the wound with an
insoluble patch that prevents entry of
microorganisms that could cause infection
It remains in place until new skin has grown
underneath it, sealing the skin again
When the skin is broken (i.e.
there is a wound) platelets
arrive to stop the bleeding
A series of reactions occur
within the blood plasma
Platelets release chemicals that
cause soluble fibrinogen
proteins to convert into
insoluble fibrin and form an
insoluble mesh across the
wound, trapping red blood cells
and therefore forming a clot
The clot eventually dries and
develops into a scab to protect
the wound from bacteria
entering
Lymphatic system
The walls of the capillaries are so thin that
water, dissolved solutes and dissolved gases
easily leak out of them / pass through the
walls from the plasma into the tissue fluid
surrounding the cells
Cells exchange materials (such as water,
oxygen, glucose, carbon dioxide, mineral ions)
across their cell membranes with the tissue
fluid surrounding them by diffusion, osmosis
or active transport
More fluid leaks out of the capillaries than is
returned to them, and this excess of leaked
fluid surrounding the capillaries then passes
into the lymphatic system, becoming lymph
fluid
Lymph Vessels & Nodes
The lymphatic system is formed from a series of
tubes which flow from tissues back to the heart
It connects with the blood system near to the
heart, where lymph fluid is returned to the blood
plasma
Lymph nodes are small clusters of lymphatic
tissue found throughout the lymphatic system,
especially in the neck and armpits
Large numbers of lymphocytes are found in
lymph nodes
Tissues associated with the lymphatic system,
such as bone marrow, produce these
lymphocytes
Lymphocytes play an important role in
defending the body against infection
