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TRANSPORT IN HUMANS
7.2.Transport in humans
Core Describe the circulatory system as a system of tubes with a pump and valves to ensure one -way flow of
blood Describe the double circulation in terms of a low pressure circulation to the lungs and a high pressure
circulation to the body tissues and relate these differences to the different functions of the two circuits
7.2.1 Heart
Core Describe the structure of the heart including the muscular wall and septum, chambers, valves and
associated blood vessels Describe the function of the heart in terms of muscular contraction and the working of the valves Investigate, state and explain the effect of physical activity on pulse rate Describe coronary heart disease in terms of the blockage of coronary arteries and state the
possible causes (diet, stress and smoking) and preventive measures.
7.2.2 Arteries, veins and capillaries
Core Name the main blood vessels to and from theheart, lungs, liver and kidney Describe the structure and functions of arteries, veins and capillariesSupplement Explain how structure and function are related in arteries, veins and capillaries Describe the transfer ofmaterials between capillaries and tissue fluid
7.2.3 Blood
Core Identify red and white blood cells as seen under the light microscope on prepared slides, and in
diagrams and photomicrographs List the components of blood as red blood cells, white blood cells, platelets and plasma State the functions of blood: red blood cells haemoglobin and oxygen transport white blood cells phagocytosis and antibody formation platelets causing clotting (no details) plasma transport of blood cells, ions, soluble nutrients, hormones, carbon dioxide, urea and plasma-
Proteins
Supplement
Describe the immune system in terms ofantibody production, tissue rejection and phagocytosis Describe the function of the lymphatic system in circulation of body fluids, and the production of-
lymphocytes Describe the process of clotting (fibrinogen to fibrin only)
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Transport in humans
The main transport system of humans is the blood system, also known as the
circulatory system.
Human circulatory system is made up of a pump called the heart, a net work of tubes
called blood vessels, and the blood.
Functions of circulatory system:
It transports useful things like oxygen from the lungs to the cells and digested food from
the small intestine to the cells.
It removes waste chemicals like carbon dioxide from the cells to the lungs and other
wastes from cells to the kidneys.
It transports hormones, antibodies and blood proteins.
Blood circulation:
The heart is the pump which circulates the blood through the blood vessels. Blood flows in arteries away from the heart to the different organs of the body. Blood
flows back to the hearty in veins.
Arteries are connected to veins by means of the smallest blood vessels called capillaries.
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The circulatory system allows a one-way flow of blood around the body.
The heart pumps blood giving it pressure so that it flows inside arteries and this helps to
maintain a one-way flow. This is good for getting blood to the capillaries.
We have valves called semi-lunar valves in our veins to make sure blood does not flow
backwards away from the heart. If this happened, blood would collect in veins, which
would swell, preventing proper circulation. These valves open when the pressure of theblood pushes against them, but they close when blood flows back to fill the pockets.
Double circulation:
Humans have a double circulatory system because the blood travels through the heart twice
during one complete circuit around the body. It includes a low pressure circulation to the lungs
and a high pressure circulation to the body tissues.
The heart is divided into two halves: right and left. The two halves are separated by a thick wall
of muscle called septum. It stops blood in the right side of the heart mixing with blood in the
left side.
The right side of the heart pumps blood to the lungs and back to the heart again. The pressure
need to force blood to the lungs is not very high because there is little resistance to flow in the
lungs as there is a spongy tissue filled with air. As blood flows through the capillaries in the
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lungs, gas exchange occurs. Blood absorbs oxygen and loses carbon dioxide. The blood that
flows through the lungs is rich in oxygen so it is called oxygenated blood and it is bright red in
color.
The left side of the heart pumps blood to the rest of the body and back to the heart again. The
pressure of blood leaving the left side is much greater than on the right side because there ismuch more resistance to flow than there is through the lungs. Gas exchange occurs as blood
flows through capillaries in organs such as muscles, the gut, liver and kidneys. Oxygen leaves
the blood and carbon dioxide enters. Blood that leaves capillaries and flows through veins
contains less oxygen and is called deoxygenated blood. It is dark red in color but is always
shown as blue in diagrams.
The double circulatory system helps to maintain blood pressure and making circulation
efficient
Structure of the heart:
It is a pump made of a special type of muscle called cardiac muscle. This muscle
contracts and relaxes regularly throughout life.
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The muscle is constantly active, so it needs its own blood supply, through the coronary
arteryto provide it with oxygen and glucose. Coronary arteries are present on the
surface of the heart.
The heart has two sides-the right side receives deoxygenated bloodfrom the body and
pumps it to the lungs for oxygenation while the left side receives oxygenated blood
from the lungs and pump it to the body. The heart is divided into 4 chambers-the two upper chambers are called atria and the
two lower chambers are called ventricles.
The chambers on the left side are completely separated from the ones on the right side
by the septum which prevents deoxygenated blood on the right side mixing with
oxygenated blood on the left side.
Both of the atria receive blood. The left atrium receives blood from the pulmonary
veins, which comes from the lungs. The right atrium receives blood from the rest of the
body, arriving through the vena cavae.
When the atria contract, they pump blood into ventricles.
When the ventricles contract, they pump blood out into arteries at higher pressure. Theblood in the left ventricle is pumped into the aorta, which takes blood around the body
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The right ventricle pumps blood into thepulmonary artery, which takes it to the lungs.
The ventricles have much thicker, more muscular walls than the atria. It helps them to
pump blood out of the heart and all around the body.
The wall of the left ventricle is much thicker than that of the right ventricle. This is
because the right ventricle pumps blood to the lungs, which are very close to the heart
But the left ventricle pumps blood all around the body and has to overcome more
resistance to flow. The thick wall helps to generate greater pressure to pump blood all
around the body.
Between each atrium and ventricle is a valve called AV valves, which prevent the blood
flowing back in to the right and left atrium when the right and left ventricles contract.
The AV valve between the right atrium and the right ventricle is called tricuspid valve
and that between the left atrium and left ventricle is called bicuspid valve or mitralvalve. There are tendons attached to the valves which stop the valves from going up too
far as the ventricles contract.
The place where the pulmonary artery and aorta opens in to the ventricles, there are
valves called semilunar valves which prevent the back flow of blood from these arteries
back to the ventricles.
Working of human heart (pumping of blood by the heart):
The heart pumps blood when its muscles contract. Contraction of the heart muscles is
called systole. When they contract, the heart becomes smaller and squeezes the bloodout.
After contraction, the heart muscles relax. When they relax, the heart becomes larger,
allowing blood to flow into the atria and ventricles. Relaxation of the heart muscles is
called diastole.
One systole and one diastole together called a heartbeat.
The normal healthy heart beats 70 times per minute.
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The rate at which the heart beats is controlled by a patch of muscle in the right atrium
calledpace maker. It sends electrical through the walls of the heart at regular intervals
which make the muscle contract.
Cardiac cycle: the changes that occur in the heart during one heart beat. It involves three
changes-diastole, atrial systole and ventricular systole.
Diastole: During this process:
All muscles of the heart chambers are relaxed. Blood flows into the heart.
The muscles of the atria relax allowing blood to flow into the heart from the veins- from
the body to the right atrium via vena cava and from the lungs to the left atrium via
pulmonary vein.
The AV valves open
The semilunar valves shut, preventing blood from flowing into the ventricles
Atrial systole:
The muscles of the atria contract. The muscles of the ventricles remain relaxed. Blood is forced from the atria into the ventricles through the open AV valves.
The semilunar valves remain shut.
The valves in the veins are forced to shut by the pressure of the blood, stopping the
blood from flowing back into the veins.
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Ventricular systole:
The muscles of the atria relax. The muscles of the ventricles contract.
Blood is forced out of the ventricles into the arteries- from the right atrium into the
pulmonary artery and from the left ventricle into the aorta.
The AV valves are forced shut by the pressure of the blood.
The semilunar valves are forces open by the pressure of the blood.
Investigate, state and explain the effect of physical activity on pulse rate.Describe coronary heart disease in terms of the blockage of coronary arteries and state thepossible causes (diet, stress and smoking) and preventive measures.
Effect of physical exercise on pulse rate:
The heart beats about 70 times a minute.
During exercise the heart rate increases to supply the muscles with more oxygen and
glucose and removing carbon dioxide quicker. These are needed to allow the muscles to
respire aerobically, so they have sufficient energy to contract.
Regular exercise is important to keep the heart muscle in good tone. This results in the
heart being more efficient in maintaining blood pressure and reduces the risk of coronary
heart disease and stroke.
How to measure the rate of heart beat:
The best way to measure the rate of heart beat is to take the pulse.
Use the first two fingers of your right hand and rest them on the inside of your wrist.
Feel for the tendon near the outside of your wrist.
If you rest your fingers lightly just over this tendon, you can feel the artery in your wrist
pulsing as your heart pumps blood through it.
Coronary heart disease:
Heart disease caused by blockage of coronary arteries that supply heart muscles with
blood.
Heart muscles need oxygen and glucose to keep it contracting. These are transported to
the heart in the coronary arteries.
If a coronary artery gets blocked-for example, by a blood clot-the cardiac muscles run
short of oxygen and glucose. They cannot obtain energy to allow them to contract. The
heart therefore stops beating. This is called a heart attack or cardiac arrest.
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Risk factors for CHD (Factors that increase a persons risk of getting coronary heart disease):
Cause Explanation Preventive measure
Diet: eating a diet with too
much saturated(animal) fat
Leads to cholesterol which
deposit in arteries, finally
blocking the blood vessel orallowing a blood clot to form
Eat a diet containing a very
wide variety of foods with
little fat in it. Use oils fromplants, and fish. Eat more
fresh fruits and vegetables.
Eat less red meat. Reduce
fried foods
Smoking Nicotine present in the cigarette
smoke cause damage to the
heart and blood vessels.
Stop smoking
Obesity Being overweight puts extra
strain on the heart and makes it
more difficult for the person toexercise.
Go on a controlled diet and
take regular exercise
Stress Tends to increase blood
pressure, which can result in
deposition of fatty materials in
the arteries.
Find ways of relaxing. Identify
the causes of stress and avoid
them.
Inherited factors (genes) Heart disease appears to be
passed from one generation to
the next in some families.
Make sure other factors do
not increase the risk of heart
disease. Monitor health.
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The main blood vessels to and from the heart, lungs, liver and kidney:
Vessel Organs
heart lungs liver kidneys
Bringing blood to
organ
Venacava to
right atrium;pulmonary vein
to left atrium
Pulmonary
artery
Hepatic artery;
hepatic vein
Renal artery
Taking blood
away from organ
Pulmonary
artery from right
ventricle; aorta
from left
ventricle
Pulmonary vein Hepatic vein Renal vein
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Structure and functions of arteries, veins and capillaries:
Arteries carry blood at high pressure, away from the heart to organs of the body.
They divide again and again and finally form very tiny vessels called capillaries.
Capillaries supply all cells with requirements like oxygen, glucose etc. and take away
waste products like carbon dioxide (exchange of materials). The capillaries gradually join up with one another to form large vessels called veins.
Veins return blood at low pressure from organs towards the heart.
Arteries:
Wall is thick and strong containing muscles and elastic fibres.
Narrow lumen
Smooth lining
Valves absent
Capillaries:
Permeable wall, one cell thick, with no muscle or elastic tissue.
Very narrow lumen, just wide enough for a red blood cell to pass through.
Presence of pores between the cells in the wall.
Valves absent.
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Veins:
Thin wall, containing very less muscle and elastic tissue than arteries.
Wide lumen.
Valves present
How the structure and functions are related in arteries, veins and capillaries
Blood vessel structure How structure is related to function
Artery 1. Thick and strong wallcontaining
muscles and elastic fibres.
2. Lumen very narrow, but
increases as a pulse of blood
passes through.3.Valves absent
1.Helps to carries blood at high
pressure.
1. Prevent bursting and maintain
pressure wave.
2. helps to maintain blood pressure.
3. high pressure prevents bloodflowing back.
Vein 1. Thin wall containing very less
muscle and elastic tissue than
arteries.
2. wide lumen
3. valves present
1. carries blood at low pressure.
2. reduce resistance to blood flow.
3. prevent back flow of blood
Capillary 1. very thin, permeable, one cell thick
wall with no muscle or elastic fibres.
2. very narrow lumen, one red blood
cell wide.
3. valves absent
4.pores present between cells in the
wall
1. allows diffusion of materials
between capillary and surrounding
tissues.
2. white blood cells can squeeze
between cells of the wall.
3. blood cells pass through slowly to
diffusion of materials and tissue
fluid.
4. allows easy diffusion of materials.
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Transfer of materials between capillaries and tissue fluid:
Tissue fluid: it is the fluid that surrounds all the cells in the body, formed from blood plasma
that leaks out of capillaries.
Formation of tissue fluid: When blood at high pressure flowing through the capillaries reach
body tissues, some of the constituents of the blood plasma and some white blood cells move
out through the small gaps in the capillary walls. The fluid formed in this way is called tissuefluid. It surrounds all the cells in the body. Red blood cells cannot get out because they are too
large and cannot change their shape to pass through the wall.
Function of tissue fluid: It helps substances to diffuse into and out of cells. Useful substances
like glucose,amino acids, fatty acids, vitamins, ions and oxygen pass from tissue fluid into
cells. Carbon dioxide and waste chemicals like urea and excess ions pass out of the cells intothe tissue fluid.
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7.2.3 BloodCore Identify red and white blood cells as seen under the light microscope on prepared slides, and in
diagrams and photomicrographs List the components of blood as red blood cells, white blood cells, platelets and plasma
State the functions of blood: red blood cells haemoglobin and oxygen transport white blood cells phagocytosis and antibody formation platelets causing clotting (no details) plasma transport of blood cells, ions, soluble nutrients, hormones, carbon dioxide, urea and plasma
Proteins.Supplement Describe the immune system in terms of antibody production, tissue rejection and phagocytosis Describe the function of the lymphatic system in circulation of body fluids, and the production of
lymphocytes Describe the process of clotting (fibrinogen to fibrin only)----------------------------------------------------------------------------------------------------------------------------- ---------------
Blood:
Composition of blood: Blood is made of a liquid called plasmain which 3 types of blood cells-red blood cells, white blood cells and platelets- are suspended.
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Functions of blood:
1. Blood plasma: It is the liquid part of the blood which forms 50% of blood volume.
Its functionis transportof blood cells, mineral ions like sodium and chloride ions, solublenutrients like amino acids, glucose, lipids and vitamins, hormones like insulin, glucagon etc.,carbon dioxide, urea and plasma proteins. It acts as a pool for amino acidsand containsblood proteins that are important in blood clotting.
Main substances carried by plasma:
Substances carried inplasma
from to
Amino acids Small intestine Sites of growth and repair
Carbon dioxide Respiring tissues lungs
Glucose Small intestine All tissues
Heat Liver, muscles All tissues
Hormones eg. Insulin Endocrine glands, eg.pancreas
Target organ, eg.liver
urea liver kidneys
2. Red blood cells: Their cytoplasm contains haemoglobin which transport oxygen from thelungs to the respiring tissues.
3. White blood cells:phagocytosis (fight diseases by surrounding bacteria and engulfing
them), and antibody production.
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4.platelets:form blood clots, which stop blood loss at a wound and prevents the entry of
germs into the blood.
Process of blood clotting:
When a blood vessel is cut, the blood platelets bump into the rough edges of the cut,
and react by releasing a chemical.
The chemicals released by the platelets and the damaged tissues set off a chain ofreactions which cause the fibrinogen, a soluble protein in the blood plasma, to change
into insoluble fibrin.
Fibrin forms fibres which form a mesh across the wound.
Red blood cells and platelets get trapped in the tangle of fibrin fibres, forming a blood
clot.
Advantages of blood clotting:
stops too much blood loss at a wound.
Stops pathogens getting into the body through breaks in the skin.
Differences between red blood cells and white blood cells:
Red blood cells White blood cells
More in number (5 million in every mm3) than
WBCs.
Very less in number than RBCs
Contain the pigment haemoglobin Haemoglobin absent
nucleus absent Nucleus present
Biconcave disc shaped No definite shape
Live only for 120 days as they have no nucleus Can live more than 120 days
Only one type of cells Two types-phagocytes and lymphocytes
Transport oxygen Fight pathogen, and clear up dead body cells
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Structural adaptations of RBCs for oxygen transport:
Contain haemoglobin which carries oxygen. Nucleus absent so more space for packing in haemoglobin.
Biconcave disc shape and small size give them large surface area compared with
their volume which speeds up rate of diffusion of oxygen.
IMMUNE SYSTEM
The function of WBCs is to fight pathogens (disease-causing bacteria and
viruses), and to clear up any dead body cells. There are many different kinds of WBCs. They all have the function of destroying
pathogens in our body, but they do it in different ways.
Generally there are two types of WBCs present in the blood; they are phagocytes
and lymphocytes.
Phagocytes:
A phagocyte cell
- larger than lymphocytes
- have lobed nucleus
- can move around the body, engulfing and destroying pathogens by a process
called phagocytosis.
Phagocytosis:
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Lymphocytes:
A lymphocyte cell
- smaller than phagocytes.
- have large spherical nucleus.
- function is to produce chemicals called antibodies, which are carried in the
blood to every part of the body which can destroy pathogens.
Function of lymphocytes:
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In our body, we have 1000s of different kinds of lymphocytes. Each kind is able
to produce a different type of antibody.
An antibody is a protein molecule with a particular shape and this shape is just
right to fit into another molecule on the outside of the pathogen. These
pathogen molecules are called antigens. When a pathogen enters the body, its antigen is recognized by one particular
type of lymphocyte.
This lymphocyte will start to divide repeatedly by mitosis, making a clone of the
same type.
These lymphocytes then produce their antibody, destroying the pathogen.
Antibodies attack the pathogens in a number of ways:
They make them stick together (agglutinate).
They dissolve their cell membranes.
They neutralize the toxins (poisons) that some pathogens produce.
Alert phagocytes to the presence of pathogens so that phagocytes will come anddestroy them.
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The fig. 4.2 shows the action of WBCs when bacteria enters the body.