Chapter 2 –Blood Circulatory System Page 1 of 10
Kenneth Wong 019-363 9338
Blood Circulatory System
- Consists of heart, blood and blood vessels
- Functions :
o Transport oxygen and nutrients to all body cells
o Transport waste products (carbon dioxide and urea) for elimination
o Transport chemicals such as hormones and antibodies
- Humans have a closed blood circulatory system which means blood flows in closed vessels and
exchange of food and gas takes place in the walls of the capillaries
Artery Vein
Blood Capillaries
- All arteries carry blood out
of the heart except the
pulmonary artery
- Thick, muscular, strong
elastic wall to support high
pressure
- Small lumen (hole) and has
no valves
- All veins carry blood to the heart
except the pulmonary vein
- Thin, less muscular and less
elastic wall because there is no need
to withstand the low pressure
- Large lumen (hole) and has valves
to ensure blood flows in one
direction
- Fine blood vessels which act as connectors that join the blood vessel system of
arteries and veins
- Functions :
o Carry blood from the artery to the vein
o Carry oxygenated blood from artery to body cells
o Carry deoxygenated blood from body cells to the vein
- Blood flows slowly due to low pressure which enables diffusion and exchange
of substances to proceed at maximum rate
- It is one cell thick, has a small lumen and has no valves
Chapter 2 –Blood Circulatory System Page 2 of 10
Kenneth Wong 019-363 9338
Structure of the Heart and its Function
Heart
- Muscular organ which contracts and relaxes simultaneously to pump and circulate blood to the whole body
- Situated in the thoracic cavity between the left lung and the right lung with 4 large chambers : left atrium
and right atrium (upper chambers), left ventricle and right ventricle (lower chambers)
- Ventricles have a larger space, thicker and more muscular walls than the atria
- The wall of the left ventricle is thicker and more muscular than the right ventricle because stronger
pressure is needed to pump blood to the whole body while the right ventricle only has to pump to the lungs
- Valves in the heart prevent back flow and makes sure it flows in only one direction
- The left chamber of the heart contains oxygenated blood while the right deoxygenated
Vena Cava Aorta
Channels deoxygenated blood from all parts of the
body to the right atrium
Carries oxygenated blood from the heart to the whole
body
Pulmonary Artery Pulmonary Vein
Carries deoxygenated blood from the heart to the
lungs
Carries oxygenated blood from the lungs to the heart
Valves in the Heart
Tricuspid Valve : Prevents blood in the right ventricle
from flowing back to the right atrium
Bicuspid Valve : Prevents blood in the left ventricle
from flowing back to the left atrium
Semilunar Valve : Prevents blood leaving the heart
from flowing back
Chapter 2 –Blood Circulatory System Page 3 of 10
Kenneth Wong 019-363 9338
Blood Circulation
Pulmonary Circulation Systemic Circulation
- Transport blood from the heart to the lungs and back to the heart
- Ensures that blood lacking in oxygen gets a new supply of oxygen
- Carbon Dioxide is eliminated in the lungs
- Oxygen diffuses into the blood from the lungs
- Oxygenation of red blood cells occurs in the alveolus
- Goes to the lungs through the pulmonary artery and comes back
through the pulmonary vein
- Consists of all blood vessels from the heart to all the parts of the
body (except the lungs) and back to the heart
- Blood that reaches the body tissues through the blood capillaries will
release oxygen and digested food (nutrients) to the body tissues
- Pumps blood to the whole body through the aorta and collects
deoxygenated blood through the vena cava
- Blood lacking oxygen is collected through the veins
Pathway of Blood Flow
Vena Cava (collected deoxygenated blood) → Right Atrium → Tricuspid Valve → Right Ventricle → Semilunar Valve → Pulmonary Artery → Lungs →
Pulmonary Vein → Left Atrium → Bicuspid Valve → Left Ventricle → Semilunar Valve → Aorta → Whole Body → Vena Cava (repeat)
Chapter 2 –Blood Circulatory System Page 4 of 10
Kenneth Wong 019-363 9338
Difference between Oxygenated Blood and Deoxygenated Blood
Oxygenated Blood Deoxygenated Blood
High Oxygen Concentration Low Oxygen Concentration
Low Carbon Dioxide Concentration High Carbon Dioxide Concentration
High Concentration of digested food (glucose and amino acid) Low Concentration of digested food (glucose and amino acid)
No waste products present (Urea) Waste products present (Urea)
Artery and Pulmonary Vein carries it Vein and Pulmonary Artery carries it
Bright Red Colour Dark Red Colour
Maintaining a Healthy Heart
- Balanced food intake, exercise, low work pressure and reduced intake of food rich
in fat (cholesterol) helps
- Causes of heart diseases :
o Damage to valves in the heart
o Failure of ventricles and atrium muscular walls to contract
o Blockage of blood supply to the heart (cholesterol deposits)
- Importance :
o Avoid contracting heart disease which can cause death
o Ensure cells get enough supply of oxygen and food
Chapter 2 –Blood Circulatory System Page 5 of 10
Kenneth Wong 019-363 9338
Human Blood
- Contains : plasma, red blood cells, white blood cells and platelets
- Functions :
o Transport oxygen and digested food (nutrients) to cells
o Transport waste products (urea and carbon dioxide) from body tissues to
excretory organs
o Maintain a body temperature at 37 oc by spreading heart to all parts of the body
o Carry hormones to body tissues, regulate body processes and fight diseases
Red Blood Cells Platelets
- Biconcave-disc shaped with no nucleus
- Functions to transport oxygen to body cells with a lifespan of 4
months
- They are destroyed in the liver and the spleen but created in the
bone marrow
- Small pieces in the blood that has no definite shape
- They do not have a nucleus and is very small
- Functions to clot blood in a wound to prevent excessive blood loss
- It is produced in the bone marrow and dies within a few hours to
nine days
Chapter 2 –Blood Circulatory System Page 6 of 10
Kenneth Wong 019-363 9338
Plasma
White Blood Cells
- Liquid part of the blood, yellow and has alkaline properties
- Slightly sticky and contains dissolved substances
Composition of Plasma
Component Percentage (%)
Water 92
Protein 6 - Larger in size than red blood cells but does not have a definite
shape
- They have a nucleus and is part of the body’s defense system
- Functions to protect the body from pathogens (microorganisms)
like bacteria and viruses
- They are produced in the bone marrow and lymph glands
- They can kill bacteria in the blood or produce antibodies to
neutralize toxins (poisonous substances) produced by
microorganisms
Mineral Salts 0.8
Lipid 0.6
Glucose (blood sugar) 0.1
Others 0.5
Blood Groups
- Classified into 4 groups : A, B, AB, O
- Blood Donor : one who donates blood
- Recipient : one who receives blood
- Blood Transfusion : Transfer of blood from a donor to a recipient
- The blood of the recipient and the donor has to be compatible or
blood clotting (agglutination) will occur which can cause death
- People with blood group O are universal donors
- People with blood group AB are universal recipients
Chapter 2 –Blood Circulatory System Page 7 of 10
Kenneth Wong 019-363 9338
Blood Donation Storage and handling of
Blood
- An accident or an operation causes loss of blood
- This blood needs to be replaced with blood transfused from
another person
- Massive blood loss can damage bodily functions and cause death
- Must be carried out with care to prevent blood coagulation
- Blood transfused has to be suitable and compatible
- Important because there is no substitute
- Two types of transfusion :
o Through blood kept in a bank
o Direct channeling from the donor to the recipient
- Each blood donor must be
tested to know the blood
group and examined if
they are healthy
- The blood must be tested
for diseases like Hepatitis
B and C, HIV and
venereal diseases like
syphilis
- Blood must be stored in a
cold place before use
Chapter 2 –Blood Circulatory System Page 8 of 10
Kenneth Wong 019-363 9338
Transpiration
- Process in plants where water is lost through evaporation
from the surface of the leaves
- If too much water is lost, the cells of the plant would lose
turgor (support) pressure and wilt then die
- If a plant is wrapped in a bag, droplets of water will be
formed on the surface of the bag
- The presence of water vapour can be tested with dry cobalt
chloride paper which turns from blue to red
Stomata
- Pores / openings on the surface of the leaves and normally
found on the undersurface of leaves
- Most water vapour is lost through the stomata of leaves
- The pore size is controlled by the guard cells to control the
loss of water from the plants
Factors Affecting the Rate of Transpiration
- When the plant is put under a hot Sun, the
water droplets are more than when it was not
exposed to the Sun
- When the plant is put under a fan without the
plastic bag, the weight of the plant will decrease
- When the plant is put in the forest (high
humidity), the plant does not lose as much water
as it did when it was under the fan
Temperature Wind Intensity
Higher temperature, higher transpiration rate Higher wind intensity, higher transpiration rate
Light Intensity Humidity (surrounding water)
Higher light intensity, higher transpiration rate Higher humidity, lower transpiration rate
Importance of Transpiration
Get rid of excess water from plants Cool plants on hot days Transport water and mineral salts
Chapter 2 –Blood Circulatory System Page 9 of 10
Kenneth Wong 019-363 9338
Transport in Plants through Xylem and Phloem
Monocotyledonous Plant Dicotyledonous plant
- One Cotyledon Seed
- Parallel Veins
(leaves)
- Fibrous Roots
- Flower Parts in
Threes or multiples
of Threes
- Two Cotyledon Seed
- Network-like Veins
(leaves)
- Tap Roots
- Flower parts in Four
or Fives or multiples
of Four and Fives
Leaf Leaf
Stem Stem
Root Root
Chapter 2 –Blood Circulatory System Page 10 of 10
Kenneth Wong 019-363 9338
Functions of Phloem and Xylem
Test for Xylem Test for Phloem
Experiment :
1. A few drops of red colouring is added to the
water
2. The plant is observed after a few days
3. The xylem appears to be reddish and proves
that water flows through the xylem vessels
4. Coloured water is added to make the
transport visible
Experiment :
1. A plant is ringed and is observed after a few
days
2. A little paraffin oil is applied to the exposed part
3. There seems to be a swelling on the upper part
of the stem
4. However the plant has still not wilted because
there is still a supply of water
Facts :
Xylem is a vessel that transports water and
mineral salts from the roots to the leaves
Facts :
Phloem is a vessel that transports food (glucose) from
the leaves to the stem and roots after synthesizing it
through photosynthesis
Examples of Monocotyledonous Plants Examples of Dicotyledonous Plants
Legumes (pea, beans, lentils, peanuts) daisies, mint,
lettuce, tomato and oak
Balsam Plant, Rambutan Tree, Hibiscus Plant, Grains,
(wheat, corn, rice, millet) lilies, daffodils, sugarcane,
banana, palm, ginger, onions, bamboo, sugar, cone, palm
tree, banana tree, and grass