Transport in Humans
Topics
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Overview of human transport system
Components of Blood
Structure of Heart
Coronary Heart Disease
Blood Vessels
OVERVIEW
Overview
• Recall in Sec 1, we studied respiration
• All living cells in our body (from our brain to
our muscles to our organs) perform
respiration to have the energy to function
• Recall that in order to respire, oxygen is
required, and carbon dioxide is given out
• Where does all this oxygen come from?
Where does all this carbon dioxide go?
Lungs
Overview
• Recall in Sec 1 we studied about the lungs in
respiration
• The lungs is where gaseous exchange take
place in our body
• We absorb oxygen from the atmosphere at
the lungs
• We also give out carbon dioxide to the
atmosphere at the lungs
• Gaseous exchange occurs by diffusion
Overview
• How does oxygen from the lungs reach the
rest of the body (which needs it for
respiration?)
• How does carbon dioxide from the rest of the
body reach the lungs?
• Through the movement of our blood
• The system where our blood moves to and fro
from our lungs to the rest of the body is
known as the cardiovascular system
• Note: “cardio” is the root word for “heart”
Did you know? (not in syllabus)
• The cardiovascular
system is not the only
system of moving fluids
in the body
• There is another
system called the
lymphatic system,
which is an important
part of our immune
system
COMPONENTS OF BLOOD
Components of Blood
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1. Red Blood Cells
2. Plasma
3. White Blood Cells
4. Platelets
Red Blood Cells
• Red Blood Cells (also called erythrocytes)
account for the red colour of our blood
• It is biconcave in shape and has no nucleus
• Contains the protein haemoglobin (which
contains Iron), which is the protein which
absorbs oxygen to the red blood cell
Red Blood Cells
• Is bright red when oxygenated, dark red when
deoxygenated
• Produced in our bone marrow
• Anemia is the disease when you have too few red
blood cells (or haemoglobin) in your blood
Blood Plasma
• Plasma is the liquid portion of our blood
• It is actually pale yellow (“straw”) in colour
• It contains mostly water, with dissolved
proteins, sugars, minerals and other
substances (including carbon dioxide)
White Blood Cells
• Also known as leukocytes, white blood cells have
a nucleus (unlike red blood cells)
• There are different types of white blood cells, but
they all assist in the role of immunity
• Lymphocytes produce antibodies (which attack
pathogens or flag them for other cells to kill
them)
• Phagocytes attack pathogens by devouring them
• Leukemia is a disease where the body produces
too much white blood cells
Platelets
• Also known as thrombocytes, platelets are
mainly used for clotting the blood to stop
bleeding (e.g. during a cut)
• Platelets also have no nucleus
Components of Blood
• When you put blood in a centrifugue, the
components of blood will separate as shown:
STRUCTURE OF THE HEART
Structure of the Heart
• Recall the basic purpose of the heart:
– bring oxygenated blood from lungs to rest of body
– bring deoxygenated blood from rest of body to lungs
• A blood vessel which carries blood AWAY from
the heart is called an artery
• A blood vessel which carries blood TOWARDS the
heart is called a vein
• The pulmonary artery / vein connect the heart to
the lungs
Structure of the Heart
• Note the left/right inversion
• Left side of the heart is slightly bigger than the
right side
• Each side of the heart has 2 chambers – an
atrium and a ventricle
Structure of the Heart
• Blood enters from outside the heart into the
atrium
• Blood the flows from the atrium into the
corresponding ventricle. A one-way valve
prevents the blood from flowing back from the
ventricle into the atrium
• The muscle in the ventricle wall contracts,
pushing the blood out of the heart through the
pulmonary artery (right) or aorta (left)
• Semi-lunar valves prevent the blood from flowing
back into the ventricles
BLOOD VESSELS
Blood Vessels
• 1) Arteries
• 2) Vein
• 3) Capillaries
Arteries
• Blood which is pumped out of the heart
(ventricles) goes straight into the arteries first
• That is why blood pressure in the arteries is
the highest
• Arteries have the thickest layer of muscular
wall to withstand this high pressure
• Pulmonary artery brings deoxygenated blood
from heart to lungs
• Aorta brings oxygenated blood from heart to
other parts of body
Veins
• Veins are the blood vessels which bring back the
blood to the heart
• Much lower pressure than arteries, so their walls
need not be as thick
• Veins contact valves to prevent backflow of
deoxygenated blood (note: pulmonary vein does
not have valves because it carries oxygenated
blood)
• You can see this using your own veins!
(https://www.youtube.com/watch?v=A6isZ4dCT
Mo)
Capillaries
• After oxygenated blood has been pumped into
the arteries, they bring it to the various parts of
the body which needs the oxygenated blood (e.g.
brain, muscles, etc.)
• When it reaches this destination, diffusion occurs
between the blood and the destination tissue,
– allowing for oxygen (and other nutrients) to be
transferred from the bloodstream to tissue
– carbon dioxide (and other waste products) to be
transferred to the bloodstream from tissue
• Capillaries have very very thin walls (only one cell
thick) to facilitate this diffusion.
Careful!!
• Do not use the term “cell wall” to refer to the
thickness of the artery, vein or capillary.
• Recall what is a cell wall!
• Cells in humans don’t have cell walls!!!
• Use “artery wall” or “the wall of the vein”, etc.
CORONARY HEART DISEASE
Coronary Heart Disease
• The heart beats around 115 200 times per
day. The muscles of the heart (particularly the
ventricular muscles) do a lot of work
• Recall that muscles need oxygen (and blood!)
in order to do their work
• The coronary arteries supply blood to the
heart muscles
• However, if the arteries don’t manage to
supply sufficient blood, the person suffers
from coronary heart disease
Coronary Heart Disease
• How does that happen?
• The coronary arteries may start to build up
fatty deposits INSIDE the artery wall
• When that happens the lumen of the artery
becomes smaller and smaller, constricting the
artery
• Blood pressure will also increase when the
artery is constricted
Coronary Heart Disease
Factors Causing Coronary Heart
Disease
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High fat (and cholesterol) diet
Smoking
Stress
Lack of Exercise