Download 6.2 Blood

 English physician
 First known person to
completely describe
the detail for the
circulatory system
and the properties of
blood.
- Demonstrated that blood flows in one
direction in larger blood vessel's
(unidirectional) and these vessels contain
valves to prevent back flow.
- Also demonstrated that the heart pumps
blood out in arteries, and blood returns in the
veins ready to be ‘recycled’ by the body
- He predicted the existence of capillaries (no
microscopes yet)
- Blood was seen flowing in capillaries in 1660,
after his death.
Galen was an ancient Greek philosopher.
Galen’s theories included the ‘vital spirit’
(for details see page 290). Harvey would
never have been able to disprove Galen’s
theories without evidence from systematic
scientific investigations.
“Diligent observation is therefore requisite in
every science, and the senses are frequently
to be appealed to. We are, I say, to strive after
personal experience, not to rely on the
experience of others, without which no one
can properly become a student of any
branch of natural science” Harvey, W., 1651.
On the Generation of Animals.
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The body has 4–6 liters of blood.
About 45% of blood volume is cells.
The other 55% is plasma —a straw-colored fluid.
Plasma is 90% water
and 10% dissolved gases, salts, nutrients, enzymes,
hormones, waste products, and plasma proteins.
Blood Composition
Plasma
Platelets
White blood
cells
Red blood
cell
Whole Blood
Sample
Sample Placed
in Centrifuge
Blood Sample
That Has Been
Centrifuged
Blood Cells
 The cellular portion of
blood consists of:
 red blood cells
(erthrocytes)
 white blood cells
(Leucocytes)
 platelets
Red Blood Cells
The most numerous cells in the blood are the red
blood cells.
Red blood cells are called Erythrocytes
Red blood cells transport oxygen.
Red blood cells get their color from hemoglobin.
Hemoglobin is an iron-containing protein that
transports oxygen from the lungs to tissues of the
body.
Red blood cells (erythrocytes) look like disks that
are thinner in the center.
They are produced in red bone marrow.
They have no nuclei.
They live for about 120 days.
Then they are destroyed by the liver.
White Blood Cells -- Leukocytes
 White blood cells do not contain hemoglobin.
 They are less common than red cells.
 White blood cells are produced in bone
marrow.
 They contain nuclei.
 White blood cells may live for days, months, or
years.
White blood cells are the “army” of the circulatory
system—they
 guard against infection,
 fight parasites,
 attack bacteria.
There are many types of white blood cells.
Phagocytes engulf (eat) and digest bacteria and
other disease-causing microorganisms.
B Lymphocytes produce antibodies.
Antibodies are essential to fighting infection and
help to produce immunity to many diseases.
• Thick muscular, elastic
walls
• Blood away from heart
• Blood at v. high pressures
• No valves (except aorta &
pulmonary artery)
• Blood flow is rapid in
pulses (pulsatile)
Systolic pressure: highest pressure lumen widens, and the elastic
stretches storing potential energy.
Diastolic pressure: at the end of the heart beat, pressure falls.
Stretched elastic fibers, squeeze blood in the lumen.
Vasoconstriction: circular muscles in arteries contract, lumen
narrows. Blood pressure increases. Controlled through
hormones/nervous system – when might this happen?
Vasodilation: opposite of vasoconstriction.
• Blood back to heart
• Blood at lower pressure
• Thinner walls than arteries
• Can dilate and be flattened
• Contain valves
• Moderate speed blood flow
Prevent backflow
A valve is described as a three cupshaped flap of tissue (pocket valve)
Ensure blood circulates in the correct
direction.
• Microscopic
• Form network throughout body
• Blood at moderate pressure but low speed
• V. thin, permeable walls (10µm), materials easily
exchange
• No valves
Figure 6, page 294.
1. Sketch this diagram
2. Use this table to make sure you are
able to distinguish between and
correctly identify the different blood
vessels.