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Title: The blood system
Description: International Baccalaureate Biology SL Topic 6.2 2017 Clear and detailed notes of topic 6.2 from the book and lecture
Description: International Baccalaureate Biology SL Topic 6.2 2017 Clear and detailed notes of topic 6.2 from the book and lecture
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The blood system
Topic 6
...
2
Biology SL
➢ When blood leaves an arteriole it enters a capillary bed rather than a single
capillary
○
Much of the blood pressure is lost
➢ They are extremely thin (one cell thick) and therefore chemical exchanges occur
here, as it’s more efficient
➢ Blood cells make their way through capillaries one cell at a time
Veins
➢ Veins are blood vessels that collect blood from capillaries and returns it to the heart
➢ Pulmonary veins are blood vessels that lead oxygenated blood from the lungs back
to the heart
➢ The blood flow through veins is slower than through arteries, because the blood has
lost a great deal of pressure
○
That’s why they have thin walls and larger diameter
➢ They also have internal “one-way” valves that help keep the blood flowing toward
the heart
➢ Vena cava is the biggest vein in our bodies
➢ Vanule is the smallest type of vein
Artery
Capillary
Vein
Thick walled
1 cell thick
Thin walled
No exchanges
Exchanges
No exchanges
No internal valves
No internal valves
Internal valves
High internal pressure
Low internal pressure
Low internal pressure
The heart
➢ Each side of the heart has a collection of chambers for the blood that moves in from
the veins
○
They are thin-walled, muscular chambers that are called atria (sing
...
2
Biology SL
The muscle around the left ventricle is the thickest, because it sends blood
to the body
○
The force by which the blood is sent out is referred to as blood pressure
➢ The blood that is pumped out of the heart makes a circuit through the following
sequence of blood vessels
○
Aorta
○
A large artery
○
Smaller arteries
○
An arteriole
○
A capillary bed
○
A venule
○
Larger veins
○
A large vein
○
Vena cava
➢ The right side of the heart sends out blood along our pulmonary circulation
○
Oxygen poor blood goes from the heart to the lungs and oxygen rich blood
from the lungs to the heart
➢ The left side of the heart sends blood along the systemic circulation
○
Blood goes from the heart to our organs leaving oxygen and taking carbon
dioxide
Control of the heart rate
➢ The heart consists of a special kind of muscle called cardiac muscle
○
It spontaneously contracts and relaxes without any cont
Title: The blood system
Description: International Baccalaureate Biology SL Topic 6.2 2017 Clear and detailed notes of topic 6.2 from the book and lecture
Description: International Baccalaureate Biology SL Topic 6.2 2017 Clear and detailed notes of topic 6.2 from the book and lecture