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Why do we need a circulatory system?
•  The cells in your body must be supplied with
Nutrients (in the Plasma) and Oxygen (by the
Erythrocytes) so that they can respire to
generate the energy needed for life.
•  The waste products from respiration (Carbon
Dioxide and Heat) have to be carted away and
•  The army that defends your cells, the
Lymphocytes, has to be delivered to the site of
the conflict.
•  The patch-up merchants, ie the Platelets, that
stop excessive bleeding also have to delivered.
We have a closed system - what does that mean?
The same blood that run to your toes one minute, is
re-circulated to your head the next
Here’s another version of the human
circulatory system
Anatomy of the heart
Mammals have a heart with 4 chambers
Not all hearts have 4 chambers –
Reptiles and Amphibia have 3 chambered hearts
the septum between the ventricles is incomplete
The heart carries Deoxygenated
and Oxygenated Blood
- Three types of blood vessels
arteries, which carry blood away from the heart
to either the lungs or body tissues,
capillaries which are minute vessels which
deliver nutrients, water, and oxygen to the
body cells and pick up cellular wastes,
and the veins which transport blood back to
the heart.
Arteries – high pressure vessels
Veins – Low pressure vessels
Muscles contraction helps push
blood flow back to the heart
What is blood made up of:
Cellular component
•  Red blood cells( Erythrocytes) - their
function is to transport oxygen
•  White blood cells (Leucocytes) - their
function is to fight of infection
•  Platelets ( Thrombocytes) - their function
is to form network over any holes that
become apparent in the capillary beds
The source of all blood cells – Bone
Structure of Red Blood cells
•  Red blood cells – biconcave to increase
surface area and allow greater flexibility
White blood cells, also known as
leukocytes, are larger than erythrocytes,
have a nucleus, and lack haemoglobin.
They function in the cellular immune