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Chapter 25: Blood

Composition of Blood

Plasma

  • 55% of blood

  • 90% is water

  • 7% is protein

  • 3% is dissolved materials

  • Golden straw colour

Function

  • Transport of dissolved substances e.g:

  • Digested foods - glucose, water, vitamins, minerals

  • Wastes- urea, salt, carbon dioxide

  • Hormones - insulin

  • Antibodies

Red Blood Cells (red blood corpuscles/erythrocytes)

  • Made in bone marrow of large bones e.g. long bones in arms and legs - sternum, ribs.

  • No nucleus

  • No mitochondria

  • Biconcave shape - larger surface area

  • Flexible cell membranes

  • Contain haemoglobin - high affinity for oxygen

  • 5 million per cubic millimetre

  • 3 million replaced every second

  • Life of 4 months

  • Function: Transport oxygen

White Blood Cells

  • Have a nucelus

  • No definite shape

  • Formed in bone marrow - mature in spleen and lymphatic system.

  • Life of a few days to a few years

  • Less numerous than RBCs

Function

Protect against disease in two ways:

  • Lymphocytes - produce antibodies (25% of WBCs, 10 year lifespan, large round nucleus)

  • Phagocytes - engluf bacteria by phagocytosis, also known as macrophages (survive 6-9 days, nucleus kidney shaped)

Platelets (thrombocytes)

  • Made in bone marrow

  • Cell fragments

  • Function: Clot blood (damaged cells produce chemical that causes platelets to clot)

Functions of Blood

  • Transport heat

  • Transport of food, hormones etc.

  • Fight infection through phagocytosis, lymphocytes producing antibodies, and platelets clotting to prevent microorganism entry.

Blood Groups

  • A

  • B

  • AB

  • O

400 other blood groups, most common is Rhesus factor, which is a chemical on the surface of red blood cells.

85% Rh+ 15% Rh- (irish population)

Rhesus negative mother with rhesus positive baby can result in problems.