12.1: Blood and its Components
Blood is made up of four main components; plasma (55%), white blood cells and platelets (1%)
and red blood cells (44%). The components of blood are essential in helping the circulatory
system carry out its main functions.
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Red blood cells, or erythrocytes, have no nucleus. Each contains approximately 280 million
molecules of Hemoglobin, which transports oxygen in the blood.
White blood cells, or leukocytes, help fight infection by destroying pathogens.
Platelets, or thrombocytes, are fragments of cells that play a key role in blood clotting.
Transportation of gases, nutrients, wastes, and other chemical substances
Many substances are dissolved in the blood plasma and are transported from the blood vessels
to cell and vise versa by diffusion. Blood transport nutrients to all parts of the body and carries
waste products from the cells to eventually be removed. Hemoglobin is responsible for
transport large quantities of oxygen and is a protein found in red blood cells.
Protection against Disease
White blood cells (different types) work together to destroy pathogens. Phagocytes engulf and
destroy viruses, bacteria, and other pathogens using a process of phagocytosis.
Preventing Blood Loss
When the body is injured, platelets release chemicals that lead to the formation of blood clot,
preventing the loss of large amounts of blood
Definition:
Vasodilation:
Vasoconstriction:
Learning Check:
1. Which component of blood is primarily responsible for each event? [k/u]
a) initiating blood clots
b) transporting wastes
c) transporting glucose
d) killing bacteria
2. How does the amount of hemoglobin in the blood relate to the blood’s ability to
transport oxygen? [k/u]
3. Vasodilation also occurs during physical activity even if the body temperature does not
rise. What function might this serve? [k/u]