CIRCULATORY SYSTEM
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March 01, 2016 |
1 Comment |
CIRCULATORY SYSTEM
Circulatory
system:
• Efficient distribution system
• Network of 100,000 km of blood vessels
•Supplies cells with nutrients and
oxygen and removes carbon dioxide and waste products
• Transports hormones
•Plays an important role repairing tissues and protecting the body from
infection
Organs
of the Circulatory System
* Blood: Type of connective
tissue (cells & liquid)
* Heart: Multi-chambered,
muscular organ
-Overall flow of blood via blood vessels à from the heart to the tissues
throughout the body back to the
heart
- Body contains 5 L
of blood
—
Types
of Blood Vessels
1.Capillaries:
•Microscopic blood
vessels- make contact with all cells of the body
•Walls of capillaries
consist of a thin layer of epithelial tissue à enables
diffusion of nutrients and oxygen out of the blood & the diffusion of waste
products into the blood
2.Arteries:
•Blood flows from the
heart to the capillaries through thick walled blood vessels = arteries
•Walls of arteries =
epithelial tissue wrapped in layers of smooth muscle and connective tissue
•Muscle tissue enables
arteries to constrict & dilate; Blood in arteries is under pressure due to
the heart’s pumping action
.
Veins:
—Blood returns from
the capillaries to the heart through vessels = veins
—Walls of veins
consist of epithelial tissue surrounded by smooth muscle & connective
tissue… but muscle layer is thinner than that in arteries
—Blood is under little
pressure
—Contracting skeletal
muscles squeezes the
veins and forces blood back to the heart
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