About Lesson
Closed circulatory system
The blood is confined in blood vessels and does not therefore come into contact with body tissues.
The only entry or exit is through the walls of the capillaries.
The blood transports respiratory gases, nutrients and metabolic waste materials.
Blood flows at high pressure and therefore the tissues receive oxygen and nutrients at a high rate. Wastes materials are also removed at a faster rate and this makes the organism more active.
This is common in mammals, Aves, Pisces, amphibians and reptiles.
