FACT
The average adult
heart beats:- 72 times a
minute - 100 000
times a day - 3 600 000
times a year - A billion
times during
a lifetime.
Figure 8.16: Cross-section showing the differences between a) arteries, b) veins and c) capillaries.8.3 Lymphatic circulatory system
The lymphatic system is part of the circulatory system, comprising a network of inter-connected
tubes known aslymphatic vesselsthat carry a clear fluid calledlymphtowards the heart.
The lymphatic organs play an important part in the immune system. The lymphatic sys-
tem transports the white blood cells which are important in the immune response against
pathogens.
See video: SHORTCODEat http://www.everythingscience.co.zaChapter 8. Transport systems in animals 239