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- The Human Circulatory System
- The vertebrate heart consists of muscular chambers whose contraction is controlled by electrical impulses.
- Blood transports dissolved nutrients, wastes, and hormones throughout the body.
- The blood vessels carry blood to all parts of the body.
- The Lymphatic System
- Lymphatic vessels resemble the veins and capillaries of the circulatory system.
- The lymphatic system returns fluids to the blood.
- The lymphatic system transports fats from the intestine to the blood.
- The lymphatic system helps defend the body against disease.
- Respiratory Systems Facilitate Gas Exchange by Diffusion
- The Human Respiratory System
- The conducting portion of the respiratory system carries air to the lungs.
- Gas exchange occurs in the alveoli.
- Oxygen and carbon dioxide are transported using different mechanisms.
- Air is inhaled actively and exhaled passively.
- Breathing rate is controlled by the respiratory center of the brain.
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