The heart is a pump that provides the energy to drive blood through the circulatory system.

Parity of the heart is understandable from the embryological point of view. Separation of the left and right hearts ensures supply of well-oxygenated blood to the tissues.

Control of the heart rate is by the electrical conduction system.

THE BLOOD CIRCULATORY SYSTEM

The circulatory system is an illustration of the natural physical laws of equilibrium and control.

Blood circulation follows biophysical principles and is another illustration of the unity of creation because physical and biological phenomena follow the same laws.

The efficiency of the heart’s energy conversion is 20%, better than many machines.

The circulatory system adjusts to changes. Blood flow to the skin increases in hot temperature to release heat. During digestion more blood flows into the GIT. During exercise cardiac output increases ten-fold and work done by the heart can increase 500-fold.

RESPIRATORY SYSTEM

The lungs are the main organs of respiration. The lungs provide a big opportunity for exchange between the internal and external environments.

The term respiration can be used in 2 different ways to mean ventilation or tissue respiration.

Coughing and sneezing expel irritants. In coughing the glottis is closed raising intra-ductal pressure to 100mm of mercury. When the glottis is opened suddenly, a jet of air under high pressure is released accompanied by the familiar sound of coughing. The glottis is not closed in sneezing but pressure still builds up.