Sarah noticed his hot red face after physical activity. This was because when her body temperature began to rise, the body sweated and dilated the blood vessels in her skin to reduce this temperature. Because oxygenated blood runs down the surface of the skin, which helps radiate heat and prevent overheating, the face turns red and gets a little warm from blood circulation. This whole process was done by Sarah's skeletal muscles and blood vessels as a homeostatic response that sought to establish a balance in the girl's body.
Health, population and environment education is introduced as an integrated subject due to profound interrelationship that exists among the subject matters of these three disciplines. The natural physical aspects and man- made things come under the physical aspect.
