The circulatory system
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The Circulatory System
The circulatory system constitutes of the blood vessels, lymph and blood, and serves various roles in the body. It transports oxygenated gases from the lungs to the cells, nutrients such as glucose, waste material from the cells for excretion in urine, and hormones from the glands to other body parts for maintenance of various conditions. Not all animals have a circulatory system because some like invertebrates have cells close to the environment where the exchange of materials occurs. The animal species that lack a circulatory system lack a heart too, and rely on blood vessels for pumping of blood and transport. The circulatory system is believed to have evolved in animals because it undergoes various developmental stages to form all the chambers. The earliest animals had a two-chambered heart, which evolved into a four-chambered heart.
There is an epidemic of heart diseases in the country because there are drastic lifestyle changes that have led to the accumulation of cholesterol in the heart vessels or atherosclerosis. Accumulation of cholesterol blocks the heart arteries, causing blood clots and other congenital disorders, some of which are fatal. Unhealthy lifestyles such as smoking, lack of exercises, eating foods rich in fats, cholesterol and high sugars are contributing factors to heart diseases. Genes may also contribute to heart diseases, but lifestyle plays the greatest role in acquiring heart diseases.
The risk factors for heart diseases include both controllable and uncontrollable factors. Uncontrollable factors are natural factors such as being male, post-menopausal women, old age, race, and family history of the disease. Controllable factors include lifestyle habits such as smoking, high levels of bad cholesterol, obesity, hypertension, physical inactivity, and stress. Anybody is at risk of contracting heart diseases, but those predisposed to the above-mentioned risk factors are at higher risk. However, an individual can reduce the risk of acquiring heart diseases by avoiding the controllable factors. The society can carry out campaigns to promote healthy living by encouraging people to eat foods low in cholesterol, exercise regularly and avoid smoking in order to reduce the incidences of heart diseases. I have not had any experience of a heart disease, but I recently lost a close friend who succumbed to heart attack due to obesity.
