Dr Jones Nghaamwaones Nghaamwa
This article is a prelude to future articles that will explain different heart conditions to the lay public. Understanding normal function of the heart is important when considering different disease states affecting that organ.
What is the function of the heart?
The heart is one of the vital organs of the body. In it’s purest form it is a natural pump whose main function is to ensure that blood is circulated around the body. It’s functions are closely related to the functions of all the other organs mainly the lungs. Together with pipes that carry blood (blood vessels) to and from different organs, the heart makes up the circulatory system.
Blood carries nutrients to the body cells (building blocks) ensuring vitality. After nourishing an organ the same blood picks up the metabolic waste products which are delivered to other organs responsible for getting rid off or altering such products. Lungs take in air that we breath (oxygen) vital for cellular function. Within the substance of the lungs are millions of small pipes through which blood flows. As this blood traverses the lungs oxygen enters and carbon dioxide exits. Blood leaving the lungs can be considered clean and returns to the heart for pumping to the rest of the body.
Structure of the heart
The heart is made up of muscle that cannot be controlled voluntarily. There are 4 compartments or pumps within the heart separated by valves. The top chambers called atria are receiving chambers but also contribute a small percentage of the heart’s pumping function. The bottom chambers referred to as ventricles are the main pumps responsible for ejecting blood to the lungs or body. Two separate pumps thus exist connected in series. A right sided pump responsible for receiving blood from the body and pumping it to the lungs. Similarly there is a left sided pump receiving blood from the lungs pumping it to the body. Between the atrial and ventricular chambers there are valves that prevent back flow of blood. Other valves exist between the heart and the large pipes (blood vessels) carrying blood to the lungs or body.
An electric circuit is wired within the heart muscle. Under the influence of brain, hormonal and other factors, the pumping rate of the heart is controlled. Normally the heart beats in a rhythmic fashion at a rate between 50-100 beats per minute. Also, the strength with which the heart beats is under the influence of various factors. As an example, under conditions of high demand for nutrients in various organs such as exercise, the heart pumps faster and stronger. A sac called the pericardium surrounds the heart and normally contains a small amount of fluid.
As the heart pumps blood to nourish other organs it also pumps blood to itself via small blood pipes called the coronary arteries. Such pipes originate from the large artery leaving the left heart carrying oxygenated blood and form a distribution network around the heart muscle. Coronary arteries supply vital nutrients required for heart to continue pumping. Blockage of the coronary arteries leads or inadequate blood supply in relation to demand leads to what is commonly referred to as a heart attack.
Diseases of the cardiovascular system can affect different components of the heart structure. Manifestation of such disease reflect the abnormal functioning of the heart and it’s consequences on the other function vital organs of the body. An understanding of the structure and function of the heart is thus important to comprehend heart diseases which we feature in subsequent articles titled.
* Dr Jones Nghaamwa is a cardiothoracic, heart and lung surgeon at Windhoek Central Hospital and Lady Pohamba Hospital.