I appreciate that many of you who have been kindly following the blog for a long time will have seen this post before. However, if you are new to Smorgasbord, I hope you will find interesting.
In the series Top to Toe I will be covering the major organs in the body and their health.
We tend to think of the heart from an emotional perspective but in reality it is a pump that has a number of moving parts that is vital to our survival. Since the 1960s, the heart is one of the organs that can be replaced with a transplanted organ, but there are far more patients waiting for a new heart than there are donors.
This means that we need to take care of the one we have. However, like all our major organs it is hidden from view and we really only pay it the attention it deserves when something is wrong with it. Over the next few days I am going to look at the heart as an organ and the basics of how it functions. This will be followed by an overview of some of the more common diseases and then the foods that should be included in our diet to help maintain its health. Next week I will feature a silent killer which is contributory factor in heart disease… Stress.
The heart is the pump that powers the circulatory or cardiovascular system formed by a network of arteries, veins and smaller blood vessels. Blood is continuously pumped out from the heart around the venal and arterial circuits carrying oxygen and vital nutrients to all parts of the body. The arteries take the blood away from the heart and the veins bring the blood back.
The heart itself is a muscle, approximately the size of a clenched fist, and is shaped like a large upside down pear, located just to the left of the centre of the chest.
The heart weighs around 11 ounces or 310 grams and rests in a moist chamber, called the pericardial cavity, between the lungs and surrounded by the rib cage.
The muscle is called the myocardium and forms a shell around four cavities or spaces inside the heart that fill with blood. The two upper cavities are called atria and the bottom two spaces are called ventricles. Each side of the heart is separated by a wall called the septum and a valve connects each atrium to the ventricle below it. The valve on the left side of the body is called the mitral valve and the right side connection is called the tricuspid valve. The Endocardium lines the inside of the heart, and the heart valves, and the pericardium is a fibrous sac surrounding the heart.
The top of the heart is connected to some major blood vessels – the largest being the aorta, or main artery, which carries the nutrient rich blood away from the heart to the rest of the body. Another important blood vessel is the pulmonary artery, which connects the heart to the lungs.
The two largest veins that carry blood back to the heart are called the superior vena cava and the inferior vena cava. The superior vena cava takes de-oxygenated blood from the head and the arms to the right atrium, and the inferior vena cava brings de-oxygenated blood back up from the legs and lower body also into the right atrium.
The cardiac muscle contracts between 70 and 80 beats per minute and if it is to last the normal life-span it will beat over 3 billion times. This means that the muscle has to be incredibly strong and healthy.
De-oxygenated blood always returns to the body through the right side of the heart into the atrium and then onto the lungs to pick up the oxygen. It is then returned to the heart where it enters the left side into the atrium and ventricle to be pumped to all the other parts of the body in a continuous cycle.
How does the heart beat?
The heart beats automatically without our thought or intervention and the number of beats is maintained by an electrical impulse that originates from the body’s own natural pacemaker called the sinoatrial node. The electrical impulse is sent through the atria which stimulates a contraction then through to the atrioventricular node where it will pause for a fraction of a second before continuing down special conducting fibres to the ventricles, causing them to contract.
Specific nerves called autonomic nerves, the main one being the vagus nerve, regulate the amount of times our heart beats. The ideal rate is maintained at around 70 beats at rest but is then speeded up during exercise or stress. The cardiac nerves react to messages sent from the hypothalamus, in the medulla part of the brain, and the beat rate will also increase when the “fight or flight” hormone, adrenaline, is released. This increases the amount of blood and therefore oxygen that is made available to the heart and the rest of the body.
Risk factors for heart disease and stroke are largely similar for men and women.
- Factors such as age and family history play a role, but it is estimated that the majority of CVD deaths are due to modifiable risk factors such as smoking, high cholesterol, unhealthy diet, high blood pressure, obesity, stress or diabetes
- Heart disease was associated with men until the last twenty years and now cardiovascular disease (CVD) – heart disease and stroke – is the biggest killer of women globally, killing more women than all cancers, tuberculosis, HIV/AIDS and malaria combined.
Next time I will be covering Angina and other common heart health conditions.
©sallycronin Just Food For Health 1999 – 2017
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