The Human Heart by Sandra Landinguin

THEHUMAN HEART

EARLY DEVELOPMENT OF THE HUMAN

HEARTThe mammalian heart is derived from embryonic mesoderm germ-layer cells that differentiate after gastrulation into mesothelium, endothelium, and myocardium. Mesothelial pericardium forms the inner lining of the heart. The outer lining of the heart, lymphatic and blood vessels develop from endothelium. Myocardium develops into heart muscle.

EARLY DEVELOPMENT OF THE HUMAN HEART

From splachnopleuric mesoderm tissue, the cardiogenic plate develops cranially and laterally to the neural plate. In the cardiogenic plate, two separate angiogenic cell clusters form on either side of the embryo. Each cell cluster coalesces to form an endocardial tube continuous with a dorsal aorta and a vitteloumbilical vein. As embryonic tissue continues to fold, the two endocardial tubes are pushed into the thoracic cavity and begin to fuse together and are completely fused at approximately 21 days.

The human embryonic heart begins beating around 21 days after conception, or five weeks after the last normal menstrual period (LMP), which is the date normally used to date pregnancy. It is unknown how blood in the human embryo circulates for the first 21 days in the absence of a functioning heart. The human heart begins beating at a rate near the mother’s, about 75-80 beats per minute (BPM).

EARLY DEVELOPMENT OF THE HEART

The human embryonic heart begins beating around 21 days after conception, or five weeks after the last normal menstrual period (LMP), which is the date normally used to date pregnancy. It is unknown how blood in the human embryo circulates for the first 21 days in the absence of a functioning heart. The human heart begins beating at a rate near the mother’s, about 75-80 beats per minute (BPM).

THE HEART RATE AND AGE

THE HEART RATE AND AGE

The embryonic heart rate (EHR) then accelerates approximately 100 BPM during the first month of beating, peaking at 165-185 BPM during the early 7th week, (early 9th week after the LMP). This acceleration is approximately 3.3 BPM per day, or about 10 BPM every three days, an increase of 100 BPM in the first month. After 9.1 weeks after the LMP, it decelerates to about 152 BPM (+/-25 BPM) during the 15th week after the LMP. After the 15th week the deceleration slows reaching an average rate of about 145 (+/-25 BPM) BPM at term. The regression formula which describes this acceleration before the embryo reaches 25 mm in crown-rump length or 9.2 LMP weeks is: Age in days = EHR(0.3)+6.

There is no difference in male and female heart rates before birth.

STRUCTURE OF THE HUMAN

HEART

The human heart is

primarily a shell.

STRUCTURE OF THE HUMAN HEART The human heart is primarily a shell. There are four

cavities, or open spaces, inside the heart that fill with blood. Two of these cavities are called atria. The other two are called ventricles. The two atria form the curved top of the heart. The ventricles meet at the bottom of the heart to form a pointed base which points toward the left side of your chest. The left ventricle contracts most forcefully, so you can best feel your heart pumping on the left side of your chest.

The left side of the heart houses one atrium and one ventricle. The right side of the heart houses the others. A wall, called the septum, separates the right and left sides of the heart. A valve connects each atrium to the ventricle below it. The mitral valve connects the left atrium with the left ventricle. The tricuspid valve connects the right atrium with the right ventricle.

STRUCTURE OF THE HUMAN HEART The top of the heart connects to a few large blood vessels.

The largest of these is the aorta, or main artery, which carries nutrient-rich blood away from the heart. Another important vessel is the pulmonary artery which connects the heart with the lungs as part of the pulmonary circulation system. The two largest veins that carry blood into the heart are the superior vena cava and the inferior vena cava. They are called "vena cava" because they are the "heart's veins." The superior is located near the top of the heart. The inferior is located beneath the superior.

The heart's structure makes it an efficient, never-ceasing pump. From the moment of development through the moment of death, the heart pumps. The heart, therefore, has to be strong. The average heart's muscle, called cardiac muscle, contracts and relaxes about 70 to 80 times per minute without you ever having to think about it. As the cardiac muscle contracts it pushes blood through the chambers and into the vessels. Nerves connected to the heart regulate the speed with which the muscle contracts. When you run, your heart pumps more quickly. When you sleep, your heart pumps more slowly.

STRUCTURE OF THE HEART

Considering how much work it has to do, the heart is surprisingly small. The average adult heart is about the size of a clenched fist and weighs about 11 ounces (310 grams). Located in the middle of the chest behind the breastbone, between the lungs, the heart rests in a moistened chamber called the pericardial cavity which is surrounded by the ribcage. The diaphragm, a tough layer of muscle, lies below. As a result, the heart is well protected.

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HOW THE HEART

FUNCTIONS ELECTRICALLY

The heart's natural pacemaker - the SA node - sends out regular electrical impulses from the top chamber (the atrium) causing it to contract and pump blood into the bottom chamber (the ventricle). The electrical impulse is then conducted to the ventricles through a form of 'junction box' called the AV node. The impulse spreads into the ventricles, causing the muscle to contract and to pump out the blood. The blood from the right ventricle goes to the lungs, and the blood from the left ventricle goes to the body.

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HOW THE HEART CAN CAUSE

SUDDEN DEATH

HOW THE HEART CAN CAUSE SUDDEN DEATH

A death is described as sudden when it occurs unexpectedly, spontaneously and/or even dramatically. Some will be unwitnessed; some may occur during sleep or during or just after exercise. Most sudden deaths are due to a heart condition and are then called sudden cardiac death (SCD). Up to 95 in every 100 sudden cardiac deaths are due to disease that causes abnormality of the structure of the heart. The actual mechanism of death is most commonly a serious disturbance of the heart's rhythm known as a 'ventricular arrhythmia' (a disturbance in the heart rhythm in the ventricles) or 'ventricular tachycardia' (a rapid heart rate in the ventricles). This can disrupt the ability of the ventricles to pump blood effectively to the body and can cause a loss of all blood pressure. This is known as a cardiac arrest. If this problem is not resolved in about two minutes, and if no-one is available to begin resuscitation, the brain and heart become significantly damaged and death follows quickly.

HEART DISEASES AND

DISORDERSUnfortunately there are too many

people around the world who suffer from having a heart disorders……..

CIRCULATORY HEART DISEASES AND DISORDERS

The cause of the StrokeThe cause of the Heart

Attack

CIRCULATORY HEART DISEASES AND DISORDERS

Stroke Heart Attack (Myocardial Infarction)

Although not true "heart" disorders, strokes are a related condition. While some strokes occur when a blood vessel bursts, most strokes happen for the same reasons as a heart attack, clogged or blocked vessels.All strokes pose serious health threats.

When arteries are clogged to the point of decreasing or stopping the flow of blood to the heart muscle, a lack of oxygen damages or kills heart muscle causing a heart attack. Recognizing symptoms and getting prompt emergency treatment can eliminate, prevent or limit the amount of heart muscle damage.

ELECTRICAL HEART DISORDERS

Arrhythmias that originate in the heart’s UPPER CHAMBERS, the ATRIA:

• Atrial Fibrillation (AF or A Fib) – the heart rhythm disorder (irregular & rapid).

• Atrial Flutter (AFL) – rapid heartbeat.

• Arrhythmias that originate in the heart’s LOWER CHAMBERS, the VENTRICLES:

• Ventricular Tachycardia (VT) – very fast heartrate.

• Ventricular Fibrillation (VF) – sudden cardiac death.

DON’T YOU WISH TO

AVOID A HEART PROBLEMS???You can prevent heart disease by following a heart-healthy lifestyle.

5 MEDICATION-FREE STRATEGIES TO HELP PREVENT HEART DISEASE

1. Don't smoke or use tobacco products

2. Get active 3. Eat a heart-healthy diet 4. Maintain a healthy weight

5. Get regular health screenings

TAKE CARE OF YOURSELF AND KEEP IN MIND THOSE 5 MEDICATION-FREE

STRATEGIES TO PREVENT HEART DISEASE