The Human Heart

The heart is an organ which pumps the body fluid throughout the body, hence we can compare it with an ordinary water pump at our home. However, ordinary does not indicate that it is not important. It is one of the vital organs of the body.

"Cardiology is the branch of biology in which the study of heart is done and the whole system is called cardiovascular system."

We know that the multi-cellular organism has to transport the body fluids throughout the body so that each and every cell will get the energy to do the work. When we talk about the heart, it arises in our mind that it only transports the blood but here as mentioned above, cardiac, this word means body fluids which include
i) Blood and
ii) Lymph

Blood -> It is the connective tissue which carries vital substances such as oxygen, hormones, carbon dioxide, nutrients, waste, water etc. Blood also contains WBC’s, RBC’s and platelets. The substances carried by the blood are essential for various organs and cells. 

Lymph -> Lymph is the fluid that circulates throughout the lymphatic system. The lymph is formed when the interstitial fluid (the fluid which lies in the interstices of all body tissues) is collected through lymph capillaries. It is then transported through lymph vessel to lymph nodes emptying ultimately into the right of the left subclavian vein, where it mixes back with the blood.

The structure of Heart

The heart is a muscular organ found in all organisms ( human being and animals) which pump the blood through the blood vessels of the circulatory system. The heart is enclosed in a pericardial sac i.e. lined with the parietal layers of serous membrane.

Heart has three layers
i) Outermost layer is pericardium
ii) Middle layer is myocardium
And
iii) The innermost layer is Endocardium.

Measurements: 

• The length of the human heart is 12 cm.
• The breadth of the human heart is 9 cm.
• The thickness of the human heart is 6 cm.
• The weight of the human heart is 300 gm.

A healthy heart pumps 70 ml of blood in one cycle and heart beats for 72 times in a minute which is termed as the “heart rate” or “pulse rate”. 

The instrument used for measuring the pulse rate is stethoscope which is measured on the radial artery. 5 liter of total blood is pumped in one minute which is called “Heart Capacity”.

Blood Pressure (B.P.)

Scientist “Hales” (1733) for the first time measured the blood pressure of Horse. The blood pressure of a healthy person is 120/80 mm Hg.

Blood pressure is of two types:

i) Hypotension – (low BP) -> When the blood pressure in arteries is abnormally low. It is less than or equal to 90/60 mm Hg.
ii) Hypertension – (High BP) -> When the force of the blood against the artery walls is too high. It is more than or equal to 140/90 mm Hg.

The instrument used for measuring the blood pressure is called “sphygmomanometer.”

The location of the human heart is just behind and slightly left of the breastbone or it is located between the lungs in the middle compartment of the chest.

Based on whether the blood is transported by means of vessels or not, the circulatory system is divided into two parts.

Open Circulatory System -> When the blood is not get pumped into the blood vessels and the organs directly are in contact with blood. This type of system is seen generally in primitive organisms, especially initial non-chordates. This system is not properly efficient.

Closed Circulatory System -> It is the system in which the blood is pumped through the blood vessels i.e. arteries, veins, and capillaries.

Based on the type of blood contained (oxygenated or deoxygenated), the blood vessels are divided into three types.

i) Arteries -> It takes blood from the heart which is oxygenated blood. It is the most thick blood vessel.
ii) Veins -> It carries deoxygenated blood from the organs to the heart. These vessels are intermediate in terms of thickness.
iii) Capillaries -> A capillary is an extremely thin blood vessel, located within the tissues of the body that transport blood from arteries to veins. Capillaries are most abundant in tissues and organs that are metabolically active.

We know that some organisms are less active and hence need not require fast respiration while others are very active and needs a high rate of respiration. Therefore based on this the heart is also evolved and is characterized into three types.

i) Two-Chambered Heart – > It contains one auricle (atrium) and one ventricle. It is a characteristic feature of the class Pisces. Pisces which are fishes have to live in water and hence there is less effort in living so they have two chambered heart.
ii) Three-Chambered Heart -> It contains 2 auricles and 1 ventricle. It is a characteristic feature of reptiles and amphibians as they have to strive for their lives.
iii) Four Chambered Heart -> It contains 2 auricles and 2 ventricles. It is a characteristic feature of mammals. They require high energy to perform their function.

Anatomy of heart

The heart is mesodermally derived organ situated in the thoracic cavity in between the two lungs, slightly tilted towards left. It has the size of a clenched fist.

Pericardium -> Heart is protected by a double walled Membraneous bag called Pericardium. It encloses the pericardial fluid.

Atria -> Human heart has four chambers, the two upper and relatively small chambers are called atria.

Ventricles -> The remaining two lower and slightly bigger chamber are called ventricles.

Interatrial Septum -> A thin muscular wall that separates the right and left atria.

Interventricular Septum -> A thick muscular wall that separates left and right ventricles.

Atrio – Ventricular Septum -> The atrium and the ventricles of the same side are separated by a thick fibrous tissue called A-V (Atrio – Ventricular) Septum.

Tricuspid Value -> However, each of these septa is provided with an opening through which the two chambers of the same side are connected. The opening between the right atrium and right ventricle is guarded by a valve which is three muscular flaps or cusps called as tricuspid valve.

Bicuspid Valve -> Bicuspid valve is also called as mitral valve guards and found in the opening between the left atrium and the left ventricle.

Semilunar Valve -> The opening of the right and left ventricles into the pulmonary artery and the aorta respectively are provided with the semilunar valve.

The entire heart is made of cardiac mammals. The walls of ventricles are much thicker than that of the atria. A specific cardiac musculature called nodal tissue is also distributed in the heart. A patch of this tissue is present in the right upper corner of the right atrium called SAN i.e. Sino-Atrial Node.

Another mass of this tissue is seen in the lower left corner of the right atrium close to the atrioventricular septum called the AVN i.e. Atrio Ventricular node.

A bundle of nodal fibre atria-ventricular bundle continuous from the AVN which passes through the atrioventricular septa to emerge on the top of the interventricular septum and immediately divides into a right and left bundle.

Functioning of Heart

As mentioned earlier, the blood pumped by the right ventricle enters the pulmonary artery whereas the left ventricle pumps blood into the aorta. The deoxygenated blood pumped into the pulmonary artery is passed on to the lungs from where the oxygenated blood is carried by the pulmonary veins into the left atrium. This pathway constitutes the pulmonary circulation. The oxygenated blood entering the aorta is carried by a network of arteries, arterioles and capillaries to the tissues from where the deoxygenated blood is collected by a system of venules, veins, and vena cana are emptied into the right atrium. This is the systemic circulation. The systemic circulation provides nutrient-rich oxygen and other essential substances to the tissues and takes Carbon dioxide and other harmful substance away for elimination. A unique vascular connection exists between the digestive tract and liver called hepatic portal system. The hepatic portal vein carries blood from the intestine to the liver before it is delivered to the systemic circulation. A special ceremony system of the blood vessel is present in our body exclusively for the circulation of blood to and from the cardiac musculature.

Conclusion:

Now, as you know that heart is one of the essential organ of the body which perform vital functions in the body. And now a days due to very busy lifestyle, pesticides, deficiency of nutrients, stress, overweight etc. heart is getting surrounded by various diseases such as Hypertension, CAD (Coronary Artery Disease), Angina and heart failure etc.
We have to take care of our heart by changing our lifestyle, diet etc. Regular exercise, yoga and meditation helps one to keep his/her heart healthy, wealthy and fit.

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