Location of Human Heart
The heart is right in the center between the two lungs and above the diaphragm. The narrow end of the roughly triangular heart is pointed to the left side and during working, the contraction of the heart is most powerful at this end giving a feeling that the heart is on the left side.
Structure of Heart
Heart is protected by a double walled membranous covering called pericardium. It contains lubricating pericardial fluid which reduces friction during heart beat and protects it from mechanical injuries.
Chambers of Heart
The heart consists of four chambers
- Two upper Auricles
- Two lower Ventricles.
The Atria/ Auricles
- Atria is also called Auricles.
- It has thinner walls because their major function is to receive blood from the body and pump it into the very next ventricles.
- It has thick muscular walls because they have to pump blood to long distances.
- The right ventricle pumps blood only up to the lungs for oxygenation.
- The left ventricle pumps it up to the farthest points in the body, such as, up to the toes in the feet or up to the brain against gravity, and so its walls are thicker.
Blood Vessels Entering and Leaving The Heart
Blood Vessels Entering The Heart
The right auricle receives blood from two large vessels –
Superior vena cava / Anterior vena cava
It brings deoxygenated blood from the upper regions of the body including head, chest and arms.
Inferior Vena Cava / Posterior Vena Cava
- It brings blood from the lower region of the body including abdomen and legs.
- The left atrium receives 4 pulmonary veins (two from each lung).
- The pulmonary veins bring oxygenated blood.
Blood Vessels Leaving the Heart
Blood vessels leaving the heart arising from the ventricles are two large blood vessels.
The pulmonary artery arises from the right ventricle and carries deoxygenated blood to the lungs for oxygenation.
The aorta arises from the left ventricle and carries oxygenated blood to supply it to all parts of the body.
Valves regulate the flow of blood in a single direction
There are four valves in the human heart-
- Right atrio-ventricular valve
- Left atrio-ventricular valve
- Pulmonary semilunar valves
- Aortic semilunar valves
- This valve is located at the aperture between the right auricle and the right ventricle.
- It has three thin triangular leaf-like flaps (cusps) and is therefore also called tricuspid valve.
- The apices of the flaps are held in position by tendinous cords arising from the muscular projections of the ventricle wall known as papillary muscles.
2.Left atrio-ventricular valve
- This Valve is located in a similar way on the left side of the heart.
- It has two cusps, and is, therefore, called bicuspid valve.
3. Pulmonary semilunar valves
- These Valves are located at the opening of the right ventricle into the pulmonary artery.
- These are pocket shaped and three in number.
4. Aortic semilunar valves
These valves are located at the point of origin of aorta from the left ventricle.
These are also three in number and pocket-shaped
- Left atrium receives oxygenated blood from the lungs via pulmonary vein.
- During this collection, the left atrium relaxes.
- It then contracts, while in the next chamber, the left ventricle expands, so that the blood is transferred to it.
- As the left ventricle contracts, the blood is then pumped out for circulation in the body. Deoxygenated blood collected from the body enters to the right atrium as it expands.
- When the right atrium the right atrium contracts, the corresponding lower chamber, i.e. the right ventricle dilates.
- Deoxygenated blood thus enters in it which inturn is pumped to the lungs for oxygenation.
- This whole process is repeated continuously.
- Valves are the muscular flaps which ensure that blood does not flow backwards when the atria or ventricles contract.
The tubes through which Blood flows are called as blood Vessels. Read More
Blood pressure is the pressure which the blood flowing through the arteries exerts on their walls.
There are two limits of this pressure
The upper limit (systolic pressure)
Systolic Pressure is at the time when fresh blood is pushing through the artery as a result of theventricular contraction of the heart.
The lower limit (diastolic pressure)
Diastolic Pressure is the one recorded when the wave has passed over.
The normal blood pressure for adultsis 100-140 mm (systolic) and 60-80 mm (diastolic).
A rise in blood pressure above 140/90 is known as hypertension (high blood pressure in popular language).
Blood pressure can be measured with the help of an instrument called sphygmomanometer