Cardiovascular System

heartCardiovascular system (CVS) is responsible for circulation of blood throughout the body. It is also called as circulatory system. It consists of heart, blood vessels &blood.



The heart is a hollow muscular organ present in the centre of the chest. An average adult heart is about the shape and size of a closed fist and weighs around 300 gms. The heart beats about 60-70 times per minute and helps in pumping the blood to all parts of the body.chamber-heart
Chambers of the heart
Heart is divided into 4 chambers.

  1. Right atrium, 2. Left atrium
  2. Right ventricle & 4. Left ventricle

Each chamber is like a separate compartment, with valves between them, which allow the blood in and out.



Heart Valves: The heart valves maintain the unidirectional flow of the blood.heart-valves

The heart has four valves:

  1. Tricuspid valve: Present between right atrium and right ventricle
  2. Bicuspid valve: Present between left atrium and left ventricle
  3. Pulmonary valve: Present between right ventricle and pulmonary artery
  4. Aortic valve: Present between left ventricle and aorta



Circulation of the blood:circulation-blood-vessels

De-oxygenated blood from all over the body reaches the Right Atrium through the Superior & Inferior Vena Cava.

It is then sent to the Right Ventricle from where it is pumped to both the lungs through the Pulmonary arteries.

After oxygenation in the lungs, blood is brought back to the Left Atrium via the pulmonary veins, goes to the Left Ventricle from where it is pumped to all body parts through the aorta.



BLOOD VESSELStypes-blood-vessels

They are the tubular structures of different sizes through which blood is distributed to the various parts of the body.

 Types of Blood Vessels: The 3 types of blood vessels are Artery, Vein & Capillaries.

Arteries: The blood vessels taking blood away from the heart are known as arteries.

 Capillaries: It connects arteries to veins. As the tiniest blood vessels, capillaries carry blood to and from every cell in the body.

 Veins: The blood vessels carrying blood from the body towards the heart are known as Veins.

Blood Pressure

Definition: Blood Pressure (BP) is defined as the lateral force exerted by the blood on the walls of the blood vessels.



Functions of Blood Pressure:

  • To maintain a sufficient pressure, so that the blood keeps flowing
  • To provide the force of filtration at the capillary bed, so that nutrients reach target tissues and cells.

A healthy individual must have an optimum BP. The BP is measured by Sphygmomanometer.


Heart has to contract and relax in a systemic manner to ensure blood supply to all the organs.

Systole: It is the state when heart is contracted. As the heart contracts, blood is pumped in to the arteries, this leads to increased pressure of blood in artery. The blood pressure during a systole is called as the ‘Systolic Blood Pressure’

Diastole: This is the state when heart is relaxed and receiving blood from veins. During a diastole, pressure of blood in arteries is relatively low, and it is called as ‘Diastolic Blood Pressure’.

The difference between systolic and diastolic pressure is called as Pulse Pressure.



Blood pressure is measured in millimetres of mercury (mm Hg) and denoted as Systolic BP/ Diastolic BP mm/Hg.

For example, if a person’s Systolic BP is 120 and Diastolic BP is 80, it will be denoted as 120/80 mm/Hg

Equation for BP

BP=Cardiac Output (CO) X Peripheral Vascular Resistance (PVR)

  • At each heartbeat, certain amount of blood is pumped out by each ventricle into the circulation, this is called as cardiac output.
  • When blood passes through the blood vessels, some resistance is exerted by the walls of vessels against the flow of blood. This is called as peripheral resistance.

Cardiac Output (CO) and Peripheral Vascular Resistance (PVR) depends upon four factors each.


Factors affecting CO

  • Venous return– Amount of blood carried by the veins to the heart
  • Force of contraction– It is the force applied by heart/myocardium during a contraction
  • Heart rate – Is the number of heartbeats per unit of time, typically expressed as beats per minute.
  • Blood volume – It is the volume of blood in the circulatory system


Factors affecting PVR

  • Lumen Size – It is the diameter of a blood vessel.
  • Elasticity of Vessel – It is the ability of blood vessel to expand or constrict
  • Viscosity of Blood – It means the ratio of plasma and cells in blood
  • Velocity of Blood – It is the speed by which blood is flowing


High blood pressure (hypertension) is a risk factor that can increase the chance of developing heart disease, a stroke, and other serious conditions. As a rule, the higher the blood pressure, the greater the risk.


Definition – Persistent rise in BP is called Hypertension. More specifically – Blood pressure that is 140/90 mm Hg or above each time it is measured can be classified as hypertension.

Blood pressure of 140/90 mm Hg or above will have a risk of developing cardiovascular diseases and damage to other vital organs.



The causes of high blood pressure (hypertension)

The cause is not known in most cases, and this is called essential hypertension / Primary Hypertension.

If there is some underlying condition leading to high blood pressure it is then called Secondary hypertension/Non-essential Hypertension. For example, certain kidney or hormone problems can cause high blood pressure.

Complications of Hypertension

High blood pressure is a risk factor for developing a cardiovascular disease (such as a heart attack or stroke), and kidney damage, sometime in the future. If patient have high blood pressure, over the years it may do some damage to the blood vessels (arteries) and put a strain on the heart. In general, the higher the blood pressure, the greater the health risks.


Hypertension Management

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Frequently Asked Questions

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