Cardio - Vascular System (Circulatory System)

Figure 1: Heart Anatomy

1. Heart:
• The heart is made up of involuntary striated muscle and about the size of a fist, and is roughly cone-shaped, base pointing superiorly and apex inferiorly and towards the left side.
•  It is about 12cm long, 9cm broad, and about 6cm thick. It is situated in the thoracic cavity, at mediastinum, 2/3rd of it is on the left side 1/3rd of it is on the right side hence left lung is a little smaller than the right lung.
• The Heart is covered by 2 Pericardium fibrous linings around it and between these 2 pericardium linings, there is a cavity that has fluid called Pericardium fluid. This helps to prevent friction during constant heart contraction and relaxation or heart beating.
• The wall of the heart is made up of a special type of muscle called Cardiac Muscle.
2. Chambers of the Heart : 
• The heart has 2 septums, one is horizontal, and the other is vertical and because of these septums, the Heart is divided into 4 Chambers, upper ones are called Atria(Plural of Atrium) and the lower ones are called as Ventricles. 
• Atria are the blood receivers, Left Atrium receives oxygenated blood from the lungs via pulmonary veins. Right Atrium receives DE-oxygenated blood from the body via superior vena cava and inferior vena cava. 
• Ventricles on the other hand are those from where the blood goes away from the heart to the body and to the lungs for oxygenation, from Left Ventricle oxygenated blood transfers to the body via Aorta. From Right Ventricle DE-oxygenated blood transfers to Lungs for oxygenation via Pulmonary trunk. 
3. Heart Valves: 
• Valves are fibrous flaps of tissue that prevent blood from flowing in the wrong direction.
• There are 2 sets of Valves- Atrio-Ventricular and Semilunar.  
• atrioventricular valves are between atria and ventricles. The valve between the right atrium and the right ventricle is known as the tricuspid valve. The valve between the left atrium and left ventricle is known as the bicuspid or mitral valve. 
• Valves between the ventricles and the great arteries(Aorta and Pulmonary trunk) are known as the semilunar valves. The aortic valve is found at the base of the aorta, while the pulmonary valve is found at the base of the pulmonary trunk.
4. Blood Vessels:
•  Arteries- are the blood vessels that carry blood away from the heart to the other body parts. 
• Veins- are the blood vessels that carry blood to the heart from other body parts.
• Capillaries- are the microscopic blood vessels that connect Arteries and Veins together. 
• Aorta- is the largest Artery which begins at Left Ventricle. The heart pumps oxygenated blood from the left ventricle into Aorta which then carries to the rest of the body through many smaller arteries.
• Pulmonary trunk- is a large artery that begins at Right Ventricle. The heart pumps DE-oxygenated blood from the right ventricle into Pulmonary Trunk which then carries to Lungs via many Pulmonary arteries. 
• Pulmonary Veins- takes oxygenated blood from the lungs to the Heart(Left Atrium).
•  Superior and Inferior Vena Cava - These are large Veins which takes DE-oxygenated blood to the Heart(Right Atrium) from other body parts. 
• Coronary Arteries- these are the first branches of Aorta and through which blood supplied to Heart itself.
• Coronary Sinus- DE-oxygenated blood from heart carried to Right Atrium
5. The function of the Heart: 
• Heart’s function is to supply blood to each and every cell of the body during rest and various other conditions (Exercise, Pregnancy). The blood circulation is the movement of blood through our body. 
• This happens in 2 regions: 
1.  Systemic Circulation (Heart --> Body --> Heart) 
2. Pulmonary Circulation (Heart --> Lungs --> Heart) 
1. Systemic Circulation:
• This consists of pushing oxygenated blood from the left ventricle to reach the body and receiving DE-oxygenated blood from the body into the Right Atrium.
2. Pulmonary Circulation:
• This consists of pushing DE-oxygenated blood from Right Ventricle to reach the Lungs for oxygenation and receiving oxygenated blood from the lungs into the Left Atrium. 
• Even though the Heart is filled with blood, cannot use this blood. It has a blood supply of its own using Coronary arteries, there are 2 branches Left & Right Coronary arteries, penetrates through the cardiac muscle and supplies blood to them. The heart also has a venous system that carries DE-oxygenated blood and emptied into Right Atrium via Coronary Sinus.
• SA Node (Pace Maker of Heart): Cardiac muscle has the ability of Automocity and Rhythmicity. I.e. cardiac muscle has a special modified cell, the main cell is called SA node, which gets stimulated on their own in a rhythmic pattern. 
• The Autonomous nervous system can have an impact on this cardiac function: 
• Para-sympathetic system via the Vagus nerve has an effect on Heart when stimulated, it reduces our heart rate. (e.g. resting in peaceful condition).
•  The sympathetic system via T1, T2, T3, T4 nerve, when stimulated, it increases Heart rate and increases the strength of contraction.

Figure 2: Circulatory System

Some Fun Facts about the Heart:

• Your heart beats around 100,000 times a day.
• Your heart pumps 2,000 gallons of blood a day.
• No one knows why the heart is associated with love.
• Horses can mirror a human’s heart rate.

References:

• Gnosis Medical Yoga Teacher Textbook