Cardiovascular System

The weight of the average human heart is 10 -12 ounces for a male and 8 - 10 ounces for a female. The weight increases with age, and is especially noticeable in males. The average weight of the male heart is 300g and that of female is 200g.

It is the thick middle layer and muscular tissue of the heart that forms the bulk of the heart wall. Specially modified fibres of myocardial muscle constitute the conduction system of the heart including the sinoatrial node, the atrioventricular (AV) node, the AV bundle, and the purkinje fibres.

In order for the heart to deliver oxygenated blood to all cells, blood is pumped through arteries. Veins bring deoxygenated blood cells to the lungs, which are oxygenated and sent back to heart. In this way, a continuous cycle is formed by pumping oxygenated blood and deoxygenated blood out to their designated destinations. Therefore, the heart helps to maintain the circulatory system.

Echocardiography is routinely used in the diagnosis, management and follow up of patients with any suspected or known heart diseases. In this technique, pulses of ultrasonic waves are emitted towards the organ and reflected waves are analysed. Recording of echoes and changes in the acoustic impedence provides information about the movement of wall of the heart, valves and the septum.

The ability of junctional tissue of the heart to generate its own impulses without external stimulation is called autorhythmicity. This is due to a small percentage of muscle cells called autorhythmic cells that are specialised to generate and conduct action potentials and make up the conduction system of the heart.

An electrocardiogram, also called an EKG or ECG is a simple test that detects and records the electrical activity of the heart. It is recorded using an active or exploring electrode and an indifferent electrode at zero potential or by using two active electrodes as in bipolar recording. It is also used in detecting functional abnormalities of heart like heart blocks, arrhythmias and myocardial infarction.

The lower two chambers are called ventricles. They can pump blood from the heart to the body.

It is a decrease in pulse rate below 60 beats/minutes. At this rate, the heart is not able to pump enough oxygen rich blood to our body during normal activity or exercise. Physiologically, it is seen in athletes and during sleep. Pathologically, it is observed in myxoedema and in heart blocks.

It is used together with other medicines to treat tuberculosis in many different parts of the body. It is also used by patients who have a meningitis bacterium in their nose or throat to prevent the spread of the bacteria to other patients. It does not work for colds, flu or other virus infections.

An atherectomy is a procedure in which the vascular surgeon inserts a specialized catheter into a blocked artery to remove a buildup of atherosclerotic plaque from within the vessel. It is typically used to treat blockages where angioplasty and stenting cannot be performed.

Venae cavae are the two largest veins in the body that carry deoxygenated blood from various regions of the body to the right atrium of the heart. The superior vena cava located in the upper chest region is formed by the joining of the brachiocephalic veins and the inferior vena cava is formed by the joining of the common iliac veins, which meet a little below the small of the neck.

Myogenic heart contracts without having a message from the brain as in the pacemaker. In the human heart, contraction is initiated by a special modified heart muscle known as sinoatrial node. Since the heart beat is initiated by the SA node and the impulse of contraction originates in the heart itself, the human heart is termed myogenic. The heart of vertebrates and molluscs are also myogenic.

It is the largest artery in the body originating from the left ventricle of the heart and extending down to the abdomen, where it bifurcates into two smaller arteries. The aorta distributes oxygenated blood to all parts of the body through the systemic circulation. Damage to the aorta can threaten vital functions and can even cause death.

Sino atrial node is a specialised cardiac tissue present at the junction of superior vena cava and right atrium. It generates the maximum number of impulses (70 to 80 per minute) and sets the pace for the heart. Hence, it is called pacemaker of the heart. The cardiac impulse originates at the SA node.

A venule is a very small blood vessel in the microcirculation that allows blood to return from the capillary beds to the larger blood vessels called veins. Venules are blood vessels that drain blood directly from the capillary beds. Many venules unite to form a vein.