Body Fluids
* Blood liquid connective tissue that consists of 55% liquid plasma and 45% formed elements called blood cells.
* Major proteins in plasma include albumins, globulins and fibrinogens.
* Formed elements include erythrocytes, leucocytes and platelets.
* Erythrocytes of Red Blood Cells (RBCs) are involved in the transport of respiratory gases.
* Leucocytes or White Blood Cells (WBCs) include neutrophils, eosinophils, basophils, lymphocytes and monocytes.
* Clotting or coagulation is a protective mechanism that takes place at an injured site to prevent loss of blood.
* Interstitial fluid or tissue fluid is formed when some quantity of water and water-soluble substances squeeze out from the blood capillaries into the inter-cellular spaces.
* Lymph is a colourless fluid that contains lymphocytes, nutrients, hormones and proteins.
Blood Groups
* The presence or absence of ‘A’ and ‘B’ antigens on the surface of RBCs determines ABO blood groups.
* The presence or absence of the ‘Rh’ antigen on the surface of the RBCs determines Rh blood groups.
* Antibodies are present in the blood plasma.
* Specific antigen and antibody reactions result in the clumping or agglutination of RBCs.
* Individuals with blood group ‘AB’ are called universal recipients.
* Rh incompatibility in an Rh negative women an Rh positive foetus results in erythroblastosis foetalis.
Circulatory System
* The circulatory system is of two types, namely, open and closed.
* Blood pumped from the heart reaches the open spaces or body cavities called sinuses in an open circulatory system.
* Blood pumped from the heart reaches the tissues through closed blood vessels in a closed circulatory system.
* Arteries carry oxygenated blood from the heart to all the body tissues except the pulmonary artery, which carries deoxygenated blood from the heart to the lungs.
* Veins carry deoxygenated blood from all the body tissues to the heart except the pulmonary vein, which carries oxygenated blood from the lungs to the heart.
* The heart in humans is made of cardiac muscles and has four chambers-two atria and two ventricles.
* The closure of the tricuspid, bicuspid and semilunar valves produces a lubdub sound causing a heartbeat.
* The Sino-atrial Node(SAN), the pacemaker of the heart, automatically generates action potentials and causes rhythmic contractions.
Cardiac Cycle
* Double circulation involves pulmonary and systemic circulation.
* Pulmonary circulation refers to the circulation of blood between the heart and the lungs.
* Systemic circulation refers to the circulation of blood between the heart and the tissues of the body.
* A heartbeat is caused by the systole or contraction and diastole or relaxation of the chambers during the circulation of blood.
* The sequence of events that include systole and diastole forms a cardiac cycle.
* The cardiac cycle is driven by the action potential generated by the SAN and distributed through the ventricles by the Bundle of His.
* Cardiac output equals the product of the stroke volume and the number of beats/minute.
Regulation of Cardiac Activity
* The heart carries out the cardiac out the cardiac cycle automatically and is hence called myogenic.
* The cardiac cycle is controlled by the medulla oblongata of the brain.
* Sympathetic nerves from the brain increases cardiac output in contrast to parasympathetic nerves which decrease cardiac output.
* An electrocardiograph records the heartbeat as voltage traces and is called an electrocardiogram (ECG).
* A healthy individual has a systolic and diastolic pressure of 120/80 mmHg.
* The accumulation of plaque in the coronary artery is called artherosclerosis and it causes Coronary Artery Disease (CAD).
* Some of the symptoms of CAD include angina, heart attack, cardiac arrest or heart failure.