The Circulatory System

Circulatory System: Network of organs and vessels that transport blood, nutrients, gases, and waste throughout the body.

Functions: (1) Transport of oxygen and nutrients to cells, (2) Removal of CO₂ and waste, (3) Distribution of hormones, (4) Maintenance of body temperature, (5) Protection against diseases.

Components: Heart, blood vessels (arteries, veins, capillaries), blood.

Types of Circulation: (1) Systemic circulation (body tissues), (2) Pulmonary circulation (lungs).

Double Circulation: Blood passes through heart twice in one complete cycle. Ensures oxygenated and deoxygenated blood don't mix.

Diagram Importance: Diagram showing double circulation pathway is crucial for ICSE exams.

Blood: Fluid connective tissue. Red in color due to hemoglobin. pH 7.4. Volume: 5-6 liters in adults.

Components: (1) Plasma (55%) - liquid part, (2) Blood cells (45%) - RBCs, WBCs, platelets.

Plasma: Straw-colored fluid. Contains water (90%), proteins (albumin, globulin, fibrinogen), nutrients, hormones, waste.

Red Blood Cells (RBCs): Biconcave, disc-shaped. Contain hemoglobin. No nucleus. Lifespan: 120 days. Produced in bone marrow.

White Blood Cells (WBCs): Irregular shape. Have nucleus. Fight infections. Types: Granulocytes (neutrophils, eosinophils, basophils), Agranulocytes (lymphocytes, monocytes).

Platelets: Cell fragments. Help in blood clotting. Lifespan: 7-10 days.

Blood Groups: ABO system. A, B, AB, O. Rh factor (positive/negative).

Blood Clotting: Mechanism to prevent blood loss. Involves platelets, thrombin, fibrinogen → fibrin clot.

Diagram Importance: Labeled diagram of blood components and clotting mechanism is frequently asked.

Heart: Muscular organ. Size of clenched fist. Located in thoracic cavity between lungs. Beats 70-80 times/minute.

Structure: Four chambers - two atria (upper, receiving), two ventricles (lower, pumping).

External Structure: Pericardium (protective membrane), aorta, pulmonary artery, vena cava, pulmonary veins.

Internal Structure: (1) Right atrium receives deoxygenated blood, (2) Right ventricle pumps to lungs, (3) Left atrium receives oxygenated blood, (4) Left ventricle pumps to body.

Valves: (1) Tricuspid (right AV), (2) Pulmonary (pulmonary valve), (3) Mitral/Bicuspid (left AV), (4) Aortic (aortic valve). Prevent backflow.

Cardiac Cycle: Systole (contraction) and diastole (relaxation) of heart chambers.

Heartbeat Regulation: SA node (pacemaker), AV node, Bundle of His, Purkinje fibers.

Diagram Importance: Detailed labeled diagram of human heart (internal and external) is essential for ICSE.

Arteries: Carry oxygenated blood from heart to tissues (except pulmonary artery). Thick-walled, elastic, no valves (except semi-lunar).

Veins: Carry deoxygenated blood to heart (except pulmonary veins). Thin-walled, less elastic, have valves to prevent backflow.

Capillaries: Microscopic vessels connecting arteries and veins. Single cell thick. Site of exchange of materials.

Comparison: Arteries - thick muscular walls, high pressure; Veins - thin walls, low pressure; Capillaries - very thin, allow diffusion.

Structure-Function Relationship: Thick walls of arteries withstand high pressure; valves in veins prevent backflow.

Diagram Importance: Comparative diagrams of artery, vein, and capillary showing structural differences are crucial.

Pulmonary Circulation: Deoxygenated blood from right ventricle → pulmonary artery → lungs (gas exchange) → oxygenated blood → pulmonary veins → left atrium.

Systemic Circulation: Oxygenated blood from left ventricle → aorta → body tissues (oxygen delivery) → deoxygenated blood → vena cava → right atrium.

Coronary Circulation: Blood supply to heart muscle. Coronary arteries from aorta supply heart.

Hepatic Portal Circulation: Blood from intestines → hepatic portal vein → liver (nutrient processing) → hepatic vein → vena cava.

Renal Circulation: Blood to kidneys for filtration and urine formation.

Diagram Importance: Diagram of double circulation and hepatic portal system is important for understanding flow.

Lymph: Tissue fluid collected from blood capillaries. Returns to blood via lymph vessels.

Lymphatic System: Network of vessels, nodes, and organs. Supplements circulatory system.

Functions: (1) Returns excess tissue fluid to blood, (2) Absorbs fats from intestines, (3) Fights infections (lymphocytes), (4) Filters blood (lymph nodes).

Components: Lymph capillaries, vessels, nodes, spleen, thymus, tonsils.

Lymph Nodes: Bean-shaped. Filter lymph, produce lymphocytes. Swell during infection.

Difference from Blood Circulation: Lymph flows unidirectionally toward heart; no pump like heart.

Hypertension: High blood pressure. Causes: stress, obesity, smoking. Damages blood vessels.

Atherosclerosis: Plaque buildup in arteries. Narrows vessels, reduces blood flow.

Heart Attack (Myocardial Infarction): Blockage of coronary artery. Heart muscle damage.

Stroke: Interruption of blood to brain. Causes paralysis or death.

Anemia: Low RBC count or hemoglobin. Causes fatigue, weakness.

Leukemia: Cancer of blood-forming tissues. Abnormal WBC production.

Prevention: Healthy diet, exercise, no smoking, regular checkups.