Body Fluids and Circulation Exercise Solutions | KalviGavani

| Feature | Open Circulation | Closed Circulation | |---|---|---| | Blood flow | Flows through body cavities (haemocoel) | Flows through blood vessels | | Blood vessels | Absent or ill-defined | Well-defined (arteries, veins, capillaries) | | Blood pressure | Low | High | | Flow regulation | Cannot be regulated | Can be regulated | | Examples | Arthropods, molluscs | Humans, fish, earthworms |

Double circulation means blood passes through the heart twice per complete circuit: 1. Pulmonary circulation: Right ventricle → lungs → left atrium (deoxygenated → oxygenated) 2. Systemic circulation: Left ventricle → body → right atrium (oxygenated → deoxygenated) Importance: Oxygenated and deoxygenated blood are kept completely separate, ensuring efficient oxygen delivery to tissues. This is essential for warm-blooded animals with high metabolic demands.

1. Bicuspid (mitral) valve: Between left atrium and left ventricle 2. Tricuspid valve: Between right atrium and right ventricle 3. Aortic semilunar valve: Between left ventricle and aorta 4. Pulmonary semilunar valve: Between right ventricle and pulmonary artery Function: Valves prevent backflow of blood, ensuring one-way flow through the heart.

1. Transport: O₂ (by haemoglobin in RBCs), nutrients, hormones, CO₂, waste products 2. Defence: WBCs fight infection (phagocytosis and antibodies) 3. Clotting: Platelets prevent blood loss from injuries 4. Temperature regulation: Blood distributes heat throughout the body 5. pH balance: Buffers in plasma maintain blood pH at ~7.4 6. Water balance: Maintains osmotic balance through plasma proteins

Location and Covering: - Located in the thoracic cavity, between the two lungs, slightly to the left - Surrounded by a double-walled sac called the pericardium, filled with pericardial fluid (reduces friction) Chambers (4): - Right atrium: Receives deoxygenated blood from the body via superior and inferior vena cava - Left atrium: Receives oxygenated blood from the lungs via pulmonary veins - Right ventricle: Pumps deoxygenated blood to the lungs via pulmonary artery - Left ventricle: Pumps oxygenated blood to the body via aorta (thickest wall) Valves: - Bicuspid (mitral) valve: Between left atrium and left ventricle (2 cusps) - Tricuspid valve: Between right atrium and right ventricle (3 cusps) - Aortic semilunar valve: Between left ventricle and aorta - Pulmonary semilunar valve: Between right ventricle and pulmonary artery - Chordae tendineae: Fibrous cords connecting valve cusps to papillary muscles (prevent valve inversion) Blood Supply to the Heart: - Coronary arteries (branches of the aorta) supply oxygenated blood to the heart muscle - Blockage of coronary arteries causes a heart attack (myocardial infarction) Conduction System: - SA node (pacemaker): In right atrium — generates impulse (72 beats/min) - AV node: In the septum — relays impulse from atria to ventricles - Bundle of His and Purkinje fibres: Conduct impulse through ventricles

The cardiac cycle is the sequence of events in one complete heartbeat (~0.8 seconds at 72 beats/min): 1. Atrial Systole (0.1 seconds): - Both atria contract simultaneously - The tricuspid and bicuspid valves open - Blood flows from atria into ventricles - About 70% of blood flows passively; atrial contraction adds the remaining 30% 2. Ventricular Systole (0.3 seconds): - Both ventricles contract simultaneously - The tricuspid and bicuspid valves close (produces the first heart sound — "LUBB") - The semilunar valves open - Right ventricle pumps deoxygenated blood to the lungs via the pulmonary artery - Left ventricle pumps oxygenated blood to the body via the aorta 3. Cardiac Diastole (0.4 seconds): - All four chambers relax - The semilunar valves close (produces the second heart sound — "DUP") - Blood fills the atria from the vena cava and pulmonary veins - The tricuspid and bicuspid valves remain closed during early diastole, then open as atrial pressure rises Heart Sounds: - First sound (LUBB): Caused by closure of AV valves (bicuspid and tricuspid) during ventricular systole — louder and longer - Second sound (DUP): Caused by closure of semilunar valves during ventricular diastole — softer and shorter Cardiac Output: - Cardiac output = Heart rate × Stroke volume = 72 beats/min × 70 mL = 5040 mL/min ≈ 5 L/min

ABO Blood Grouping System: The ABO system is based on the presence or absence of antigens (A and B) on the surface of RBCs: | Blood Group | Antigens on RBC | Antibodies in Plasma | Can Donate to | Can Receive from | |---|---|---|---|---| | A | A antigen | Anti-B | A, AB | A, O | | B | B antigen | Anti-A | B, AB | B, O | | AB | A and B antigens | None | AB only | A, B, AB, O | | O | No antigens | Anti-A and Anti-B | A, B, AB, O | O only | Key Points: - If antigen A meets anti-A antibody, the RBCs will clump (agglutinate) — this is dangerous and can be fatal - Group AB is the universal recipient (no antibodies in plasma, so no agglutination) - Group O is the universal donor (no antigens on RBCs, so no agglutination in recipient) Rh Factor: - Rh factor is another antigen on RBCs (first discovered in Rhesus monkeys) - Rh positive (Rh+): Has Rh antigen on RBCs (~85% of people) - Rh negative (Rh−): Lacks Rh antigen (~15% of people) - An Rh− person receiving Rh+ blood will produce anti-Rh antibodies Erythroblastosis Foetalis: - Occurs when an Rh− mother carries an Rh+ foetus - In the first pregnancy: Some Rh+ foetal blood enters the mother's body → mother produces anti-Rh antibodies (slow, no harm to first child) - In subsequent Rh+ pregnancies: Mother's anti-Rh antibodies cross the placenta and attack foetal RBCs → severe anaemia, jaundice, or death of the foetus - Prevention: Anti-Rh antibodies (RhoGAM) are given to the Rh− mother after the first delivery