1. Plasma vs Formed Elements
| Feature | Plasma | Formed elements |
|---|---|---|
| Share of blood | About 55% | About 45% |
| Nature | Straw-coloured, viscous fluid matrix | RBCs, WBCs and platelets |
| Composition | 90-92% water; 6-8% proteins, minerals, glucose, amino acids, lipids and inactive clotting factors | Cells and cell fragments suspended in plasma |
| Key roles | Fibrinogen: clotting; globulins: defence; albumins: osmotic balance | RBCs: gas transport; WBCs: defence; platelets: clotting |
| Related term | Plasma without clotting factors is serum | Collectively form the cellular component of blood |
2. RBCs vs WBCs vs Platelets
| Feature | RBCs / erythrocytes | WBCs / leucocytes | Platelets / thrombocytes |
|---|---|---|---|
| Typical count | 5-5.5 million mm-3 in healthy adult male | 6000-8000 mm-3 | 1.5-3.5 lakh mm-3 |
| Structure | Biconcave; non-nucleated in most mammals; haemoglobin present | Nucleated, colourless due to absence of haemoglobin | Cell fragments formed from megakaryocytes |
| Origin / fate | Red bone marrow; life span about 120 days; destroyed in spleen | Generally short-lived | Bone marrow origin |
| Main function | Transport respiratory gases | Defence and immune responses | Release substances needed for coagulation |
3. Granulocytes vs Agranulocytes
| Group | Cells included | Key functions / proportions |
|---|---|---|
| Granulocytes | Neutrophils, eosinophils and basophils | Neutrophils: 60-65%, phagocytic. Eosinophils: 2-3%, resist infection and associated with allergy. Basophils: 0.5-1%, secrete histamine, serotonin and heparin in inflammation. |
| Agranulocytes | Monocytes and lymphocytes | Monocytes: 6-8%, phagocytic. Lymphocytes: 20-25%, B and T forms carry out immune responses. |
4. ABO Blood Groups and Rh Factor
| ABO group | Antigen on RBCs | Antibody in plasma | Compatible donor groups |
|---|---|---|---|
| A | A | Anti-B | A, O |
| B | B | Anti-A | B, O |
| AB | A and B | Nil | AB, A, B, O |
| O | Nil | Anti-A and anti-B | O |
| Rh-positive | Rh-negative |
|---|---|
| Rh antigen present on RBC surface; about 80% of humans. | Rh antigen absent. Exposure to Rh-positive blood causes production of anti-Rh antibodies. |
| In an Rh-negative mother with Rh-positive foetus, antibodies generated after first delivery may destroy foetal RBCs in later pregnancies, causing erythroblastosis foetalis. Anti-Rh antibodies given after first delivery prevent it. | |
5. Blood vs Lymph; Open vs Closed Circulation
| Feature | Blood | Lymph |
|---|---|---|
| Colour / composition | Red, with plasma and all formed elements including RBCs | Colourless; tissue fluid with specialised lymphocytes, lower proteins and no most formed elements |
| Pathway | Heart pumps it through closed blood vessels | Lymphatic vessels collect tissue fluid and drain it into major veins |
| Main role | Transport gases, nutrients, hormones and wastes | Immune responses, transport of nutrients and hormones, and absorption of fats via intestinal lacteals |
| Feature | Open circulatory system | Closed circulatory system |
|---|---|---|
| Occurrence | Arthropods and molluscs | Annelids and chordates |
| Blood route | Heart pumps blood into open spaces/body cavities called sinuses | Blood remains in a closed network of vessels |
| Control of flow | Less precise | More precisely regulated |
6. Vertebrate Heart and Circulation Patterns
| Group | Heart chambers | Circulation pattern |
|---|---|---|
| Fishes | Two: one atrium and one ventricle | Single circulation; heart pumps deoxygenated blood to gills, then body, then heart. |
| Amphibians and reptiles except crocodiles | Three: two atria and one ventricle | Incomplete double circulation; oxygenated and deoxygenated blood mix in the single ventricle. |
| Crocodiles, birds and mammals | Four: two atria and two ventricles | Complete double circulation; separate pathways and no mixing. |
7. Right Side vs Left Side of Human Heart
| Feature | Right side | Left side |
|---|---|---|
| Atrium receives | Deoxygenated blood through vena cava | Oxygenated blood through pulmonary veins |
| AV valve | Tricuspid valve with three cusps | Bicuspid / mitral valve |
| Ventricle pumps to | Pulmonary artery | Aorta |
| Circulation entered | Pulmonary circulation | Systemic circulation |
| Associated semilunar valve | At pulmonary artery opening | At aortic opening |
Nodal system SAN in right atrium produces 70-75 action potentials per minute and acts as pacemaker. AVN, AV bundle and Purkinje fibres conduct excitation to ventricles. This intrinsic activity makes the heart myogenic.
8. Cardiac Cycle, ECG and Cardiac Regulation
| Event / term | NCERT key point |
|---|---|
| Joint diastole | All four chambers relaxed; AV valves open and semilunar valves closed; blood flows into ventricles through atria. |
| Atrial systole | SAN impulse contracts both atria, adding about 30% more blood to ventricles. |
| Ventricular systole | AV valves close (lub); semilunar valves open and blood enters pulmonary artery and aorta. |
| Ventricular diastole | Semilunar valves close (dub), preventing backflow; AV valves later reopen. |
| Cardiac output | Stroke volume x heart rate. Stroke volume is about 70 mL; normal cardiac output about 5 L min-1. |
| P, QRS and T waves | P: atrial depolarisation; QRS: ventricular depolarisation and start of ventricular systole; T: ventricular repolarisation and end of systole. |
| Autonomic regulation | Sympathetic nerves and adrenal medullary hormones increase heart rate/force/output; parasympathetic nerves decrease rate, impulse conduction and output. |
Disorders Hypertension is repeated BP >=140/90 mm Hg. CAD narrows coronary arteries through deposits. Angina is chest pain due to inadequate O2 to heart muscle. Heart failure is ineffective pumping, not cardiac arrest or heart attack.