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State Board · Class 12 · Biology

Lesson 8: Respiration and Circulation

7 concepts · 56 practice questions with answers · Free to read

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Respiratory organs and the human respiratory system

Link to Std 9–10

The last lesson covered plant nutrition; here we see how oxygen enters the human lungs and how blood carries it to every cell.

From daily life

Blowing on a fire sends air in and out through the airways.

Simple definition

A respiratory surface is where O₂ and CO₂ are exchanged: large area, thin, moist and vascular.

Respiratory systemRespiratory organs and the human respiratory systemNosePharynxLarynxTrachea → BronchiBronchioles → alveolilarge, thin, moist areaSurface: large area, thin, moist, vascularProtists/sponges: membrane; earthworm/frog: skin; insects: spiracles/tracheaeNose: vestibule (filters), respiratory (warms, moistens), olfactoryLarynx = voice box; epiglottis blocks food; glottisTrachea 10–12 cm; C-shaped cartilage; bronchi → bronchioles → alveoliLungs: right 3 lobes, left 2; pleura (parietal + visceral)~700 million alveoli; single-layer squamous epitheliumDiaphragm: dome-shaped muscle; flattens on contraction

In the figure : Airway and lungs.

Rule 1 : Respiratory organs — Gas exchange is a simple physical process; the surface is large, thin, moist and vascular. Protozoa, sponges: membrane; earthworm, leech, frog: moist skin; insects: spiracles/tracheae; fish: gills; mammals: lungs. Large animals need a circulatory system because diffusion alone is too slow. Plants exchange gases by diffusion through stomata, lenticels and root surfaces.

  • Easy : Skin: earthworm.
  • Medium : Tracheae: insects.
  • Exam-type (CET) : The surface must be moist.

Rule 2 : The human air passage — Nose: vestibule (hairs filter dust), respiratory part (warms and moistens), olfactory part (smell). Pharynx (naso-, oro-, laryngo-) → larynx (voice box; vocal cords; glottis guarded by epiglottis) → trachea (10–12 cm; C-shaped incomplete cartilage rings) → right and left bronchi → bronchioles → alveoli. Lungs: right larger, 3 lobes; left smaller, 2 lobes; double pleura (parietal + visceral) with pleural fluid. About 700 million alveoli; single-layer squamous epithelium. Diaphragm = dome-shaped muscle separating thorax and abdomen.

  • Easy : Right lung 3 lobes.
  • Medium : Epiglottis = lid.
  • Exam-type (CET) : 700 million alveoli.
Remember

Right lung has 3 lobes; left has 2.

Common mistake and CET trap

‘Trachea has complete rings’ is wrong (C-shaped). Trap: ‘alveoli have thick walls’ is wrong.

Shortcut

Memory clue : "NPL-TBBA order of passage".

Spot the difference

PartRole
LarynxVoice
TracheaAir passage
AlveoliGas exchange

Practice questions

Easy
  1. 1A property of respiratory surface?
  2. 2Insect respiratory organ?
  3. 3Length of trachea?
Medium
  1. 4What stops food entering the trachea?
  2. 5Lobes in left lung?
  3. 6Number of alveoli?
Challenging
  1. 7What is pleura?
  2. 8Shape of diaphragm?
Show answers (try them yourself first)
  1. 1Moist, thin, large.
  2. 2Tracheae / spiracles.
  3. 310–12 cm.
  4. 4Epiglottis.
  5. 52.
  6. 6~700 million.
  7. 7Double membrane around lungs.
  8. 8Dome-shaped.

Mechanism of breathing

From daily life

Hand on chest while inhaling — it rises forward, then falls.

Simple definition

Breathing = movement of air between atmosphere and lungs (inspiration + expiration). Vital capacity = maximum air breathed out after a maximum inspiration.

BreathingBreathing and lung volumesInspiration: diaphragm flat ↓Expiration: diaphragm dome ↑thorax volume ↑, pressure ↓ → air involume ↓, pressure ↑ → air outTidal volume (TV) 500 ml; IRV 2000–3000; ERV 1000–1100Residual volume 1100–1200 ml; dead space 150 mlVital capacity = TV + IRV + ERV = 4100–4600 mlTotal lung capacity 5200–5800 mlpO₂: alveoli 104, blood 40 mmHg → O₂ inpCO₂: blood 45, alveoli 40 mmHg → CO₂ outRespiration: breathing → external → internal → cellularRespiratory membrane: alveolus + capillary = two thin layers

In the figure : Breathing and lung volumes.

Rule 1 : Inspiration and expiration — Inspiration (active): diaphragm contracts, flattens and moves down; external intercostal muscles contract, ribs move up and out ⇒ thoracic volume increases, pressure falls ⇒ outside air rushes in. Expiration: diaphragm relaxes and domes up; ribs move down and in ⇒ volume falls, pressure rises ⇒ air leaves. One inspiration + one expiration = one breath. Stages of respiration: breathing, external (alveoli ↔ blood), internal (blood ↔ tissues), cellular.

  • Easy : Inspiration: diaphragm flat.
  • Medium : Low pressure → air in.
  • Exam-type (CET) : Expiration: diaphragm dome.

Rule 2 : Volumes and gas exchange — Tidal volume 500 ml; IRV 2000–3000 ml; ERV 1000–1100 ml; dead space 150 ml; residual volume 1100–1200 ml. Vital capacity = TV + IRV + ERV = 4100–4600 ml (e.g. 500 + 2500 + 1100 = 4100). Total lung capacity = 5200–5800 ml. Diffusion goes from high to low partial pressure: pO₂ alveoli 104, blood 40 mmHg ⇒ O₂ in; pCO₂ blood 45, alveoli 40 mmHg ⇒ CO₂ out. Respiratory membrane = alveolar wall + capillary wall, two thin layers.

  • Easy : VC = TV + IRV + ERV.
  • Medium : TV = 500 ml.
  • Exam-type (CET) : pO₂ in alveoli 104.
Remember

VC = TIE: tidal + inspiratory + expiratory reserve.

Common mistake and CET trap

‘Vital capacity includes residual volume’ is wrong. Trap: ‘diaphragm is flat in expiration’ is wrong.

Shortcut

Memory clue : "In = flat; out = dome".

Spot the difference

VolumeValue (ml)
Tidal500
IRV2000–3000
ERV1000–1100
Residual1100–1200

Practice questions

Easy
  1. 1Tidal volume?
  2. 2VC formula?
  3. 3TV 500, IRV 2500, ERV 1100; VC?
Medium
  1. 4Dead space?
  2. 5Diaphragm in inspiration?
  3. 6Alveolar pO₂?
Challenging
  1. 7Direction of CO₂ diffusion?
  2. 8Residual volume?
Show answers (try them yourself first)
  1. 1500 ml.
  2. 2TV + IRV + ERV.
  3. 34100 ml.
  4. 4150 ml.
  5. 5Flat, moves down.
  6. 6104 mmHg.
  7. 7Blood → alveoli.
  8. 81100–1200 ml.

Gas transport, regulation and disorders

From daily life

After running we pant — a rise in blood CO₂ signals the brain.

Simple definition

Oxyhaemoglobin = Hb + O₂. Bohr effect = rise in H⁺, CO₂, temperature shifts Hb towards releasing O₂.

Gas transportGas transport, control and disordersO₂: 97% Hb, 3% dissolvedCO₂: 70% HCO₃⁻23% carbamino-Hb; 7% dissolvedHb + 4 O₂ → oxyhaemoglobin; sigmoid curveBohr effect: H⁺, pCO₂, temp ↑ → curve shifts right → O₂ releasedCO: 250× affinity for Hb → carboxyhaemoglobin → poisoningRBC carbonic anhydrase (Zn): CO₂ + H₂O ⇄ H₂CO₃ ⇄ H⁺ + HCO₃⁻Chloride shift (Hamburger): HCO₃⁻ out, Cl⁻ inControl: pons + medulla; adult 12/min, newborn 44/min; Hering–BreuerDisorders: emphysema, bronchitis, asthma, pneumonia, silicosisArtificial ventilation: mouth-to-mouth / ventilator

In the figure : Transport of O₂ and CO₂; control.

Live figure

Gas transport, regulation and disorders

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Rule 1 : Transport of O₂ and CO₂ — O₂: 3% dissolved, 97% on Hb; 1 Hb = 4 O₂ (oxyhaemoglobin); sigmoid curve; 95–97% saturation in alveoli, ~75% in resting tissue (pO₂ 40 mmHg); 50% saturation at ~27 mmHg (P50). Bohr effect: H⁺, pCO₂, temperature ↑ ⇒ curve shifts right ⇒ O₂ released in tissues. CO poisoning: CO binds Hb ~250× more strongly than O₂ ⇒ carboxyhaemoglobin. CO₂: 7% dissolved, ~70% as HCO₃⁻ (carbonic anhydrase in RBC: CO₂ + H₂O ⇄ H₂CO₃ ⇄ H⁺ + HCO₃⁻), ~23% carbaminohaemoglobin. Chloride shift (Hamburger): HCO₃⁻ out, Cl⁻ in. Haldane effect: oxyHb is acidic ⇒ releases CO₂.

  • Easy : 97% of O₂ on Hb.
  • Medium : 70% of CO₂ = HCO₃⁻.
  • Exam-type (CET) : CO: 250× affinity.

Rule 2 : Regulation and disorders — Control: nervous + chemical. Respiratory centres in pons and medulla; adult ~12/min, newborn ~44/min. Hering–Breuer reflex: lung stretch stops inspiration via vagus. Raised CO₂/H⁺ stimulates the centre. Modified movements: cough, sneeze, yawn, sob, laugh. Disorders: emphysema (alveoli break down; smoking), bronchitis, asthma (bronchiole constriction; allergy), pneumonia, silicosis/fibrosis (dust particles). Remedies: stop smoking, masks, antibiotics (bacterial). Artificial ventilation: mouth-to-mouth, ventilator.

  • Easy : Pons + medulla = centres.
  • Medium : Emphysema: smoking.
  • Exam-type (CET) : Asthma: allergy.
Remember

O₂ 97% on Hb; CO₂ is 7-70-23 (dissolved - bicarbonate - carbamino).

Common mistake and CET trap

‘Most CO₂ binds Hb’ is wrong (as HCO₃⁻). Trap: ‘Bohr shift is to the left’ is wrong.

Shortcut

Memory clue : "Bohr = more O₂ released; CO = clings to Hb".

Spot the difference

GasForm%
O₂On Hb97
CO₂HCO₃⁻~70
CO₂Carbamino-Hb~23

Practice questions

Easy
  1. 1% of O₂ on Hb?
  2. 2Carbonic anhydrase is in?
  3. 3Chloride shift is?
Medium
  1. 4CO affinity vs O₂?
  2. 5Respiratory centre?
  3. 6Newborn breaths/min?
Challenging
  1. 7Cause of emphysema?
  2. 8Bohr effect?
Show answers (try them yourself first)
  1. 197%.
  2. 2RBCs.
  3. 3HCO₃⁻ out, Cl⁻ in.
  4. 4~250 times.
  5. 5Pons and medulla.
  6. 6~44.
  7. 7Smoking / pollution.
  8. 8More CO₂/H⁺ releases O₂.

Types of circulation and composition of blood

From daily life

The body's road network — blood carries food, O₂ and wastes.

Simple definition

Blood = fluid connective tissue: plasma (55%) + formed elements. Double circulation = blood passes through the heart twice per cycle.

CirculationTypes of circulation and bloodSingle (fish)Double (birds, mammals)Open (insects)Open: haemolymph in cavities; closed: blood in vesselsFish: blood passes heart once; ‘venous heart’Double: pulmonary + systemic; heart twiceBlood 4–6 L; pH 7.4; plasma 55%, cells 44–45%Plasma: water 90%, proteins 7–8% (albumin, globulin, fibrinogen)Salts 1%; food, wastes, hormones, heparin, gases 1–2%Serum = plasma − fibrinogenFormed elements: RBC, WBC, platelets

In the figure : Types of circulation; plasma.

Rule 1 : Types of circulation — Open (insects, molluscs): blood (haemolymph) in cavities; closed (annelids, fish, birds, mammals): in vessels. Closed is of two kinds: single — once through the heart (fish; heart carries only deoxygenated blood = ‘venous heart’); double — twice (birds, mammals): pulmonary (heart → lungs → heart) and systemic (heart → body → heart). Intermediate between tissue and blood = lymph.

  • Easy : Fish: single.
  • Medium : Birds, humans: double.
  • Exam-type (CET) : Pulmonary + systemic.

Rule 2 : Blood and plasma — Blood 4–6 litres; pH 7.4 (alkaline); from mesoderm. Plasma 55%: water 90%, proteins 7–8% (albumin, globulin, prothrombin, fibrinogen), salts 1%, others 1–2% (glucose, amino acids, urea, hormones, enzymes, heparin anticoagulant, antibodies, gases). Serum = plasma − fibrinogen (fluid of clotted blood). Formed elements (~45%): RBC, WBC, platelets. Haematocrit = volume fraction of cells in blood. Study = haematology.

  • Easy : Plasma water 90%.
  • Medium : Serum = plasma − fibrinogen.
  • Exam-type (CET) : pH 7.4.
Remember

Plasma = 90 water + 7–8 protein + 1 salt + 1–2 others.

Common mistake and CET trap

‘Serum contains fibrinogen’ is wrong. Trap: ‘a fish heart pumps oxygenated blood’ is wrong.

Shortcut

Memory clue : "Single = fish; double = mammals".

Spot the difference

TypeThrough heartExample
SingleOnceFish
DoubleTwiceHuman

Practice questions

Easy
  1. 1Single circulation in?
  2. 2Two circuits of double circulation?
  3. 3Open circulation example?
Medium
  1. 4Blood pH?
  2. 5Plasma percentage?
  3. 6Water in plasma?
Challenging
  1. 7What is serum?
  2. 8Role of heparin?
Show answers (try them yourself first)
  1. 1Fish.
  2. 2Pulmonary + systemic.
  3. 3Insects.
  4. 47.4.
  5. 555%.
  6. 690%.
  7. 7Plasma − fibrinogen.
  8. 8Anticoagulant.

RBC, WBC, platelets and blood groups

From daily life

After a cut, the bleeding stops once the blood clots.

Simple definition

Erythrocytes (RBC) = red cells with Hb. Leucocytes (WBC) = colourless, nucleated defence cells. Thrombocytes = fragments that clot blood.

Blood cellsRBC, WBC, platelets and blood groupsRBCWBCPlateletsA B AB ORh + / −RBC: biconcave, no nucleus; men 5.1–5.8, women 4.3–5.2 million/mm³Life 120 days; erythropoietin (kidney); bone marrow; B₁₂, ironHb: 4 globin + 4 haem; men 14–17, women 13–15 g%; anaemiaWBC 5000–11000/mm³; neutrophils ~70% (phagocytosis); leucopenia <4000Granulocytes: neutrophil, eosinophil, basophil; agranulocytes: lympho, monoPlatelets: clotting; thrombin: fibrinogen → fibrinABO: antigens A/B; O = universal donor; AB = universal recipientRh: Rh⁻ mother and Rh⁺ foetus → erythroblastosis foetalis

In the figure : RBC, WBC, platelets; blood groups.

Rule 1 : RBC and haemoglobin — RBC: circular, biconcave, no nucleus (camel, llama exceptions); men 5.1–5.8, women 4.3–5.2 million/mm³; life 120 days; formation (erythropoiesis) in foetal liver-spleen, adult red bone marrow; needs B₁₂, folic acid, iron; stimulated by erythropoietin (kidney); destroyed in liver, spleen. Hb = 4 globin chains (2α + 2β), each with one haem (iron) ⇒ 4 O₂; men 14–17, women 13–15 g%; anaemia = low RBC/Hb. Breakdown: iron (ferritin), biliverdin → bilirubin (into bile).

  • Easy : RBC life = 120 days.
  • Medium : Hb carries 4 O₂.
  • Exam-type (CET) : Erythropoietin = kidney.

Rule 2 : WBC, platelets, blood groups and clotting — WBC 5000–11000/mm³; amoeboid, diapedesis; <4000 = leucopenia; rise = leucocytosis; uncontrolled = leukaemia. Granulocytes: neutrophil (~70%; phagocytosis; pus), eosinophil, basophil; agranulocytes: lymphocyte, monocyte. Platelets clot blood: injury → platelets + thromboplastin → prothrombin → thrombin → fibrinogen → fibrin mesh → clot. ABO (antigens A, B; Landsteiner): O = universal donor, AB = universal recipient. Rh: Rh⁻ mother with Rh⁺ foetus ⇒ erythroblastosis foetalis.

  • Easy : Neutrophils ~70%.
  • Medium : Fibrinogen → fibrin.
  • Exam-type (CET) : O = universal donor.
Remember

Never Let Monkeys Eat Bananas: neutrophil, lymphocyte, monocyte, eosinophil, basophil (by count).

Common mistake and CET trap

‘Human RBCs have a nucleus’ is wrong. Trap: ‘AB is universal donor’ is wrong (recipient).

Shortcut

Memory clue : "O gives to all; AB receives from all".

Spot the difference

CellNucleusFunction
RBCNoO₂ transport
WBCYesDefence
PlateletsNoClotting

Practice questions

Easy
  1. 1Life of RBC?
  2. 2RBC formed in?
  3. 3Erythropoietin from?
Medium
  1. 4O₂ per Hb?
  2. 5Leucopenia is?
  3. 6Neutrophil %?
Challenging
  1. 7Fibrin forms from?
  2. 8Universal donor?
Show answers (try them yourself first)
  1. 1120 days.
  2. 2Red bone marrow.
  3. 3Kidney.
  4. 44.
  5. 5WBC < 4000.
  6. 6~70%.
  7. 7Fibrinogen (by thrombin).
  8. 8O.

The heart and the cardiac cycle

From daily life

Listening to a chest you hear ‘lubb-dubb’ — valves closing.

Simple definition

Cardiac cycle = one systole + one diastole (0.8 s). Cardiac output = stroke volume × heart rate.

HeartHeart, cardiac cycle and ECGRARVLALVTricuspidBicuspid (mitral)PQRSTSA node (pacemaker) → AV node → His → PurkinjeCycle 0.8 s; 72/min; SV 70 ml; CO = 5040 ml ≈ 5 L/minAS 0.1, AD 0.7; VS 0.3, VD 0.5 sLubb = AV valves close; dub = semilunar valves closeECG: P (atria), QRS (ventricles), T (repolarisation)Control: sympathetic ↑ (adrenaline), parasympathetic ↓ (ACh)Heart = 4 chambers; left ventricle ~3× thickerRight: deoxygenated; left: oxygenated

In the figure : Heart chambers and ECG.

Live figure

The heart and the cardiac cycle

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Rule 1 : Structure and conduction — Heart: 4 chambers — 2 atria + 2 ventricles; right carries deoxygenated, left oxygenated blood; left ventricle ~3× thicker. Valves: right tricuspid, left bicuspid (mitral); semilunar at aorta/pulmonary artery; Eustachian and Thebesian valves. Conducting tissue: SA node (right atrium; pacemaker) → AV node → bundle of His (two branches) → Purkinje fibres. Control: sympathetic (adrenaline) increases, parasympathetic (acetylcholine) decreases; medulla, hormones.

  • Easy : SA node = pacemaker.
  • Medium : Left = bicuspid.
  • Exam-type (CET) : Left ventricle thickest.

Rule 2 : Cardiac cycle, CO and ECG — Cycle 0.8 s; ~72 beats/min. Atrial systole 0.1 s, atrial diastole 0.7 s; ventricular systole 0.3 s, diastole 0.5 s. In systole AV valves shut ⇒ ‘lubb’; in diastole semilunar valves shut ⇒ ‘dubb’. Joint diastole = all chambers relaxed. Stroke volume ≈ 70 ml; CO = 70 × 72 = 5040 ml ≈ 5 L/min. ECG: P (atrial depolarisation), QRS (ventricular depolarisation), T (ventricular repolarisation). Defective valves cause a ‘heart murmur’.

  • Easy : Cycle = 0.8 s.
  • Medium : CO = SV × HR.
  • Exam-type (CET) : QRS = ventricles.
Remember

Lubb = AV valves lock; dubb = semilunar valves.

Common mistake and CET trap

‘Pacemaker is the AV node’ is wrong (SA node). Trap: ‘tricuspid on the left’ is wrong (bicuspid).

Shortcut

Memory clue : "Right = tricuspid; left = bicuspid".

Spot the difference

PhaseTime (s)
Atrial systole0.1
Ventricular systole0.3
Joint diastole0.4

Practice questions

Easy
  1. 1Pacemaker?
  2. 2Right AV valve?
  3. 3Cycle duration?
Medium
  1. 4‘Lubb’ occurs when?
  2. 5SV 70 ml, HR 72; CO?
  3. 6QRS represents?
Challenging
  1. 7Sympathetic effect?
  2. 8Ventricular systole time?
Show answers (try them yourself first)
  1. 1SA node.
  2. 2Tricuspid.
  3. 30.8 s.
  4. 4AV valves close.
  5. 55040 ml/min.
  6. 6Ventricular depolarisation.
  7. 7Increases heart rate.
  8. 80.3 s.

Blood vessels, blood pressure and lymphatic system

From daily life

Finger on the wrist feels the pulse — an artery's beat.

Simple definition

Blood pressure = force of blood on vessel walls; 120/80 mmHg (systolic/diastolic). Lymph = colourless fluid derived from tissue fluid.

VesselsBlood vessels, pressure and lymphArteryCapillaryVeinthick wall, narrowone cell thickthin, valvesThree layers: tunica externa, media, internaPulmonary artery = deoxygenated; pulmonary vein = oxygenatedPortal vein: second capillary bed (hepatic portal)BP 120/80 mmHg; <90/60 = hypotension; >140/90 = hypertensionAtherosclerosis (cholesterol), CAD, angina, heart attackLymph: colourless; nodes, ducts; fat absorption (lacteal)Lymph: intermediary between tissue and blood; immunityPulse = artery beat (radial, carotid)

In the figure : Artery, capillary, vein and lymph.

Rule 1 : Vessels and blood pressure — Artery: away from heart; thick elastic wall, narrow lumen; oxygenated blood (exception: pulmonary artery). Vein: towards heart; thin wall, wide lumen, valves; deoxygenated blood (exception: pulmonary vein). Capillary: one cell thick; exchange. Three layers: tunica externa, media, interna. Portal vein: breaks into capillaries again in another organ (liver). BP 120/80 mmHg; <90/60 = hypotension; >140/90 = hypertension. Pulse = arterial beat (radial, carotid).

  • Easy : Artery: away; vein: toward.
  • Medium : Veins have valves.
  • Exam-type (CET) : BP 120/80.

Rule 2 : Heart disorders and the lymphatic system — Atherosclerosis: cholesterol deposits narrow arteries; CAD, angina (chest pain), heart attack (myocardial infarction), hypertension; remedies: diet, exercise, no smoking. Lymphatic system: lymph vessels, lymph nodes, thymus, spleen; lymph is colourless; no RBCs, has lymphocytes; mediates tissue ↔ blood; fat absorption (lacteals); immunity; returns excess tissue fluid to blood.

  • Easy : Atherosclerosis = cholesterol.
  • Medium : Lymph: no RBCs.
  • Exam-type (CET) : Lacteal = fat.
Remember

Artery = away; vein = valves, toward heart.

Common mistake and CET trap

‘All arteries carry oxygenated blood’ is wrong (pulmonary). Trap: ‘lymph has RBCs’ is wrong.

Shortcut

Memory clue : "120/80 = systolic over diastolic".

Spot the difference

VesselWallValves
ArteryThickNo
VeinThinYes
CapillaryOne layerNo

Practice questions

Easy
  1. 1Artery direction?
  2. 2What do veins have?
  3. 3Normal BP?
Medium
  1. 4Hypotension is?
  2. 5Portal vein feature?
  3. 6Atherosclerosis cause?
Challenging
  1. 7Lacteal absorbs?
  2. 8Lymph contains?
Show answers (try them yourself first)
  1. 1Away from heart.
  2. 2Valves.
  3. 3120/80 mmHg.
  4. 4<90/60.
  5. 5Breaks into capillaries again.
  6. 6Cholesterol deposits.
  7. 7Fat.
  8. 8Lymphocytes; no RBC.

Quick revision of the whole lesson

ConceptKey fact
Air passageNose → … → alveoli; 700 million
BreathingVC = TV + IRV + ERV; TV 500 ml
Gas transportO₂ 97% Hb; CO₂ 70% HCO₃⁻
BloodPlasma 55%; water 90%; pH 7.4
CellsRBC 120 days; neutrophils 70%
Heart0.8 s; SV 70; CO 5040 ml
VesselsBP 120/80; veins have valves

🎯 Most important points for the exam

  • Structure of respiratory system.
  • Breathing and volumes.
  • O₂/CO₂ transport, Bohr effect.
  • Circulation and plasma.
  • RBC, WBC, blood groups, clotting.
  • Cardiac cycle, ECG, CO.
  • Vessels, BP, lymph.
Study mantra

Understand the concept → draw the figure → memorise the key points → solve questions yourself.