Body Fluids and Circulation ISC Class 11: Blood, Heart and Cardiac Cycle

What Body Fluids and Circulation is about

Weightage: Body Fluids and Circulation belongs to the unit Human Physiology, which CISCE weights at 18 of the 70 marks in the ISC Class XI Biology Paper I (Theory). Class XI is examined by the school, so your school sets the paper within this weightage.Source: CISCE ISC Biology syllabus, examination year 2028, Class XI unit weightage

Key concepts

Blood: plasma, plasma proteins and formed elements

Plasma is a straw-coloured, slightly alkaline fluid forming about 55% of blood. It is about 90–92% water; proteins make up 6–8%: fibrinogen (clotting), globulins (mainly defence: antibodies) and albumins (maintain osmotic balance and carry substances). Plasma also carries minerals (Na⁺, Ca²⁺, Mg²⁺, HCO₃⁻, Cl⁻), glucose, amino acids, lipids, hormones and wastes. Plasma without clotting factors is serum. Formed elements (about 45%): (1) Red blood cells (erythrocytes): the most numerous cells, about 5–5.5 million per mm³; formed in red bone marrow in adults; biconcave and without a nucleus in most mammals; contain haemoglobin (about 12–16 g per 100 mL of blood), which carries O₂ and CO₂; live about 120 days and are destroyed in the spleen ('graveyard of RBCs'). (2) White blood cells (leucocytes): nucleated, colourless, about 6000–8000 per mm³, short-lived. Granulocytes: neutrophils (most abundant, 60–65%; phagocytic), eosinophils (2–3%; resist infection, allergy), basophils (least, 0.5–1%; secrete histamine, serotonin, heparin; involved in inflammation). Agranulocytes: lymphocytes (20–25%; B and T cells for immunity) and monocytes (6–8%; phagocytic). (3) Platelets (thrombocytes): cell fragments from megakaryocytes in bone marrow, about 1.5–3.5 lakh per mm³; release factors for clotting. A fall in platelets can cause bleeding.

Worked example

A blood report shows a very high neutrophil count. What does this suggest, and why?

Try it first, then show the solutionSolution

1. Neutrophils are the most abundant phagocytic WBCs and are the first to respond to bacteria
2. Their numbers rise sharply during acute bacterial infection

Answer: An acute bacterial infection; neutrophils multiply to engulf the bacteria

Blood groups: ABO and Rh, in transfusion and pregnancy

ABO grouping depends on two surface antigens on RBCs, A and B; plasma carries the opposite natural antibodies. Group A: antigen A, antibody anti-B. Group B: antigen B, antibody anti-A. Group AB: both antigens, no antibodies: can receive from all groups (universal recipient). Group O: no antigens, both antibodies: its RBCs can be given to all groups (universal donor). In transfusion, donor RBC antigens must not meet matching antibodies in the recipient's plasma, or the donor cells clump (agglutinate) and are destroyed. Rh grouping: another antigen, the Rh factor (first found in Rhesus monkeys), is present in about 80% of people (Rh⁺); those lacking it are Rh⁻. An Rh⁻ person given Rh⁺ blood forms anti-Rh antibodies, so Rh must also be matched. Rh incompatibility in pregnancy: if an Rh⁻ mother carries an Rh⁺ foetus, the blood of mother and foetus is normally kept separate by the placenta, so the first pregnancy usually goes well. During delivery, some foetal Rh⁺ blood can enter the mother, who then makes anti-Rh antibodies. In a later Rh⁺ pregnancy, these antibodies cross the placenta and destroy the foetal RBCs, causing severe anaemia and jaundice in the foetus: erythroblastosis foetalis, which can be fatal. It is prevented by giving the mother anti-Rh antibodies immediately after the first delivery, which destroy any foetal Rh⁺ cells before her immune system responds.

Worked example

A patient with blood group A needs a transfusion. Which donor groups can be used and why?

Try it first, then show the solutionSolution

1. The patient's plasma has anti-B antibodies, so donor RBCs must not carry antigen B
2. Donors A (antigen A only) and O (no antigens) are safe; B and AB would agglutinate

Answer: Groups A and O

Coagulation of blood (brief) and lymph

Coagulation prevents excessive loss of blood after injury. When a vessel is damaged, platelets and injured tissues release factors that start a chain (cascade) of enzyme reactions. These lead to an enzyme complex (thrombokinase / prothrombinase) that converts inactive prothrombin in plasma into active thrombin. Thrombin converts soluble fibrinogen into insoluble fibrin threads, which form a mesh trapping blood cells: the clot (coagulum). Calcium ions play a very important role. Lymph (brief): as blood flows through capillaries, some water and small solutes filter out into spaces between cells, forming tissue (interstitial) fluid, which has a similar mineral make-up to plasma but fewer proteins and no RBCs. Exchange of nutrients and gases between blood and cells occurs through this fluid. Part of it returns to capillaries; the rest is collected by blind-ended lymphatic capillaries, becoming lymph, which flows through lymph vessels and enters the large veins near the heart (through the thoracic and right lymphatic ducts). Lymph nodes along the vessels filter lymph and contain many lymphocytes, which fight infection. Functions of lymph: returns tissue fluid and proteins to blood; carries fats absorbed by lacteals in intestinal villi; takes part in immune responses (lymphocytes); carries nutrients and hormones.

Worked example

Why do lymph nodes in the neck sometimes swell during a throat infection?

Try it first, then show the solutionSolution

1. Lymph draining the infected area carries microbes to nearby lymph nodes
2. Lymphocytes in the nodes multiply to fight the infection, making the nodes swell

Answer: Lymph nodes trap microbes and lymphocytes multiply there

Open and closed circulation; external and internal structure of the human heart

Open circulatory system: blood is pumped by the heart into vessels that open into body spaces (sinuses or haemocoel); found in arthropods and molluscs. Closed circulatory system: blood always flows in a network of vessels, so its flow can be precisely regulated; found in annelids and chordates. Vertebrate hearts: fishes have two chambers (single circulation); amphibians and most reptiles three (two atria, one ventricle; incomplete double circulation); crocodiles, birds and mammals four (complete double circulation). Human heart, external: a hollow, muscular organ of mesodermal origin, about the size of a clenched fist, lying in the thoracic cavity between the lungs, slightly tilted to the left; enclosed in a double-walled pericardium with pericardial fluid. Grooves on the surface (coronary sulcus between atria and ventricles; interventricular sulci) carry coronary arteries and veins that supply the heart muscle itself. Great vessels: venae cavae entering the right atrium, pulmonary veins entering the left atrium, pulmonary artery leaving the right ventricle and aorta leaving the left ventricle. Internal: four chambers, two thin-walled atria above and two thick-walled ventricles below. The atria are separated by the interatrial septum, the ventricles by the thick interventricular septum. Each atrium opens into the ventricle on its side through an atrioventricular aperture guarded by a valve: tricuspid (three flaps) on the right, bicuspid (mitral) (two flaps) on the left. The flaps are held by chordae tendineae attached to papillary muscles, which stop them turning inside out. Semilunar valves guard the openings of the pulmonary artery and aorta. Valves allow blood to flow one way only. The left ventricle has the thickest wall because it pumps blood to the whole body. Nodal tissue: the sinoatrial node (SAN) in the upper right corner of the right atrium; the atrioventricular node (AVN) in the lower left corner of the right atrium near the atrioventricular septum; from it the bundle of His runs through the septum and divides into right and left bundle branches, which end as Purkinje fibres in the ventricular walls.

Worked example

Why is the wall of the left ventricle thicker than that of the right ventricle?

Try it first, then show the solutionSolution

1. The right ventricle pumps blood only to the nearby lungs (pulmonary circulation)
2. The left ventricle must push blood through the whole body (systemic circulation) at higher pressure

Answer: It must generate a much higher pressure to drive systemic circulation

Cardiac cycle and double circulation

The heart is myogenic: the SAN generates about 70–75 impulses per minute on its own and sets the pace, so it is the pacemaker. One complete heartbeat, a sequence of contraction (systole) and relaxation (diastole) of atria and ventricles, is a cardiac cycle. At about 72 beats per minute, one cycle lasts about 0.8 s (60 ÷ 72 = 0.83 s). Phases (approximate, for 0.8 s): (1) Joint diastole (about 0.4 s): all four chambers relaxed; AV valves open, semilunar valves closed; blood from the venae cavae and pulmonary veins flows into the atria and on into the ventricles (most ventricular filling occurs now). (2) Atrial (auricular) systole (about 0.1 s): SAN fires, atria contract and push in the remaining blood (about 30% more). (3) Ventricular systole (about 0.3 s): the impulse passes via AVN, bundle of His and Purkinje fibres; ventricles contract; pressure rises, AV valves close (first heart sound, 'lub'); when ventricular pressure exceeds that in the arteries, semilunar valves open and blood enters the pulmonary artery and aorta. Atria are in diastole during this time (atrial diastole lasts about 0.7 s). (4) Ventricular diastole (about 0.5 s): ventricles relax; pressure falls; semilunar valves close (second sound, 'dub'), preventing backflow; AV valves reopen and filling begins again. Double circulation: blood passes through the heart twice in one round of the body. Pulmonary circulation: right ventricle → pulmonary artery → lungs (oxygenated) → pulmonary veins → left atrium. Systemic circulation: left ventricle → aorta → arteries, arterioles, capillaries of tissues → venules, veins → venae cavae → right atrium. Oxygenated and deoxygenated blood never mix. A special arrangement, the hepatic portal system, carries blood from the intestine to the liver before it returns to the heart; the heart's own muscle is supplied by the coronary system.

Worked example

When do the two heart sounds occur, and what causes them?

Try it first, then show the solutionSolution

1. 'Lub': at the start of ventricular systole, when the tricuspid and bicuspid valves close
2. 'Dub': at the start of ventricular diastole, when the semilunar valves close

Answer: Closure of AV valves (lub) and of semilunar valves (dub)

Stroke volume, cardiac output, blood pressure and ECG

Stroke volume (SV): volume of blood pumped by each ventricle in one beat, about 70 mL at rest. Cardiac output (CO): volume pumped by each ventricle per minute: CO = SV × heart rate, about 70 × 72 ≈ 5 L per minute at rest. It rises greatly in exercise (both SV and rate increase); athletes have a larger SV and so a lower resting rate. Arterial blood pressure: the pressure of blood on the walls of arteries. It is highest during ventricular systole (systolic pressure, about 120 mm Hg) and lowest during diastole (diastolic pressure, about 80 mm Hg), written as 120/80 mm Hg. It is measured with a sphygmomanometer. The difference (about 40 mm Hg) is the pulse pressure. Electrocardiogram (ECG): a graph of the heart's electrical activity, recorded by electrodes on the wrists, ankle and chest. P wave: depolarisation (excitation) of the atria, leading to atrial contraction. QRS complex: depolarisation of the ventricles, starting ventricular contraction (contraction starts shortly after Q and marks the start of systole). T wave: return of the ventricles to normal (repolarisation); its end marks the end of systole. Counting the QRS complexes in a given time gives the heart rate. Deviations from the normal shape point to heart abnormalities, so the ECG has great clinical value.

Worked example

An ECG is recorded at a paper speed of 25 mm per second. The distance between two successive R peaks is 20 mm. Find the heart rate.

Try it first, then show the solutionSolution

1. Time for one cycle = 20 mm ÷ 25 mm s⁻¹ = 0.8 s
2. Heart rate = 60 ÷ 0.8 = 75 beats per minute

Answer: 75 beats per minute

Blood vessels and regulation of cardiac activity

Arteries carry blood away from the heart (all carry oxygenated blood except the pulmonary artery). Veins carry blood towards the heart (all deoxygenated except the pulmonary veins). Both have three layers: an outer tunica externa (fibrous connective tissue with collagen fibres), a middle tunica media (smooth muscle and elastic fibres) and an inner tunica intima (squamous endothelium). In arteries the tunica media is thick and elastic, the lumen is narrow and there are no valves, so they withstand and smooth out high, pulsating pressure. In veins the tunica media is thin, the lumen wide, and valves prevent backflow of blood moving at low pressure. Capillaries have walls only one cell thick (endothelium), allowing exchange of materials with tissues. Regulation: normal activity is auto-regulated by nodal tissue (myogenic). Its rate and strength are modified by a cardiovascular centre in the medulla oblongata through the autonomic nervous system: sympathetic nerves increase heart rate, the force of ventricular contraction and so cardiac output; parasympathetic nerves (vagus) decrease heart rate and the speed of conduction, reducing cardiac output. Hormones of the adrenal medulla (adrenaline, noradrenaline) also increase cardiac output.

Worked example

Why do veins in the legs need valves while arteries do not?

Try it first, then show the solutionSolution

1. Blood in leg veins is at low pressure and must flow upward against gravity
2. Valves prevent it from flowing back when muscles relax; arteries carry blood at high pressure from the heart, so backflow is not a problem

Answer: Low venous pressure against gravity requires valves to stop backflow

Disorders of the circulatory system

Hypertension (high blood pressure): blood pressure repeatedly 140/90 mm Hg or higher. It increases the workload of the heart and can damage vital organs such as the heart, brain and kidneys; it is a major risk factor for heart disease and stroke. Coronary artery disease (CAD), often linked to atherosclerosis: the vessels supplying the heart muscle are narrowed by deposits of calcium, fat, cholesterol and fibrous tissue, reducing blood flow to the heart. Angina pectoris: acute chest pain felt when not enough oxygen reaches the heart muscle, often during exertion or stress, because of narrowed coronary arteries; it is more common in middle-aged and elderly people. Heart failure: the heart cannot pump blood effectively enough to meet the body's needs; it is sometimes called congestive heart failure because fluid congestion of the lungs is a main symptom. Heart failure is not the same as cardiac arrest (the heart stops beating) or a heart attack (heart muscle is suddenly damaged by an inadequate blood supply). Risk factors include smoking, a diet high in fats and salt, lack of exercise, obesity, stress and diabetes.

Worked example

A middle-aged man feels chest pain when climbing stairs, which goes away on rest. Suggest the disorder and its cause.

Try it first, then show the solutionSolution

1. Climbing stairs increases the heart's need for O₂
2. Narrowed coronary arteries cannot increase blood flow enough, so the heart muscle is short of O₂ and pain results

Answer: Angina pectoris due to coronary artery narrowing

Body Fluids and Circulation in real life

Each concept, met in an everyday situation. Read the situation, answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Topics in this chapter

• Blood Composition, Blood Groups and Coagulation
• Heart, Cardiac Cycle, ECG and Circulation

Body Fluids and Circulation: key facts

Cardiac output

$CO=SV\times HR\approx 70\text{mL}\times 72{\text{min}}^{-1}\approx 5{\text{L min}}^{-1}$

Per ventricle.

Duration of one cardiac cycle

$T=\frac{60}{\text{heart rate}}\text{s};0.8\text{s}=0.1(\text{atrial systole})+0.3(\text{ventricular systole})+0.4(\text{joint diastole})$

At 75 beats per minute.

Blood pressure terms

$\text{pulse pressure}=\text{systolic}-\text{diastolic}=120-80=40\text{mm Hg}$

Hypertension: 140/90 mm Hg or more.

Heart rate from ECG

$HR=\frac{60}{RR\text{interval (s)}};RR=\frac{\text{distance (mm)}}{{\text{paper speed (mm s}}^{-1})}$

Or count QRS complexes in a known time.

Clotting cascade (outline)

$\text{prothrombin}\stackrel{\text{thrombokinase},C{a}^{2+}}{\to }\text{thrombin};\text{fibrinogen}\stackrel{\text{thrombin}}{\to }\text{fibrin}$

Fibrin mesh traps cells to form a clot.

Body Fluids and Circulation: diagrams to practise

Practise each one on paper: draw it from the checklist, then tick off every label.

How the school exam asks Body Fluids and Circulation

The question patterns to expect, and the method that works for each.

Tricks to remember Body Fluids and Circulation

Short memory aids. Say each one aloud once, then use it on a question the same day.

• Never Let Monkeys Eat Bananas

  Neutrophils > Lymphocytes > Monocytes > Eosinophils > Basophils (most to least).

  Use it when: WBC proportions.

• Try before you Bi

  Blood meets the tricuspid (right) before the bicuspid (left).

  Use it when: Valve positions.

• SA → AV → His → Purkinje

  'Some Athletes Have Power': SAN, AVN, His, Purkinje.

  Use it when: Conducting system.

• P for atria, QRS for ventricles, T to reset

  P = atrial depolarisation; QRS = ventricular depolarisation; T = ventricular repolarisation.

  Use it when: ECG waves.

• Arteries Away, Veins Valves

  Arteries carry blood away and have thick walls; veins have valves and wide lumens.

  Use it when: Blood vessels.

Body Fluids and Circulation: exam-level solved questions

Ordered from exam level to HOTS. Cover the solution, write your own, then compare step by step.

Case-study practice (Section D style)

Read the situation, then answer every part. In a school exam set on the board pattern this is a 5-mark question split into 1 + 1 + 1 + 2 marks.

Where the marks are

How a typical answer is split into step marks. Show every step: a right final answer alone rarely earns full marks.

Where students lose marks in Body Fluids and Circulation

The slips examiners see most often, and what to write instead.

• ✗Mistake: Saying all arteries carry oxygenated blood

  The rule is learned without exceptions.

  Wrong working

  Arteries carry oxygenated blood; veins carry deoxygenated blood.

  Right working

  Arteries carry blood away from the heart; the pulmonary artery carries deoxygenated blood and pulmonary veins carry oxygenated blood.

  ✓Do this: Define by direction, not by oxygen.

  Usually costs: 1 mark.

• ✗Mistake: Explaining universal donor by antibodies

  Antigen and antibody roles are mixed up.

  Wrong working

  Group O is a universal donor because it has no antibodies.

  Right working

  Group O RBCs have no A or B antigens; group AB plasma has no antibodies (universal recipient).

  ✓Do this: Donor: look at RBC antigens; recipient: look at plasma antibodies.

  Usually costs: 1-2 marks.

• ✗Mistake: Wrong ECG wave meanings

  Contraction and depolarisation are confused.

  Wrong working

  The T wave shows atrial contraction.

  Right working

  P: atrial depolarisation; QRS: ventricular depolarisation; T: ventricular repolarisation.

  ✓Do this: Learn the three letters in order.

  Usually costs: 1 mark.

• ✗Mistake: Saying the first Rh⁺ baby is affected

  The sensitisation sequence is not understood.

  Wrong working

  Erythroblastosis foetalis affects the first Rh⁺ baby of an Rh⁻ mother.

  Right working

  The mother is usually sensitised at the first delivery; later Rh⁺ babies are at risk.

  ✓Do this: First sensitises, second suffers.

  Usually costs: 1 mark.

• ✗Mistake: Confusing heart failure with heart attack

  The terms sound similar.

  Wrong working

  Heart failure means the heart has stopped.

  Right working

  Heart failure: heart pumps ineffectively; cardiac arrest: heart stops; heart attack: heart muscle suddenly damaged by poor blood supply.

  ✓Do this: Learn the three definitions together.

  Usually costs: 1 mark.

Practice questions on Body Fluids and Circulation

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQExam level

   The valve between the left atrium and left ventricle is the:
   (a) tricuspid
   (b) bicuspid
   (c) semilunar
   (d) pulmonary

   Hint

   Mitral.

   Answer

   (b)

2. Q2 · 1 mark · MCQExam level

   The most abundant WBCs are:
   (a) lymphocytes
   (b) monocytes
   (c) neutrophils
   (d) basophils

   Hint

   60–65%.

   Answer

   (c)

3. Q3 · 1 mark · Very short answerExam level

   Name the plasma protein needed for clotting.

   Hint

   Becomes fibrin.

   Answer

   Fibrinogen

4. Q4 · 1 mark · Very short answerExam level

   What does the QRS complex of an ECG represent?

   Hint

   Ventricles.

   Answer

   Depolarisation of the ventricles, which starts ventricular contraction.

5. Q5 · 2 marks · Short answerExam level

   State two functions of lymph.

   Hint

   Fluid return and fats.

   Answer

   Returns tissue fluid and proteins to the blood; carries fats absorbed by lacteals; lymphocytes in lymph and lymph nodes provide immunity.

6. Q6 · 2 marks · Short answerHarder exam level

   Why is the heart called myogenic? Name the pacemaker.

   Hint

   Starts in muscle.

   Answer

   The heartbeat originates in specialised cardiac muscle (nodal tissue) itself, not from nerves. The SA node, which generates 70–75 impulses per minute, is the pacemaker.

7. Q7 · 2 marks · Short answerHarder exam level

   Distinguish between systolic and diastolic blood pressure, giving normal values.

   Hint

   120/80.

   Answer

   Systolic: highest arterial pressure during ventricular contraction, about 120 mm Hg. Diastolic: lowest pressure during ventricular relaxation, about 80 mm Hg.

8. Q8 · 3 marks · Short answerHarder exam level

   Explain how the nervous system and hormones regulate cardiac activity.

   Hint

   Medulla, ANS.

   Answer

   A centre in the medulla oblongata acts through the autonomic nervous system: sympathetic nerves increase heart rate, force of contraction and cardiac output; parasympathetic (vagus) nerves decrease heart rate and conduction speed. Adrenal medullary hormones also raise cardiac output.

9. Q9 · 3 marks · Short answerHarder exam level

   What is double circulation? Trace the pathway of blood in each circuit.

   Hint

   Twice through the heart.

   Answer

   Blood passes through the heart twice in one complete circuit. Pulmonary: right ventricle → pulmonary artery → lungs → pulmonary veins → left atrium. Systemic: left ventricle → aorta → body tissues → venae cavae → right atrium.

10. Q10 · 3 marks · Short answerHarder exam level

    Describe hypertension and coronary artery disease.

    Hint

    140/90; atherosclerosis.

    Answer

    Hypertension: blood pressure repeatedly 140/90 mm Hg or higher; strains the heart and can damage heart, brain and kidneys. CAD: narrowing of coronary arteries by deposits of calcium, fat, cholesterol and fibrous tissue (atherosclerosis), reducing blood supply to the heart muscle.

11. Q11 · 5 marks · Long answerHarder exam level

    (a) Describe the composition of blood. [3]
    (b) Explain the ABO blood group system and its importance in transfusion. [2]

    Hint

    Plasma and formed elements.

    Answer

    (a) Plasma (55%): 90–92% water, 6–8% proteins (fibrinogen, globulins, albumins), minerals, nutrients, hormones, wastes. Formed elements (45%): RBCs (5–5.5 million/mm³, with haemoglobin, 120-day life), WBCs (6000–8000/mm³: neutrophils, eosinophils, basophils, lymphocytes, monocytes), platelets (1.5–3.5 lakh/mm³). (b) Groups A, B, AB and O depend on A and B antigens on RBCs, with opposite antibodies in plasma; donor antigens must not meet matching recipient antibodies or the RBCs agglutinate; O is universal donor and AB universal recipient.

12. Q12 · 5 marks · Long answerHarder exam level

    (a) Draw a labelled diagram of a standard ECG and explain each wave. [3]
    (b) If the R–R interval is 0.75 s, what is the heart rate? [2]

    Hint

    60 ÷ RR.

    Answer

    (a) P wave (atrial depolarisation), QRS complex (ventricular depolarisation, start of ventricular systole), T wave (ventricular repolarisation, end of systole). (b) 60 ÷ 0.75 = 80 beats per minute.

13. Q13 · 2 marks · Short answerHarder exam level

    A person's heart beats 80 times per minute. Calculate the duration of one cardiac cycle and the cardiac output if the stroke volume is 65 mL.

    Hint

    60 ÷ rate.

    Answer

    Cycle = 60 ÷ 80 = 0.75 s; cardiac output = 65 × 80 = 5200 mL per minute (5.2 L/min).

14. Q14 · 3 marks · Short answerHOTS / competency

    Why do the AV node and bundle of His delay and then rapidly spread the impulse, instead of letting it pass straight from atria to ventricles?

    Hint

    Filling and coordination.

    Answer

    The atria and ventricles are separated by non-conducting tissue, so the impulse reaches the ventricles only through the AV node, which delays it briefly. This lets the atria finish contracting and fill the ventricles. The bundle of His and Purkinje fibres then spread the impulse rapidly through the ventricles so they contract together from the apex upward, pushing blood efficiently into the arteries.

15. Q15 · 3 marks · Short answerHOTS / competency

    Tissue swelling (oedema) can occur when plasma albumin levels fall in severe malnutrition. Explain using the formation of tissue fluid.

    Hint

    Osmotic balance.

    Answer

    Albumins keep the osmotic pressure of plasma high, which draws tissue fluid back into capillaries. When albumin falls, less fluid returns to the blood; more remains in tissue spaces than the lymphatic system can drain, so tissues swell.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.Plasma proteins?Show answer

   Fibrinogen, globulins, albumins.

2. 2.Life span of RBC?Show answer

   About 120 days.

3. 3.Universal recipient?Show answer

   Group AB.

4. 4.Ion essential for clotting?Show answer

   Calcium (Ca²⁺).

5. 5.Duration of a cardiac cycle at 72 bpm?Show answer

   About 0.8 s.

6. 6.Normal cardiac output?Show answer

   About 5 L per minute.

7. 7.Instrument for blood pressure?Show answer

   Sphygmomanometer.

8. 8.Vessel with valves?Show answer

   Vein.

Quick revision checklist

The night before the exam: can you do each of these without looking?

• ☐Can you list three plasma proteins with functions?
• ☐Can you give the percentage of each WBC type?
• ☐Can you decide safe donors for each blood group?
• ☐Can you explain erythroblastosis foetalis?
• ☐Can you draw the internal structure of the heart?
• ☐Can you describe each phase of the cardiac cycle?
• ☐Can you calculate cardiac output and heart rate from an ECG?
• ☐Can you distinguish hypertension, angina and heart failure?

Body Fluids and Circulation: frequently asked questions