Q1: What are the components of blood?
Answer: Blood is made of two main parts:
- Plasma (about 55%) → the liquid part
- Formed elements (about 45%) → the cells and cell fragments
- RBCs (carry oxygen)
- WBCs (fight infection)
- Platelets (help in clotting)
Key Points to Remember:
- Plasma = 55%
- Formed elements = 45%
- RBC → O₂, WBC → defence, Platelets → clotting
Q2: What is the difference between lymph and blood?
Answer: Blood is a red fluid because it has RBCs with haemoglobin, while lymph is colourless because it doesn’t have RBCs. Blood has more proteins and carries oxygen, but lymph has fewer proteins and mainly helps in returning tissue fluid, immunity, and fat transport.
| Feature | Blood | Lymph |
|---|---|---|
| Colour | Red (haemoglobin) | Colourless (no RBCs) |
| Main cells | RBCs, WBCs, platelets | Mainly lymphocytes |
| Proteins | More | Fewer |
| Main roles | Transport O₂, nutrients, wastes | Fat absorption, immunity, tissue fluid balance |
| Flow | Faster in blood vessels | Slower in lymph vessels |
Key Points to Remember:
- Blood = RBCs + haemoglobin → red
- Lymph = no RBCs → colourless
- Lymph transports fats (lacteals) + immunity (lymphocytes)
Q3: Why do we call our heart myogenic?
Answer: We call the heart myogenic because the heartbeat starts from the heart muscles itself, not from the nerves. The SA node produces the impulse and sets the rhythm, so the heart is auto-excitable.
Key Points to Remember:
- Myogenic = impulse originates in heart muscle
- SA node = natural pacemaker
- No need of external nerve to start each beat
Q4: Describe the evolutionary change in the pattern of heart among vertebrates.
Answer: As vertebrates evolved, the heart became more chambered to reduce mixing of blood and improve oxygen supply.
- Fishes: 2 chambers (1 atrium + 1 ventricle) → single circulation, blood goes to gills.
- Amphibians & most reptiles: 3 chambers (2 atria + 1 ventricle) → some mixing happens.
- Crocodiles, birds, mammals: 4 chambers → complete separation of oxygenated and deoxygenated blood, best for high metabolism.
Key Points to Remember:
- 2 → 3 → 4 chambers (evolution trend)
- 4-chambered = no mixing = most efficient
- Crocodile is reptile but has 4 chambers
Q5: Describe the structure of human heart.
Answer: The human heart is a muscular, four-chambered organ with two atria on top and two ventricles below. Septa separate right and left sides. Valves make sure blood flows only in one direction:
- Tricuspid valve (right atrium → right ventricle)
- Bicuspid/Mitral valve (left atrium → left ventricle)
- Semilunar valves at the bases of aorta and pulmonary artery.
Key Points to Remember:
- 4 chambers: RA, RV, LA, LV
- Valves prevent backflow
- Tricuspid (right), Mitral (left), Semilunar (arteries)
Q6: Explain the significance of the AV node and the AV bundle.
Answer: The AV node receives the impulse from the SA node and makes a small delay so the ventricles get enough time to fill completely. The AV bundle (Bundle of His) carries the impulse to the ventricles through Purkinje fibres so both ventricles contract in a proper coordinated way.
Key Points to Remember:
- AV node = delay → better ventricular filling
- AV bundle = carries impulse to ventricles
- Helps in synchronized ventricular contraction
Q7: Explain the ABO blood group system.
Answer: ABO blood group depends on the presence of A and B antigens on RBCs and anti-A / anti-B antibodies in plasma:
- A: A antigen, anti-B antibody
- B: B antigen, anti-A antibody
- AB: A and B antigens, no antibodies → universal recipient (ABO)
- O: no antigens, both antibodies → universal donor (ABO)
Key Points to Remember:
- Antigen on RBC decides group
- AB = no antibodies (can receive)
- O = no antigens (can donate)
Q8: What is Rh incompatibility? How can it be prevented?
Answer: Rh incompatibility happens when an Rh− mother carries an Rh+ baby. During the first delivery, some baby blood can mix with the mother’s blood, so the mother starts making anti-Rh antibodies. In the next Rh+ pregnancy, these antibodies can cross the placenta and destroy foetal RBCs, causing erythroblastosis foetalis. It can be prevented by giving anti-Rh injection (RhoGAM) to the mother after the first delivery.
Key Points to Remember:
- Rh− mother + Rh+ foetus = risk
- Problem mainly in second pregnancy
- Prevention: RhoGAM after first delivery
Q9: Describe blood coagulation (clotting).
Answer: Blood clotting prevents excess bleeding after injury. Damaged tissues and platelets start a chain reaction that converts:
- Prothrombin → Thrombin
- Fibrinogen → Fibrin Fibrin forms a mesh that traps blood cells and makes a clot. Calcium ions (Ca²⁺) are important for this process.
Key Points to Remember:
- Prothrombin → Thrombin
- Fibrinogen → Fibrin (mesh)
- Ca²⁺ is essential
Q10: Define a cardiac cycle and cardiac output.
Answer:
- Cardiac cycle is one complete heartbeat, including contraction (systole) and relaxation (diastole) of atria and ventricles. In a normal person, it takes about 0.8 second.
- Cardiac output is the total blood pumped by each ventricle in one minute.
Key Points to Remember:
- Cardiac cycle ≈ 0.8 s
- CO = SV × HR
- Output is higher in athletes
Q11: What causes heart sounds (Lub and Dub)?
Answer: Heart sounds happen due to closure of valves:
- Lub (S1): closing of AV valves (tricuspid + bicuspid) at the start of ventricular systole.
- Dub (S2): closing of semilunar valves at the end of ventricular systole.
Key Points to Remember:
- Lub = AV valves close
- Dub = semilunar valves close
Q12: What is ECG and what does it represent?
Answer: ECG is a graph that shows the electrical activity of the heart during a cardiac cycle.
- P wave: atrial depolarisation
- QRS complex: ventricular depolarisation
- T wave: ventricular repolarisation
Key Points to Remember:
- P = atria depolarise
- QRS = ventricles depolarise
- T = ventricles repolarise
Q13: How is cardiac activity regulated?
Answer: The heart is myogenic, but its rate and force can be changed by the autonomic nervous system:
- Sympathetic nerves: increase heart rate and force.
- Parasympathetic (vagus): decrease heart rate. Also, hormones like adrenaline increase heart rate during stress.
Key Points to Remember:
- Sympathetic = faster, stronger
- Parasympathetic (vagus) = slower
- Adrenaline increases cardiac output
Q14: Differentiate between arteries and veins.
Answer: Arteries carry blood away from the heart at high pressure, so they have thick elastic walls. Veins bring blood towards the heart at lower pressure, so they have thinner walls and valves to prevent backflow.
Key Points to Remember:
- Artery: away, high pressure, thick wall
- Vein: towards, low pressure, valves present
Q15: What is the importance of plasma proteins?
Answer: Plasma proteins do major jobs:
- Fibrinogen: helps in clotting.
- Globulins: help in immunity (antibodies).
- Albumin: maintains osmotic balance and helps keep water in blood.
Key Points to Remember:
- Fibrinogen → clotting
- Globulins → defence
- Albumin → osmotic pressure
Q16: What is lymph? Mention its functions.
Answer: Lymph is a colourless fluid formed from tissue fluid that enters lymph vessels. It mainly contains lymphocytes. Functions:
- Returns extra tissue fluid back to blood
- Absorbs fats from intestine through lacteals
- Helps in immunity
Key Points to Remember:
- Lymph = tissue fluid in lymph vessels
- Lacteals absorb fats
- Lymphocytes = immunity
Q17: Explain double circulation in humans.
Answer: In double circulation, blood passes through the heart two times in one complete cycle:
- Pulmonary circulation: heart → lungs → heart (for oxygenation)
- Systemic circulation: heart → body → heart (to supply O₂ and nutrients) This keeps oxygenated and deoxygenated blood mostly separate and makes circulation efficient.
Key Points to Remember:
- Two circuits: pulmonary + systemic
- Better oxygen supply
- Helps in efficient separation
Q18: Write short notes on hypertension.
Answer: Hypertension means blood pressure stays high for a long time, usually 140/90 mm Hg or more on repeated readings. It increases risk of heart disease and can damage organs like the brain and kidneys.
Key Points to Remember:
- Hypertension ≥ 140/90 (repeated)
- Risks: heart + brain + kidney
Q19: What is angina pectoris?
Answer: Angina pectoris is chest pain that happens when the heart muscle temporarily gets less oxygen, usually because coronary blood flow is reduced.
Key Points to Remember:
- Angina = chest pain
- Cause = less O₂ to myocardium
Q20: Differentiate between heart failure and cardiac arrest.
Answer:
- Heart failure: heart is beating but cannot pump enough blood (weak/inefficient pumping).
- Cardiac arrest: heart stops beating suddenly.
Key Points to Remember:
- Failure = weak pump
- Arrest = sudden stop