Lesson 12 of 12 · 12 min
Chapter review
Watch a class
The whole chapter on YouTube
Whole chapter with NCERT diagrams
PW Class 11 Science · Hinglish · Whole chapter · Open on YouTube
Quick full-chapter revision
Arjuna NEET · Hinglish · Whole chapter · Open on YouTube
Loading the full lesson
Must-know facts
18 facts
- 1Plasma ≈ 55% of blood (90–92% water, 6–8% proteins); formed elements ≈ 45%.
- 2Fibrinogen: clotting. Globulins: defence. Albumins: osmotic balance. Serum = plasma without clotting factors.
- 3RBC: 5–5.5 million per mm³; haemoglobin 12–16 g per 100 mL; life 120 days; destroyed in spleen.
- 4WBC: 6000–8000 per mm³. Neutrophils 60–65% (most), lymphocytes 20–25%, monocytes 6–8%, eosinophils 2–3%, basophils 0.5–1% (least).
- 5Platelets: 1,50,000–3,50,000 per mm³, from megakaryocytes.
- 6Group O: universal donor. Group AB: universal recipient. Rh positive: nearly 80% of humans.
- 7Erythroblastosis foetalis: Rh negative mother, Rh positive foetus, second pregnancy; prevented by anti-Rh antibodies after first delivery.
- 8Clotting chain: thrombokinase converts prothrombin → thrombin; thrombin converts fibrinogen → fibrin. Ca²⁺ is essential.
- 9Open circulation: arthropods, molluscs. Closed: annelids, chordates.
- 10Hearts: fish 2 chambers; amphibians and reptiles 3 (crocodiles 4); birds and mammals 4.
- 11SAN: pacemaker, 70–75 action potentials per minute; heart averages 72 beats per minute.
- 12Atrial systole raises ventricular filling by about 30%.
- 13Cardiac cycle 0.8 s; stroke volume about 70 mL; cardiac output about 5000 mL (5 L) per minute.
- 14Lub: closure of tricuspid and bicuspid valves. Dub: closure of semilunar valves.
- 15ECG: P = atrial depolarisation; QRS = ventricular depolarisation; T = ventricular repolarisation (end of T = end of systole).
- 16Hepatic portal vein: intestine to liver. Coronary vessels: heart muscle only.
- 17Heart is myogenic; sympathetic raises, parasympathetic lowers heart rate; medulla oblongata moderates.
- 18Normal BP 120/80 mm Hg; repeated 140/90 or higher = hypertension.
Common traps
Where marks are lost
Saying lub is caused by the semilunar valves closing.
Lub is the closure of the tricuspid and bicuspid (AV) valves at the start of ventricular systole; dub is the semilunar valves closing as ventricular diastole begins.
Calling group AB the universal donor.
AB has no anti-A or anti-B and can receive from all groups, so it is the universal recipient; O is the universal donor.
Expecting erythroblastosis foetalis in the first pregnancy.
The mother is sensitised only at the first delivery; the danger is to the Rh positive foetus of a later pregnancy.
Treating serum and plasma as the same.
Serum is plasma without the clotting factors.
Thinking thrombin comes straight from fibrinogen.
Thrombokinase converts prothrombin to thrombin; thrombin then converts fibrinogen to fibrin.
Putting the SAN in the left atrium.
Both SAN (right upper corner) and AVN (lower left corner) are in the right atrium.
Saying the QRS complex marks the end of systole.
Contraction begins shortly after Q, so QRS marks the start of systole; the end of the T-wave marks its end.
Using heart failure, cardiac arrest and heart attack interchangeably.
Heart failure: pumping not effective enough. Cardiac arrest: the heart stops beating. Heart attack: heart muscle suddenly damaged by poor blood supply.
Saying all reptiles have a three-chambered heart.
Crocodiles are the exception with four chambers.
Key terms
22 terms
- Plasma
- The straw-coloured fluid matrix of blood, about 55 per cent of its volume.
- Serum
- Plasma without its clotting factors.
- Formed elements
- RBCs, WBCs and platelets, about 45 per cent of blood.
- Haemoglobin
- The red, iron-containing protein of RBCs that carries respiratory gases.
- Megakaryocyte
- A special bone marrow cell whose fragments are platelets.
- Antigen
- A chemical that can induce an immune response, such as A, B or Rh on RBCs.
- Antibody
- A protein made in response to an antigen, such as anti-A or anti-B in plasma.
- Universal donor
- A person of group O, whose blood can be given to any ABO group.
- Universal recipient
- A person of group AB, who can receive blood of any ABO group.
- Erythroblastosis foetalis
- Destruction of an Rh positive foetus's RBCs by anti-Rh antibodies from an Rh negative mother.
- Thrombokinase
- The enzyme complex, formed by a cascade, that converts prothrombin to thrombin.
- Fibrin
- Threads formed from fibrinogen by thrombin; the mesh of a clot.
- Tissue fluid
- Fluid that leaks from capillaries into spaces between cells; the medium of exchange.
- Lymph
- Tissue fluid inside the lymphatic system, colourless and carrying lymphocytes.
- Lacteal
- A lymph vessel in an intestinal villus that absorbs fats.
- Pacemaker
- The SAN, which generates the most action potentials and sets the heart's rhythm.
- Systole
- Contraction of a heart chamber.
- Diastole
- Relaxation of a heart chamber.
- Stroke volume
- Blood pumped by each ventricle in one cardiac cycle, about 70 mL.
- Cardiac output
- Blood pumped by each ventricle per minute: stroke volume × heart rate, about 5 litres.
- Myogenic heart
- A heart whose beat is started from within, by nodal muscle tissue.
- Hepatic portal system
- Vessels carrying blood from the intestine to the liver before it joins systemic circulation.