Lesson 12 of 12 · 12 min
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Must-know facts
18 facts
- 01Plasma ≈ 55% of blood (90–92% water, 6–8% proteins); formed elements ≈ 45%.
- 02Fibrinogen: clotting. Globulins: defence. Albumins: osmotic balance. Serum = plasma without clotting factors.
- 03RBC: 5–5.5 million per mm³; haemoglobin 12–16 g per 100 mL; life 120 days; destroyed in spleen.
- 04WBC: 6000–8000 per mm³. Neutrophils 60–65% (most), lymphocytes 20–25%, monocytes 6–8%, eosinophils 2–3%, basophils 0.5–1% (least).
- 05Platelets: 1,50,000–3,50,000 per mm³, from megakaryocytes.
- 06Group O: universal donor. Group AB: universal recipient. Rh positive: nearly 80% of humans.
- 07Erythroblastosis foetalis: Rh negative mother, Rh positive foetus, second pregnancy; prevented by anti-Rh antibodies after first delivery.
- 08Clotting chain: thrombokinase converts prothrombin → thrombin; thrombin converts fibrinogen → fibrin. Ca²⁺ is essential.
- 09Open 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.
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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.