The human heart has four chambers - two atria and two ventricles - that work together to circulate blood throughout the body. The heart beats regularly due to a group of pacemaker cells in the right atrium that initiate each heartbeat. Factors like blood pressure, oxygen levels, and hormones can influence the heart rate. Blood vessels carry oxygenated and deoxygenated blood between the heart and tissues via arteries and veins. Coronary heart disease occurs when fatty deposits build up in the arteries and restrict blood flow.

1. TRANSPORT IN HUMANS

2. THE HEART

3. HumanHeart4 chambers: - 2 atria (thin-walled) - 2 ventricles (thick- walled)Veins: deoxygenatedbloodexceptpulmonaryveinArteries: OxygenatedbloodexceptpulmonaryarteryValves: They stop bloodflowingbackwards. Coronaryarteries: Theysupplytheheartmusclewithfood and oxygen.

4. Humanheart

5. Valves of the heart

6. CONTROL OF THE HEART BEATAt rest: normal heartrate, 50-100 beats per minutes.Duringexercise: 200 beats/minTheheart beat isinitiatedbythepacemaker, a smallgroup of specializedmusclescells at the top of therightatrium.

7. Control of theheart beatBloodpressure↑ ↓ heartrateBloodpressure↓ ↑ heartrate↓ O₂ concentration↑ CO₂ concentrationHormone adrenaline

8. THE CIRCULATION

9. CIRCULATION

10. BLOOD VESSELS

11. Bloodvessels

12. Arteries, veins: hystology

13. CORONARY HEART DISEASES

14. ATHEROMA and THROMBOSIS

15. Possible causes of coronaryheartdiseasesSMOKINGFATTY DIETSTRESSLACK OF EXERCISEOBESITYGENES

16. COMPOSITION OF BLOODRED CELLSWHITE CELLSPLATELETSfloating in a liquidcalled PLASMA

17. COMPOSITION OF BLOOD

18. COMPOSITION OF BLOOD

19. RED BLOOD CELLSBiconcave discsNo nucleiSpongycytoplasmenclosed in anelasticcellmembraneRed pigmentcalledhaemoglobinAre madebythe red bonemarrow of certainbones in theskeleton: ribs, vertebrae and breastbone

20. Red bloodcells: hystology

21. Red bonemarrow

22. HAEMOGLOBIN

23. Haemoglobin (Hb)Hb + O₂ oxyhaemoglobin (OHb)In places wherethe O₂ concentrationislow, OHbbreaksdown and releasesitsO₂. Where??Oxygenatedblood : containsmainlyOHb.Deoxygenatedblood : withlittleOHb.

24. Oxyhaemoglobin

25. Red bloodcellsAfter 4 monthsHbIronBilirubinStored in theliverBile

26. WHITE CELLSDifferenttypesLargerthan red cellsTheyhavenucleiThey are made in thesamebonemarrowthat red cellsThetwo more numeroustypes are: - Phagocytes - Lymphocytes

27. White bloodcells

28. White bloodcells

29. White bloodcells: PhagocytesTheycollect at thesite of aninfection, engulfing (ingesting) and digestingharmful bacteria. Theypreventthe spread of infectionthroughthebody.

30. Phagocytes

31. White bloodcells: LymphocytesProduction of antibodies (proteins)

32. PLATELETSTheyhelptoclottheblood

33. PLASMAIons: sodium, potassium, calcium, chloride, hydrogen carbonate.Proteins: fibrinogen (clotting), albuminand globulins (antibodies).Foodsubstances: aa, glucoseand fats.HormonesUrea

35. Functions of thebloodHomeostaticfunctionsTransportDefenceagainstinfections - Clotting - White cells

36. Functions of blood: Transport

37. Bloodfunctions: DEFENCE AGAINST INFECTIONSWHITE CELLS: - Phagocytes: - at thesites of a wound - in thebloodcapillaries - in lymphnodesingestharmful bacteria and stop thementeringthe general circulation - Lymphocytes:Production of antibodiesCLOTTING

38. CLOTTINGWhentissueisdamaged and bloodvesselscutPlateletsclumptogether and block thesmallercapillaries.Fibrinogenfibrin(network of fibresacrossthewound)Red cellsbecometrapped in thisnetwork and form a bloodclot.↓ entry of harmful bacteriapreventsfurtherloss of blood

39. Clotting

40. Bloodclotting