RED BLOOD CELLS Biconcave discs No nuclei Spongycytoplasmenclosed in anelasticcellmembrane Red pigmentcalledhaemoglobin Are madebythe red bonemarrow of certainbones in theskeleton: ribs, vertebrae and breastbone
CONTROL OF THE HEART BEAT At rest: normal heartrate, 50-100 beats per minutes. Duringexercise: 200 beats/min Theheart beat isinitiatedbythepacemaker, a smallgroup of specializedmusclescells at the top of therightatrium.
Control of theheart beat Bloodpressure↑ ↓ heartrate Bloodpressure↓ ↑ heartrate ↓ O₂ concentration ↑ CO₂ concentration Hormone adrenaline
Lymphaticsystem Thin-walledvesselscalledlymphatics. Theyemptytheircontentsintothebloodsystem. The fluid iscalledlymph. Most of thelymphflowresultsfromthevesselsbeingcompressedwhenthebodymusclescontract in movementssuch as walkingorbreathing. There are valves, whichforcethe fluid in onedirection: towardstheheart. Lymphnodes: storage of lymphocytes. There are alsophagocytes. Lymphaticorgans:Spleenandthymus
SPLEEN: functions Removeworn-out red cells, bacteria and cellfragmentsfromtheblood. Produce lymphocytes and antibodies.
THYMUS: functions Particularlyimportantlymphoidorgan in thenewborn: - controlsthedevelopment of thespleen and thelymphnodes. - produces lymphocytes (immunity) Afterpuberty, importantimmunologicalorgan, althoughitbecomessmaller. - storage of whitecells - production of a largepopulation of lymphocytes T.
Bloodfunctions: DEFENCE AGAINST INFECTIONS WHITE CELLS: - Phagocytes: - at thesites of a wound - in thebloodcapillaries - in lymphnodes ingestharmful bacteria and stop thementeringthe general circulation - Lymphocytes:Production of antibodies CLOTTING
CLOTTING Whentissueisdamaged and bloodvesselscut Plateletsclumptogether and block thesmallercapillaries. Fibrinogenfibrin(network of fibresacross thewound) Red cellsbecometrapped in thisnetwork and form a bloodclot. ↓ entry of harmful bacteria prevents furtherloss of blood