DESCRIBE THE FUNCTIONS OF VARIOUS PARTS OF THE MAMMALIAN HEART (20MKS)

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Describe the functions of various parts of the mammalian heart (20mks)

         Pericardial membrane – secretes a lubricating fluid.
                             - encloses and protects the heart.
                             - prevents over-dilation of the heart. 
Fat layer – prevents mechanical shock/cushions the heart
Blood vessels – coronary artery supplies the heart muscles with oxygen and nutrients
       -   coronary vein carries away CO2 and waste products of metabolism
         Valves – prevent backflow of blood into the auricles and into the ventricles
         Valve tendons – prevents valves from turning inside out when systolic pressure is high.
         Ventricles – are thick walled to pump blood out of the heart
         S.A.N (Sino-Atrial Node) – acts as a pacemaker to set pace for heart to beat.
         Cardiac muscles – contract and relax without fatigue
         Vagus nerve parasympathetic branch – slows down the heartbeat
        Vagus nerve sympathetic branch – speeds up the hear beat                                                 

         (20mks)

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