Pumping Organ heart I Chapter 14 Biology I F.Sc First Year Lec # 24

#biology11class #biologyfirstyear #F.Sc. #chapter14 #Transport Like Our Facebook page. -----------------------------------   / bismacademy   ------------------------------------ PUMPING ORGAN- The Heart. Structure and action. Pericardium The heart of humans is located in the chest cavity. The heart is enclosed in a double membranous sac - the pericardial cavity, which contains the pericardial fluid. Pericardium protects the heart, prevents it from over extension. Walls of heart. The wall of the heart is composed of three layers. (i) Epicardium (outermost) (ii) Myocardium (middle) (iii) Endocardium (Inner most) Myocardium. Myocardium of the heart is made up of special type of muscles, the cardiac muscles. Composition. These muscles contain myofibrils, and myofilament of myosin and actin. Differ from skeletal. Their arrangement is similar to those in skeletal muscle fibres, and their mechanism of contraction is essentially the same, except that they are branched cells, in which the successive cells are separated by junctions called intercalated discs. Control. The heart contracts automatically with rhythmicity, under the control of the autonomic nervous system of the body.