EXPLAIN HOW THE MAMMALIAN HEART IS ADAPTED TO PERFORM ITS FUNCTION. (20MKS)

Explain how the mammalian heart is adapted to perform its function. (mks)

- Muscular to pump blood over long distance;

- Myogenic cardiac muscles which contract and relax rhythmically without fatigue; hence heart continues pumping;

- Cardiac muscle fibres interconnected to form a network of fibre to ensure rapid and uniform spread of excitation throughout the walls of the heart;

- Heart divided into 4 chambers which are hollow to accommodate more blood;

- Ventricles have thicker walls than auricles to generate higher pressure to drive blood over long

distance into more elaborate  circulation/to the lungs and to all body tissues; 

- Walls of left ventricles are thicker than those of right ventricles to generate more pressure to pump

blood to longer distance in the systemic circulation/rest of the body;

- Longitudinal septum which separates the heart into two halves to prevent mixing of oxygenated and deoxygenated blood;

- Valves to prevent back flow of blood;

- Valves have strands of connecting tissue (chordas tendinae) to prevent them from being pushed

inside out when ventricles contract;

- Has coronary artery and coronary vein to supply myocardium with oxygen and nutrients; and remove waste products/carbon IV oxide and nitrogenous wastes;

- Fibrous layer of pericardium surrounds the heart to keep it in position; and prevent overdilation;

- Inner percadium secretes the pericardial fluid; which reduces friction between the two layers during contraction;

- outer pericardium surrounded by layer of fat which acts as shock absorber; protect it from

mechanical damage

- Sino Atrial Node (S.A.N) acts a pacemaker regulating rate of beating and excitation of heart;

- Heart located in the thoracic cavity where it is protected from any external mechanical damage;

- Atrio Ventricular node (A.V.N) which delays depolarization wave from Sino Atrial Node to ensure that auricles empty completely before the ventricles contract;

- Purkinje tissues to relay waves from A.V.N to ventricular myocardium; (20 mks)