Heart

• It is the size of a clench fist and lies in thoracic cavity in between lung and protected by sternum.
• the heart has four chamber:

  • two thin-wall called right and left ATRIA on top which receives blood
  • two thick-wall called right & left ventricles underneath which pumps blood.
• TThe right and left side of the heart is separated by INTERVENTRICULAR septum and prevents oxygenated and deoxygenated blood from mixing.
• The heart is made up of muscle tissues which is supplied with blood by coronary arteries.
• the right side deals with deoxygenated blood 


  the left side deals with oxygenated blood
• between the atria and the ventricle are atrioventricular valves which prevent backflow of blood from the ventricles to the atria
• the left valve has two flaps; is called bicuspid valve


  the right valve has three flaps; is called tricuspid valve
• there are two semilunar valves in the arteries called the pulmonary and aortic valves (only example of valve in artery)
• the valve are held in place by valve tendons(heart strings) attached to papillary muscles which contract at the same time as the venricles holding the valves closed
• • The left ventricle has a thicker muscle wall than the right ventricle as it has to pump blood at high pressure around the entire body, whereas the right ventricle pumps blood at lower pressure to the lungs
• In the pulmonary circuit less fluid passes from the capillaries to the alveoli because of a low pressure.
• the atria is thinner than the wall of the ventricles because atria pumps blood to the ventricles which are found inside the heart
• the atrioventricular valves are pushed open when the atria contract but when the ventricles contract they are pushed closed to prevent blood from flowing back into the atria
• The semi-lunar valves are open when the ventricles contract so blood squeezes past them out of the heart, but then close to avoid blood flowing back into the heart
• the right atrium act as a pacemaker which produce small electrical impulses which spread through the muscular wall of the heart making them to contract
• the activity of the heart can be monitered by Electrocardiogram (ECG), Pulse rate, and listening to Valves closing.
• coronary areteries provide a good and constant supply of oxygen from the blood stream to the heart muscle.
• coronary artery an be clogged with fatty deposits or blood clot reducing the supply of nutrients and oxygen to the heart muscle
• a sudden and severe blockage in the coronary artery can cause a heart attack
• Effect of physical exercise on heart rate:

  when physical activity is carried out muscles respire to produce energy for movement. thus,

  • muscular contraction requires energy from respiration
  • more respiration requires for oxygen and carbon dioxide
  • heart pumps faster to provide more oxygen to the respiration and to remove the carbon dioxide quickly.
• RISK FACTORS OF CHD:

  • STRESS
  • smoking
  • genetic predisposition
  • age
  • gender
  • diet
  • sedentary lifestyle
• By limiting processed foods, saturated fats and eating plenty of freshed fruits, vegetables and proteins based foods can lower your blood pressure and cholesterol reducing risk of heart diseases.
• exercising regularlly can strengthen your heart and improving your circulation and maintaining a healthy weight and lower cholesterol reducing risk of heart diseases.
• the cardiac cycle consist of alternate contraction-systole and relaxation-diastole of the heat muscle in order to maintain a continous circulation of blood throughout the body.