HHS O Level School
Handout for Class VI (General Science – Chapter 2)
Organs involved in breathing system:
 Sinus cavity is the area around the nose and eyes that clean the air people breathe in.
 Pharynx is behind the nose and mouth.
 Larynx is in the neck and contains the vocal cords.
 Trachea connects the pharynx and larynx to the lungs and is responsible for the passage of air.
 Bronchi (singular: bronchus) are small tubes that bring air to and from the lungs.
 Lung is the main part of the gas exchange system and puts oxygen into the bloodstream.
 Diaphragm is a muscle that moves up and down to expand the lungs. This helps a person breath
 Intercostal muscle is attached to ribs, pulling ribs up and out during inhalation and down and in during exhalation.
 Thorax is the area between the neck and abdomen.
Function of circulatory system: It is responsible for transporting oxygen, nutrients, and other essential substances to
cells and removing waste products from the body.
Double circulatory system: It consists of two circuits; the pulmonary circulation (which carries blood between the
heart and the lungs) and the systemic circulation (which carries blood between the heart and the rest of the body
Pulmonary artery: A blood vessel that takes deoxygenated blood away from the heart into the lungs.
Pulmonary vein: A blood vessel that brings oxygenated blood towards the heart from the lungs.
Aorta: Main artery that takes the blood away from the heart to all parts of the body
Vena cava: Main vein that brings blood to the heart from the body
Atrium: Upper chamber of heart that receives the blood from the lungs and body.
Ventricle: Lower chamber of heart that are distributing chambers of blood.
Pulse: The pulse is the pressure caused by each heartbeat.
Path of blood:
 Oxygen enters your blood in your lungs. As the blood flows through the tiny capillaries in the lungs, it picks
up oxygen. The blood is oxygenated.
 The oxygenated blood flows back to the left atrium of heart through the pulmonary vein
 It is then pumped out from the left ventricle to the rest of the body through aorta.
 By the time it gets back to the right atrium again through vena cava, it has given up most of its oxygen. It is
deoxygenated.
 Then it flows into the lungs through pulmonary artery to get oxygenated again.
Platelets: A component of blood that helps in blood clotting to prevent excessive bleeding.
Three types of blood vessels: