Respiratory system Respiratory system Cells use oxygen in metabolic reactions to create Cells se o gen in metabolic reactions to create energy. At the same time, these reactions produce carbon dioxide. The cardiorespiratory system is made up of the cardiovascular and respiratory systems. It p yg provides oxygen and eliminates carbon Lungs The lungs are paired organs lying in the thoracic cavity. y f They are located either side of the heart. Each lung is surrounded by strong connective tissue called the pleural membrane. Each lung is divided by fissures into lobes. The left lung has two lobes; the right lung has three. has two lobes; the right lung has three The right lung is slightly thicker, broader and shorter than The right lung is slightly thicker broader and shorter than the left. The left lung has a cardiac notch in it to accommodate the shape of the heart. Bronchi The right and left primary bronchi are Th i ht d l ft i b hi formed from the branching of the trachea. Inside the lung, the primary bronchus in each lung branches into secondary and then tertiary bronchi. then tertiary bronchi The process continues until the tiniest The process continues until the tiniest branches of the whole system are the air passages called the bronchioles, which are less than 1 millimetre in diameter. less than 1 millimetre in diameter Because of this branching pattern, we Because of this branching pattern, we apply the terms bronchial tree or respiratory tree when describing the bronchi. bronchi Alveoli The very ends of the bronchioles (terminal bronchioles) feed into the pulmonary bronchioles. bronchioles) feed into the pulmonary bronchioles Protruding from these microscopic bronchioles are small sacs called alveoli Alveoli are covered in small sacs called alveoli. Alveoli are covered in tiny capillaries. It is here, between the alveolar and capillary walls, that the actual exchange of g gases occurs across a thin membrane. Lung Function Respiration is the exchange of gases between the cells, blood and atmosphere. It involves four processes: • pulmonary ventilation (breathing)—movement of air from the atmosphere into the alveoli • pulmonary diffusion—exchange of oxygen and carbon dioxide between the lungs and the blood dioxide between the lungs and the blood transport of respiratory gases transportation of oxygen • transport of respiratory gases—transportation of oxygen and carbon dioxide between the lungs and the tissue cells of the body via the blood • internal respiration—exchange of gases between the blood capillaries and the tissue cells. p Inspiration and expiration Inspiration and expiration Pulmonary ventilation, or breathing, allows a ti fl f i f th t id i t d continuous flow of air from the outside into and out of the lung alveoli. At rest, an adult averages 12 respirations in one At rest, an adult averages 12 respirations in one minute, resulting in the movement of 6 litres of air into and out of the lungs per minute. air into and out of the lungs per minute. i fl i h b d d fi f h Air flows into the body and out of it for the same reason that blood flows through the body: a pressure gradient exists. Gases will generally move from areas of high pressure into areas of lower pressure. into areas of lower pressure Breathing in, or inspiration, occurs due to the air outside having a higher pressure than the air in the lungs, because your muscles have increased the size and volume inside the lungs. p g ( When the diaphragm and external intercostals (muscle tissue between the ribs) relax, the pressure inside the g g g lungs is greater than that outside because the lung size and volume have decreased. Hence, we breathe out in the process of expiration. g g Exchange of gases The exchange of gases begins with the inspiration and ends with the expiration of a breath When the pressure is lower inside the lungs expiration of a breath. When the pressure is lower inside the lungs (upon expiration), air that is laden with oxygen is drawn into the lungs via the nasal passages. As the pressure increases as a result of inspiration, gaseous exchange occurs in the alveoli. Air that is rich in carbon dioxide is exhaled to equalise the pressure inside and outside the body. Gas exchanges between the air in the alveoli and the blood capillaries h i b i k occur across the respiratory membrane in a process known as pulmonary diffusion. The most critical factor for gas exchange between alveoli and the blood is the pressure gradient between the between alveoli and the blood is the pressure gradient between the gases in the two areas. Differences between the partial pressures of the individual gases in the blood and the alveoli create a pressure gradient, so one moves into the other: from high partial pressure to low partial pressure. Therefore, oxygen diffuses from the alveoli into the blood. Therefore oxygen diffuses from the alveoli into the blood The opposite is true for carbon dioxide. A spirometer can be used to measure the following lung volumes: • vital capacity—the volume of air inspired in a normal breath after we have forcibly exhaled the air remaining breath after we have forcibly exhaled the air remaining in the lungs • residual volume—the air that is still trapped in our l f h f ibl h l d lungs after we have forcibly exhaled • total lung volume—the combination of vital capacity and residual volume.
Pages to are hidden for
"Respiratory system Respiratory system"Please download to view full document