Respiratory System 🫁

• The respiratory system is used to intake oxygen and remove carbon dioxide
• The respiratory system is specialized to facilitate the intake of oxygen and the removal of carbon dioxide.
• • In the lungs, oxygen is taken from air into the blood
  • The blood transports the oxygen to the cells in all tissues of the body.
  • In the tissues, the blood picks up carbon dioxide and takes it to the lungs where it is passed into air.
  • The organs of the respiratory system include the nose, through which air is taken in; the trachea, or 'windpipe', which branches into two tubes; the bronchi; and the two lungs.
• Air enters the body through the mouth and nose. The lining of the nose and nasal cavity is convoluted and lined by mucus membranes. As the air passes over the membranes, it is warmed and humidified. There are also hairs and mucus lining the nose that trap debris, preventing it from entering the lungs.
• The pharynx, or throat, is the region from the nasal cavity to the top of the trachea and esophagus. Air travels through before being diverted into the trachea by the epiglottis, a flap of elastic cartilage.

  • Inhalation = epiglottis covering esophagus
  • Swallowing = epiglottis covers larynx
• The larynx contains vocal cords (mucus membranes that are able to vibrate as air passes over them.)

  Larynx = voice box
• The trachea is the windpipe made up of 'c-shaped' cartilage rings that hold the structure open. At the base it splits into two branches for each lung. The epithelial lining of the trachea produces mucus, which is able to move in a wave-like motion to take the mucus and debris up to the pharynx so it can be swallowed and digested.
• At the end of the trachea, the structure splits into 2 primary bronchi, one for each lung. These then split further into secondary bronchi which take the air into each lobe of the lung. The secondary bronchi continue to divide, forming tertiary bronchi. The bronchi have c-shaped cartilage rings that spread out as the bronchi get smaller. Smooth muscles and elastin form more of the structure.
• When the tertiary bronchi divide, they form smaller airways called bronchioles, when continue to split until they end in millions of terminal bronchioles. They are made of smooth muscle and elastin that allows the bronchioles to control the flow of air in the lungs. Cilia and mucus are also present.
• The left lung has 2 lobes; the right lung has 3. The pleura (membrane) covers the surface of the lungs and also lines the inside of the chest. Between the two layers of membrane is a thin layer of pleural fluid, which holds the lung against the inside of the chest wall and allows them to slide along the wall when breathing. Inside the lung the smallest bronchioles open into clusters of tiny air sacs called alveoli. Each alveolus has a wall where gases move between the blood in the capillaries and the air in the alveoli.
• Intercostal muscles are between the ribs. They move the rib cage upwards and outwards to increase the volume of the chest cavity and thus the lungs when breathing in.
• The diaphragm is a muscle that separates the chest from the abdomen. It contracts and flattens downwards, thereby increasing the volume of the chest cavity, and lungs, during breathing in.
• Inhalation is the process of taking air into the lungs.
• • For air to flow into the lungs, the pressure of air in the lungs must be less than the atmospheric pressure outside the body.
  • Decreasing the pressure of air in the lungs is achieved by increasing the volume of the lungs.
  • The diaphragm becomes flatter, and the ribcage moves upwards and outwards, increasing the volume of the chest cavity.
  • As the pleura adheres to the internal wall of the chest cavity, the lungs expand with the expanding chest cavity.
  • Increased lung volume means that air pressure inside the lungs is slightly lower than the pressure outside.
• Expiration is breathing out.
• • The diaphragm and external intercostal muscles relax, so the diaphragm bulges more into the chest cavity and the rib cage moves downwards.
  • Air pressure in the lungs is now greater than pressure outside the body.
  • When a person is breathing quietly at rest, expiration is a passive process, involving relaxation of the muscles that have contracted during inspiration.
• The nose warms, filters and humidifies air, contains smell receptors.
• The pharynx roughs air coming in the nose down to the larynx.
• The larynx protects the lower respiratory tract from aspiring food into the trachea while breathing.
• The trachea is the windpipe made up of c shaped cartilage rings that carry air in and out of the lungs.
• The left lung has 2 lobes, and the right has 3. It allows oxygen in the air to be taken into the body while also letting the CO2 out.
• The bronchi carry air to and from the lungs.
• The bronchioles deliver oxygen to diffuse network of around 300 million alveoli in the lungs.
• The alveoli are where the lungs and the blood exchange oxygen and CO2 during the process of breathing in and out.
• The pleural membrane provides mechanical protection and a smooth lubricating elastic surface for the lungs to move during breathing.
• The diaphragm flattens and contracts downwards to increase the volume of the chest cavity and lungs.
• The intercostal muscles move the ribcage upwards and outwards
• The vocal cords produce sound of the voice
• For air to flow into the lungs, the pressure of the air in the lungs must be less than the atmospheric pressure outside the body. The intercostal muscles and diaphragm contract to increase the volume of the lungs. Increased lung volume means that the air pressure inside the lungs is slightly lower than outside the body.
• Air is forced out of the lungs when the diaphragm and intercostal muscles relax, so the diaphragm and ribcage moves downwards. Air pressure in the lungs is now greater than the pressure outside the lungs, so air is forced out of the lungs.
• nasal cavity --> pharynx --> larynx --> trachea --> bronchi --> bronchioles --> alveoli
• Oxygen moves from the alveolus into the erythrocytes because the partial pressure of oxygen is high in the alveoli and low in the blood of the pulmonary capillaries.
• CO2 moves in the opposite direction of oxygen because pressure of CO2 is high in the pulmonary capillaries and low in the alveoli.
• Alveolus characteristics that make it effective for gas exchange:

  • Thin walls- short diffusion distance (1 cell thick)
  • Moist walls- gases dissolve in moisture
  • Permeable walls- allow gas to pass through
• Gases move across the membrane with oxygen entering the bloodstream and carbon dioxide exiting.