Respiratory System PDF

# The Respiratory System ## Introduction The respiratory system is designed to maximize gas exchange across the tissues of the body. It encompasses two main processes, and there are many structures involved that span other body systems as well. The goal is to deliver oxygen to the body's tissues an...

# The Respiratory System ## Introduction The respiratory system is designed to maximize gas exchange across the tissues of the body. It encompasses two main processes, and there are many structures involved that span other body systems as well. The goal is to deliver oxygen to the body's tissues and remove carbon dioxide. You will need to understand the order of organs air passes, specializations the organs have, as well as what happens to gases once they diffuse into the body, as there are several pathways these gases can take. ## Structures Let's follow the pathway that air will take as it is drawn into the body! ### 1. Nasal Cavity - This space is where breathed in air is warmed, filtered, and moistened. - The nose and nasal cavity are lined with mucous membranes, a type of epithelial tissue that produces mucus. Mucous helps humidify the incoming air, while also trapping debris. - The nose also contains cilia hairs that clean and trap debris in the air before pushing it out of the nose. ### 2. Pharynx - The pharynx is the shared space at the back of throat between the nasal cavity and mouth. It is the common passage for air and food. ### 3. Glottis - The end of the pharynx and start of the upper windpipe. - It is covered by the epiglottis when swallowing. This way, you can never breathe and swallow at the same time - otherwise, you'd choke! ### 4. Larynx - The space right under the glottis, leading into the windpipe - It is also called the "Voice box", and contains the vocal cords. - Vocal cords are two bands of muscle that open or close depending on if you're breathing or speaking. When speaking, they are closed and will vibrate together as air passes them. The frequency of the vibrations, as well as the movement of other structures (tongue, lips, teeth, palate) produces different pitches in your speaking voice. - The vocal cords are protected on the outside by a cartilaginous structure called the "Adam's Apple". ### 5. Trachea - Also known overall as the windpipe. - It is composed of multiple rings of cartilage to prevent it from collapsing. The tube leads all the way down to the lungs. - It is lined with cilia, which beat rhythmically to move debris-laden mucous up the trachea and out. Once it hits the pharynx, it is either coughed out or swallowed. ### 6. Bronchi - These are branches of the trachea. One goes to each lung. They are still rigid with cartilage. ### 7. Bronchioles - Smaller branches of the bronchi. They are numerous and contain no cartilage for support. ### 8. Alveoli - Means "little cavity" - these are the ends of the bronchioles and are shaped like little balloons. We think of these as the "inside" of the lungs, but they make up the lungs themselves. - They are made of simple squamous epithelium (one layer of cells). Why must they be so thin? > Diffusion can happen more quickly (less distance!) ## What Happens to Air on its Way to the Alveoli? ### 1. Cleaned of Debris - Initial cleaning occurs by the nose hairs and mucous in nasal cavity. - The mucous membranes and cilia line the entire tract along the trachea and bronchi. - Mucous traps debris and cilia beat it upwards until it is swallowed or coughed out. ### 2. Adjusted to Body Temperature - The more contact that occurs between air and moist tissues, the closer the air acclimates to tissue temperature (about 37 degrees Celsius). - When it reaches the alveoli, there is no difference in temperature between the air and the alveoli. ### 3. Adjusted to 100% Humidity - The air becomes saturated with water as it passes moist mucous pathways. - The lungs are also saturated with water (a product of respiration). ## Specializations of the Alveoli - $C_6H_{12}O_6 + O_2 \longrightarrow CO_2 + ATP + H_2O$ - Alveoli are numerous: there are up to 300 million in a single human lung! Why so many? SURFACE AREA!!! - Only one cell layer thick. - Each alveolus has a coating of lipoprotein on its inner surface. This helps maintain surface tension to prevent the alveoli from collapsing and sticking together. - Stretch receptors signal when the alveoli are full of air so the body can exhale. - They are highly vascularized, meaning there are capillary networks surrounding each alveolus ## Some Extra Structures That Aid in breathing... ### 1. Pleural Membranes - Create the surfaces of the lungs. - There are two sets of pleural membranes that make up the lungs. - 1 membrane is directly joined to the lung (contains the alveoli). - 1 membrane is joined to the ribs + diaphragm on the outside of the first membrane. - Both are separated by a fluid, creating a vacuum. This is referred to as the intrapleural space. - The pressure in the intrapleural space is maintained at a level that is lower than atmospheric pressure. This holds the lungs open! - If any part of the membrane punctures, air will enter the intrapleural space, and the lungs will collapse. - The pleural membranes also allow the surfaces of the lungs to slide over the inner body wall easily (reducing friction). And seals off the thoracic cavity. ### 2. Thoracic Cavity - Also known as the chest cavity, it encompasses the area from the larynx to the diaphragm. ### 3. Diaphragm - This is a horizontal band of muscle just below the lungs. It is attached to the outer pleural membrane. - It separates the thoracic cavity from the abdominal cavity (the digestive system and its accessory organs). - When it contracts, it pulls the lungs downward, forcing air into them (inhalation). The opposite occurs when it relaxes. ### 4. Ribs - Help protect the internal organs and lungs. - Rib bones are surrounded by the intercostal muscles. When they contract, the thoracic cavity rises and increases in volume, thus forcing air into the lungs (inhalation).