Respiratory System Chapter 4 PDF

All cells in the body need oxygen for cellular respiration as well to remove carbon dioxide that they produce. In the lungs oxygen is taken from the air into the blood and taken to cells in all tissues of body and blood picks up carbon dioxide and takes it to lungs where it's passed into the air....

All cells in the body need oxygen for cellular respiration as well to remove carbon dioxide that they produce. In the lungs oxygen is taken from the air into the blood and taken to cells in all tissues of body and blood picks up carbon dioxide and takes it to lungs where it's passed into the air. The circulatory and respiratory systems work together to make cells have a constant supply of oxygen and that carbon dioxide is continually removed from the cells. In this way amounts of oxygen and carbon dioxide are kept relatively constant Main Components of Respiratory System: Nose, Trachea, Bronchi, Lungs Air enter body through mouth and **nose**: - Lining of nose and nasal cavity is convoluted and lined with mucus membranes which warms and humidifies the air that passes over membranes. - Also, hairs and mucus lining the nose which tarps debris preventing it reaching the lungs. **Pharynx:** - Region from nasal cavity to top of trachea and oesophagus. - Air travels through pharynx before being diverted into trachea by epiglottis which is a flap of elastic cartilage. - During inhalation the epiglottis covers oesophagus and when swallowing epiglottis covers larynx. Air travels through **larynx** into trachea: - Larynx is a cartilage structure joining pharynx and trachea. - It contains vocal cords which are mucous membranes that vibrate as air passes over them. - Also known as voice box Air travels through **trachea**: - Tracheas is known as windpipe as it carries are in and out of lungs. - It is made up of c-shaped cartilage rings that hold the structure open ensuring that air can always pass through it. - At its base it splits into two branches, one branch each taking air into each lung. - Epithelial lining of trachea produces mucus which traps dust and debris preventing it entering lungs. - Cilia line the trachea which move in a wave-like motion to take mucus and debris up to pharynx to be swallowed and digested. Air travels through the trachea to the **bronchi** in which the air travels through the primary secondary and tertiary bronchi: - At end of tracheae the structure splits into two primary bronchi which split further into secondary bronchi. - As the bronchi gets smaller cartilage is more spread out with smooth muscle and elastin forming more of the structure. - In bronchi cilia and mucus work together to trap and remove dust The secondary bronchi take the air into the **lungs:** - the two lungs take up the whole of the chest cavity, expect for the space between them, the mediastinum which is occupied by the heart and blood vessels. - each lung is divided into lobes: - the left lung has two lobes. - the right lung has three lobes. - a membrane called visceral pleura covers the surface of the lungs and parietal pleura also lines the inside of the chest. - between these two layers of membrane is a thin layer of pleural fluid which holds the lungs against the inside of the chest wall and allows them to slide along the wall when breathing From the tertiary bronchi the air then travels into the **bronchioles** in which the smallest bronchioles open into tiny air sacs called alveoli: - when the tertiary bronchi divide, they form smaller airways called bronchioles, which continue to split until they end in millions of terminal bronchioles. - Bronchioles don't contain cartilage; they are made up of smooth muscle and elastin allowing the bronchioles to control flow of air in the lungs so they can expand when body needs more oxygen. - Cilia and mucus protect bronchioles from contaminants. **Bronchioles** open into clusters of tiny air sacs called alveoli: - each alveolus has a wall that is only one cell thick and is surrounded by a network of blood capillaries where gases move between blood in capillaries and air in alveoli. - therefore, alveoli are functional unit of lungs. - This makes it possible for the alveoli to be the surface for gaseous exchange, allowing a net flow of oxygen to pass from the airways into the blood and carbon dioxide to pass from the blood into the airways. **Diaphragm**: - Muscle that separates the chest from abdomen - Contracts & flattens downwards thereby volume of chest cavity and lungs. [Mechanics of Breathing:] - For efficient exchange between blood and air in alveoli the air in the lung must change continuously. - Process by which air is moved into and out of lungs is ventilation. - Air flows from places of higher pressure to places of lower pressure therefore air flows in and out of lunges due to differences in air pressure Inspiration: - Process of taking air into lungs is called inspiration. - For air to flow into lungs pressure of air in lungs must be lower compared to the outside of body - Decreasing the pressure of air in lungs is achieved by increasing the volume of lungs. - To increase the volume diaphragm and intercostal muscles contract. - Diaphragm becomes flatter and rib cage moves upwards and outwards increasing volume of chest cavity. - Pleura attached to wall of chest cavity draws lungs to expand. - Increased lung volume means air pressure inside lungs is lower than pressure outside. - Air flows in through nose and trachea util pressure is equal. - Normal 'quiet breathing' -- diaphragm only - Heavier breathing -- diaphragm & ribcage Expiration: - Breathing out is expiration. - Diaphragm and intercostal muscles relax so diaphragm bulges more into the chest cavity. - Rib cage moves downwards. - This reduces the volume of chest cavity and lungs. - So, the air pressure in lungs is now greater than pressure outside the body. - Air flows out through the trachea and nose until pressure becomes equal. - when a person is breathing quietly at rest, expiration is a passive process, involving relaxation of the muscles that have contracted during inspiration. - Heavier breathing involves more forceful expiration, and the intercostal muscles contract to actively lower the rib cage. The diaphragm and intercostal muscles work together to change the volume and pressure of lungs resulting in airflow in and out of lungs. [Structure of the lungs:] The lungs have been well suited to gas exchange because: - **Alveoli give lungs large internal surface area so that large number of gases can be exchanged in a short period of time rapid diffusion.** - **Each alveolus is well supplied with blood vessels so that as much as blood as possible is close to air in alveolus. The continuous flow of blood helps maintain a difference in concentrations of oxygen and carbon dioxide between blood and air in lungs.** - **Alveoli have very thin membrane walls, so gas molecules don't have far to travel when moving in and out of blood. Only one layer of cells and 1 micrometre thick** - The lungs are positioned deep inside body to prevent excess evaporation of fluid that covers respiratory surface. The membrane of alveolus is covered by a thin layer of moisture because gases can diffuse in and out of blood only when dissolved in fluid. - Lung volume can be changed by movements of respiratory muscles, so air is made to flow in and out. - Constant changing of air in alveoli helps to ensure that there is always a concentration gradient of oxygen and carbon dioxide between air and blood. [Process of Gas Exchange:] - Deoxygenated blood from being used up in the cell come to the alveoli via the pulmonary arteries. - The blood that comes in the capillaries around the alveoli has a lower conc of oxygen compared to air in alveolus. - O^2^ dissolves in moisture on the inside of the alveoli, diffuses through membrane and capillary and into the blood. - Blood arriving at capillaries has high CO~2~ concentration than air in alveoli where it has picked up CO2 produced by respiration of cells. - Therefore, CO2 diffuses out of blood and into air in alveolus. For diffusion of gases there must be a concentration gradient meaning a difference in gas concentrations between air in alveoli and blood in capillaries. The concentration gradient is maintained by: - The constant flow of blood through the capillaries. As the blood around alveolus pick up oxygen and loses carbon dioxide it is replaced by 'new' blood being pumped into capillaries. This 'new' blood is low in oxygen and high in carbon dioxide so con gradient is maintained. - The movement of air in and out of alveoli as we breath in and out. The air that has picked up carbon dioxide and lost oxygen to, the blood is replaced by 'new' air with each breath. The 'new' air is low in co2 and high in oxygen. [Some effects of lifestyle and environment on gas exchange:] How we live and the environment in which we work and spend our leisure time can affect the efficiency of the respiratory surfaces: Emphysema: - Disease caused by long-term exposure to irritate particles in the air taken into lungs. - Some people are exposed to high levels of irritating particles. - E.g. smokers, dust, polluted air - The irritating particles cause damage to alveoli. They lose their elasticity and get replaced with fibrous tissue and may break down reducing surface are of lungs. - The loss of elasticity cause lungs to be constant inflated and breathing out becomes voluntary. - Problems of someone with emphysema: - Inadequate surface area for gas exchange - Difficulty in ventilating lungs - Once lung damaged cannot be cured Lung Cancer: - involves the development of a mass of cells that divide uncontrollably forming a tumour. - exposure to asbestos fibres and other pollutants and tobacco smoking is a great risk. - some chemical substances initiate cancerous tumour others promote growth of tumour. - it begins in the walls of the bronchi. Inhaled smoke particles irritate the mucous membranes that line the air passages. - this results in excessive production of mucus so cells at the base of membrane begin to divide more rapidly, and accumulating mucus can't be removed causing rupture of alveoli. - then emphysema has developed, and cancerous growth may spread to other parts of body. Lung Infections -- Pneumonia: - caused by bacteria, viruses, fungi. - inflammation from infection causes secretion of fluid and mucus into alveoli thus reducing the amount of air they can contain and the surface area. - breathing difficulty is a symptom. Lung Infections -- Tuberculosis: - infection of the lung caused by bacterium, *Mycobacterium tuberculosis.* - one of the top three infectious diseases causing death in the world - it is spready by droplets so when infected people cough, sneeze or spit tiny droplets of moisture contain bacteria and viruses maybe be inhaled by others causing the spread of infection. - good hygiene practises e.g. coughing into a handkerchief help to reduce lung infection. Asthma: - medical condition that causes difficulty breathing due to narrowing of airway, it can be due to - smooth muscle contracting, narrowing airway. - inflammation causing lining of airways to thicken, narrowing diameter. - mucus filling the airway narrowing tube. - triggers: smoke, dust, cold weather, stress, emotions, some substances in food - during an asthma attack muscles that surround bronchioles go into spasm, involuntary action causing narrowing of air passages and excessive production of mucus therefore difficulty breathing. - the reduced volume of air going in and out of lungs means exchange of gases is impaired and blood doesn't carry normal oxygen.