FMD002 Respiratory Lecture PDF

Respiratory System Feisal Subhan SoBS, FoH  OBJECTIVES At the end of this session, you should be able to: 1. define external, internal and cellular respiration. 2. name the organs of the respiratory system and state the function of each. 3. discuss inspiration and expira...

Respiratory System Feisal Subhan SoBS, FoH  OBJECTIVES At the end of this session, you should be able to: 1. define external, internal and cellular respiration. 2. name the organs of the respiratory system and state the function of each. 3. discuss inspiration and expiration with emphasis of the role of respiratory muscles. Health Canada started this on 1 Aug 2023  Respiration definitions 1) External respiration: gas exchange between blood capillaries and air sacs of the lung. 2) Internal respiration: gas exchange between blood capillaries and body cells. 3) Cellular respiration: the breakdown of organic molecules (usually glucose) in the cell to release energy.  Activity 1 (don’t use Google!) 1. In pairs or individually, rank the following gases in order of the highest gas concentration in the atmosphere: carbon dioxide; oxygen; noble gases; nitrogen 2. Estimate the % of these gases in the atmosphere. You have 3 min Gas 1. 2. 3. 4. % in air Structure of the respiratory system The respiratory system consists of tubes that filter incoming air and transport it into the microscopic alveoli where gases are exchanged. The respiratory system can be divided into: 1.Structures of the nose and mouth 2.Air passages and associated structures 3.Lungs 4.Diaphragm, ribs & intercostal muscles.  The nose, nasal cavity & pharynx are organs of the Upper Respiratory Tract (URT)  The Trachea, bronchi and lungs are organs of the Lower Respiratory Tract (LRT) Why are some highlighted?  STRUCTURES OF THE NOSE & MOUTH The nose is supported by bone & cartilage and provides an entrance for air. It is lined with mucous membrane, and contains fine hairs. The hairs filter the air and the mucosa warms & moistens it. The air is separated from the food in the mouth by the hard and soft palates. The pharynx (throat) is a common passageway for air and food.  The Air Passages and Associated Structures Larynx It is made up of cartilages and located on the trachea. It prevents particles from entering the trachea. In case any particles enter, they are removed by the coughing reflex. Epiglottis closes the trachea during swallowing. Larynx also houses the vocal cords. When air passes over the vocal cords, they vibrate and produce sound. Trachea The trachea is located in the mediastinum, anterior to the oesophagus. The trachea is kept open by cartilages. The cartilages are C- shaped to allow the oesophagus to expand during swallowing. The inner wall of the trachea is lined with mucous membrane composed of ciliated epithelium with many goblet cells. The mucus serves to trap At its lower end, it splits into right and left bronchi. Each bronchus divides into smaller & smaller branches. The smallest branches are called the bronchioles. In smokers, the air passages are covered with tar. This irritates the lungs and makes gas exchange more difficult. Smokers are more likely to suffer from bronchitis and lung cancer. LUNGS The lungs are spongy, cone shaped organs that occupy most of the space in the thoracic cavity. They are separated medially by the mediastinum, and are enclosed by the diaphragm and thoracic cage. The visceral pleura is attached to the surface of the lung, and the parietal pleura lines the thoracic cavity. Between the visceral & parietal layers is the watery pleural fluid Microscopic structure of the lungs The bronchi divide repeatedly to form bronchioles that lead to the alveolar ducts. The alveolar ducts open into the alveoli. The alveoli have thin walls of simple squamous epithelium and a rich supply of blood capillaries. Oxygen passes into the blood where it combines with haemoglobin, while carbon dioxide diffuses out of the blood into the alveoli.  Blood flow Blood flow Pulmonary venule Bronchiole Pulmonary arteriole Smooth muscle fibers Blood flow Alveolus Pulmonary artery Capillary network on Pulmonary surface of alveolus vein Terminal bronchiole Alveolar duct Alveoli Alveolar sac Diaphragm, ribs and intercostal muscles The diaphragm is a large, semi-circular sheet of muscle and tendon, attached to the base of the ribs and the vertebral column. Movements of the diaphragm are used in breathing, coughing and vomiting. Ribs protect the heart and lungs and are used in breathing. Ribs are moved by intercostal muscles. Break  Activity 2 1.What happens to the O2 percentage at 8,848 m (Mount Everest)? 2.And what about in a pressurised aircraft cabin?  BREATHING Ventilation (breathing): the movement of air in and out of the lungs, is composed of inspiration and expiration. It is composed of inspiration and expiration. End of expiration Start of inspiration INSPIRATION The diaphragm contracts and moves downwards The external intercostal muscles (between the ribs) contract to raise the ribs and sternum. As the thoracic cavity becomes larger, the lungs enlarge and the air pressure in the alveoli drops. This causes fresh air to enter the lungs. EXPIRATION During expiration, the diaphragm relaxes and moves back upwards. The intercostal muscles relax to allow the ribs to move downwards and inwards. As the chest cavity becomes smaller, the air pressure in the alveoli increases. This causes the air to be forced out of the lungs. The total volume of the lungs is about 3-5 liters, but only about 1/2 liter of air moves in and out of the lungs with each breath. This is termed Tidal Volume. Breathing rate is controlled by the brain and is mainly involuntary. Breathing will be faster during and after exercise to remove the extra carbon dioxide from the blood. Since the diaphragm and intercostals muscles are skeletal muscles then it is possible to have some voluntary control over breathing. Breathing rate varies with age, for example it is 40 breaths/minute in a new born baby and about 12- 16 breaths/minute in adults.  Gas transport and diffusion The pressure exerted by a gas in a mixture of gases is the partial pressure (P). PB at sea level is 760 mmHg (101.3 Kpa/1 atmosphere). Therefore PO2 = 0.2098 x 760 = 159 mmHg/21.2 KPa (at sea level).  What do these What is 21.3 KPa pressures represent? this volume? 25 20 Kpa 10 KPa 26  Gas diffusion Diffusion occurs across the alveolar-capillary membrane. It is 0.6 μm thick. There  100 ml of lung capillary blood spread over 70 m2. The diffusing capacity (DLCO or TLCO) is affected by 4 main factors: 1. Membrane thickness (ed in oedema/fibrosis) 2. S. area of membrane (ed in unilateral lung removal/emphysema) 3. Diffusion coefficient of gas 4. Pressure difference (gradient) of gases across membrane O2 transport is by: 1. Haemoglobin (97 %) 2. Dissolved in plasma & cells (3 %)  Control mechanisms 1. Neural 2. Chemical 3. Intra-pulmonary receptors  Chemical control There are peripheral & central chemoreceptors. Central are in the medulla and are very sensitive to changes in blood PCO2 or pH. Neurons here can excite the DRG. 34 Intra-pulmonary receptors These are receptors are found in the lung. They include cough, stretch and C fibre receptors. They send afferent neural information to the medulla and can change the pattern of breathing. 35 Questions?  Which one of the following respiratory muscles is utilised for resting expiration in a healthy adult? A. External intercostals B. Abdominals C. Diaphragm D. Sternocleidomastoids E. None of the above  In the human body, the maximum oxygen partial pressure (PO2) would normally be found in the… A. alveoli B. blood of the aorta C. left atrium of the heart D. pulmonary vein E. tissues