Respiratory System 2023 S (1) PDF

Respiratory System Emma Kemp-Gee  Learning Objectives Name and describe the organs that form the respiratory system Describe the function of the respiratory organs Describe the structure of the respiratory membrane Described the process of respiration Define external/in...

Respiratory System Emma Kemp-Gee  Learning Objectives Name and describe the organs that form the respiratory system Describe the function of the respiratory organs Describe the structure of the respiratory membrane Described the process of respiration Define external/internal respiration Define the respiratory volumes: tidal volume, residual volume, expiratory reserve volume and Inspiratory reserve volume Name non-respiratory air movements Describe gas exchange and transport (CO2/O2) Explain control of respiration Name and describe respiratory disorders  Respiratory Tract The respiratory tract carries air to and from the lungs. Air drawn in through the of the: Upper respiratory tract: nose or mouth, the pharynx and larynx Lower respiratory tract: trachea, bronchial tree, and the lungs. Lungs are divided into lobes: 2 left Hilum – entry/ exit point of all other structures to/ from the lungs 3 right Pulmonary veins and arteries – blood from/ to the heart Bronchial arteries and veins – blood supply to/ from the lung The lungs are supplied with deoxygenated blood via the pulmonary arteries and oxygenated blood is carried away from the lungs to the heart by the pulmonary veins. The lung tissue itself is supplied with oxygenated blood via the bronchial arteries that are direct branches of the thoracic aorta. The principal bronchi, and the pulmonary and bronchial vasculature all enter or exit the lungs at the hilum.  Respiratory System Functions: Ventilation. The delivery of O2 to the lungs and the expulsion of CO2 and H2O out of the lungs. Gas exchange. The diffusion of O2 into the bloodstream and the diffusion of CO2 out of the bloodstream. Blood pH. The regulation of the acid-base levels of blood Air preparation. Filtering, warming, and humidifying inspired air. Vocalization The production of speech and melody created by the vibration of the vocal folds. Olfaction The process of detecting smell by the use of olfactory receptors Protection and defence. The process of protecting respiratory surfaces from dehydration and temperature change and defending the body against inhaled pathogens  Basis of respiration Difference in pressure between lungs and atmosphere Inhalation/inspiration: lower pressure in the lungs (increase volume) vs atmospheric Volume depends on the ribcage volume (intercostal muscles, and lowering the diaphragm). The lungs move with the chest wall because the cavities which contain them are closed spaces. Each lung is protected by a double membrane called the pleural membrane.  Upper respiratory tract – nasal cavity Anterior nares: Nostrils - supported by alar cartilages Vestibules: Covered with a dense network of hair/mucous membrane (mucus with lysozyme). Function is to filter/warm/moisten inhaled air The mucous membrane that covers the top of the nasal cavity is the olfactory mucosa as it contains the sensory cells that detect odour Nare s Palate (hard and soft): Bone and muscle, separates oral cavity and nasopharynx. Upper respiratory tract -pharynx Pharynx: A muscular tube lined with mucous membrane, which joins the nasal and oral cavities to the esophagus and larynx. Nasopharynx connects the nasal cavity to the oropharynx and is separated from the oral cavity by the soft palate. It receives the auditory or pharyngotympanic tubes. Contains pharyngeal tonsils Oropharynx sits between the soft palate and upper border of the epiglottis, and posterior to the oral cavity and tongue. Contains palatine, and lingual tonsils Laryngopharynx lies behind the larynx and terminates at the level of the cricoid cartilage by becoming continuous with the esophagus.  Upper respiratory tract - larynx Larynx The larynx or 'voice box' is a cartilaginous structure composed of several different cartilage elements. Epiglottis (‘lid’ of the larynx) Thyroid cartilage (Adam’s apple- protects the vocal folds) Cricoid (unites with the trachea) The larynx also consist of accessory muscles (movements), and structural tissues. Functions: Protecting the airway and closing and Sealing the lower respiratory tract, Voice production.  Vocal Folds Voicing, relies on bringing the two vocal folds together, closing the rima glottidis, the space between the vocal cords. The vocal folds must be adducted. With the folds closed, air from the lungs is driven through the vocal folds, forcing them apart and to vibrate, producing sound. The modulation and modification of these sounds by surrounding soft tissues is termed phonation. Moving the vocal folds together (adduction) and apart (abduction) is achieved by the actions of the intrinsic laryngeal muscles. Lower respiratory tract - trachea It descends through the thorax and divides into two principle bronchi. It is comprised of c-shaped tracheal cartilage rings anteriorly united by a fibroelastic membrane. Posteriorly, the gaps in the c-shaped cartilages are united by the trachealis muscle. Inside, is lined with a specialized mucous membrane containing cilia which beat upwards.  Lower respiratory tract - bronchi Principal (primary) bronchi They have a similar structure to the trachea with incomplete rings of cartilage anteriorly united by a fibroelastic membrane. They travel obliquely to enter each lung through the hilum, And begin dividing further into smaller branches. The right principal bronchus is more vertical, shorter (2.5cm), and wider The left principal bronchus is more horizontal, longer (5cm), and thinner Secondary bronchi are branches of the principal bronchi, of which there is one for each lobe of the lungs: two left and three right. Tertiary bronchi serves a specific bronchopulmonary segment (10 R/ 8L). They branch into bronchioles Bronchioles are composed of a fibroelastic membrane and smooth muscle and usually do not contain cartilage. They branch in turn repeatedly until they form small branches called terminal bronchioles. The primary function of bronchioles is to control the resistance to airflow, and the distribution of air in the lungs.  Lower respiratory tract - alveoli Terminal bronchioles The respiratory bronchioles branch into several alveolar ducts, as well as having alveoli attached directly to them. There are 300 million alveoli in the human lungs, providing a large surface area for gas exchange. Alveoli are tiny, thin-walled air sacs with a rich blood supply. Their walls are just one cell thick, as are the capillaries that surround them, meaning that gases diffuse across a distance of only two cells thick to gain access to the bloodstream. The internal surface of an alveolus is covered with a moist film of alveolar fluid allowing oxygen from the air to dissolve into it. It contains surfactant (septal cell), a fluid rich in phospholipids and proteins that decreases the surface tension in the alveoli, preventing them from collapsing. Each alveolus contains a large number of macrophages that phagocytose foreign particles and debris, killing bacteria that have entered the lungs and have been trapped on the moist walls.  Pleura The lungs are covered with a double sheet of thin membrane called pleura. Each membrane is a closed sac with a lung invaginated into it. This creates two layers over the surface of the lungs: The visceral pleura is the innermost layer that adheres closely to the surface of the lungs. It cannot be separated from the lung surface The parietal pleura is the outer layer which lines the thoracic wall, diaphragm, and structures within the mediastinum. The space between the two membranes is know as the pleural cavity; however, in a normal person this is only a potential space, as both layers are in close contact. During normal respiration, the layers slide over each other with the aid of pleural fluid. Muscles of Inhalation The diaphragm (musculofibrous) divides the thorax from the abdomen. The fibers of the external intercostals run obliquely forwards from the bottom of one rib to the top of the adjacent rib. Diaphragm is responsible for 75%/ External intercostal muscles are responsible for 25%. of the air entering the lungs and the Passive except in forceful breathing (excessing), engaging abdominal and internal intercostal muscles Pulmonary ventilation/breathing Gases moves from high  low pressure Inhalation: the lungs expand (pressure decrease), by contracting the muscles of inhalation. High pressure Low pressure Inspiration Atmosphere Lungs Exhalation Lungs Atmosphere Pulmonary ventilation/breathing Gases moves from high  low pressure Exhalation, the lungs revert back (increase pressure) to their original size by relaxing the muscles of inhalation and air moves out. High pressure Low pressure Inspiration Atmosphere Lungs Exhalation Lungs Atmosphere  Factors aff ecting pulmonary ventilation These differences in air pressure provide the primary force for airflow during pulmonary ventilation. Three other factors affect the ease of breathing: 1. Surface tension of alveolar fluid, forces created between an air- fluid barrier. Surfactant is a fluid produced by type 2 alveolar cells septal cells) that lowers the surface tension of alveolar fluid and reduces the effort needed to inflate the alveoli. 2. Lung compliance the effort needed to stretch the lungs and thoracic cavity. Elasticity and surface tension of alveolar fluid 3. Airway resistance. Refers to the opposition of airflow in the respiratory system. In general, larger diameter airways have a decreased resistance and as a result, airflow through the airways is increased  Lung volumes - spirometer Pulmonary volumes and capacities vary from person to person depending on their age, relative size, and build They can be used to investigate disease too  Lung volumes There are four major pulmonary volumes: Tidal volume: is the volume of air inhaled or exhaled with one normal breath ~500ml Expiratory reserve volume: the volume of air that can be forcefully expelled from the lungs after a normal expiration. 0.7-1.2L Residual volume: the volume of air that remains in the alveoli after a forced expiration. ~ 1.1-1.2 L Inspiratory reserve volume: the additional volume of air you can inspire following a normal inspiration. 1.9-3.1L The relative sums of these volumes make up the pulmonary capacities. Non respiratory air movements Respiratory membranes and gas exchange The respiratory membrane alveolar wall / capillary wall The respiratory membrane provides a large surface area and a thin, permeable, and moist surface where the gaseous exchange of oxygen and carbon dioxide can take place. External respiration: exchange of oxygen and carbon dioxide between the air in our alveoli and the blood in our pulmonary circulation. Internal respiration :exchange of oxygen and carbon dioxide between the cells of our body and the blood in our systemic capillaries. The rate at which these gases diffuse is dependent on their partial pressures (gases move from an area of high partial pressure to an area of low partial pressure).  Oxygen transport Oxygen (98.5%) binds to haemoglobin (oxyhemoglobin/ deoxyhemoglobin) and the rest dissolved in plasma Hb + O2 ⇌ Hb-O2 Temperature. A by-product of increased metabolism is increased production of heat. This, together with a decrease in pH, reduces the affinity of hemoglobin for O2 and promotes its dissociation. The opposite is true for a decrease in temperature, which increases hemoglobin's affinity for O2 Tissue pH metabolically active tissues produce acids and reduce the pH of tissues. Hemoglobin acts as a pH buffer and mops up excess hydrogen ions, but in doing so alters its structure so that less oxygen can bind to it. The majority of carbon dioxide is transported as bicarbonate ions, a smaller percentage as carbaminohemoglobin, and an even smaller percentage is directly dissolved in blood plasma. CO2 + H2O ⇌ H2CO3⇌ H+ + HCO3-  Control of respiration Respiratory rate, or the number of breaths we take per minute (12-15- eupnea), and the depth at which we respire with each breath is controlled by the respiratory centre, located in the brainstem. It ensures that our respiratory effort matches the metabolic demands of our body. Two parts of the brainstem are primarily responsible for this control: The pons. Communicates with VRG. Smooth the transition (timing) during activities like singing, sleeping or exercising Medulla oblongata Ventral respiratory group (VRG) both Insp/ Exp- keeps normal beating rate Dorsal respiratory group (DRG) integrate sensory information (chemoreceptors and peripheral stretch receptors)- modify rhythms Chemoreceptors monitoring CO2, O2, and H+ levels in the blood Stretch receptors (bronchioles and alveoli) Hyperpnea- exercise, more muscle involved and expiration is active  Associated disorders Infectious and inflammatory disorders Common cold. Rhinovirus, mild. Influenza. Influenza virus, can be more severe. Primary viral- secondary bacterial Sinusitis. Infection of paranasal sinuses. Primary viral- secondary bacterial Tonsillitis. Virus and Streptococcus pyogenes Pharyngitis, laryngitis and tracheitis. Normally secondary to other upper respiratory infections Diphtheria. Bacterial infection of the pharynx (Corynebacterium diphtheriae). Could be severe. Vaccination made it rare Hay fever. Allergic rhinitis Obstructive Lung disorders Bronchitis. Secondary bacterial infection of the bronchi (from cold/flu) Emphysema. Progressive destruction of the elastic tissue Asthma. Over-reactive inflammation of the airway (anti-inflammatory/ bronchodilator agents help) Bronchiectasis. Permanent abnormal dilation of bronchi/bronchioles. Chronic bacterial infection Restrictive disorders Associated disorders Pneumoconiosis. Generalised inflammation and progressive fibrosis. Prolonged exposure to organic dust (coal, silicone, asbestos fibers, mouldy hay, mouldy sugar waste, mould bird droppings, mouldy barley, cotton fibers) Pulmonary toxins. Paraquat, drugs, high concentration of O2 therapy Lung infections Pneumonia. Infection of the alveoli (bacteria, virus, mycoplasma, fungi). Failed pulmonary defences (impaired coughing, damage of the epithelia lining, impaired alveolar phagocytosis. Lobar/Bronco pneumonia. Tuberculosis (TB). Mycobacterium tuberculosis Lung Tumour Bronchial carcinoma. 90% due to smocking, Pleural mesothelioma. Associated with asbestos exposure Lung Collapse Obstruction of an airway. Due to obstructions Impaired surfactant function. In premature babies (before 34W), or when there is liquid in the alveoli (pulmonary oedema) Pressure collapse. When air or liquid enters the pleural cavity (pneumothorax/haemothorax)  Associated disorders Asthma is a common, chronic disease which primarily affects the small conducting airways of the lungs, that narrow by specific stimuli (house dust mites, pollen, cigarette smoke, and animal dander, as well as stress and exercise). This airway narrowing is usually reversible upon removal of the trigger and treatment with appropriate medication.  Associated disorders Lung cancer has the highest mortality of all cancers in the United States and is the most commonly diagnosed cancer worldwide. Despite advances in therapies, lung neoplasms are associated with a poor prognosis and 5 year survival rates are low. Cigarette smoking remains the greatest cause of lung malignancy, causing approximately 90% of cases. Exposure to other carcinogens, such as radon gas and asbestos, contribute to many of the remaining cases of lung cancer. Other risk factors include long term chronic lung conditions, such as chronic obstructive pulmonary disease and tuberculosis.  Associated disorders https://www.primalpictures.com/disease-and-  Associated disorders Emphysema is a type of chronic obstructive pulmonary disease (COPD). Progressive loss of the elasticity(becomes distended). The main cause of emphysema is smoking. Distended Walls bronchioles, between decrease alveoli pressure, reduce break ventilation down,  Associated disorders Pneumonia is acute inflammation of the lung tissue which leads to the alveoli filling with inflammatory fluid and cells. It is usually caused by a bacterial infection, although viruses and other agents can trigger it. The affected alveoli cannot be ventilated and therefore the surface area available for gas exchange is reduced. It is a common disorder that can affect anyone, although particularly susceptible groups include the elderly, infants, and those with an underlying lung disease or impaired immune system. Distribution of infected tissue. (A) Lobar pneumonia. (B)Bronchopneumonia.  Associated disorders Collapse of a lung. Obstruction of an airway. Due to obstructions Pressure collapse. When air or liquid enters the pleural cavity (pneumothorax/haemothorax) (A) Absorption collapse. (B) Pressure collapse Tension pneumothorax. (A) Inhalation. (B) Exhalation. Pneumothorax is a condition where there is air within the pleural cavity. The presence of the air means that the lung on the affected side cannot expand, and may be partially or completely collapsed. This limits the surface area available for gas exchange.  Associated disorders The diagnosis of pulmonary embolus (PE) remains a common and important cause of morbidity and mortality in all age groups. Microthrombi (small blood clots) within the pulmonary arterial vasculature may cause and then subsequently present with a variety of symptoms and signs. Despite the frequency of their formation and the severity of their implications, PE remains a diagnosis that is often missed.