Respiratory Anatomy 2023.pptx

Respiratory Anatomy HEA1091 OFFICI AL Learning Objectives   Describe the anatomy of the respiratory system from nose to alveoli. Describe the structure and functions of the components found in the upper and lower airways. OFFICI AL Sections of the system  Sinuses  Nasal cavity/ Oral cavity  Pha...

Respiratory Anatomy HEA1091 OFFICI AL Learning Objectives   Describe the anatomy of the respiratory system from nose to alveoli. Describe the structure and functions of the components found in the upper and lower airways. OFFICI AL Sections of the system  Sinuses  Nasal cavity/ Oral cavity  Pharynx  Larynx  Epiglottis  Trachea  Bronchi  Bronchiole  Lungs  Pleura  Diaphragm OFFICI AL Upper airway  Upper respiratory tract begins at the external orifice  Nasal cavity/ Oral cavity  Sinuses  Pharynx  Larynx  Epiglottis OFFICI AL Nasal cavity OFFICI AL The nasal cavity is lined with very vascular ciliated columnar epithelium which contains mucussecreting goblet cells, and has coarse hairs, covered in sticky mucus. The nasal mucosa is very vascular, and rapidly warms the air flowing over its surface. This also explains the large blood loss when a nosebleed (epistaxis) occurs. Hairs at the anterior nares trap larger particles. Smaller particles such as dust and bacteria settle and adhere to the mucus. Mucus protects the underlying epithelium from irritation and prevents drying. Synchronous beating of the cilia wafts the mucus towards the throat, where it is swallowed or coughed up. As air travels over the moist mucosa, it becomes saturated with water vapour. Irritation of the nasal mucosa results in sneezing, a reflex action that forcibly expels an irritant. OFFICI AL Pharynx  12cm-14cm in length  Connects from posterior nasal cavity to the oesophagus- runs behind the mouth and the larynx to the level of the 6th cervical vertebra, where it becomes the oesophagus.  Split into three parts OFFICI AL Pharynx- Functions The pharyngeal muscles help to keep the pharynx permanently open so that breathing is not obstructed. The pharynx is involved in both the respiratory and the digestive systems: air passes through the nasal and oral sections into the larynx, and food through the oral and laryngeal sections into the oesophagus. Immune cells in the pharyngeal and laryngeal tonsils defend against swallowed or inhaled antigens OFFICI AL Nasopharynx Superior part of the pharynx   Extends from the internal nares to the uvula Uvula and soft palates involuntary muscle action prevents food entering it.  Mucus often bypasses through to be swallowed.  OFFICI AL Oropharynx  Extends from the uvula to the epiglottis  Oral cavity allowing food and drink to pass OFFICI AL Laryngopharynx  Posterior to the larynx  Runs from the epiglottis to the oesophagus OFFICI AL Larynx OFFICI AL  The larynx, or voice box, links the laryngopharynx and the trachea. It lies in front of the laryngopharynx and the 3rd, 4th, 5th and 6th cervical vertebrae. Until puberty there is little difference in the size of the larynx between the sexes. Thereafter, it grows larger in the male, giving men generally deeper voices than women. OFFICI AL  The larynx is composed of nine irregularly shaped cartilages attached to each other by ligaments and membranes. The main cartilages are the epiglottis, the thyroid cartilage, the cricoid cartilage and two arytenoid cartilages. Several ligaments attach the cartilages to each other and to the hyoid bone OFFICI AL Thyroid Cartilage The thyroid cartilage is made of hyaline cartilage, is the most prominent of the laryngeal cartilages. It lies at the front of the neck and forms most of the anterior and lateral walls of the larynx. Its anterior wall projects into the soft tissues of the throat forming the laryngeal prominence (Adam’s apple), easily palpated and often visible in adult males. OFFICI AL OFFICI AL Cricoid Cartilage The cricoid cartilage lies below the thyroid cartilage and is also composed of hyaline cartilage. It is shaped like a signet ring, completely encircling the larynx with the narrow part anteriorly and the broad part posteriorly. OFFICI AL OFFICI AL https://www.youtube.com/watch? v=odTYa1t7JfY&t=49s OFFICI AL Epiglottis The epiglottis is a leaf-shaped fibroelastic cartilage. It is attached by a flexible stalk of cartilage to the inner surface of the anterior wall of the thyroid cartilage. It rises obliquely upwards behind the tongue and the body of the hyoid bone. If the larynx is likened to a box, then the epiglottis acts as the lid; it closes off the larynx during swallowing, protecting the lungs from accidental inhalation of foreign objects. OFFICI AL OFFICI AL OFFICI AL OFFICI AL OFFICI AL OFFICI AL The vocal cords are two pale folds of mucous membrane with cord-like free edges, stretched across the laryngeal opening. The space between the vocal cords is called the glottis. When the muscles controlling the vocal cords are relaxed, the vocal cords open and the passageway for air coming up through the larynx is clear; the vocal cords are said to be open. When the muscles controlling the vocal cords contract, the vocal cords are stretched out tightly and pulled across the glottis and are said to be closed. When not in OFFICI AL Trachea Known as the windpipe   2.5 cm in diameter    Attaches to the cricoid ring of the larynx (only complete ring in the airway) Begins at the level of the 6th cervical vertebrae    11 cm in length Ends at the 5 thoracic vertebrae This is known as the carina Branches into the left and right primary bronchi OFFICI AL OFFICI AL The trachea is held open by between 16 and 20 incomplete (Cshaped) rings of hyaline cartilage stacked one above the other. The rings are incomplete posteriorly, where the trachea lies against the oesophagus. The cartilages are embedded in a sleeve of smooth muscle and OFFICI AL  Tracheal cartilages hold the trachea permanently open (patent), but the soft tissue bands between the cartilages allow flexibility so that the head and neck can move freely without obstructing or kinking the trachea. The absence of cartilage posteriorly permits the oesophagus to expand comfortably during swallowing. OFFICI AL Cillia This is the synchronous and regular beating of the cilia of the mucous membrane lining that wafts mucus with adherent particles upwards towards the larynx, where it is either swallowed or coughed up. OFFICI AL endings in the larynx, trachea and bronchi are highly sensitive to irritation, which generates nerve impulses conducted by the vagus nerves brain stem. The reflex motor response is deep inspiration followed by closure of the glottis, i.e. closure of the vocal cords. The abdominal and respiratory muscles then contract, causing a sudden and rapid pressure increase in the lungs. Then the glottis opens suddenly, forcibly flex to the respiratory centre in the re gh Cou  Nerve OFFICI AL The Lungs OFFICI AL There are two cone-shaped lungs, one on each side of the midline in the thoracic cavity. The space between the lungs is called the mediastinum and contains the heart, great vessels, trachea, right and left primary bronchi, lymph nodes and, vessels and nerves. The lungs are not symmetrical: the left lung is slightly smaller than the right because the heart occupies space left of the midline, and the right sits slightly higher in the thorax than the left because of the bulky liver in the abdominal cavity below. Each lung is divided into individual subunits called lobes, which are separated by fissures. The right lung has three lobes: the superior (upper), medial (middle) and inferior (lower) lobes, and the left lung has only two, the superior and inferior lobes. The right lung, therefore has two fissures: the horizontal fissure separates the superior and medial lobes, and the oblique fissure separates the medial and inferior lobes. The oblique fissure OFFICI AL The pleura consists of a closed sac of serous membrane, one for each lung, which contains a small amount of serous fluid called pleural fluid. The lung can expand and recoil within the pleural sac, lubricated by the pleural fluid. Although the pleural membrane is described as two sheets, the visceral and the pleural membranes, the description refers to whether the layer is the outer or inner: it is still all one membrane. The pericardium forms a similar arrangement around the heart, allowing it to beat without friction. OFFICI AL OFFICI AL OFFICI AL The pulmonary trunk divides into the right and left pulmonary arteries, carrying deoxygenated blood to each lung. Within the lungs, each pulmonary artery divides into many branches, which in turn subdivide and eventually produce dense capillary networks wrapped around the alveoli. The alveolar and capillary walls contain only one layer of flattened epithelial cells on a thin basement membrane. The exchange of gases between air in the alveoli and blood in the capillaries occurs here. The pulmonary capillaries merge into a network of larger pulmonary venules, forming two pulmonary veins carrying OFFICI AL The two primary bronchi are formed when the trachea divides at about the level of the 5th thoracic vertebra. Right bronchus This is wider, shorter and more vertical than the left bronchus and is, therefore, more likely to become obstructed by an inhaled foreign body. It is approximately 2.5 cm long. Left bronchus This is about 5 cm long and is narrower than the right. After entering the lung, it divides into two branches, one to each lobe. Each branch then subdivides into progressively smaller airways within the lung. OFFICI AL OFFICI AL OFFICI AL ontrol of air entry The capacity of the bronchi and other large airways to significantly affect air entry is limited because they are held open by cartilage and cannot adjust in diameter. Cartilage disappears with the progressive division of the respiratory tree and is replaced with increasing amounts of smooth muscle. This means the diameter of the smaller respiratory passages can be altered considerably by contraction or relaxation of the smooth muscle in their walls, regulating the speed and volume of airflow into and within the lungs. The autonomic nerve supply controls these changes: parasympathetic stimulation causes constriction, and sympathetic stimulation causes dilation. OFFICI AL The lung tissue is further divided within each lobe by fine sheets of connective tissue into lobules. Each lobule is supplied with air by a terminal bronchiole, subdividing into respiratory bronchioles, alveolar ducts and large numbers of alveoli (air sacs). There are about 150 million alveoli in the adult lung. It is in these structures that gas exchange occurs. As airways progressively divide and become smaller and smaller, their walls gradually become thinner until muscle and connective tissue disappear, leaving a single layer of epithelial cells in the alveolar ducts and alveoli. These distal respiratory passages are supported by a loose network of elastic connective tissue in which macrophages, fibroblasts, nerves, and blood and lymph vessels are embedded. A dense network of capillaries surrounds the alveoli. The exchange OFFICI AL  Surfactant is a substance produced in the lungs, and it plays a crucial role in respiratory function. Here's a breakdown:  Function: Surfactant is a mixture of lipids and proteins that lines the inner surface of the alveoli (the tiny air sacs in the lungs). Its primary function is to reduce surface tension within the alveoli.  Reducing Surface Tension: Without surfactant, the surface tension within the alveoli would be high. This high tension could cause the alveoli to collapse, making it difficult for the lungs to expand during inhalation and potentially leading to respiratory issues.  Facilitating Breathing: Surfactant reduces surface tension, making it easier for the alveoli to expand during inhalation. This makes breathing more efficient by preventing the Surfactant OFFICI AL Muscles of breathing Chest expansion during inspiration occurs as a result of muscular activity, partly voluntary and partly involuntary. The main muscles used in normal quiet breathing are the external intercostal muscles and the diaphragm. OFFICI AL Intercostal muscles There are 11 pairs of intercostal muscles occupying the spaces between the 12 pairs of ribs. They are arranged in two layers, the external and internal intercostal muscles and are supplied by the intercostal nerves. OFFICI AL External intercostal muscles  These extend downwards and forwards from the lower border of the rib above to the upper border below. They lift the ribcage upwards and outwards in inspiration. Internal intercostal muscles  These extend downwards and backward from the lower border of the rib above to the upper border below, crossing the external intercostal muscle fibres at right angles. They are used when expiration becomes active, as in exercise. OFFICI AL  The diaphragm is a dome-shaped muscular structure supplied by the phrenic nerve, separating the thoracic and abdominal cavities. It forms the floor of the thoracic cavity and the roof of the abdominal cavity and consists of a central tendon from which muscle fibres radiate to be attached to the lower ribs and sternum. OFFICI AL Accessory muscles of respiration  Accessory muscles of forced inspiration  Forced inspiration is assisted by the sternocleidomastoid and scalene muscles, which link the cervical vertebrae to the first two ribs and increase ribcage expansion. When these muscles contract, they pull the ribcage upwards, supplementing the action of the external intercostal muscles.   Accessory muscles of forced expiration Quiet exhalation takes around 3 to 4 seconds. Recruiting accessory muscles of expiration shortens the expiration time, increases the speed and force of exhalation, and increases the respiratory rate. Forced expiration is helped by the contraction of the internal intercostal muscles, which pull the ribcage downwards and inwards, compressing the lungs and aiding exhalation. Sometimes, the rectus abdominis OFFICI AL Learning Objectives   Describe the anatomy of the respiratory system from nose to alveoli. Describe the structure and functions of the components found in the upper and lower airways.