Respiratory System PDF

Respiratory system Presented by: Lect.Dr. Alaa Abdl-hussain naeem  Introduction The respiratory system consists of the paired lungs and a series of air passages that lead to and from the lungs. Within the lung, the air passages branch into increasingly smaller tubes unti...

Respiratory system Presented by: Lect.Dr. Alaa Abdl-hussain naeem  Introduction The respiratory system consists of the paired lungs and a series of air passages that lead to and from the lungs. Within the lung, the air passages branch into increasingly smaller tubes until the very smallest air spaces, called alveoli, are reached. Three principal functions are performed by this system: 1-air conduction, air filtration, Cleaning, moistening & warming of the air, and gas exchange (respiration) in the alveoli. 2-In addition, air passing through the larynx is used to produce speech. 3-Air passing over the olfactory mucosa in the nasal cavities carries stimuli for the sense of smell and flavour. Anatomy of the respiratoy system  Two Functional Parts of the Respiratory Tract Conducting portion:  Conduct air to and from alveoli.  Condition the air (warm, humidify, filter). Respiratory portion:  Gas exchange took place. Conducting portion: Nasal cavity Larynx Trachea Bronchi Bronchioles  Walls of the Conducting System Components include: Epithelium (“respiratory epithelium”) Lamina propria Mucous and serous glands Cartilage Smooth muscle Adventitia  Respiratory Epithelium Cell Types Ciliated columnar cells (pseudostratified columnar cells): most abundant cell type. Cilia beat in unison and move mucus and trapped particles to oropharynx, where it is swallowed or expectorated. Goblet cells:the second most numerous type of cells, columnar in shape or goblet like they are scattered in between the ciliated columnar cells. They produce mucus. Basal cells: small rounded cells lie on the basement membrane, they are not in contact with the lumen, and they form stem cells from which other cell types develop.  Brush cells: Columnar cells. No cilia but have apical microvilli. Neuroendocrine cells:small rounded cells with dark nuclei & cytoplasm filled with endocrine granules that regulate the interaction between mucous and serous secretory functions of the system. Cartilages in the respiratory system:  Cartilages are mainly hyaline in type, they have various forms ranging from small plaques in the bronchi to irregular rings & in the trachea C- shaped cartilages.  The cartilages generally produce support to the wall of the conducting part to prevent collapse of the lumen during expiration & to ensure continuous air entry to the lungs  Nasal Cavity Respiratory epithelium every where except at the top (which has specialized olfactory epithelium). Serous and mucous glands and numerous blood vessels in lamina propria. Nasal septum: midline structure consisting of bone and hyaline cartilage. Nasal fossa: chambers on each side of septum.  Larynex Epiglottis covers laryngeal opening during swallowing. Laryngeal cartilages Core of elastic cartilage. support the wall of the Superior surface: larynx and serve as nonkeratinized stratified attachments for vocalis squamous epithelium. muscles. Inferior surface: respiratory epithelium False vocal folds are Vocal folds are covered covered by respiratory by nonkeratinized epithelium stratified squamous epithelium  Trachea Is a tubular structure its wall contain about 15-20 incomplete circular rings of cartilage & only a narrow area in the posterior wall of the trachea is devoid of cartilage. This gab between the two cartilaginous rings is bridged by dense fibrous ligament & bundles of smooth muscle called trachealis muscle. Contraction of this muscle leads to narrowing of the tracheal lumen as a part of the cough reflex  Trachea Extends from larynx and divides into two primary bronchi. Lined by respiratory epithelium. Seromucous glands in lamina propria and submucosa.  Bronchi Trachea divides into two primary bronchi, which divide into secondary bronchi. Secondary bronchi divide into tertiary bronchi, which supply bronchopulmonary segments. Tertiary bronchi divide into smaller bronchi, which divide into bronchioles.  The primary bronchi generally have the same histological appearance as the trachea: 1-mucosa : consist of a pseudostratified columnar ciliated epithelium with goblet cells become less columnar in smaller branches. 2-lamina propria: the lamina propria contains variable amounts of smooth muscle fibers and elastic fibers that are arranged spirally around the bronchus. numerous lymphocytes are present in the lamina propria & lymphatic nodules are found mainly at the branching points of the bronchial tree. 3- Muscularis: a continuous layer of smooth muscle in the larger bronchi. It is more attenuated and loosely organized in smalle bronchi, where it may appear discontinuous because of its spiral course. Contraction of the muscle regulates the appropriate diameter 4-Submucosa :large amount of serous and mucous glands whose ducts open in the bronchial lumen. 5- cartilage 6-Adventitia : is moderately dense connective tissue that is continuous with that of adjacent structures, such as pulmonary artery and lung parenchyma  Bronchioles Air-conducting ducts that measure 1 mm or less in diameter. It has no cartilage & no glands in their walls, and with the absence of the cartilage the smooth muscle become a major component of their wall. The larger bronchioles are lined with ciliated columnar epithelium and these cells become low columnar and even cuboidal in the smaller terminal bronchioles. Goblet cells are only found occasionally in the wall of the bronchioles and there are no seromucous glands In asthma, the smooth muscle in the bronchioles constricts, causing difficulty breathing.  Terminal Bronchioles Simple cuboidal epithelium with cilia. Also: Clara cells (non-ciliated epithelial cells with secretory granules). Make surfactant components, break down mucus,detoxify harmful substances, transfer IgA, fight bacteria… No goblet cells. Functions of Clara cells : 1. protection against the effect of inhaled toxins & carcinogens substances. 2. They secrete a surface-active agent, a lipoprotein that prevents luminal adhesion should the wall of the airway collapse on itself, some role in surfactant production. 3. 3- they secret Clara cell secretory protein (CC16),which is an abundant component of the airway secretion 4. possible role as stem cells capable of producing other types of cells.  Airways Preceding Alveoli Respiratory bronchioles As you go distally along the respiratory bronchioles, alveoli increase in number. Cilia are gone by the end of the respiratory bronchiole. Alveolar ducts Back-to-back alveolar openings along wall Smooth muscle between alveolar openings looks like knobs  Alveoli Sac-like structures with super-thin walls so O2 and CO2 can diffuse between air and blood. Separated by interalveolar septae, which contain capillaries. Cells lining interalveolar septae: Type I cells (thin, flat squamous cells) Type II cells (pneumocytes): produce surfactant Alveolar macrophages (dust cells)  Type I Cells Cover 95% of alveolar surface Simple squamous cells with thin cytoplasm Blood-air barrier includes (from air to blood):  Type I cells  Fused basal laminae of type I cells and capillary endothelial cells  Capillary endothelial cells  Type II Cells (Pneumocytes) Cover 5% of alveolar surface. Large cuboidal cells with round nuclei. Typical secretory cell structure. Lamellar bodies in cytoplasm make and store surfactant. Surfactant decreases surface tension in alveoli and prevents collapse of alveoli during expiration  Parietal and Visceral Pleura The outer surface of the lung and the inner surface of the thoracic cavity are covered by the pleura, which is a serous membrane. Parietal pleura lines the thoracic cavity; visceral pleura covers the lungs. Serous membranes consist of simple squamous epithelial cells called mesothelium plus a thin layer of connective tissue. The pleural cavity contains serous fluid made by the pleura.