Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Anatomy of the Respiratory System The re spiratory s ystem or ( Latin = classified into (Figure 1): s ystema re spiratorium) functionality c an be ▪ Conducting zone ▪ Respiratory zone In t he conducting zone, air moves in continuous passages: Nose Pharynx Larynx Trachea Bronchi Bronchioles In t he respiratory zone (lungs), consists of thre e pa ssages which a re responsible for inhaled ox ygen to be passages include: Figure 1. Respiratory system exchanged for c arbon diox ide. The thre e Respiratory bronchioles Alveolar ducts Alveoli The respiratory system structures are divided into: ▪ Upper respiratory tract ▪ Lower respiratory tract Upper respiratory tract is located in the head a nd ne ck a nd c onsists of three re gions (Figure 2): Nose Pharynx Figure 2. Respiratory system Larynx Nose Region The region of the no se c onsists of the external nose and the nasal c avity. The a ir travels from the nostrils to the back of the nasal cavity where it e xits through the posterior na res. The n asal mucosa c overing the nasal cavity is made up of thre e la yers: ciliated e pithelium, basement membr ane, and lamina p ropria. The c iliated e pithelium is the top portion of the na sal mucosa that contains hair-like processes called the cilia Figure 3. Ciliated cells (Figure 3). The ciliated epithelium rests on the basement membr ane. The lamina propria (layer of connective tissue) lies below the basement membrane. The na sal epithelium contains three diff erent type of c ells (Figure 4) . T he c iliated or non-ciliated, goblet, and basal cells. The ciliated cells with their movement forward and back create a flow of mucus (with any trapped material: bacteria, viruses, etc.) that ends in the pharynx. W hen t he mucus arrives in the pha rynx, the mucus is swallowed. This movement of mucus (which is known a s mucociliary clearance) is not random; rather, it is pr ogrammed so that the mucus moves along in a specific p attern (a ctive p rocess). The goblet cells are specialized cells that are responsible for c onstant secretion of the mucus layer. While the secretion of mucus is being seen in both the uppe r and low er respiratory tr act, it is most pr onounced in Figure 4. Nasal epithelium the nasal cavity and paranasal sinuses. The mucus has multiple functions that c an includ e ke eping the nasal passages moist, trapping debris and infection material, and worm the incoming air. The paranasal sinuses are air-filled pockets located within the bones of the face and around the nasal cavity. Each sinus is name for the bone in which it is located: Maxillary (one sinus located in each cheek) Ethmoid (approximately 6-12 small sinuses per side, located between the eyes) Frontal (one sinus per side, located in the forehead) Sphenoid (one sinus per side, located behind the ethmoid sinuses, near the middle of the skull) Each of these pockets has an opening that connects to the nose. This opening is called an ostium. 2 The nose and sinuses are closely related. The nasal septum divides the nose into two nasal cavities. The side wall of the nose (the lateral nasal wall) has three important structures, which are known as the superior, middle and inferior turbinates. Each turbinate is a rounded projection that extends the length of the nasal cavity. The space between each turbinate is called a meatus, and each meatus is named for the meatus above it. Figure 5. Nasal epithelium The inferior turbinate, which is larger than the other turbinates, runs parallel to the floor of the nose. The nasolacrimal duct drains tears into the inferior meatus. (This explains why one develops nasal congestion when one cries.) The middle turbinate is located above the inferior turbinate. The anterior (or front) ethmoid cells open into the middle meatus. The term "frontal recess" refers "antechamber" just below the frontal sinus ostium. Therefore, the frontal sinus drains into the middle meatus. The frontal recess contains a variable number of ethmoid cells. The superior turbinate, which is the smallest turbinate, is above the middle turbinate. The posterior (or back) ethmoid cells drain into the superior meatus. The space between the superior turbinate, the septum and the sphenoid sinus front wall is known as the sphenoethmoid recess. The sphenoid drains here. Pharynx Region There are three distinct parts in the pharynx region: nasopharynx, oropharynx, and laryngopharynx. Through the nostrils (nasopharynx) air moves into the nasal cavity The oropharynx opens into the oral cavity which encloses the lips, teeth, cheek, hard and soft palates, tongue and tonsils. Extending from the tip of the epiglottis to the glottis and the esophagus is the laryngopharynx and positioned in the anterior neck is the larynx. The tonsils and adenoids are located in the pharynx. The middle ear communicates with the nasopharynx thorough the Eustachian tubes. 3 Larynx Region The passageway between the pharynx and the lower a irway structures is the lar ynx. It is a short tube made up of supportive cartilage, ligaments, muscle a nd mucosal lining. The larynx mucosa forms the fa lse a nd tru e voc al cords. The vocal cords and the space between is c alled glottis. The glottis is re sponsible to generate voice. The function of the supportive cartilage (epiglottis) is to pr event food a nd liquid c ontents from e ntering the lar ynx during swallowing.. T he lar ynx c ontains typical upper respiratory e pithelia, c onsisting of ciliated cells that are responsible for mucus transport a nd goblet cells where mucus production occurs. Lower respiratory tract (lung) is located in the chest and makes up the (Figure 6): Figure 6. Lower respiratory track Trachea Bronchial tree Lungs Trachea Air passes from the larynx to the trachea. The trachea (know n is the windpipe) is 10-12 c m tube that runs through the lower ne ck a nd chest and divi des int o the right and lef t primary br onchi (bronchial tre e) The wa ll of the trachea is made of hyaline cartilage which enables the trachea to stay open so that air can be conducted between the larynx and primary bronchi. Note that the trachea mucosa contains no smooth muscles (Figure 7). Bronchial tree: The br onchial tre e c onsists of a pr imary, secondary (lob ar) a nd ter tiary b ronchi (segmental bronchi). The tra chea spli ts into the right a nd left bronchi a t the level of the sternal angle. Th e se condary br onchi forms Figure 7. Trachea epithelium 4 when the primary bronchus enters the lung; and conducts air directly to one of the five lobes within the lung. Tertiary bronchi derive from the secondary bronchi and conduct air to and from the bronchial segment. There are eight bronchial segments in the left lung and 10 in the right lung. Note the smooth muscles (SM) in the lamina propria that are responsible for the respiratory complications due to allergic Figure 8. Bronchial epithelium reaction. The respiratory complications include airway constriction (narrowing bronchial lumen, Figure 9, also see Figure 10), due to swelling of the smooth muscles in the airway tract, bronchospasm (constriction of bronchi), and angioedema (swelling in the tissue – beneath the skin). Angioedema of the upper respiratory (pharynx, larynx and trachea) produces upper airway obstruction, whereas bronchospasm and mucosal edema produce lower respiratory obstruction. Histamine tends to cause constriction of the large airway tracts and leukotrienes affect the smaller peripheral airways.11 The airway obstruction can be just as life threatening as a result of the laryngeal edema and/or bronchial spasm. Death can occur due to asphyxiation. Figure 9. Bronchial lumen Figure 10. Bronchial lumen 5