The amount of smooth muscle increases as the amount of cartilage decreases, and smooth muscle is also present continuously around the bronchi. The alveolus is the basic anatomic unit of gas exchange. Formed of a cartilaginous skeleton of nine cartilages, it includes the important organs of the epiglottis and the vocal folds (vocal cords) which are the opening to the glottis. In: StatPearls [Internet]. The airway, or respiratory tract, describes the organs of the respiratory tract that allow airflow during ventilation. (1991) Archives of internal medicine. Segmentum apicoposterius pulmonis sinistri. Additionally, hyaline cartilage forms an incomplete ring in the bronchi that gives them the characteristic "D"-shaped appearance in the larger bronchi, and as small plates and islands in smaller-sized bronchi. This marks the level of a number of other anatomical structures: It marks the point at which the costal cartilages of the second rib articulate with the sternum. Both articular surfaces are irregularly shaped and covered by hyaline cartilage. American journal of roentgenology. Seyfer AE, Shriver CD, Miller TR, Graeber GM. The trachea marks the beginning of the tracheobronchial tree. Bifurcation of trachea at sternal angle What are the 3 components of the middle. 3.6. . Onoe R, Yamashiro T, Handa H, Azagami S, Matsuoka S, Inoue T, Miyazawa T, Mineshita M. Int J Chron Obstruct Pulmon Dis. Once you've finished editing, click 'Submit for Review', and your changes will be reviewed by our team before publishing on the site. Wang J, Zhou B, Yang X, Zhou C, Ling T, Hu B, Song Y, Liu L. Eur Spine J. Within the thorax at this point, the trachea is displaced slightly to the right by the arch of the aorta on its left. American journal of roentgenology. Transverse section of the trachea, just above its bifurcation, with a birds-eye view of the interior. By clicking Accept, you consent to the use of ALL the cookies. Dimitrios Mytilinaios MD, PhD In addition, there are several lateral relations, as follows: The thoracic part of trachea has several relations as it travels within the superior mediastinum. Copyright [1][2][3], Thisangle of Louisis a synarthrosis, a type of joint characterized as a fibrous connection between two bones (the manubrium and the sternal body in the case of the angle of Louis) which does not allow any significant movement. Instant Anatomy. Am J Roentgenol Radium Ther Nucl Med. Kim Bengochea, Regis University, Denver. It travels inferiorly into the superior mediastinum , bifurcating at the level of the sternal angle (forming the right and left main bronchi). Bifurcation of the trachea. Common causes of congenital stridor in infants. Last reviewed: October 25, 2022 1988 Nov;6(4):639-69. The inferior thyroid veins, manubrium of sternum and attachments of sternohyoid and sternothyroid muscles. Fig 4 Diagram showing the effects of an acute asthma exacerbation upon the small airways. The tracheal bifurcation angle can have a wide range of normal values in patients and can vary significantly in serial radiographs. This is particularly useful when counting ribs to identify landmarks as rib one is often impalpable. Access free multiple choice questions on this topic. All content published on Kenhub is reviewed by medical and anatomy experts. The bronchi derive innervation from pulmonary branches of the vagus nerve (CN X). If the blood supply to the sternum is poor or if the adjacent ribs have been traumatized, the wires can loosen, and this can result in sternal dehiscence. All rights reserved. This is where the 2nd rib joins with the sternum. All content published on Kenhub is reviewed by medical and anatomy experts. There was only a weak correlation between bifurcation angle and height or width or the thorax. (Carina not labeled; the ridge that separates the left and right bronchus. It can be palpated easily. Importantly, the ribcage provides support for and allows ventilation through movement of the thoracic cage. Each main bronchus branches out into smaller intrapulmonary bronchi that supply air to the various pulmonary lobes and segments. Please enable it to take advantage of the complete set of features! The information we provide is grounded on academic literature and peer-reviewed research. Sternal angle (of Louis) Bifurcation of trachea Arch of aorta begins and ends Azygous vein enters superior vena cava: T5-8: Body of sternum: T6: Upper border of liver: T7: Inferior angle of the scapula: T8: Caval opening in the diaphragm Phrenic nerves traverse diaphragm: T8/9: Xiphisternal junction: T9: Xiphoid Superior epigastric vessels . The carinal bifurcation of the trachea into the left and right main bronchi. 9. 2012 Jan-Feb;53(1):28-33. doi: 10.1111/j.1740-8261.2011.01871.x. This website uses cookies to improve your experience while you navigate through the website. {"url":"/signup-modal-props.json?lang=us"}, Anderson J, Bickle I, Bell D, et al. These cookies do not store any personal information. On this Wikipedia the language links are at the top of the page across from the article title. In the child, the trachea is smaller, more deeply placed, and more movable than in the adult. (1995) AJR. Many different sternal anomalies can occur following abnormal development. Required fields are marked *. The Angle of Louis. The 2nd rib is continuous with the sternal angle; slide your finger down to localize the 2nd intercostal space. 5. This plane passes anteriorly through the sternal angle and posteriorly to the inferior margin of fourth thoracic vertebra. Bronchopulmonary segments are subdivisions of the lung lobes, and act as the functional unit of the lungs. respiratory system quizzes and labeled diagrams. 7. [citation needed], Anatomical dissection of trachea and main bronchi showing the carina. Unable to process the form. The right main bronchus is shorter, wider and courses almost vertically compared to the left one. -The lower end is attached to..? Anterior surface of sternum and costal cartilages. The trachea receives innervation from the pulmonary plexus. It is at the level of the T4-T5 intervertebral disc. The sternal angle is a crucial clinical marker for locating numerous other anatomical . The counting of ribs is essential when one is attempting to make a thoracic incision. http://creativecommons.org/licenses/by-nc-nd/4.0/. It is at the level of the sternal angle - the inferior margin of the fourth thoracic vertebra. It is the synarthrotic joint formed by the articulation of the manubrium and the body of the sternum. official website and that any information you provide is encrypted and grab your free ultimate anatomy study guide! Careers. ADVERTISEMENT: Supporters see fewer/no ads, Please Note: You can also scroll through stacks with your mouse wheel or the keyboard arrow keys. 1. If the wrong rib is counted, access to the internal chest organs can be difficult. Identification of the second rib and thus the second intercostal space inferiorly is also useful when auscultating heart sounds. Sternal blood flow after median sternotomy and mobilization of the internal mammary arteries. The sternum develops at the same time as the rest of the ribcage from mesenchymal bands or bars which develop chondritic tissues as they move ventrally and medially forming cartilaginous shapes of the adult bones. Careers. Sternalis, a rare anatomical variation, occurs in a single-digit percentage of the population (some estimates pointing to roughly 4%). ), which permits others to distribute the work, provided that the article is not altered or used commercially. It marks the level of the transverse thoracic plane which divides the mediastinum into the superior and inferior mediastinum. The counting of ribs is essential when one is attempting to make a thoracic incision. It marks the point at which the costal cartilages of the second rib articulate with the sternum. (1982) AJR. Alveolar is the final portion of the airway and is lined with a single-cell layer of pneumocytes and in proximity to capillaries. Airway Epithelium Dysfunction in Cystic Fibrosis and COPD. The pericardium extends from just superior to the angle of Louis to the level of the xiphisternal joint. 3. As it descends, the trachea is located anteriorly to the oesophagus, and inclines slightly to the right. 2005 Sep;78(933):787-90. doi: 10.1259/bjr/75107416. In diseases such as emphysema that occurs in COPD, the alveoli are damaged or destroyed, which reduces the surface area available for effective gas exchange. Reading time: 10 minutes. These terminal bronchioles branch even further into respiratory bronchioles, which are distinguishable by the presence of alveoli extending from their lumens. Aortic ach begins 8. Alveolar sacs are the blind-ended spaces from which the alveoli clusters are formed and to where they connect. 139 (5): 883-7. The left main bronchus enters the root of the left lung opposite to the sixth thoracic vertebra, passes underneath the aortic arch, and crosses in front of the esophagus, the thoracic duct, and the descending aorta. Get instant access to this gallery, plus: Introduction to the musculoskeletal system, Nerves, vessels and lymphatics of the abdomen, Nerves, vessels and lymphatics of the pelvis, Infratemporal region and pterygopalatine fossa, Meninges, ventricular system and subarachnoid space, respiratory system quizzes and labeled diagrams, Anterolaterally: 16-20 tracheal cartilages, Air transport in and out of the lungs; protection. Tracheostomies and continuous night-time ventilatory support may also be required. Need a refresher on the basic anatomy of the respiratory system before diving into all things bronchi related? 10. The lobar bronchi then bifurcate into several segmental (tertiary) bronchi, each of which supplies a bronchopulmonary segment. Reading time: 13 minutes. Complete fusion of the angle of Louis generally occurs atapproximately 30 years of age. Reference article, Radiopaedia.org (Accessed on 04 Mar 2023) https://doi.org/10.53347/rID-65324, Case 1: splayed to 160 degrees in a mitral heart, View Joseph Anderson's current disclosures, see full revision history and disclosures, acute unilateral airspace opacification (differential), acute bilateral airspace opacification (differential), acute airspace opacification with lymphadenopathy (differential), chronic unilateral airspace opacification (differential), chronic bilateral airspace opacification (differential), osteophyte induced adjacent pulmonary atelectasis and fibrosis, pediatric chest x-ray in the exam setting, normal chest x-ray appearance of the diaphragm, posterior tracheal stripe/tracheo-esophageal stripe, obliteration of the retrosternal airspace, Anti-Jo-1 antibody-positive interstitial lung disease, leflunomide-induced acute interstitial pneumonia, fibrotic non-specific interstitial pneumonia, cellular non-specific interstitial pneumonia, respiratory bronchiolitisassociated interstitial lung disease, diagnostic HRCT criteria for UIP pattern - ATS/ERS/JRS/ALAT (2011), diagnostic HRCT criteria for UIP pattern - Fleischner society guideline (2018), domestically acquired particulate lung disease, lepidic predominant adenocarcinoma (formerly non-mucinous BAC), micropapillary predominant adenocarcinoma, invasive mucinous adenocarcinoma (formerly mucinous BAC), lung cancer associated with cystic airspaces, primary sarcomatoid carcinoma of the lung, large cell neuroendocrine cell carcinoma of the lung, squamous cell carcinoma in situ (CIS) of lung, minimally invasive adenocarcinoma of the lung, diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH), calcifying fibrous pseudotumor of the lung, IASLC (International Association for the Study of Lung Cancer) 8th edition (current), IASLC (International Association for the Study of Lung Cancer) 7th edition (superseeded), 1996 AJCC-UICC Regional Lymph Node Classification for Lung Cancer Staging, the tracheal bifurcation angle may be measured either as the interbronchial angle or the subcarinal angle, can have a wide range of normal values and its absolute measurement is of little diagnostic value, widening of the tracheal bifurcation angle is an insensitive and non-specific sign which must be interpreted in correlation with the clinical presentation. 2022 Jul 25. The tracheal cartilages are composed of hyaline cartilage and interconnected by fibroelastic tissue. These airways are located in the neck and thorax. Reviewer: The structure of bronchi are very similar to that of the trachea, though differences are seen in the shape of their cartilage. While an angle of tracheal bifurcation greater than 100 may predict left atrial enlargement, this is an insensitive and non-specific sign 4,5. Value of tracheal bifurcation angle measurement as a radiographic sign of left atrial enlargement in dogs. sternal angle of Louis arch of aorta bifurcation of trachea (carina) division between superior and inferior mediastinum azygos vein drains into SVC T8 inferior vena cava hiatus of the diaphragm T9 xiphisternal joint T10 esophageal hiatus of the diaphragm T12 aortic hiatus of the diaphragm L1 also known as transpyloric plane (see article) 72. 1970. These include the bifurcation of the trachea into primary (main stem . 1. MeSH This problem has been solved! Let's remove the manubrium and ascending aorta to see the trachea bifurcate at the sternal angle of Louis. It is roughly at the level of the bifurcation of the trachea. We use cookies to improve your experience on our site and to show you relevant advertising. Philadelphia, PA: Lippincott Williams & Wilkins. In the main bronchi, cartilage rings completely encircle the lumen. 5. These are connected by pores which allow air pressure to equalize between them. Read more. Within the lungs, the main (primary) bronchi branch into lobar (secondary) bronchi. Please enable it to take advantage of the complete set of features! Get instant access to this gallery, plus: Introduction to the musculoskeletal system, Nerves, vessels and lymphatics of the abdomen, Nerves, vessels and lymphatics of the pelvis, Infratemporal region and pterygopalatine fossa, Meninges, ventricular system and subarachnoid space. StatPearls Publishing, Treasure Island (FL). inferiorly by the transverse thoracic plane. Call Us: (02) 9223 2502 . Asthma is a chronic inflammatory disorder of the airways, characterised by hypersensitivity, reversible outflow obstruction and bronchospasm. It's an important structure because it marks the location of other structures in the body. This website uses cookies to improve your experience while you navigate through the website. FOIA sublaryngeal airway is also known as. Please note that some texts differ slightly on certain levels and levels may be altered by patient positioning (supine versus erect) and patient body habitus. The angle decreases by 10 on expiration. Asthma attacks are acute exacerbations of the condition whereby a trigger (e.g. The superior articular surface is located on the inferior border of the manubrium. The bronchi, the main bifurcation of the trachea, are similar in structure but have complete circular cartilage rings. 2017 Jun;10(2):188-192. doi: 10.21053/ceo.2016.00185. The angle of tracheal bifurcation may be widened in the following conditions due to the mechanical splaying of the bronchi 1,2: The mean angle of tracheal bifurcation is 60 (+/-10 ), i.e. The trachea (windpipe) is found inferior to the thyroid cartilage and superior to division into the left and right main bronchus. Read more. government site. The right main bronchus has a larger diameter and is aligned more vertically than the left, Lobar bronchi: Two on the left and three on the right supply each of the main lobes of the lung. The lobes of thyroid gland which extend inferiorly until the sixth tracheal cartilage. Berdajs D, Znd G, Turina MI, Genoni M. Blood supply of the sternum and its importance in internal thoracic artery harvesting. In contrast, the left main bronchus is smaller in size, but longer in length (~5 cm, as opposed to 2-3 cm long) than the right main bronchus. Together, with the capillaries, they form the air-blood barrier. The smallest airways, bronchioles do not contain any cartilage or mucus-secreting goblet cells. Learn the anatomy of all the remaining organs easily and efficiently using Kenhubs respiratory system quizzes and labeled diagrams! Alavi SM, Keats TE, OBrian WM. and transmitted securely. Microscopic anatomy of the lower respiratory tract of the grey short-tailed opossum (Monodelphis domestica). 2023 Essom-Sherrier C, Neelon FA. 2018;2018:1309746. Epub 2016 Jun 18. The segmental bronchi divide into many smaller bronchioles that divide into terminal bronchioles, and then into respiratory bronchioles, which divide into 2 to 11 alveolar ducts. Haskin PH, Goodman LR. At the time the article was last revised Luke Plant had no recorded disclosures. Tracheomalacia is a congenital anomaly that affects the development of the tracheal cartilage rings. It is divided into two parts: The trachea and bronchi collectively form the tracheobronchial tree. It consists of connective tissue that contains mucus glands, smooth muscle, vessels, nerves and lymphatics. The hypopharynx connects the oropharynx to the esophagus and the larynx, the region of pharynx below the hyoid bone. Bookshelf Ann Clin Lab Sci. 151 (2): 307-8. differential diagnoses of airspace opacification, presence of non-lepidic patterns such as acinar, papillary, solid, or micropapillary, myofibroblastic stroma associated with invasive tumor cells. Accessibility Altogether there are around 300 million alveoli in adult lungs, providing a large surface area for adequate gas exchange. In between these runs the neurovascular bundle. Parasympathetic supply originates from the recurrent laryngeal nerves, branches of the vagus nerve. The trachea consists of four histological layers. [4] The azygos vein crosses right to the trachea above the carina. 2022 May;52(3):511-525. Fig. [7][8]They later ossify in a craniocaudal direction. The sternum can also recede in pectus excavatum (known as funnel chest). Now that you've learned everything about the trachea, it's time to put that knowledge to the test with the following quiz! The mucociliary excretion is facilitated by the coughing reflex. Secondary bronchi will further subdivide into the tertiary bronchi, which are also called the segmental bronchi, each of which supplies a bronchopulmonary segment. [citation needed], The bronchial arteries supply the carina and the rest of the lower trachea. 95% of the patients have normal values between 40-80 . You are not required to obtain permission to distribute this article, provided that you credit the author and journal. The manubrium and proximal sternum are routinely opened upduring open-heart surgery. Bifurcation of trachea at sternal angle What are the 3 components of the middle. 2015 Sep;59(9):533-41. doi: 10.4103/0019-5049.165849. As it descends, the trachea is located anteriorly to the oesophagus, and inclines slightly to the right. However, studies have shown that these repairs do not always lead to improvements in scoliosis and ribcage remodeling. Anat Histol Embryol. vein joining superior vena cava. A bronchopulmonary segment is a division of the lung that is separated from the rest of the lung by a septum of connective tissue, which is an advantage during surgery since a bronchopulmonary segment can be removed without affects other nearby segments. The respiratory portion includes the respiratory bronchiole, alveolar ducts, alveolar sacs, and alveoli. Each alveolar duct has 5 or 6 associated alveolar sacs. Make the changes yourself here! This article will discuss the anatomy of the bronchi. American journal of roentgenology. This is because the manubrium normally angles posteriorly on the body of the sternum, forming a raised feature referred to as the sternal angle. 3WGUVKQP PUYGTU TO JCU QPG OCKP PCPEKCN IQCN YJKEJ KU VQ CZKOKG UCNGU. Bronchitis is defined as inflammation of the bronchi, which can be an acute or chronic condition. By visiting this site you agree to the foregoing terms and conditions. It presents with signs and symptoms of respiratory distress such as dyspnea, cough, stridor, wheezing and tachypnea. Lower border of T4. The tracheal bifurcation is the point at which the trachea divides into, and is continuous with, the two main or principal bronchi. Initially there are many generations of conducting bronchioles, which transport air but lack glands and are not involved in gas exchange. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. In such cases, a tracheal tube or airway stents are used to bypass the obstruction and maintain the trachea open. 1995 May;164(5):1089-92. doi: 10.2214/ajr.164.5.7717208. Original Author(s): Vicky Theakston Last updated: October 31, 2020 The angle of Louis is the eponymous name given to the sternal angle which is the palpable anatomical feature formed from the manubriosternal junction. They are initially ciliated and graduate to the simple columnar epithelium and their lining cells no longer contain mucous producing cells. Gross anatomy The carina represents the inferior termination of the trachea into the right and left main bronchi. A helpful mnemonic for remembering the structures that lies at the level of the sternal angle is RATPLANT: Rib (2 nd), Aortic arch, Trachea birfurcation, Pulmonary trunk bifurcation, Left recurrent laryngeal (and Ligamentum arteriosum), Azygos vein, Nerves - cardiac plexus, Thoracic duct. The free ends of these rings are supported by the trachealis muscle. Brichon PY, Wihlm JM. The intercostal space superior and inferior to the angle of Louisis spanned by a triple layer of muscle. These puffers contain a bronchodilator that will help soothe the constricted bronchi to allow them to expand the airways and allow more airflow again. Trachea -> bifurcation -> main bronchi -> lobar bronchi -> segmental bronchi -> -> bronchi of sixth generation -> terminal bronchioles -> respiratory bronchioles -> alevolar duct -> alveolar sac -> alveolus, Asthma, aspiration, bronchitis, infant respiratory distress syndrome (IRDS), elastic fibers in the interalveolar septum, Bronchioles and alveoli (overview) - Paul Kim, Left main bronchus (ventral view) -Begoa Rodriguez, Tracheal bifurcation (ventral view) -Yousun Koh, Right lobar bronchi (ventral view) - Paul Kim, Main bronchus (lateral-right view) -Yousun Koh, Type II pneumocytes (histological slide) - Smart In Media, Respiratory bronchiole (histological slide) - Smart In Media, Fresh lungs in a cadaver -Prof. Carlos Surez-Quian. Am J Roentgenol Radium Ther Nucl Med. Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. Projection of bifurcation of trachea -ant. Bookshelf 2023 But opting out of some of these cookies may affect your browsing experience. 3D-measurement of tracheobronchial angles on inspiratory and expiratory chest CT in COPD: respiratory changes and correlation with airflow limitation. Clinically oriented anatomy. Federal government websites often end in .gov or .mil. Also, the angle varies, sometimes by 20%, in serial radiographs. In addition, the lateral relations of the thoracic part are different on the right and left sides; For more details about the trachea, take a look at the articles, videos, quizzes and labeled diagrams in the following study unit: The trachea is supplied with arterial blood by tracheal branches of inferior thyroid arteries, that stem from the thyrocervical trunk. In tracheomalacia, the tracheal cartilages become abnormally soft. document. Azygos vein join SVC. Fink-Bennett DM, Shapiro EE. National Library of Medicine HHS Vulnerability Disclosure, Help 139 (5): 879-82. The goblet cells lining the trachea secrete mucus which traps any unwanted substances. In addition to oxygen and carbon dioxide, environmental air also contains many potentially harmful agents such as pathogens, debris, gases and chemicals. Tracheal carinal angle and left atrial size. This category only includes cookies that ensures basic functionalities and security features of the website. Ball M, Falkson SR, Adigun OO. By Bibi Saint-Pol [CC BY-SA 3.0], via Wikimedia Commons, [caption id="attachment_10035" align="aligncenter" width="260"], [caption id="attachment_11583" align="aligncenter" width="219"], [caption id="attachment_11584" align="aligncenter" width="356"], [caption id="attachment_11542" align="aligncenter" width="1000"]. The trachea is only one part of the respiratory system. This site needs JavaScript to work properly. Bronchi will branch into smaller tubes that become bronchioles. It overlies the aortic arch on the left and the superior vena cava on the right. Structural movements will be more pronounced in portions of the bronchial tree that are more distal to the pulmonary hilum. The trachea is a D-shaped fibrocartilaginous respiratory organ. I would honestly say that Kenhub cut my study time in half. Reference article, Radiopaedia.org (Accessed on 04 Mar 2023) https://doi.org/10.53347/rID-57629. A wide range of normal values was found. The carina of trachea (also: "tracheal carina"[1]) is a ridge[1] of cartilage[2] at the base of the trachea separating the openings of the left and right main bronchi. Venous blood is drained to the inferior thyroid venous plexus, which empties into the brachiocephalic veins. In addition, the mucous membrane will undergo a transition from ciliated pseudostratified columnar epithelium to simple cuboidal epithelium to simple squamous epithelium. The left pulmonary artery is found lying initially above the left main bronchus, then later in front of it. Clipboard, Search History, and several other advanced features are temporarily unavailable. HHS Vulnerability Disclosure, Help Bronchi are plural for bronchus and represent the passageways leading into the lungs. The trapped particles are then removed from the trachea via the mucociliary rejection current. -. The trachea, bronchi and bronchioles form the tracheobronchial tree a system of airways that allow passage of air into the lungs, where gas exchange occurs. Patients with chronic bronchitis often also suffer from chronic obstructive pulmonary disease (COPD), with common associations with smoking or long-term exposure to irritants. This is where the 2nd rib joins with the sternum. Fig 1 Overview of the tracheobronchial tree. The outermost intercostal muscles (external intercostals) have fibers running in an oblique direction. After sixth generation, the passageways are too narrow to be supported by the cartillage, and thus are called bronchioles(small bronchi). -, De Rose V, Molloy K, Gohy S, Pilette C, Greene CM. In: StatPearls [Internet]. As the volume of the lung changes with the thoracic cavity during ventilation (respiration), the entire bronchial tree will move within the lung. [9]Importantly in patients having internal mammary harvesting, these branches anastomose with the intercostal arteries and therefore indirectly with the posterior intercostal arteries providing a possible collateral blood flow. The medical information on this site is provided as an information resource only, and is not to be used or relied on for any diagnostic or treatment purposes. This article will describe the anatomy and function of the trachea. The segmental bronchi undergo further branching to form numerous smaller airways the bronchioles. As the branching continues throughout the bronchial tree, the amount of hyaline cartilage in the walls decrease until it reaches the bronchioles, which have a cartilage-free wall. Alveoli are tiny air-filled pockets with thin walls (simple squamous epithelium), and are the sites of gaseous exchange in the lungs. The sternal angle (also known as the angle of Louis, angle of Ludovic or manubriosternal junction) is the synarthrotic joint formed by the articulation of the manubrium and the body of the sternum.[1][2]. [citation needed], Tracheobronchial injury, an injury to the airways, occurs within 2.5cm of the carina 60% of the time. The first two nerves supply the proximal sternum and manubrium. Explain the . The trachea divides into the left and right main bronchus, which is known as the tracheal bifurcation, at the level of the sternal angle and of the fifth thoracic vertebra (or up to two vertebrae higher or lower, depending on lung volume changes due to breathing). This information is intended for medical education, and does not create any doctor-patient relationship, and should not be used as a substitute for professional diagnosis and treatment.