Exercise 36 Review Sheet Anatomy of the Respiratory System
Respiratory organization
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The respiratory system, also called the pulmonary arrangement, consists of several organs that function as a whole to oxygenate the body through the process of respiration (breathing). This process involves inhaling air and conducting it to the lungs where gas exchange occurs, in which oxygen is extracted from the air, and carbon dioxide expelled from the body. The respiratory tract is divided into 2 sections at the level of the song cords; the upper and lower respiratory tract.
- The upper respiratory tract includes the nasal cavity, paranasal sinuses, pharynx and the portion of the larynx in a higher place the vocal cords.
- The lower respiratory tract includes the larynx below the vocal cords, the trachea, bronchi, bronchioles and the lungs.
The lungs are most oft considered every bit part of the lower respiratory tract, merely are sometimes described as a carve up entity. They contain the respiratory bronchioles, alveolar ducts, alveolar sacs and alveoli.
This article will discuss the anatomy and function of the respiratory system.
| Upper respiratory tract | Nasal cavity, paranasal sinuses, pharynx and larynx above the song cords |
| Lower respiratory airways | Larynx below the vocal cords, trachea, bronchi, bronchioles and lungs |
| Functions | Upper respiratory tract: conduction, filtration, humidification and warming of inhaled air Lower respiratory tract: conduction and gas substitution |
Contents
- Upper respiratory tract
- Nasal cavity
- Paranasal sinuses
- Pharynx
- Larynx
- Lower respiratory tract
- Tracheobronchial tree
- Lungs
- Microanatomy
- Function
- Clinical aspects
- Upper respiratory tract infections
- Lower respiratory tract infections
- Sources
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Upper respiratory tract
The upper respiratory tract refers to the parts of the respiratory organisation that lie outside the thorax, more than specifically in a higher place the cricoid cartilage and vocal cords. It includes the nasal cavity, paranasal sinuses, pharynx and the superior portion of the larynx. Most of the upper respiratory tract is lined with the pseudostratified ciliated columnar epithelium, likewise known equally the respiratory epithelium. The exceptions are some parts of the pharynx and larynx.
Nasal cavity
The upper respiratory tract begins with the nasal cavity. The nasal cavity opens anteriorly on the face through the two nares, and posteriorly into the nasopharynx through the two choanae. The floor of the nasal cavity is formed by the hard palate, while the roof consists of the cribriform plate of the ethmoid bone posteriorly, and the frontal and nasal bones anteriorly. The nares and anterior portion of the nasal cavity incorporate sebaceous glands and hair follicles that serve to foreclose whatsoever larger harmful particles from passing into the nasal cavity.
The lateral walls of the nasal cavity contain three bony projections called nasal conchae (superior, middle and inferior), which increment the surface surface area of the nasal cavity. The nasal conchae also disrupt the laminar flow of air, making it tiresome and turbulent, thereby helping to humidify and warm up the air to body temperature.
The roof of the nasal cavity contains the olfactory epithelium which consists of specialized sensory receptors. These receptors pick upwards airborne odorant molecules and transform them into activeness potentials that travel via the olfactory nerve to the cognitive cortex, allowing the encephalon to register them and provide a sense of scent.
Some other pathway for the entry of air is the oral cavity. Although information technology is not classified as a part of the upper respiratory tract, the oral cavity provides an alternative road in the case of obstruction of the nasal cavity. The oral cavity opens anteriorly on the face through the oral fissure, while posteriorly, it opens into the oropharynx through a passage chosen the oropharyngeal isthmus.
Paranasal sinuses
Several bones that form the walls of the nasal cavity incorporate air-filled spaces chosen the paranasal sinuses, which are named afterwards their associated bones; maxillary, frontal, sphenoidal and ethmoidal sinuses.
The paranasal sinuses communicate with the nasal cavity via several openings, and thereby also receive the inhaled air and contribute to its humidifying and warming. In addition, the mucous membrane and respiratory epithelium that lines both the nasal cavity and the paranasal sinuses traps any harmful particles, dust or bacteria.
Throat
After passing through the nasal cavity and paranasal sinuses, the inhaled air exits through the choanae into the throat. The pharynx is a funnel-shaped muscular tube that contains three parts; the nasopharynx, oropharynx and laryngopharynx.
- The nasopharynx is the first and superiormost office of the throat, found posterior to the nasal cavity. This part of the pharynx serves only as an airway, and is thus lined with respiratory epithelium. Inferiorly, the uvula and soft palate swing up during swallowing to shut off the nasopharynx and prevent food from entering the nasal cavity.
- The oropharynx is found posterior to the mouth and communicates with it through the oropharyngeal isthmus. The oropharynx is a pathway for both the air incoming from the nasopharynx and the nutrient incoming from the oral cavity. Thus, the oropharynx is lined with the more protective non-keratinizing stratified squamous epithelium.
- The laryngopharynx (hypopharynx) is the near junior part of the throat. It is the betoken at which the digestive and respiratory systems diverge. Anteriorly, the laryngopharynx continues into the larynx, whereas posteriorly it continues as the esophagus.
Larynx
Following the laryngopharynx, the side by side and terminal portion of the upper respiratory tract is the superior function of the larynx. The larynx is a complex hollow structure plant anterior to the esophagus. It is supported by a cartilaginous skeleton connected past membranes, ligaments and associated muscles. Higher up the vocal cords, the larynx is lined with stratified squamous epithelium like the laryngopharynx. Below the vocal cords, this epithelium transitions into pseudostratified ciliated columnar epithelium with goblet cells (respiratory epithelium).
As well its main part to conduct the air, the larynx besides houses the vocal cords that participate in voice production. The laryngeal inlet is airtight by the epiglottis during swallowing to preclude food or liquid from entering the lower respiratory tract.
If you lot want to larn more nigh the anatomy and function of the larynx, take a look at the study unit beneath!
Lower respiratory tract
The lower respiratory tract refers to the parts of the respiratory arrangement that lie below the cricoid cartilage and vocal cords, including the junior part of the larynx, tracheobronchial tree and lungs.
Tracheobronchial tree
The tracheobronchial tree is a portion of the respiratory tract that conducts the air from the upper airways to the lung parenchyma. It consists of the trachea and the intrapulmonary airways (bronchi and bronchioles).The trachea is located in the superior mediastinum and represents the torso of the tracheobronchial tree. The trachea bifurcates at the level of the sternal angle (T5) into the left and correct principal bronchi, i for each lung.
- The left master bronchus passes inferolaterally to enter the hilum of the left lung. On its form, it passes inferior to the arch of the aorta and inductive to the esophagus and thoracic aorta.
- The correct main bronchus passes inferolaterally to enter the hilum of the right lung. The right main bronchus has a more vertical course than its left counterpart and is as well wider and shorter. This makes the right bronchus more susceptible to strange torso impaction.
As they reach the lungs, the master bronchi branch out into increasingly smaller intrapulmonary bronchi. The left master bronchus divides into two secondary lobar bronchi, while the right primary bronchus divides into 3 secondary lobar bronchi that supply the lobes of the left and correct lung, respectively.
Each of the lobar bronchi further divides into tertiary segmental bronchi that aerate the bronchopulmonary segments. The segmental bronchi and then requite rise to several generations of intrasegmental (conducting) bronchioles, which end equally terminal bronchioles. Each terminal bronchiole gives ascension to several generations of respiratory bronchioles. Respiratory bronchioles extend into several alveolar ducts, which pb into alveolar sacs, each of which contains many grape-similar outpocketings called alveoli. Since they comprise alveoli, these structures mark the site where gas commutation begins to occur.
Lungs
The lungs are a pair of spongy organs located within the thoracic cavity. The right lung is larger than the left lung and consists of three lobes (superior, centre and junior), which are divided by two fissures; oblique and horizontal fissure. The left lung has simply two lobes (superior and inferior), divided past one oblique fissure.
Each lung has three surfaces, an apex and a base. The surfaces of the lung are the costal, mediastinal and diaphragmatic surface, which are named later on the adjacent anatomical construction which that surface faces. The mediastinal surface connects the lung to the mediastinum via its hilum. The apex of the lung is where the mediastinal and costal surfaces run into. It is the most superior portion of the lung, that extends into the root of the cervix. The base is the lowest concave part of the lung that rests upon the diaphragm.
Each hilum of the lung contains the post-obit:
- Principal bronchus
- Pulmonary artery
- Ii pulmonary veins
- Bronchial vessels
- Pulmonary autonomic plexus
- Lymph nodes and vessels
Microanatomy
On the microscopic level, the lower respiratory tract is characterized by several changes of epithelial lining, serving different purposes. Beginning from the inferior part of the larynx to the tertiary segmental bronchi, the lower respiratory tract is lined with pseudostratified ciliated columnar epithelium with goblet cells. The goblet cells produce fungus that lubricates and protects the airway by trapping whatsoever inhaled harmful particles. These trapped particles are then propelled towards the upper respiratory tract by the cilia of the epithelial cells and somewhen expelled by coughing.
As the larger 3rd segmental bronchi separate into smaller bronchi, the epithelium begins to change from respiratory epithelium to a uncomplicated columnar ciliated epithelium. This epithelium is continued in the larger terminal bronchioles, and transitions into a simple cuboidal epithelium in smaller terminal bronchioles. The epithelium of the concluding bronchioles contains exocrine bronchiolar cells chosen club cells, formerly known every bit Clara cells. These are non-ciliated cuboidal cells that contribute to the product of surfactant. In add-on, the concluding bronchioles comprise polish muscle in their walls, that allows for bronchoconstriction and bronchodilation to occur.
Last bronchioles and so branch into respiratory bronchioles, which are too lined by unproblematic cuboidal epithelium. The walls of the respiratory bronchioles extend into alveoli, and the epithelium changes into a elementary squamous epithelium equanimous of blazon I and type II pneumocytes. Type I pneumocytes are sparse, squamous cells that carry out the gas commutation, while type Ii pneumocytes are larger cuboidal cells that produce surfactant.
Role
The primary office of the respiratory system is pulmonary ventilation, which is the move of air betwixt the atmosphere and the lung by inspiration and expiration driven past the respiratory muscles. The respiratory arrangement works as a whole to excerpt the oxygen from the inhaled air and eliminate the carbon dioxide from the body by exhalation. The upper respiratory mainly has an air-conducting function, while the lower respiratory tract serves both the conducting and respiratory functions.
Besides its main role to conduct the air to the lower respiratory tract, the upper respiratory also performs several other functions. Equally mentioned earlier, the nasal crenel and paranasal sinuses change the backdrop of the air by humidifying and warming it in club to prepare it for the procedure of respiration. The air is too filtered from grit, pathogens and other particles by the nasal pilus follicles and the ciliary epithelium.
The portion of the lower respiratory tract, starting from the respiratory bronchioles, is the place where gas commutation begins to occur. This process is also known as external respiration, in which the oxygen from the inhaled air diffuses from the alveoli into the adjacent capillaries, while the carbon dioxide diffuses from the capillaries into the alveoli to be exhaled. The newly oxygenated blood then goes on to supply all the tissues in the body and undergoes internal respiration. This is the procedure in which the oxygen from the systemic circulation exchanges with carbon-dioxide from the tissues. Overall, the difference between external and internal respiration is that the old represents gas substitution with the external environment and takes place in the alveoli, while the latter represents gas commutation within the body and takes identify in the tissues.
To learn more than most the complex respiratory system and solidify what you already learned in this commodity, head over to our respiratory organization quizzes and labeled diagrams!
Clinical aspects
Upper respiratory tract infections
Upper respiratory tract infections are contagious infections that can exist caused by a diversity of bacteria and viruses. The most mutual causing agents are flu virus (the influenza), rhinoviruses and streptococcus bacteria. Depending on which part of the upper respiratory tract is affected, these infections may accept dissimilar types, such equally rhinitis, sinusitis, pharyngitis, epiglottitis, laryngitis and others.
The cold is the nigh common type of upper respiratory tract infection. Information technology is a viral infection that usually involves the olfactory organ and throat, but other parts can exist afflicted also. The symptoms usually include sore throat, coughing, sneezing, runny nose, headache, and fever.
Lower respiratory tract infections
Lower respiratory tract infections are infections that impact the parts of the respiratory tract below the vocal cords. These infections tin can affect the airways and manifest as bronchitis or bronchiolitis, or they can touch the lung alveoli and present as pneumonia. These can besides occur in conjunction as bronchopneumonia.
The well-nigh common crusade of lower respiratory tract infections are leaner, but they can too occur due to viruses, mycoplasma, rickettsiae and fungi. These agents invade the epithelial lining, causing inflammation, increased fungus secretion, and impaired mucociliary function. The inflammation and build-upwardly of fluid in the lungs and airways may consequence in symptoms such as coughing, fever, sputum production, difficulty animate or in severe cases, airway obstruction and dumb gas commutation.
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