Respiratory System: Anatomy PDF

First year, Second semester, Anatomy subject.((3)). 3rd lecture. Respiratory system. Function of respiratory system: Pulmonary system. consists of several organs that function as a whole to oxygenate the body through the process of respiration (breathing). The re...

First year, Second semester, Anatomy subject.((3)). 3rd lecture. Respiratory system. Function of respiratory system: Pulmonary system. consists of several organs that function as a whole to oxygenate the body through the process of respiration (breathing). The respiratory tract is divided into two sections at the level of the vocal cords; the upper and lower respiratory tract. The upper respiratory tract includes the nasal cavity, paranasal sinuses, pharynx and the portion of the larynx above 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 often considered as part of the lower respiratory tract, but are sometimes described as a separate entity. They contain the respiratory bronchioles, alveolar ducts, alveolar sacs and alveoli.  Upper respiratory tract: Nasal cavity, paranasal sinuses, pharynx and larynx above the vocal cords. Functions Upper respiratory tract: conduction, filtration, humidification and warming of inhaled air. The upper respiratory tract: Refers to the parts of the respiratory system that lie outside the thorax, more specifically above 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, also known as the respiratory epithelium. The exceptions are some parts of the pharynx and larynx.. 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 contain sebaceous glands and hair follicles that serve to prevent any larger harmful particles from passing into the nasal cavity. Pharynx: After passing through the nasal cavity and paranasal sinuses, the inhaled air exits through the choanae into the pharynx. The pharynx is a funnel-shaped muscular tube that contains three parts; the nasopharynx, oropharynx and laryngopharynx. The nasopharynx is the first and superior most part of the pharynx, 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 upwards during swallowing to close off the nasopharynx and prevent food from entering the nasal cavity. The oropharynx is found posterior to the oral cavity and communicates with it through the oropharyngeal isthmus. The oropharynx is a pathway for both the air incoming from the nasopharynx and the food incoming from the oral cavity. Thus, the oropharynx is lined with the more protective non-keratinizing stratified squamous epithelium. The laryngopharynx (hypopharynx) is the most inferior part of the pharynx. It is the point 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 next and last portion of the upper respiratory tract is the superior part of the larynx. The larynx is a complex hollow structure found anterior to the esophagus. It is supported by a cartilaginous skeleton connected by membranes, ligaments and associated muscles. Above 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). Besides its main function to conduct the air, the larynx also houses the vocal cords that participate in voice production. The laryngeal inlet is closed by the epiglottis during swallowing to prevent food or liquid from entering the lower respiratory tract.