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INTRODUCTION

Upper airway management is an important tool both in life-threatening medical situations and when considering quality of

life conditions. Thus, understanding the anatomy of the upper airway is of critical importance. Whether it is for normalintubation methods or for necessary surgical intervention to establish an airway, knowing the minutiae of the course that a

breath takes from the oral fissure or nares to the trachea is vital. Moreover, exploring the anatomy of the upper airway(comprised of the nasal cavity, oral cavity, the pharynx, and larynx) is indicative to understanding surgical procedures.

Since the anatomical features show that this airway is vulnerable to damage from trauma and the potential for obstruction isrelatively high, we will focus on intubation procedures such as passing nasopharyngeal, oropharyngeal and laryngealmask airways, as well as thosethat establish an alternate airway; the tracheostomy and cricothyrotomy.

Anatomy:Nasopharyngeal Airway (NPA) -- The nasopharyngeal airway functions in establishing an air passage between the nose andthe oropharynx, it accomplishes this by passing through both the nasal cavity and nasopharynx. The nasal cavity extendsfrom the nares to the choanae providing a junction to the beginning of the nasopharynx. The nasal cavity is divided into

left and right by the nasal septum which acts as the medial wall. The lateral wall is formed mainly by the maxilla, thefloor by the hard palate and the roof by the cribriform plate of the ethmoid bone. Adjacent to the septum lies theinferior nasal concha, lateral to which the NPA should pass.The superior-most aspect of the pharynx is the nasopharynx. It stretches from the base of the skull to the upper surface of

the soft palate at the level of the C1 vertebra, and, in front, communicates with the nose through the choanae. The airpassageway in this area is lined by ciliated pseudo-stratified columnar epithelium. A key feature visible in the superolateralaspect of the nasopharynx is the opening of the pharyngotympanic tube. The NPA enters the nasopharynx through thechoanae and curves inferiorly to pass through the velopharynx, terminating in the superior aspect of the oropharynx.

Oropharyngeal Airway (OPA) -- The oropharyngeal airway functions in creating an air passage between the oral cavity and

the oropharynx. The upper respiratory tract commences in the oral cavity, which sits behind the teeth and terminates at theoropharyngeal isthmus. Both the soft and hard palates form the roof of the oral cavity while the floor is composed of themylohyoid and geniohyoid muscles. However, most of the floor is occupied by the tongue, which in the unconscious mayobstruct the oropharynx. Another notable feature of the oral cavity is the palatine uvula, which is pushed superiorly on

insertion of an OPA. The oropharyngeal isthmus marks the border between the oral cavity and the oropharynx.

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Laryngeal Mask Airway (LMA) -- The Laryngeal Mask airway is utilised so as to form and maintain a direct air passagebetween the oral cavity and the larynx. The LMA passes through the same structures in the oral cavity as before, however it

differs from an OPA as it deviates inferiorly through the oropharynx to insert into the hypopharynx. The oropharynxextends from thelevel of the soft palate superiorly (C1) to the superior border of the epiglottis (C3). On each of the lateral

walls lies two diverging arches, each formed by the palatoglossal and the palatopharyngeal muscles. Between these twoarches lies the tonsillarfossa which contains the palatinetonsil (a mass of lymphoid tissue). The posterior wall of the

oropharynx is formed by three pharyngealconstrictors (superior, middle, and inferior constrictor muscles) which continueinto the laryngopharynx. The LMA cuff sits in the hypopharynx, which is situated from the superior border of the epiglottis(C3) to the inferior border of the cricoid cartilage, and becomes continuous with the oesophagus.Endotracheal Tube (ETT) -- The Endotracheal tube can be inserted in either the nasal or oral cavities, in both cases the

anatomical landmarks are highly similar to the previously stated methods of intubation. The ETT then passes through thepharynx until it reaches the laryngealinlet. Here the ETT must pass through the abducted vocalfolds and through theremainder of the larynx. The cuff is then inflated to keep the ETT in place.

The features of the anterior triangles of the neck are important in surgical upper airway management. Procedures such ascricothyrotomies and tracheostomies require knowledge of important landmarks. Their superior margins, the base of thetriangles, are formed by the inferior surface of the mandible, their apices are at the supraclavicularnotch, and the lateral

borders are formed by the sternocleidomastoid muscle. The anterior midline forms the common anterior border of thetriangle. One structure that is palpable is the thyroidnotch of the thyroidcartilage located just above the laryngealprominence. One can also palpate the cricothyroid ligament, located in a small depression inferior to the inferior surface ofthe thyroid cartilage and superior to the arch of the cricoidcartilage.

Cricothyrotomy This is a procedure in which an alternate airway is created in the cricothyroid space via needle in anemergency. This creates an opening in the larynx, allowing for emergency ventilation in cases of obstruction of the upperrespiratory tract.Tracheostomy -- This is an elective procedure which creates a stoma in the trachea, this allows for long-term ventilation.

The trachea is a tubular structure constructed of 15 to 20 C-shaped cartilaginous rings separated by fibrous muscular tissue

which form the supporting framework. The upper tracheal rings and cricoid cartilage lie deep to the thyroid gland and are

connected to it via its fibrous capsule. The thyroid gland itself lies deep to the sternothyroid and sternohyoid muscles of

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the neck. Certain vessels supplying and draining the thyroid; the inferior thyroid veins and the thyroid ima(only present

in 10% of people) run along the anterior surface of the trachea and must be considered during surgical procedures.