What makes up the upper airway

Sensory function below the level of the vocal cords is transmitted through the recurrent laryngeal nerve. The vagus nerve receives sensory information from the external auditory canal as well as the hypopharynx. Thus, a reflex cough can be provoked by instrumenting the ear for cleaning, and cancer in the hypopharynx results in ear pain [ 13 ]. The tracheobronchial tree : the tracheobronchial airways form a complex series of branching tubes that culminate in the gas exchange area, with the average number of branches approximately Figure 10 [ 15 ].

Anatomical overview of the larynx and tracheobronchial tree. The trachea is a cartilage tissue that can stretch during breathing [ 14 ]. The trachea begins at the level of the cricoid cartilage and extends to the carina at the level of the fifth thoracic vertebra the lower end of the trachea can be seen in oblique radiographs of the chest to extend to the level of the fifth, or in full inspiration the sixth, thoracic vertebra ; this length is 10—15 cm in the adult.

It consists of 16—20 C-shaped cartilaginous rings that open posteriorly and are joined by fibroelastic tissue; the trachealis muscle forms the posterior wall of the trachea [ 4 , 6 , 14 ]. The cartilage at the tracheal bifurcation is the keel-shaped carina, which is seen as a very obvious sagittal protrusion when the trachea is inspected bronchoscopically [ 6 ].

The trachea bifurcates into the right and left main bronchi at the carina. In the adult, the right main bronchus branches out at a more vertical angle than the left main bronchus, as it results in a greater likelihood of foreign bodies and endotracheal tubes entering the right bronchial lumen [ 4 ]. The trachea extends from the neck to the thorax to the midline, but slightly diverges to the right by the aortic arch in the thorax.

At the lower part of the neck, the edges of the sternohyoid and sternothyroid muscles are adjacent to the trachea. This region is covered by the inferior thyroid venules with cross-communication between the anterior jugular venules and the lateral side of the thyroid gland which is branched from the aortic arch or brachiocephalic artery.

Because of this close association with the brachiocephalic artery, erosion by the tracheal wall of the tracheostomy tube can lead to sudden abdominal bleeding [ 6 ]. Laterally, the lateral lobes of the thyroid gland, which are located between the trachea and the carotid sheath [ 14 ], the esophagus, and the recurrent laryngeal nerve, lie in the posterior side [ 6 , 14 ]. Vascular, lymphatic, and nerve supply : the arterial supply to the trachea is derived from the inferior thyroid arteries, and the venous drainage is via the inferior thyroid veins.

Lymphatics pass to the deep cervical, pretracheal, and paratracheal nodes [ 6 ]. Nerve supply is from vagus and recurrent laryngeal nerves for pain and secretomotor functions [ 14 ] and sympathetic supply from the middle cervical ganglion [ 6 ]. In full inspiration, the bifurcation level is at T6. The right main bronchus is shorter, wider, and more perpendicular than the left bronchus. This situation can be explained by the transformation into a shorter and wider structure because the embryologically will feed larger lungs.

This is the result of a greater possibility of foreign bodies and endotracheal tubes entering the right bronchial lumen [ 4 ]. The bronchi are supplied by the bronchial arteries from the aorta and drained by the azygos vein on the right and the hemiazygos vein on the left, and also, some drainage by pulmonary veins and the bronchial veins [ 14 ].

The pediatric airway changes significantly from birth to adulthood. These changes affect the development of the skull, oral cavity, throat, and trachea. The head is larger than the body in infants and young children. Due to the absence of paranasal sinuses, the facial skeleton is smaller in neonates compared with neurocranium. Oral cavity is small at birth.

It grows in the first year of life due to the significant growth of the mandibles and teeth in the following period.

In neonates, the tongue has a flat surface and limited lateral mobility and appears relatively large in the small mouth space. Neonatal laryngeal and tracheal structures are especially important for anesthesiologist. The larynx appears more prominently during direct laryngoscopy, but when compared with adults, the surrounding structure is loosely embedded. External manipulation allows direct laryngoscopic intubation to be easily carried to a position where it is possible. The newborn larynx is conical, but in a larger child, it is approximately cylindrical.

Though the larynx is thought to be widest in the supraglottic region and narrowest in the subglottic region, this suggests that the narrowest portion of the magnetic resonance imaging MRI studies may be in glottic. Also, the cricoid ring is the narrowest part of the neonatal airway and is an ellipsoid-shaped mucosa layer which is highly sensitive to trauma. Bypassing the air leak at this level from the untrained tracheal tube does not guarantee avoidance from the pressure points and the next payment [ 18 ].

Intubation tubes with small tracheal internal diameter cause a significant increase in airway resistance and this can lead to an exaggerated mucosal injury. Verification of the position of the tracheal tube clinically chest movement, auscultation or by other means chest radiography, fluoroscopy, ultrasonography, or bronchoscopy is recommended.

Physiological conditions: in human, the downward movement of the laryngeal structures according to age is the main factor in transaction from nasal breathing to oral breathing. Direct result is the dissociation of the epiglottis and the soft palate. The pediatric airway cannot be assessed in young children without considering very low functional residual capacity. This situation, a high oxygen demand, an increased carbon dioxide production, and an increased closure capacity, is together.

And the situation which is in very low tolerance to apnea appears with this result. This rapidly leads to significant hypoxemia and respiratory acidosis. The smaller the child, the more limited the time is [ 19 , 20 ]. In human, one of the most strongest reflexes is laryngeal reflexes and it can be thought to prevent pulmonary aspiration. These functional reflexes are undernapped by the inner and outer branches of the larynx, recurrent laryngeal nerve, and superior laryngeal nerves.

The afferent innervation of the subglottic part of the larynx and all muscles is also provided by the recurrent laryngeal nerve, except for the cricothyroid scar. The larynx is relatively insensitive to irritant gases that are inhaled but is very sensitive to mechanical or chemical stimuli caused by fluid or solutes. It may produce abnormalities of the head, neck, or upper airway [ 9 ].

Cardiovascular, nervous, musculocutaneous, or excretory system disease is more often tabulated with these abnormalities. Crouzon, Goldenhar, Pierre Robin, and Treacher Collins syndromes are known for their abnormal head and neck. The patients with micrognatia, retrognatia, and macroglossia must be remembered for the congenital diseases in childhood [ 9 ].

The most significant vascular malformations are vascular rings, usually of aortic arch origin, encircling the trachea. Tracheomalacia, congenital tracheal stenosis, shortened trachea, and bronchogenic cysts can contribute to difficult airway management [ 21 ].

Infants with congenital malformation syndromes associated with cardiovascular anomalies and skeletal dysplasia have a shortened trachea significant percentage [ 21 ]. Soft tissue changes that cause airway management difficulties are usually divided into two categories as those that disturb the motion of the airway and limit the movements that disturb the airway by mass effects. Soft tissue changes that limit airway motion usually affect mouth opening.

Microstomy, a feature of Freeman-Sheldon syndrome, is a condition in which the movement of oral tissues that do not respond to stomach relaxation is limited. Other rare diseases that limit the movement of airway tissue include fibrofacial myositis ossificans and dermatomyositis.

The mass effects on the airway due to soft tissue abnormalities may be the result of congenital, end-of-life, or subsequent disease outcomes of surgical interventions [ 22 ]. Macroglossia is one of the most common problems appearing with birth, and the tongue expands and fills the oral cavity, making it difficult to see the larynx. Macroglossia occurs in Beckwith-Wiedemann syndrome, Down syndrome, Sturge-Weber syndrome, and in a variety of dystrophically related syndromes [ 22 ].

Perioperative management in obese patient, including airway management, is an increasing and a worldwide concern for the anesthesiologist. Since obese patients have an increased fatty tissue distributed in a truncal fashion, obesity may have an important and negative impact on the airway patency and respiratory function.

Respiratory function and airway patency can be significantly altered by this change in position [ 23 ]. Airway assessment of the obese patient should be performed with the patient in both the sitting and supine positions. Respiratory function and airway patency can be significantly altered by this change in position [ 24 ].

Body weight may not be as critical as the location of excess weight. Massive weight in the lower abdomen and hip area may be less important than when the weight is in the upper body area. A short, thick, immobile neck caused by cervical spine fat pads will interfere with rigid laryngoscopy. Furthermore, the redundancy of soft tissue structures inside the oropharyngeal and supralaryngeal area may also make visualization of the laryngeal structures difficult.

Mask ventilation should be difficult in the obese patient. When a high positive pressure is required to ventilate the patient, the chance of inflating the stomach is increased. Rapidly oxygen desaturation during apnea, secondary to a reduced functional residual capacity, limits intubation time. In the case of a cannot-intubate-cannot-ventilate situation, access to the neck for transtracheal jet ventilation or establishing a surgical airway emergency tracheostomy or cricothyroidotomy will also be more complex [ 9 ].

Maternal, fetal, surgical, and personal factors in pregnancy cause an increase in the incidence of unsuccessful intubation. The mucosa of the upper respiratory tract becomes more vascular and edematous, which increases the risk of bleeding and swelling in the airway [ 25 ]. These changes cause the Mallampati score to increase as the pregnancy progresses and during labor. Airway edema may be exacerbated by preeclampsia, oxytocin infusion, intravenous fluids, and Valsalva maneuvers during labor and delivery.

A decreased functional residual capacity and increased oxygen requirements accelerate the onset of desaturation during apnea and are further exacerbated in obese patients. Progesterone reduces the lower esophageal sphincter tonus, which results in gastric reflux. Risk of reflux is further increased because of delayed gastric emptying after prolonged painful delivery and opioid administration.

Enlarged breasts can make laryngoscopy difficult [ 26 ]. Airway anatomy may become distorted during prolonged labor or toxemia, leading to an edematous soft tissue encroachment of the upper airway [ 27 ].

At last, in cases of fetal distress or maternal hemorrhage, the emergency nature of the circumstances compounds airway management problems [ 9 ]. Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution 3. Help us write another book on this subject and reach those readers. Login to your personal dashboard for more detailed statistics on your publications. We are IntechOpen, the world's leading publisher of Open Access books.

Built by scientists, for scientists. Our readership spans scientists, professors, researchers, librarians, and students, as well as business professionals. Downloaded: Abstract In this chapter, we scope the importance of functional anatomy and physiology of the upper airway.

Keywords anatomy airway function physiology upper airway. Introduction The upper airway has an important role in conducting air to the lungs. The upper airway 2. Nasal cavity The nose originates in the cranial ectoderm and is composed of the external nose and the nasal cavity [ 2 ].

Oral cavity Oral cavity consists of mouth, palate, teeth, and tongue. Lower airway The tracheobronchial tree : the tracheobronchial airways form a complex series of branching tubes that culminate in the gas exchange area, with the average number of branches approximately Figure 10 [ 15 ].

The main bronchi In full inspiration, the bifurcation level is at T6. Pediatric airway differences The pediatric airway changes significantly from birth to adulthood. Congenital disease It may produce abnormalities of the head, neck, or upper airway [ 9 ]. Obese patients Perioperative management in obese patient, including airway management, is an increasing and a worldwide concern for the anesthesiologist.

Pregnancy Maternal, fetal, surgical, and personal factors in pregnancy cause an increase in the incidence of unsuccessful intubation. More Print chapter. How to cite and reference Link to this chapter Copy to clipboard. The nasal cavities are chambers of the internal nose. In front, the nostrils, or nares, create openings to the outside world. Air is inhaled through the nostrils and warmed as it moves further into the nasal cavities.

Scroll-shaped bones, the nasal conchae, protrude and form spaces through which the air passes. The conchae swirl the air around to allow the air time to humidify, warm, and be cleaned before it enters the lungs. The cilia, along with mucus produced by seromucous and other glands in the membrane, trap unwanted particles. Finally the filtered, warmed air passes out of the back of the nasal cavities into the nasopharynx, the uppermost part of the pharynx.

The paranasal sinuses are four paired, air-filled cavities found inside bones of the skull. These sinuses are named for the skull bones that contain them: frontal, ethmoidal, sphenoidal, and maxillary.

Mucosae line the paranasal sinuses and help to warm and humidify the air we inhale. When air enters the sinuses from the nasal cavities, mucus formed by the muscosae drains into the nasal cavities.

The pharynx, or throat, is shaped like a funnel. The pharynx includes three regions: The nasopharynx is posterior to the nasal cavity and serves only as a passageway for air. The oropharynx lies posterior to the oral cavity and contains the palatine tonsils. Each alveolus is surrounded by capillary blood vessels where oxygen and carbon dioxide exchange at a rapid rate. Click to begin.

Test Complete. Questions Score Minutes. Overall Results Total Questions. Category Results. Return to Dashboard. Practice with questions from this unit. Upper Airway Anatomy Besides being a conduit for moving air in and out, the upper airway is in responsible for warming, humidifying, and purifying the air we breathe every day.

The nasal cavities are lined with moist mucosa that contains mucus-secreting cells, fine hairs, and the olfactory smell receptors. This mucosa warms and filters air as it passes though the cavity and sinuses. Lower Airway Anatomy After passing the larynx air is considered to be in the lower airway, the general path of air at this point is as follows: Trachea , Bronchi , Bronchioles , then the Alveoli.