Anatomy And Basics Of Pediatric Pulmonology

Normal Anatomy

The trachea ends in a bronchus, the major bronchus splits into the left and right bronchi, the bronchioles, and the two lungs. The airway begins at the external nares and travels from the pharynx to the larynx. 

The classification of the airway involves its division into three parts: the extra thoracic extrapulmonary component is the first part of the airway outside the thoracic chamber.  The second portion is the intrathoracic section, which is a portion of the airway that is located inside the thoracic cavity but outside the lung's gas exchange regions. It consists of the external nares, pharynx, larynx, and upper part of the trachea.

The trachea ends in a bronchus, the major bronchus splits into the left and right bronchi, the bronchioles, and the two lungs. The airway begins at the external nares and travels from the pharynx to the larynx. The classification of the airway involves its division into three parts: the extra thoracic extrapulmonary component is the first part of the airway outside the thoracic chamber. The second portion is the intrathoracic section, which is a portion of the airway that is located inside the thoracic cavity but outside the lung's gas exchange regions. It consists of the external nares, pharynx, larynx, and upper part of the trachea.

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The Zones Of The Airway

The conducting zone includes the trachea, bronchi, their branches (bronchioles), and the terminal bronchioles. The transitional and respiratory zones include the respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli. The two are considered to be one and the same, even though gas exchange only takes place at the level of the alveolar sacs and alveoli, not the respiratory bronchiole. At the respiratory bronchiole level, some diffusion and transudation may also occur (although it is not physiological).

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Development Of Normal Pulmonary System

The normal pulmonary system is an endodermal derivation, primarily deriving from the foregut.  The pharyngeal arches give rise to the nose, nasal cavity, and upper section of the pharynx. Although they have neuroectodermal and endodermal components, these pharyngeal arches are mostly mesodermal in origin. The endoderm gives birth to the tracheal epithelium, laryngeal epithelium, and the remaining respiratory epithelium, which are foregut derivatives. Thus the proximal portion of the gut is formed by the foregut. 

The muscles, blood vessels, supporting tissue, and bronchial rings are mesodermal in origin; the laryngeal cartilages are derived from the neural crest ectodermal precursors.  Mesoderm plays a crucial role in the respiratory tract, although endoderm (foregut derivatives) account for the majority of the respiratory tract's development.
Because tracheal and gut development happen at the same time, abnormalities such tracheoesophageal fistulas can arise from defects in the foregut derivative. The pulmonary system moves in the following order from the middle to the lower portion of the respiratory tract.
Major bronchi first form during the embryonic stage, which is characterized by simple outpouching.

The main bronchi's branches emerge at the pseudo-glandular stage.  Every bronchiole is formed at the canalicular stage.  Every sac develops during the saccular stage.  Lastly, alveoli tend to mature throughout the alveolar stage.  While mature alveoli appear in the saccular stage, primitive alveoli can also arise in the alveolar stage.

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Sequence Of Fetal Lung Development And Corresponding Defects

Difference Between Pediatric Airway And Adult Airway

     A child's tongue is larger in relation to their oral cavity.  In many individuals, the epiglottis in youngsters is larger, longer, and deformed (omega shaped).  Although laryngomalacia is characterized by an excess of omega-shaped epiglottis, some asymptomatic, normal youngsters can also have this condition.

At the level of the C2 vertebra, the larynx is positioned higher and anteriorly in youngsters.  Children's narrowest portion of the airway is not the same as an adult's. In youngsters, the narrowest portion of the airway is the subglottic region in front of the cricoid cartilage.  The glottis region, or voice cords, is the narrowest portion in adults.  It is discovered that children's larynxes and pharynxes are narrower.

Types Of Sounds

 Sounds are only audible when there is a partial blockage of the airway, not when the airway is completely blocked.

Snoring

Common disorders such as obesity, adenoid and tonsillar hypertrophy, and obstructive sleep apnea (a sleep problem breathing observed with obesity) can cause snoring because they block the airway at the oropharyngeal level.

Rattling

It sounds like gurgling and is caused by secretions from the tracheobronchial tree, such as mucus and regurgitation.

Stridor

Usually an inspiratory sound; a partial blockage in the upper portion of the airway, primarily the larynx and trachea. Biphasic (both expiratory and inspiratory) can occur occasionally.  It can be observed in ailments such as upper airway foreign bodies, croup, and epiglottitis.

Wheeze

Asthma, acute bronchiolitis, and foreign body aspiration are among the illnesses that might cause this sound, which is an expiratory one and is caused by partial obstruction in the bronchi and bronchioles.  Polyphonic bilateral wheeze can be observed in asthma and acute bronchiolitis; monophonic unilateral wheeze typically occurs in foreign body aspiration and bronchial adenoma.

Grunting

The sound is produced by the glottis suddenly closing; this is a reflex process.  Usually, it's a sign of an alveolar pathology, like a propensity to collapse.  Hyaline membrane disease (HMD), a newborn disorder that affects preterm infants, may arise from it. When there is a surfactant shortage, the alveoli have a propensity to collapse. 

To prevent this from happening, the glottis will suddenly close at the end of expiration, creating positive pressure that keeps the alveoli open.
It is a reflex mechanism that activates in the event of an alveolar malfunction.Grunting is an expiratory sound made at the glottis level.

Crepitations

It happens when the alveolar lumen contains blood, mucus, or fluid; occasionally, it can also happen in interstitial lung disease. They arise in cases of interstitial lung disorders, pneumonia, pulmonary hemorrhage, and pulmonary edema.

Hope you found this blog helpful for your NEET SS Pediatrics pulmonology preparation. For more informative and interesting posts like these, keep reading PrepLadder’s blogs.