Respiratory System

Learning & Test Objectives

  1. Components of the respiratory system individually and as a unit
  2. Airways gross structure and ultrastructure
  3. Paranasal sinuses
  4. Pleurae & pleural cavity
  5. Diaphragm and muscles involved in respiration. Head and neck muscles related to respiratory system.
  6. Mechanics of breathing and phonation
  7. Clinical applications: Projection of lungs on the thorax, Thoracic X-ray, Airways endoscopy, Cricothyrotomy, Pnemothorax

Description of the test

The test is held by the general rules of written tests (see Continuous Testing – Organisation).

The test of the respiratory system follows the general rules for written tests (see Continuous testing – organisation). The test will be focused on the organs of the respiratory system, their structure, syntopy, vascular supply and innervation. For each organ it necessary to know which vessels provide blood supply and the origin of those vessels. Similarly, it is required to know which veins and lymphatics drain each organ. Topics which students should pay increased attention to when preparing for the test include the lymphatic drainage of the lungs and the innervation of the larynx. The test will include questions on the topography of the mediastinum, projections of organs on the thorax, radiological images and basic histology and embryology of the respiratory system.  In the final part of the test the students will have to draw and describe a scheme from the list of required schemes (see below).

Clinical notes

Liquorrhoea is leakage of cerebrospinal fluid from the subarachnoid space. In fractures or surgeries of the anterior cranial fossa, cerebrospinal fluid may leak from the nose (nasal liquorrhoea).

Kiesselbach's plexus is located on the cartilaginous septum near the anterior end of the inferior nasal concha. It is a frequent source of nasal bleeding (epistaxis). It is supplied by five arteries: superior labial, anterior and posterior ethmoidal, sphenopalatine and greater palatine.

During inflammation of the paranasal sinuses (sinusitis), percussion over the affected sinus becomes painful. The inflammation may erode the thin bone and enter the cranial cavity or the orbit. An X-ray may show opacity of the sinus. During inflammation of the frontal sinus (frontal sinusitis), palpation of the skin innervated by the ophthalmic nerve (N. V1) may be painful. During inflammation of the maxillary sinus (maxillary sinusitis), palpation of the skin innervated by the maxillary nerve (N. V2) may become painful. During inflammation of the ethmoidal air cells, the nasal root may be tender to palpation.

The maxillary sinus is closely related to the roots of the upper teeth, especially the canine, which has the longest root.

The laryngeal inlet and rima glottidis are very narrow regions of the respiratory tract and represent common places for foreign bodies to get stuck. This can reset in coughing, choking and asphyxiation.

Laryngoscopy is a method of examining the laryngeal cavity. It can be performed directly with a laryngoscope or indirectly using a mirror.

Injury of the recurrent laryngeal nerve occurs as a complication of thyroid surgery due to its close topographical relation to the thyroid gland. Unilateral injury may result in a quiet voice. Bilateral injury causes difficulty in breathing as a result of paralysis of the posterior cricoarytenoid.

Palsy of the posterior cricoarytenoid prevents patency through the rima glottidis during inspiration.

Tracheotomy is a surgical procedure in which a horizontal or longitudinal incision is made through the ventral side of the trachea. An upper tracheotomy (tracheotomia superior) is performed below the cricoid cartilage and above the isthmus of the thyroid gland. A lower tracheotomy (tracheotomia inferior) is performed below the isthmus of the thyroid gland at the level of the third tracheal cartilage.

Endotracheal intubation is the placement of a tube into the trachea through the oral cavity (orotracheal intubation) or the nasal cavity (nasotracheal intubation) to allow artificial ventilation of the lungs.

Aspirated foreign bodies are much more likely to enter the right main bronchus than the left main bronchus due to its wider diameter and more obtuse angle with the trachea.

Pulmonary embolism is a life-threatening condition, which occurs due to obstruction of the pulmonary artery or any of its branches. In most cases it is due to a thromboembolism originating in the pelvic veins or the deep veins of the leg. Infrequently other types of embolism may occur, such as fat embolism (from fractures), amniotic fluid embolism (during delivery), air embolism (during injury) and tumour cell embolism.

Pneumothorax is the accumulation of gas in the pleural cavity. The cause may be: injury to the thorax, rupture of a subpleural bulla or iatrogenic (e.g. cannulation of the subclavian vein or puncture of the pleural cavity).

Thoracentesis (pleural tap) is a procedure to remove fluid or air from the pleural cavity. A tube is inserted through the 2nd or 3rd intercostal space in the midclavicular line (with the patient in a half-sitting position) for pneumothorax, or through the 6th intercostal space in the anterior or middle axillary line (with the patient in a full sitting position) for fluidothorax. It is frequently performed under ultrasound guidance.

Other interesting notes

The border between the upper and lower respiratory tract is defined differently clinically than anatomically. The anatomical border is the aditus laryngis. In otorhinolaryngology the border is defined as the rima glottidis, as the mucosa under it is colonised by much fewer bacteria. The surgical border is the superior thoracic aperture, as this marks the transition of the trachea from the neck to the thorax.

A cough (tussis) is an expiratory reflex to clean the lower airways of phlegm, sputum and foreign bodies irritating or blocking the airways. A cough begins with a deep breath, followed by strong contraction of the abdominal and expiratory muscles against a closed rima glottidis. The rima glottidis suddenly opens and air is forced out. The tussigenic zones consist of areas innervated by the vagus nerve that may induce coughing when irritated. They include the larynx, trachea, main bronchi, parietal pleura, diaphragm, pericardium, oesophagus and external acoustic meatus.

The mechanism of sneezing is very similar to coughing. The difference is that during a sneeze, the uvula is depressed and most of the air is forced out through the nose. The fifth cranial nerve innervating the nasal mucosa provides the afferent limb of the sneeze reflex. During swallowing the airways are closed by elevation of the pharynx by the suprahyoid muscles and the thyrohyoid with subsequent closure of the laryngeal inlet by the epiglottis.

The bronchial tree has 23 divisions.

Nociceptive neurons (neurons perceiving the pain) are present in small numbers in the lungs and visceral pleura and thus the lungs and visceral pleura are not responsive to pain reception. The only exception is the richly innervated area around the hilum of the lung, which is supplied by the vagus nerve.

The clinical definition of the mediastinum differs from the anatomical definition as it defines it in regard to its continuation with the retroperitoneum and the visceral space of the neck.

List of required schemes

  • Frontal section through the larynx
  • Laryngoscopic view of the vocal cords
  • Bronchopulmonary segments – view from the front
  • Mediastinal surface of the lungs, including hilum of the left and right lungs and impressions of the organs
  • Mediastinum – transverse section of the thorax at the level of vertebra T6 
  • Transverse section of the neck at the C6 level

Radiological images

Radiological images

Created: 27. 2. 2017 / Modified: / Responsible person: MUDr. Azzat Al-Redouan