8.2 Respiratory system morphology

Question 1

the paranasal sinuses

Answer 1

include the bilaterally paired frontal, ethmoidal, sphenoidal and maxillary sinuses. Each maxillary sinus is somewhat pyramidal in shape, the base forming the lateral wall of the nasal cavity, the roof forming the floor of the orbit. The ethmoidal sinuses (or air cells) are unlike the others, being three groups (anterior, middle and posterior) of small multiple cavities – they are separated from the medial orbit by a very thin layer of bone, the lamina papyracea

Question 2

What are paranasal sinuses

Answer 2

air-filled cavity in a dense portion of a skull bone. Each sinus is lined with respiratory mucoperiosteum and drains into the lateral wall of the nasal cavity via small openings.

Question 3

Conchae and meati of the nose

Answer 3

The lateral walls of the cavity show three elevations, the superior, middle and inferior nasal conchae or turbinate bones. The inferior conchae is a separate bone while the superior and middle are part of the ethmoid bone. The conchae greatly increase the surface area of the nasal cavity and produce turbulence in the air flow during inhalation, warming and humidifying the air as it is drawn over the conchal mucosa.

Question 4

Conchae and meati of the nose

Answer 4

The lateral walls of the nasal cavity show three elevations, the superior, middle and inferior nasal conchae or turbinate bones. The inferior conchae is a separate bone while the superior and middle are part of the ethmoid bone.
Meati= nasal passages

Question 5

Role of conchae:

Answer 5

greatly increase the surface area of the nasal cavity and produce turbulence in the air flow during inhalation, warming and humidifying the air as it is drawn over the conchal mucosa.

Question 6

Airway components of pharynx

Answer 6

three anatomical regions:

1) nasopharynx (from the posterior nasal apertures to the lower border of the soft palate)
2) oropharynx (from the soft palate to the superior boundary of the epiglottis, with an anterior border demarcated by the palatal arches / pillars of the fauces)
3) laryngopharynx (from the superior border of the epiglottis to the cricopharyngeus muscle).

Question 7

Protection of airway during swallowing.

Answer 7

The transverse and oblique arytenoid muscles close the inlet to the larynx by pulling the arytenoids towards each other, providing a protective sphincteric action during swallowing.

Question 8

Principles of movements of the vocal cords in phonation.

Answer 8

Regulating tension in the vocal ligaments alters pitch:

Cricothyroid muscles are attached to the lower part of the thyroid cartilage, contraction pulling it forwards and downwards on the cricoid, lengthening and tightening the vocal cords. Thyroarytenoid muscles pull the arytenoid cartilages forward, relaxing the vocal ligaments. The vocalis muscles relax the posterior vocal ligament while generating tension in the anterior part, producing fine adjustments used in speech production.

Question 9

Innervation of nasal cavity

Answer 9

• The upper parts of the lateral nasal wall and the under surface of the cribriform plate possess olfactory mucosa, the site of olfactory receptor cells of the first cranial nerve (I), the olfactory nerve.
• General sensation provided by the trigeminal nerve (V):
• the anterosuperior part of the cavity is innervated by the ophthalmic division (V1) via the anterior ethmoidal nerve.
• remainder of the nasal cavity innervated by the maxillary division (V2), via nasal branches of the greater palatine nerve.
• Sensory nerves also carry sympathetic vasomotor fibres from the carotid plexus to the vasculature and parasympathetic secretomotor fibres from the pterygopalatine ganglia to the mucosal glands.

Question 10

Innervation of larynx

Answer 10

laryngeal muscles are innervated by branches of the vagus nerve (CN X).

superior laryngeal nerve: provides external laryngeal nerve which innervates the cricothyroid muscle and internal laryngeal nerve which provides sensation to the mucous membrane of the larynx above the vocal ligaments.

inferior laryngeal nerve: a continuation of the recurrent laryngeal nerve. Innervates all other intrinsic laryngeal muscles (except cricothyroid). Also provides sensation to the larynx below the vocal cords.

Question 11

Innervation of trachea

Answer 11

pulmonary plexus. Parasympathetic supply originates from the recurrent laryngeal nerves, branches of the vagus nerve.

Question 12

Movements of tongue

Answer 12

The extrinsic muscles of the tongue:
•genioglossus (attached to the midline of the mandible and hyoid, it protrudes the tongue)
•hyoglossus (which is attached to the hyoid bone and depresses and retracts the tongue)
•styloglossus (which is attached to the styloid process of the temporal bone and stylohyoid ligament and retracts and elevates the tongue)
•palatoglossus (which arises from the palatine aponeurosis of the soft palate and elevates the posterior tongue).

Question 13

Movements of soft palate

Answer 13

Palatopharyngeus aids in tensing the soft palate.

Question 14

Movements of pharynx

Answer 14

palatopharyngeus pulls the pharynx superioanterior during swallowing.

Question 15

Movements of larynx

Answer 15

primary function of the larynx is that of a sphincter to protect the respiratory tract and prevent the entry of foreign bodies into the lower respiratory passages. The secondary function of the larynx is the production of the voice.

Question 16

Rima glottidis shape changes:

Answer 16

Lateral and posterior cricoarytenoid muscles are attached to the muscular process of the arytenoids and modify the shape of the rima glottidis. The lateral cricoarytenoids close the glottis by rotating the arytenoids medially, bringing their vocal processes together: adduction. They are assisted in closing the glottis by the transverse arytenoid muscles. The posterior cricoarytenoids rotate the arytenoids laterally, abducting the vocal processes and opening the glottis – the only laryngeal muscles that do so.

Question 17

Temporomandibular joint

Answer 17

When the mouth opens, the mandibular condyles rotate upon the cartilaginous articular disc, which allows them to glide forwards and downwards- because of this, the TMJ permits the mandible to be elevated and depressed as well as protracted (moved forwards), retracted (moved backwards) and moved from side-to-side.

To help stabilise the joint, ligaments attach the mandible to the skull. The lateral ligament is a thickening of the joint capsule attaching the mandible to the zygomatic process of the temporal bone; the stylomandibular ligament connects the styloid process to the posterior ramus and angle of the mandible, preventing excessive anterior protrusion; the sphenomandibular ligament arises from the sphenoid spine to a prominent ridge on the medial surface of the mandible, the lingula.

Question 18

What is the rima glottidis?

Answer 18

the opening between the true vocal cords and the arytenoid cartilages of the larynx.

Question 19

Pleura (mesothelium):

Answer 19

• Line pleural cavities
• produces a small amount of pleural fluid that allows pleural layers to slide past each other without producing friction.
• two types: Visceral pleura, which covers the lungs (including fissures) & is continuous with parietal pleura at the hilum (parietal pleura lines the walls of the pleural cavity (cervical, mediastinal, diaphragmatic & costal)).

Question 20

Airway structure:

Answer 20

Trachea bifurcates into left and right main bronchi. Primary bronchi divide into secondary (or lobar) bronchi

Question 21

Anatomy of bronchial bifurcation -left right differences. Principles of lobar organization and bronchopulmonary segmentation

Answer 21

the right main bronchus forms three secondary bronchi and the left usually two, correlating with the typical number of lobes in each lung.

Secondary bronchi divide again into tertiary (or segmental) bronchi which serve the bronchopulmonary segments of each lobe.

Question 22

Left and right differences in relation to inhaled foreign bodies

Answer 22

The right primary bronchus is shorter (dividing before it enters the lung), more vertical and wider than the left and consequently inhaled objects are more likely to enter the right main bronchus.

Question 23

Structural features of the lungs in relation to gas exchange.

Answer 23

bronchioles, alveolar ducts and definitive alveoli have thin-walled pouches where gas exchange takes place and rich capillary network.

Question 24

What arteries supply lungs?

Answer 24

Pulmonary arterial supply to gas-exchange tissues.

Question 25

What arteries supply body?

Answer 25

Bronchial arterial supply to non-exchange tissues.

Question 26

Venous drainage of the lungs and bronchi.

Answer 26

• anterior intercostal veins return venous blood to the internal thoracic veins and and posterior intercostal veins return venous blood to the azygos system of veins (the most superior two posterior intercostal veins drain to the brachiocephalic veins).
• intercostal veins do not drain directly into the vena cava, most draining into the azygos (unpaired) venous system present on the posterior thoracic wall.
• Intercostal veins of the right side join the azygos vein which drains into the superior vena cava. The intercostal spaces of the left side are drained by the accessory hemiazygos vein and the lower hemiazygos vein, both of which usually cross the midline to join the azygous vein, although variation in this system is very common.

Question 27

Innervation of airways and lungs:

Answer 27

Afferent and efferent autonomic innervation

Question 28

Principles of lymphatic drainage of airway.

Answer 28

Lymphatic vessels surround the bronchial tree, forming a deep lymphatic plexus of the lungs while nodes surrounding the periphery of the lungs deep to the visceral pleura form the superficial lymphatic plexus.

• Lymph from the superficial plexus→ drains to bronchopulmonary lymph nodes situated at the hilum (where the bronchi, blood vessels, nerves and lymphatic vessels enter and leave the lung).
• Lymph from the deep plexus drains first to pulmonary lymph nodes surrounding the secondary bronchi and then the bronchopulmonary nodes. Bronchopulmonary nodes drain to tracheobronchial lymph nodes surrounding the tracheal bifurcation at the carina, which drain in turn to paratracheal nodes.
• Lymphatic drainage from the right lung is received by the right lymphatic trunk, as is lymphatic drainage from the lower lobe of the left lung. Lymph from the superior lobe of the left lung ultimately drains to the thoracic duct at the left venous angle.

Question 29

General structure of mucous membranes

Answer 29

Mucous membranes line viscera -all body cavities that are in continuity with the external surface. consists of a pseudostratified epithelial layer, lamina propria and muscle layer. Mucus is a viscous fluid containing glycoproteins. It lines the respiratory tract as a thin layer as far as the ends of the bronchi.

Question 30

Development and cellular structure of alveoli: Surfactant production.

Answer 30

Surfactant is released at the apical surface of cells where it forms a broad lattice-like network known as tubular myelin. Surfactant forms a monolayer on the inner alveolar surface; it reduces surface tension and this prevents collapse of alveoli during exhalation, thereby facilitating alveolar expansion during the inspiratory phase of breathing.

Question 31

Type I and type II pneumocytes:

Answer 31

Type I: squamous and cover most of the alveolar wall

Type II: cuboidal in shape but account for less than 10% of the alveolar surface, secrete surfactant

Question 32

Cystic fibrosis

Answer 32

affecting chloride ion channel (pancreas, liver, intestines, lungs) “CFTR” (cystic fibrosis transmembrane conductance regulator)- disrupts epithelial ion transport (Cl-, H2O) by submucosal glands.

Lack of chloride ion movement leads to decreased water movement by osmosis. Cells take up extra Na, mucus becomes thick and traps bacteria- lung infections. Cough chronic purulent secretions and dyspnea.

Question 33

Goblet cells

Answer 33

Produce mucinogen which becomes hydrated and known as mucin when released into an aqueous environment.

Question 34

Ciliated cells

Answer 34

Epithelium with cilia on apical surface - about 300 per cell. The cilia beat upwards and outward to shift mucous.

Question 35

Alveolar macrophages

Answer 35

• many in alveoli and to a lesser extent in the septa, where they are derived from monocytes circulating in the blood.
• They have many pseudopods (protrusions) and microvilli.
• Produce proteolytic and lysosomal enzymes. Also kill bacteria through peroxide-producing oxidative mechanisms.
• assist type II cells in the uptake of surfactant.
• wandering cells and their phagocytic activities are directed against irritants, particulate matter and mirco-organisms.
• Constantly replenished in the lung they are removed by passing into the bronchial tree or by coughing, sneezing or swallowing or they may return to the lymphatics that commence at the alveolar ducts.

Question 36

alveolar capillaries

Answer 36

supported by collagen and elastic fibres and containing wandering lymphoid cells and macrophages.