51. Respiratory system. The major organs of the respiratory system – principle structure. Larynx – position, description. Laryngeal cartilages. The cavity of the larynx. Vocal folds. Layngeal muscles. Blood supply and nerve supply.

The respiratory system:

• Fundamental for gas exchange via negative pressure breathing.
• Consists of a conduction portion (respiratory tract) and a respiratory portion (lungs)
• Involved in voice formation (larynx) and olfactory (nasal cavity)

The air passages

Upper respiratory tract

• 1 Nasal cavity (cavitas nasi)
• 1.1 Paranasal sinuses (sinus paranasales)
• 2 Pharynx
• 2.1 Nasopharynx (pars nasalis pharyngis)
• 2.2 Oropharynx (pars oralis pharyngis)
• 2.3 Laryngopharynx or hypopharynx (pars laryngea pharyngis)

Lower respiratory tract

• 3 Larynx
• 4 Trachea
• 5 Bronchi
• 6 Lungs (pulmones)

has:

• Respiratory bronchioles
• Alveolar ducts
• Alveolar ducts
• Multiple alveoli

Development of the Respiratory System:

• Begins at about the middle of the 4th week
• Develops from both endoderm & mesoderm.
• Steps:
• 4th week: a respiratory diverticulum outgrowth from the ventral wall of the foregut.
• The diverticulum expand ventrally & caudally. & eventually separates from the foregut, forming the esophagus.
• The diverticulum forms distaly lung bud & the rest forms the trachea.
• The lung bud bifurcates into right & left primary bronchial buds
• 5th week: the 1° bronchial buds gives rise to 2° then to 3° bronchial buds

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