Respiratory System: Nose, Pharynx, and More

• Functions of the respiratory system include air conduction and pulmonary ventilation (gas exchange).

Respiratory Organs

• Organs include the nose, nasal cavities, paranasal sinuses, pharynx, larynx, trachea, bronchi and their smaller branches, lungs, and alveoli.

Nose

• The nose provides an airway for respiration.
• It filters inhaled air.
• It moistens and warms the air.
• It acts as a resonating chamber for speech.
• It contains olfactory receptors.

Pharynx

• The pharynx connects the nasal cavity to the larynx, and the oral cavity to the esophagus
• It's divided into three parts: nasopharynx, oropharynx, and laryngopharynx.

Nasopharynx

• The nasopharynx is posterior to the nasal cavity and superior to the oral cavity.
• It serves only as an air passageway and closes off during swallowing.

Oropharynx

• The oropharynx is located posterior to the oral cavity.
• It's a common passage for both food and air.

Laryngopharynx

• The laryngopharynx is a joint passageway for food and air.
• It's continuous with the esophagus and larynx.

Larynx

• The larynx is a framework of 9 cartilages connected by ligaments and membranes.
• Functions: Voice production and keeping the airway open.
• Directs air and food into the trachea and esophagus.
• The epiglottis prevents food or liquids from entering lower respiratory channels.

Trachea

• The trachea descends from the larynx through the neck and into the mediastinum.
• It divides into two main (primary) bronchi.

Bronchial Tree Structure

• The trachea divides into two main (primary) bronchi, which enter the lungs.
• Lobar (secondary) bronchi: 3 on the right and 2 on the left, each supplies a lung lobe.
• Segmental (tertiary) bronchi branch into each lung segment (bronchopulmonary segment).
• Bronchioles are small bronchi, less than 1 mm in diameter.

Respiratory Zone

• The respiratory zone is the terminal part of the respiratory tree in the lungs. Gas exchange occurs in the alveoli, which are microscopic air sacs at the end of the respiratory tree.

Pleural Membranes and Cavities

• The pleura is a double-layered sac that surrounds each lung.
• Parietal pleura lines the pleural cavities.
• Visceral pleura covers the lungs.
• Pleural cavity: the potential space between the parietal and visceral layers of pleura.

Lung Features

• The right lung has 3 lobes (superior, middle, inferior), separated by an oblique and a horizontal fissure.
• The left lung has 2 lobes (superior and inferior), separated by an oblique fissure, and includes the cardiac notch.

Pulmonary Ventilation Phases

• There are two phases: inspiration and expiration.
• Inspiration is when air flows into the lungs.
• Expiration is when gases exit the lungs.

Thoracic Wall Movements During Respiration

• Inspiration increases thoracic volume.
• Expiration decreases thoracic volume.

Inspiration

• The diaphragm contracts, increasing the volume of the thorax.
• The external intercostal muscles elevate the ribs, causing the thorax to expand laterally.
• As the ribs are raised, the antero-posterior dimension of the thorax also enlarges.

Expiration

• The ribs are depressed as the external intercostal muscles relax.
• The diaphragm moves superiorly as it relaxes.