Respiratory System Functions

Functions of the Respiratory System

• The respiratory system supplies oxygen to the body.
• It eliminates carbon dioxide.
• It oversees gas exchange between the blood and external environment.
• It provides passageways for air to reach the lungs.
• It purifies, humidifies, and warms incoming air.

Anatomy of the Respiratory System

• The respiratory system includes the nose, pharynx, larynx, trachea, bronchi, and lungs.
• The lungs contain alveoli.

Larynx

• The larynx, or voice box, routes air and food into the proper channels.
• It plays a role in speech.
• It is located inferior to the pharynx.
• It is formed by eight rigid hyaline cartilages and a spoon-shaped flap of elastic cartilage, the epiglottis.
• The thyroid cartilage is the largest of the hyaline cartilages.
• The epiglottis protects the superior opening of the larynx.
• The vocal folds vibrate with expelled air to allow us to speak.
• The glottis is the slitlike passageway between the vocal folds.

Trachea

• The trachea, or windpipe, is 10-12 cm long.
• It extends from the larynx to the level of the fifth thoracic vertebra.
• Its walls are reinforced with C-shaped rings of hyaline cartilage.
• The trachea is lined with ciliated mucosa that propels mucus.

Pharynx

• The pharynx is a muscular passageway, 13 cm long.
• It serves as a common pathway for air and food.
• The pharynx has three portions: nasopharynx, oropharynx, and laryngopharynx.
• The pharyngotympanic tubes drain the middle ear and open into the nasopharynx.
• The pharyngeal tonsil, or adenoid, is located in the nasopharynx.
• The palatine tonsils are in the oropharynx.
• The lingual tonsils are at the base of the tongue.

The Nose

• The nose is the only externally visible part of the respiratory system.
• Air enters the nose through the nostrils.
• The nasal cavity is divided by a midline nasal septum.
• The olfactory receptors for the sense of smell are located in the mucosa.
• The respiratory mucosa warms the air and traps incoming bacteria and foreign debris.
• The mucus produced by the mucosa's glands moistens the air and traps incoming bacteria and foreign debris.

Additional Structures

• Ciliated cells of the nasal mucosa create a gentle current that moves the sheet of contaminated mucus posteriorly.
• The conchae are mucosa-covered projections that increase the surface area of the mucosa exposed to the air.
• The palate separates the nasal cavity from the oral cavity.
• The paranasal sinuses are located in the frontal, sphenoid, ethmoid, and maxillary bones.
• The paranasal sinuses lighten the skull and act as a resonance chamber for speech.

Main Bronchi

• The right and left main bronchi are formed by the division of the trachea.
• Each main bronchus runs obliquely before it plunges into the medial depression of the lung on its own side.
• The right main bronchus is wider, shorter, and straighter than the left.

Lungs

• The lungs occupy the entire thoracic cavity, except for the mediastinum.
• The apex of each lung is just deep to the clavicle.
• The base of each lung rests on the diaphragm.
• Each lung is divided into lobes by fissures.
• The left lung has two lobes, and the right lung has three.
• The surface of each lung is covered with a visceral serosa called the pulmonary, or visceral pleura.

Respiratory Zone Structures

• The respiratory zone includes the respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli.
• The respiratory zone is the only site of gas exchange.

The Respiratory Membrane

• The walls of the alveoli are composed of a single, thin layer of squamous epithelial cells.
• Alveolar pores connect neighboring air sacs and provide alternative routes for air.
• The respiratory membrane, or air-blood barrier, includes the alveolar and capillary walls, their fused basement membranes, and occasional elastic fibers.
• Alveolar macrophages wander in and out of the alveoli, picking up bacteria, carbon particles, and other debris.
• Cuboidal cells produce surfactant, a lipid molecule that coats the gas-exposed alveolar surfaces and is important in lung function.