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The respiratory system is divided into two divisions

Upper respiratory tract

 The organs are located outside of the thorax and consists of the nose, pharynx and larynx.

Lower respiratory tract

 The organs are located within the thorax and consists of the trachea, the bronchial tree and the lungs.

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The main role of the respiratory system is to provide gas exchange between the blood and the environment.

Primarily, oxygen is absorbed from the atmosphere into the body and carbon dioxide is expelled from the body.

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The following organs from the respiratory system

Nose

Pharynx

Larynx

Trachea

Bronchi

Lungs

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Structure;

The nose is the part of the respiratory tract superior to the hard palate and contains the peripheral organ of smell.

The external portion of the nose consists of a bony and cartilaginous frame covered by skin containing sebaceous glands.

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The two nasal bones meet and are surrounded by the frontal bone to form the root of the nose and is surrounded by the maxillary bone laterally and inferiorly.

The nasal cavity lies over the roof of the mouth, separated by the palatine bone.

Cribriform plate is a portion of the ethmoid bone that separates the roof of the nose from the cranial cavity.

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The cribriform is perforated by many openings that permit branches of the olfactory nerve responsible for the special sense of smell to enter the cranial cavity and reach the brain.

Septum separates the nasal cavity into a right and left cavity.

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Each nasal cavity is divided into three passageways

Superior meatus

Middle meatus

Inferior meatus

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The nose is lined with ciliated columnar epithelium which contains mucus secreting goblet cells.

The inferior two thirds of the nasal mucosa is the respiratory area, and the superior one third is the olfactory area.

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Air passing over the respiratory area is warmed and moistened before it passes through the rest of the upper respiratory tract to the lungs.

The olfactory area is specialized mucosa containing the peripheral organ of smell, sniffing draws air to the area

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Respiration (breathing)

The nose is the first part of the respiratory system through which the inspired air passe

The nose humidify, warming, filtering and cleaning of air

Reception and elimination of secretions from the nasal mucosa, paranasal sinuses, and nasolacrimal ducts

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Olfaction (smelling).

The nose is the organ of sense of smell

It aids speech- this is enhanced by the presence of paranasal sinuses, which act as resonating chambers for speech

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Paranasal sinuses are air-filled extensions of the respiratory part of the nasal cavity into the following cranial bones: frontal, ethmoid, sphenoid, and maxilla.

They are named according to the bones in which they are located

Each is lined with respiratory mucosa a continuation of mucous membrane lining the nasal cavity

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They include

The frontal sinus

Maxillary sinuses

Sphenoid sinus

Ethmoid sinuses

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Paranasal sinuses reduce the weight of the skull, they also give resonance to the voice

These sinuses have clinical importance,

The mucous secretion drain from the sinuses into the nasal cavity, if there is infection of the nasal cavity, the swollen mucous membrane of the nasal cavity may block this drainage increasing pressure within a sinus and causing headache

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Structure;

The larynx (plural larynges), known as the voice box, is an organ situated in the neck involved in respiration and sound production.

The larynx houses the vocal folds, and is situated just below the pharynx between the root of the tongue and upper end of the trachea.

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The larynx consists of cartilages attaches to each other by ligaments and membranes.

The framework of the larynx is formed by nine cartilages connected to one another by muscles, ligaments and membranes.

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Three cartilages are single (thyroid, cricoid, and epiglottic) and three are paired (arytenoid, corniculate, and cuneiform).

The corniculate and cuneiform cartilages appear as small nodules in the posterior part of the aryepiglottic folds.

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Epiglottis is a flap of fibro-elastic cartilage tissue covered with a mucous membrane which is stratified squamous epithelium, attached to the root of the tongue.

It projects obliquely upwards behind the tongue and the hyoid bone.

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It is often incorrectly used to refer to the uvula.

Uvula; This protects the airway during swallowing.

The inner surface is lined by a ciliated columnar epithelium membrane.

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The laryngeal muscles are divided into extrinsic and intrinsic groups

The extrinsic laryngeal muscles move the larynx as a whole, these include.

 The infrahyoid muscles; are depressors of the hyoid and larynx,

 The suprahyoid and stylopharyngeus muscles are elevators of the hyoid and larynx.

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The intrinsic laryngeal muscles move the laryngeal parts, making alterations in the length and tension of the vocal folds and in the size and shape of the rima glottidis.

All but one of the intrinsic muscles of the larynx is supplied by the recurrent laryngeal nerve, a branch of CN X.

The cricothyroid muscle is supplied by the external laryngeal nerve, one of the two terminal branches of the superior laryngeal nerve.

The actions of the intrinsic laryngeal muscles are described below.

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The intrinsic muscle of the larynx, are important in controlling vocal cord length and tension in regulating the shape of laryngeal inlet (Rima glottis), these include

Crico-thyroid muscle lengthens and stretches the vocal cords.

Posterior cricoarytenoid muscle abducts the vocal cords.

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Thyroarytenoid muscle (also called vocalis muscle) shortens vocal cords.

Transverse arytenoid muscle adducts the vocal folds.

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Blood supply is through superior and inferior laryngeal arteries.

Venous drainage is by thyroid veins which join the internal jugular

Nerve innervation is through parasympathetic and sympathetic fibres

The parasympathetic supply is from superior and recurrent laryngeal nerve which is the branch of vagus nerve.

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Injury to one of the recurrent laryngeal nerves produces hoarseness, if both are damaged the voice is completely lost and breathing becomes difficult.

Possible injury can occur during thyroid surgeries.

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Respiration, filters, humidifies and warms air as it passes to the lungs.

Swallowing

The epiglottis and vestibular folds prevent swallowed material from moving into the larynx

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Phonation; the vocal folds are the primary source of sound production

It serves as the organ of voice production- the pitch of the voice depends upon the length and tightness of the cords

The vocal folds produce audible vibrations when their free margins are closely (but not tightly) apposed during phonation and air is forcibly expired intermittently

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Complete adduction of the folds forms an effective sphincter that prevents entry of air

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 Pitch of the voice depends upon the length and tightness of the cord

 Volume of the voice depends upon the force with which the cords vibrate

 The greater the force of expired air the more the cords vibrates and the louder the sound emitted

 Resonance or tone is dependent upon the shape of the mouth, the position of the tongue and the lip, facial muscles and the air in the paranasal sinuses

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Speech – this occurs during expiration when the sound produced by the vocal cords is manipulated by the tongue, cheeks and the lips

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What are the functions of the nose?

Mention the function of the pharynx.

Mention seven openings of the pharynx.

Name the intrinsic muscles of the larynx.

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