No Introduction of the Respiratory System 1. Introduction of the Respiratory System 2. The nose 2. The nose 3. The pharynx 3. The pharynx 4. The larynx 4. The larynx

Chapter 3 The Respiratory System

Introduction In order for the cells of the body to carry on their metabolic activities under aerobic conditions, they require a constant supply of oxygen and an efficient means of removing the carbon dioxide that their activities produce. Oxygen is supplied and carbon dioxide is removed by the respiratory system, with the assistance of the circulatory system. In order for the cells of the body to carry on their metabolic activities under aerobic conditions, they require a constant supply of oxygen and an efficient means of removing the carbon dioxide that their activities produce. Oxygen is supplied and carbon dioxide is removed by the respiratory system, with the assistance of the circulatory system.

The respiratory system also makes vocalization possible. We are able to speak, sing, and laugh by varying the tension of the vocal folds as exhaled air passes over them. The respiratory system also makes vocalization possible. We are able to speak, sing, and laugh by varying the tension of the vocal folds as exhaled air passes over them. The exchange of oxygen and carbon dioxide between the air and the blood occurs in the lungs. In order to reach the exchange sites in the lungs, the air must flow through a series of conducting passageways that branch from one another much like the branches of a tree. The exchange of oxygen and carbon dioxide between the air and the blood occurs in the lungs. In order to reach the exchange sites in the lungs, the air must flow through a series of conducting passageways that branch from one another much like the branches of a tree.

Inclusion of the respiratory system: Inclusion of the respiratory system: The respiratory system includes the respiratory tract and lungs. The respiratory system includes the respiratory tract and lungs. The respiratory tract consists of the nose, pharynx, larynx, trachea and principal bronchi. The respiratory tract consists of the nose, pharynx, larynx, trachea and principal bronchi. From the clinical point of views, the upper respiratory tract is that above the larynx, and the trachea, principal bronchi with their branches belong to the lower respiratory tract. From the clinical point of views, the upper respiratory tract is that above the larynx, and the trachea, principal bronchi with their branches belong to the lower respiratory tract. The right and left lungs are the essential respiratory organs. The right and left lungs are the essential respiratory organs.

Function of respiratory system: Function of respiratory system: The primary function of the respiratory system is to supply the body with oxygen and to get rid of excess carbon dioxide resulting from cell metabolism. The primary function of the respiratory system is to supply the body with oxygen and to get rid of excess carbon dioxide resulting from cell metabolism.

Section 1 The Nose The nose is not only the first part of respiratory tract but also an organ of smell and phonation, it includes external nose, nasal cavity and paranasal sinuses. The nose is not only the first part of respiratory tract but also an organ of smell and phonation, it includes external nose, nasal cavity and paranasal sinuses.

Ⅰ. The External Nose It consists of bones and cartilages covered with skin. It consists of bones and cartilages covered with skin. It has a root, a back, an apex of nose, two alae nasi and two nares. It has a root, a back, an apex of nose, two alae nasi and two nares.

Ⅱ. The Nasal Cavity It is divided into right and left halves by the nasal septum. The right and left nasal cavities open in front through nares and communicate with the pharynx behind through the choanae. It is divided into right and left halves by the nasal septum. The right and left nasal cavities open in front through nares and communicate with the pharynx behind through the choanae. Each nasal cavity may be divided into nasal vestibule and proper nasal cavity. Each nasal cavity may be divided into nasal vestibule and proper nasal cavity.

Ⅰ ) The Nasal Vestibule The anterior portion of the nasal cavity is called the nasal vestibule which is just inside the alae nasi and posteriorly limited by the limen nasi. The anterior portion of the nasal cavity is called the nasal vestibule which is just inside the alae nasi and posteriorly limited by the limen nasi. The nasal vestibule is surrounded by cartilage and lined by skin. The nasal vestibule is surrounded by cartilage and lined by skin.

Ⅱ ) The Proper Nasal Cavity Constitution and morphology of the proper nasal cavity: Constitution and morphology of the proper nasal cavity: Each cavity has a roof, a floor, a medial wall and a lateral wall. Each cavity has a roof, a floor, a medial wall and a lateral wall. ① The roof is formed by the nasal bone, cribriform plate of the ethmoid bone. ① The roof is formed by the nasal bone, cribriform plate of the ethmoid bone. ② The floor is formed by the upper surface of the hard palate in front (2/3) and the soft palate behind (1/3). ② The floor is formed by the upper surface of the hard palate in front (2/3) and the soft palate behind (1/3). ③ The medial wall is the nasal septum. ③ The medial wall is the nasal septum.

④ The lateral wall, which are irregular, are formed by: the superior and middle conchae of the ethmoid bone, the separate inferior concha bones. ④ The lateral wall, which are irregular, are formed by: the superior and middle conchae of the ethmoid bone, the separate inferior concha bones. Beneath the shelves formed by the conchae are recesses called the superior, middle, and inferior meatuses. Beneath the shelves formed by the conchae are recesses called the superior, middle, and inferior meatuses. Sphenoethmoidal recess: above and behind the superior nasal concha there is the sphenoethmoidal recess. Sphenoethmoidal recess: above and behind the superior nasal concha there is the sphenoethmoidal recess. The inferior nasal meatus receives the termination of the nasolacrimal duct. The inferior nasal meatus receives the termination of the nasolacrimal duct. The middle and superior meatuses and sphenoethmoidal recess receive the openings of paranasal sinuses. The middle and superior meatuses and sphenoethmoidal recess receive the openings of paranasal sinuses.

The nasal mucous membrane: The nasal mucous membrane: It divided into two regions: It divided into two regions: Olfactory region: The olfactory receptors lie in the mucous membrane lining the upper portion of the nasal cavity where is called the olfactory region. Olfactory region: The olfactory receptors lie in the mucous membrane lining the upper portion of the nasal cavity where is called the olfactory region. Respiratory region: The rest of medial and lateral nasal wall covered by a thick glandular and vascular mucous membrane constitute the respiratory region. Respiratory region: The rest of medial and lateral nasal wall covered by a thick glandular and vascular mucous membrane constitute the respiratory region.

Ⅲ. The Paranasal Sinuses In the bones around the nasal cavity there are some air spaces called paranasal sinuses, they are: In the bones around the nasal cavity there are some air spaces called paranasal sinuses, they are: the frontal sinus, the frontal sinus, maxillary sinus, maxillary sinus, ethmoidal sinus, ethmoidal sinus, sphenoidal sinus. sphenoidal sinus. All these sinuses communicate with the nasal cavity and are lined by mucous membrane which is continuous with that of the nasal cavity. So the infection of nasal cavity may spread to the paranasal sinuses, resulting in sinusitis. All these sinuses communicate with the nasal cavity and are lined by mucous membrane which is continuous with that of the nasal cavity. So the infection of nasal cavity may spread to the paranasal sinuses, resulting in sinusitis.

Table 1: The paranasal sinuses NameLocationOpening(s) Frontal Sinuses In the frontal bone The middle nasal meatuses Maxillary Sinuses In the bodies of the maxilla The middle nasal meatuses Ethmoidal Sinuses Within the ethmoid bone Anterior group: Middle group: Posterior group: The middle nasal meatuses The superior nasal meatuses Sphenoidal Sinuses Within the body sphenoid bone Sphenoethmoidal recesses

Section 2 The Pharynx The pharynx is the common channel for both alimentary system and respiratory system, the food and air pathways cross each other in pharynx. The pharynx is the common channel for both alimentary system and respiratory system, the food and air pathways cross each other in pharynx.

Section 3 The Larynx The larynx is a part of respiratory passage as well as the organ of phonation. The larynx is a part of respiratory passage as well as the organ of phonation. It lies in the neck region in front of the fourth, fifth and sixth cervical vertebrae. It lies in the neck region in front of the fourth, fifth and sixth cervical vertebrae. The larynx consists of a framework of cartilages that are connected together by ligaments, membranes and joints. It also has a number of small muscles which move the cartilages. The larynx consists of a framework of cartilages that are connected together by ligaments, membranes and joints. It also has a number of small muscles which move the cartilages. The larynx is lined with mucous membrane which is continuous with that of pharynx above and that of trachea below. The larynx is lined with mucous membrane which is continuous with that of pharynx above and that of trachea below.

Ⅰ. The Laryngeal Cartilages The larynx is formed by nine cartilages — three unpaired and three paired. The larynx is formed by nine cartilages — three unpaired and three paired. These cartilages are held together, and attached to the hyoid bone above and the trachea below, by ligaments and muscles. These cartilages are held together, and attached to the hyoid bone above and the trachea below, by ligaments and muscles.

Ⅰ ) The Thyroid Cartilage It is the largest of the unpaired cartilages. It is formed by the midline junction of two broad plates anteriorly, producing the laryngeal prominence. The plates remain separated posteriorly, which leaves a wide opening in the laryngopharynx. It is the largest of the unpaired cartilages. It is formed by the midline junction of two broad plates anteriorly, producing the laryngeal prominence. The plates remain separated posteriorly, which leaves a wide opening in the laryngopharynx.

Ⅱ ) The Cricoid Cartilage Just below the thyroid cartilage is the ring-shaped cricoid cartilage. It is composed of a lamina of cricoid cartilage behind, a narrow arch of cricoid cartilage in front. Just below the thyroid cartilage is the ring-shaped cricoid cartilage. It is composed of a lamina of cricoid cartilage behind, a narrow arch of cricoid cartilage in front.

Ⅲ ) The Arytenoid Cartilages Each arytenoid cartilages is shaped like a small pyramid and rests on the superior-posterior border of the cricoid cartilage. They articulate with the superoposterior border of the cricoid cartilage. Each arytenoid cartilages is shaped like a small pyramid and rests on the superior-posterior border of the cricoid cartilage. They articulate with the superoposterior border of the cricoid cartilage. The base sends a vocal process forward for attachment of the vocal ligament and a muscular process laterally for muscular attachment. The base sends a vocal process forward for attachment of the vocal ligament and a muscular process laterally for muscular attachment.

Ⅳ ) The Epiglottic Cartilage The epiglottic cartilage is the leaf- shaped epiglottic cartilage. This cartilage covered by mucous membrane and forms the epiglottis. The epiglottic cartilage is the leaf- shaped epiglottic cartilage. This cartilage covered by mucous membrane and forms the epiglottis. The epiglottis is attached by its narrow end to the inner surface of the anterior region of the thyroid cartilage; its free upper portion projects like a flap behind the base of the tongue. The epiglottis is attached by its narrow end to the inner surface of the anterior region of the thyroid cartilage; its free upper portion projects like a flap behind the base of the tongue.

Ⅱ. The Laryngeal Joints Ⅰ ) The Cricothyroid Joint Ⅰ ) The Cricothyroid Joint Composition: Composition: Inferior cornu of the thyroid cartilage, Inferior cornu of the thyroid cartilage, The larteral surface of cricoid cartilage. The larteral surface of cricoid cartilage. Movements: Movements: It allows rotation of thyroid cartilage around the coronal axis, so that the length and the tenseness of the vocal fold can be changed. It allows rotation of thyroid cartilage around the coronal axis, so that the length and the tenseness of the vocal fold can be changed.

Ⅱ ) The Cricoarytenoid Joint Ⅱ ) The Cricoarytenoid Joint Composition: Composition: The lamina of cricoid cartilage, The lamina of cricoid cartilage, The base of the arytenoid cartilage. The base of the arytenoid cartilage. Movements: Movements: When the arytenoids cartilage glide and rotate on the cricoid, apposition and abduction of vocal folds occur. When the arytenoids cartilage glide and rotate on the cricoid, apposition and abduction of vocal folds occur.

Ⅲ. The Laryngeal Ligaments and Membranes Ⅰ ) The Thyrohyoid Membrane Ⅰ ) The Thyrohyoid Membrane Ⅱ ) The Conus Elasticus Ⅱ ) The Conus Elasticus It extends upward from the cricoid cartilage to the arytenoid cartilages and the posterior surface of the thyroid cartilage. It extends upward from the cricoid cartilage to the arytenoid cartilages and the posterior surface of the thyroid cartilage. Its superior border is free and forms the vocal ligament which extends from the posterior surface of thyroid to the vocal process of arytenoid cartilage. Its superior border is free and forms the vocal ligament which extends from the posterior surface of thyroid to the vocal process of arytenoid cartilage. Ⅲ ) The Quadrangular Membranes Ⅲ ) The Quadrangular Membranes

Ⅳ. The Muscles of Larynx They are skeletal muscle. They are skeletal muscle. They serve to open and close the glottis and regulate the tension of the vocal fold. They serve to open and close the glottis and regulate the tension of the vocal fold.

Ⅴ. The Laryngeal Cavity Ⅰ ) Morphology of lateral wall of the laryngeal cavity: Ⅰ ) Morphology of lateral wall of the laryngeal cavity: 1. Vestibular folds and vocal folds: 1. Vestibular folds and vocal folds: The mucous membrane near the entrance to the larynx forms two pairs of horizontal folds that extend on each side from the thyroid cartilages to the arytenoid cartilages. The mucous membrane near the entrance to the larynx forms two pairs of horizontal folds that extend on each side from the thyroid cartilages to the arytenoid cartilages. The upper pair of folds are called the ventricular folds (false vocal cords). The lower pair are the vocal folds (true vocal cords). The upper pair of folds are called the ventricular folds (false vocal cords). The lower pair are the vocal folds (true vocal cords). The vestibular folds extend anteroposteriorly on either side of the larynx and enclose between them a slit, the rima vestibuli. The vestibular folds extend anteroposteriorly on either side of the larynx and enclose between them a slit, the rima vestibuli.

The vocal folds are two folds of mucous membrane which are closely bound to the underlying vocal ligament. The vocal folds are two folds of mucous membrane which are closely bound to the underlying vocal ligament. The slit between the two vocal folds through which air enters the larynx is the fissure of glottis. The slit between the two vocal folds through which air enters the larynx is the fissure of glottis. The glottis consists of the vocal folds and the slit between them. The glottis consists of the vocal folds and the slit between them. Air passing through the glottis causes the vocal folds to vibrate and produce a sound. The frequency of the vibrations, and therefore the pitch of the sound produced, depends upon the tension of the vocal folds. Air passing through the glottis causes the vocal folds to vibrate and produce a sound. The frequency of the vibrations, and therefore the pitch of the sound produced, depends upon the tension of the vocal folds.

Division of the laryngeal cavity: Division of the laryngeal cavity: The laryngeal cavity is divided into three parts: The laryngeal cavity is divided into three parts: The laryngeal vestibule extends from the aperture of larynx to the vestibular folds The laryngeal vestibule extends from the aperture of larynx to the vestibular folds The intermedial cavity of larynx, the narrowest portion between the level of rima vestibuli and the fissure of glottis. The ventricles of larynx are the lateral expansions of the laryngeal cavity between the vestibular and the vocal folds. The intermedial cavity of larynx, the narrowest portion between the level of rima vestibuli and the fissure of glottis. The ventricles of larynx are the lateral expansions of the laryngeal cavity between the vestibular and the vocal folds. The Infraglottic cavity lies below the vocal folds and extending downward to the lower border of the cricoid cartilage. The Infraglottic cavity lies below the vocal folds and extending downward to the lower border of the cricoid cartilage.