Respiratory System PDF

Respiratory System The respiratory system is composed of the following structures: 1. Nose and paranasal sinuses 2. Larynx 3. Pharynx 4. Trachea 5. Bronchi 6. Pleura 7.Lung THE NOSE ❖ External nose: It is pyramidal in shape having a root and free apex....

Respiratory System The respiratory system is composed of the following structures: 1. Nose and paranasal sinuses 2. Larynx 3. Pharynx 4. Trachea 5. Bronchi 6. Pleura 7.Lung THE NOSE ❖ External nose: It is pyramidal in shape having a root and free apex. It is formed of bony (posteroinferior) and cartilaginous (anteroinferior) parts. The skin of the external nose is thick and rich in sebaceous glands. - Nerve supply of the skin of the external nose: All the nerves supplying the skin of the nose are derived from the nasociliary branch of the ophthalmic nerve. - Blood supply of external nose: The facial, infraorbital and ophthalmic vessels. ❖ Nasal Cavity: - Roof: Is formed of 3 parts: Anterior sloping part: Formed of nasal and frontal bones. Middle horizontal part: The cribriform plate of ethmoid bone. Posterior sloping part: Formed of the body of sphenoid. - Floor: It is formed by the 2 parts of the hard palate. - Medial wall (nasal septum): formed of Cartilaginous part: In front. Bony part: behind. - Lateral wall: Nearly flat, showing a number of openings which lead to the paranasal sinuses. It is formed of many bones. The lateral wall of the nasal cavity has 3 parts: A. Vestibule of nose: The small, dilated part above the nostril which is lined by skin containing sweat glands, sebaceous glands and coarse hairs for filtration of dust particles and insects. B. Atrium of middle meatus: A shallow depression above and behind the vestibule which is continuous posteriorly with the middle meatus. C.Nasal conchae and meatuses: The lateral wall shows 3 curved bony projections covered with a highly vascular mucosa called nasal conchae. They are superior concha (the smallest), middle concha, and the inferior concha (the largest). The localized space below and lateral to each concha is called nasal meatus. The space above the superior concha is called sphenoethmoidal recess. The middle meatus shows a rounded elevation called bulla ethmoidalis which is bounded below and in front by a curved groove called hiatus semilunaris. Function of nasal conchae: They increase the surface area of the nasal cavity which magnifies the turbulence of air and thus improves olfaction. The excessive mucosal area increases humidity and warming of inspired air. 9  Openings in the lateral wall of nose: A. Openings of paranasal sinuses: Four sinuses open into the middle meatus of the nose: 1. Frontal sinus: Opens in ethmoidal infundibulum which opens in the anterior end of the hiatus semilunaris. 2. Maxillary sinus: Opens in posterior end of hiatus semilunaris. 3. Anterior ethmoidal sinus: Opens in ethmoidal infundibulum or in the anterior end of hiatus semilunaris. 4. Middle ethmoidal sinus: Opens in bulla ethmoidalis. Posterior ethmoidal sinus opens into the superior meatus of the nose. Sphenoidal sinus opens into sphenoethmoidal recess. B. Other openings in the lateral wall of nose: Nasolacrimal duct opens in the anterior end of the inferior meatus. Sphenopalatine foramen lies behind the superior meatus and opens in pterygopalatine fossa. ❖ Nerve supply of nasal cavity: A- Olfactory nerve (1st cranial nerve) B- Nerves of general sensation: 1. Anterior ethmoidal nerve: It is a branch of the mucociliary neve which arises from the ophthalmic nerve 2. Nasal branches of sphenopalatine ganglion ❖ Arterial supply of nasal cavity: It arises from the ophthalmic, maxillary, and facial arteries. ❖ Applied anatomy: ▪ The area of epistaxis (Little’s area): A small area which lies in the anteroinferior part of nasal septum in the region of the vestibule. ▪ It is an area of anastomosis between the branches of arteries supplying the nasal cavity. In 90% of cases, epistaxis (bleeding from nose) occurs from Little’s area. Paranasal sinuses They are air-filled spaces in the skull bones surrounding the nose. They open in the lateral wall of nasal cavity by special foramina. - The functions of paranasal sinuses: a. Decrease the weight of the skull due to filling of the sinuses by air. b. Increase the resonance of voice. c. Increase the surface area of nasal mucosa, so they warm and moist the inspired air. d. They act as air insulator cushions for the brain, eye and pituitary gland. e. The paranasal sinuses are absent at birth (except the maxillary sinus). They show marked growth at the time of eruption of permanent teeth. - Types and site of Paranasal Sinuses: I. Frontal sinuses: They are two asymmetrical sinuses present in the squamous part of the frontal bone above and behind the superciliary arches. They are separated by a bony septum. Each sinus opens into the frontonasal duct in the middle meatus of nose. - Nerve supply: Supraorbital and anterior ethmoidal nerves (branches of frontal and nasociliary nerves, which are a branches of the ophthalmic nerve). - Arterial supply: Supraorbital artery (branch of ophthalmic artery). - Lymph drainage: Into the submandibular lymph nodes. II. Maxillary sinuses: The largest air sinus and the only one present at birth. It is pyramidal in shape and occupies the whole of the body of maxilla. - Relations: ▪ Apex: Directed laterally towards the zygomatic bone. 10  ▪ Base: Directed medially towards the nasal cavity. ▪ Roof: It is the floor of the orbit, containing infraorbital groove and canal. ▪ Floor: Formed by alveolar process of maxilla. It lies 1 cm below the floor of the nose. Its lower part lies opposite the 2nd premolar and 1st molar teeth, so the extraction of these teeth may damage and perforate the floor leading to oroantral fistula. ▪ Anterior wall: Subcutaneous ▪ Posterior wall: Separates the sinus from infratemporal and pterygopalatine fossae. - Opening of maxillary sinus: Large, rounded opening, 2 cm in diameter, present in the upper part of the base of the sinus. It opens in the middle meatus of the nose at the posterior end of hiatus semilunaris below the bulla ethmoidalis. - Clinical application: The higher position of the opening of the sinus makes the drainage of any collection of pus or blood very hard. III. Ethmoidal sinuses: They are lying inside the ethmoidal labyrinth between the orbit and upper part of nasal cavity. They vary in number from 3-18 air cells arranged into 3 groups: 1. Anterior ethmoidal sinus (or cells) opens in the ethmoidal infundibulum or in the anterior end of the hiatus semilunaris in the middle meatus of nose. 2. Middle ethmoidal sinus produces the bulla ethmoidalis on which it opens. 3. Posterior ethmoidal sinus (or cells) opens in the superior meatus. - Nerve and arterial supply: Anterior and posterior ethmoidal nerves and arteries IV. Sphenoid sinus: It occupies the body of sphenoid and lies behind the upper part of nasal cavity. The two sphenoid sinuses are separated by a bony septum which lies in the midline. Anteriorly: The opening of the sinus lies in the upper part of its anterior wall, and it opens in the sphenoethmoidal recess. - Nerve supply: Posterior ethmoidal and orbital branches of the sphenopalatine ganglion. - Arterial supply: Posterior ethmoidal artery. THE LARYNX It is an air tube belonging to the respiratory system, extending from the root of the tongue and upper border of the epiglottis (C3 ) to the lower border of cricoid cartilage (C6). ❖ Skeleton (framework) of the larynx: The larynx consists of nine cartilages connected together by ligaments and membranes. I. Cartilages of the larynx: 3 single and 3 paired: A. Single cartilages: 1. Thyroid cartilage: It consists of two quadrilateral lamina which are fused anteriorly forming an angle about 90º in males and 120º in females. The fused anterior borders form the laryngeal prominence or Adam’s apple. The upper border of the cartilage shows a V-shaped depression in the median plane above the laryngeal prominence called thyroid notch. The posterior border of each lamina is free and extends upwards and downwards as superior and inferior horns. The outer surface of each lamina shows an oblique line. 2. Cricoid cartilage: It consists of narrow arch anteriorly and broad quadrate lamina posteriorly. It forms two synovial joints with the inferior horns of thyroid and arytenoid cartilages. 3. Epiglottis: It is a leaf-like plate of elastic fibrocartilage which lies behind the root of the tongue. B. Paired cartilages: 11  1. Arytenoid cartilages: They are pyramidal shaped hyaline cartilages which lie on the upper part of the lamina of the cricoid cartilages. Each cartilage has: ▪ Apex: directed upwards backwards and medially, articulating with the corniculate cartilage and gives attachment to the aryepiglottic fold. ▪ Base: Triangular in shape articulating with the upper border of the lamina of the cricoid cartilage by a synovial joint. It has 2 processes: a. Vocal process: Is the anterior angle of the base and gives attachment to the vocal ligament. b. Muscular process: Is the lateral angle of the base and gives attachment to three muscles. 2. Corniculate and cuneiform cartilages: are small nodules of elastic fibrocartilage which lie in the posterior part of the aryepiglottic fold. Cuneiform cartilages lie in front of the corniculate cartilages. II. Ligaments, membranes & folds of Larynx: The most important are: 1. Thyrohyoid Membrane: It extends from upper border and superior horns of thyroid cartilage to upper part of posterior surface of body of hyoid bone and its greater horns. 2. Cricothyroid ligament: has 2 parts: a. Median thick anterior part called cricothyroid ligament: It connects the anterior parts of thyroid and cricoid cartilages. b. Lateral thin part called cricovocal membrane: Below: It is attached to the upper border of cricoid cartilage. Above: Its upper border is free and thick; it extends from the vocal process of arytenoid cartilage to the inner surface of angle of thyroid cartilage, it is called the vocal fold or vocal ligament. 3. Quadrangular Membranes (Ligaments): Fibroelastic membrane, extending from sides of epiglottis anteriorly to the arytenoid cartilages posteriorly. Its upper free border forms the aryepiglottic fold. Its lower free border forms the vestibular fold. ❖ The Cavity of Larynx It extends from the inlet of larynx to the lower border of cricoid cartilage. It is divided into: 1. The vestibule: The upper part of the cavity of larynx which extends from laryngeal inlet to the vestibular folds. 2. The sinus of the larynx: The middle part of the cavity which is present between the vestibular folds above and the vocal folds below. The narrow gap between the two vocal folds is called rima glottidis. 3. The infraglottic part: The lower part of the cavity of larynx extending from the vocal folds till the lower border of cricoid cartilage. ❖ The inlet of larynx: It is directed upwards and backwards and communicates the larynx with laryngopharynx ❖ Muscles of the Larynx: They are divided into 3 groups: A. Muscles which close the inlet of larynx: 1. Transverse arytenoid muscle: It extends between the lateral margins of both arytenoid cartilages. 2. Oblique arytenoid muscles: 2 muscles crossing each other like the letter (x), Each one extends from the posterior surface of muscular process of one arytenoid to the apex of the other arytenoid cartilage. 3. Aryepiglottic muscle: It arises from the apex of arytenoid cartilage and is inserted into the side of epiglottis. 12  B. Muscles which stretch and relax the vocal cords: Muscles which stretch the vocal cords Muscles which relax the vocal cords 1- Cricothyroid muscle: 1- Thyroarytenoid muscle: Origin: Anterolateral aspect of arch of Origin: Lower ½ of the inner surface of cricoid cartilage. angle of thyroid cartilage. Insertion: Lower border and inferior horn Insertion: Anterolateral surface of arytenoid of thyroid cartilage. cartilage. 2- Vocalis muscle (anterior part): Lies 2- Vocalis muscle (posterior part): It relaxes lateral to vocal cord. It stretches the the post. part of the cord. anterior part of the cord. C. Muscles which adduct and abduct the vocal cords: Muscles which adduct the vocal cordsMuscles with abduct the vocal cords 1- Lateral cricoarytenoid muscle: Posterior cricoarytenoid muscle. Origin: Superior surface of the arch Origin: Posterior surface of the cricoid lamina. of cricoid cartilage. Insertion: Posterior surface of the muscular process Insertion: Anterior surface of the of arytenoid cartilage. muscular process of arytenoid cartilage. 2- Transverse arytenoid muscle. 3- Cricothyroid muscle. ❖ Nerve Supply of Larynx 1. Recurrent laryngeal nerve: a. Motor for all muscles of larynx except cricothyroid muscle. b. Sensory for mucosa of larynx below vocal cords. 2. Superior laryngeal nerve: It divides into 2 nerves: a. External laryngeal nerve: Supplies one muscle (cricothyroid muscle). b. Internal laryngeal nerve: supplies the mucosa of larynx above vocal cords and epiglottis. ❖ Blood Supply of Larynx 1. Superior laryngeal artery: Arises from superior thyroid artery and accompanies the internal laryngeal nerve to supply the upper part of larynx. 2. Inferior laryngeal artery: Arises from inferior thyroid artery (from subclavian artery) and ascends with recurrent laryngeal nerve to reach and supply the lower part of larynx. ❖ Applied Anatomy: 1. Injury to both external laryngeal nerves: Leads to paralysis of both cricothyroid muscles and relaxation of vocal cords, leading to weakness and hoarseness of voice. 2. Injury of recurrent laryngeal nerves: a. On one side: It leads to monotonous voice (loss of high-pitched voice). b. On both sides: complete injury leads to aphonia, and incomplete injury leads to stridor. The Trachea and Bronchi I. Trachea - Beginning: It begins in the neck, at the level of the lower border of C6, as a continuation of the larynx. - End: It ends in the thorax, at the level of the disc between T4/T5 (sternal angle) by dividing into 2 principal bronchi. - Length: It is about 10-12 cm long and about 1½-2 cm in diameter. - Position: Its upper 1/2 lies in the neck, while its lower 1/2 lies in the thorax. The thoracic part of the trachea passes through the whole length of the superior mediastinum extending from the suprasternal notch to the sternal angle. 13