ANATOMY OF THE RESPIRATORY SYSTEM

Kaan Yücel M.D., Ph.D.

25.November.2011 Friday 1

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NOSE & ASSOCIATED STRUCTURES Nose is divisible into two parts as external nose and nasal cavity.

Functions of the nose and the nasal cavities are:o Olfaction (sense of smell)o Respirationo Filtration of the dust in the inspired air o Humidification and warming of the inspired airo Reception of the secretions from the paranasal sinuses and

nasolacrimal ducts

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EXTERNAL NOSE

Extends the nasal cavities onto the front of the face and positions the nares so that they point downward.

Pyramidal in shape with its apex anterior in position.

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External Nose has five parts:1) Dorsum2) Root3) Apex4) Nares (nostrils, anterior nasal apertures)5) Alae of the noseExternal nose has bony and cartilaginous parts.

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Bones contributing to the structure of the external nose: Nasal bones Frontal process of maxilla Nasal part of frontal bone

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Cartilages contributing to the structure of the external nose: Lateral cartilages (paired) Alar cartilages (paired) Septal cartilage (single)

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Nasal Cavities:• The two nasal cavities are the uppermost parts of the respiratory

tract.

• They contain the olfactory receptors.

The nasal cavities are separated: from each other by a midline nasal septum from the oral cavity below by the hard palate from the cranial cavity above by parts of the frontal, ethmoid,

and sphenoid bones.

Nasal septum is composed of three structures:• Perpendicular plate of the ethmoid bone• Vomer• Septal cartilage

Each nasal cavity is divided into olfactory area (upper 1/3) and respiratory area (lower 2/3).

Posteriorly, each nasal cavity communicates with the nasopharynx through two openings called choana.

Walls of the nasal cavityRoof of the nasal cavity (anterior to posterior) nasal bone frontal bone cribriform plate of the ethmoid bone body of the sphenoid bone

Floor of the nasal cavity is formed by the hard palate (palatine process of maxilla and horizontal plate of the palatine bone).

Atrium: Anterior part of middle nasal meatus

Lateral wall of the nasal cavity (anterior to posterior) frontal process of maxilla lacrimal bone superior nasal concha (of the ethmoid bone), middle nasal

concha (of the ethmoid bone), inferior nasal concha perpendicular plate of the palatine bone medial lamina of the pterygoid process

Medial wall of the nasal cavity is formed by the nasal septum.

The medial wall has a smooth surface, whereas the lateral wall is uneven due to the existance of the nasal conchae.

The spaces between the nasal conchae and the lateral wall of the nasal cavity are called the meatus.

• Superior nasal meatus• Middle nasal meatus• Inferior nasal meatus

The following sinuses open into the middle nasal meatus Frontal sinus Maxillary sinus Ethmoid air cellsSphenoid sinus opens into the sphenoethmoid recessNasolacrimal duct opens into the inferior nasal meatus

Arterial supply of the noseThe nose has an extensive arterial supply. The branches of the maxillary, ophthalmic and facial arteries supply the nose.

Veins of the nose There is a rich network of veins deep to the mucosa of the

nose.

This venous network is important in warming the air before it enters the trachea and the lungs.

Nerves of the noseSensory innervation of the nose is mainly from the maxillary nerve and the ophthalmic nerve.

Nerves of the noseSensory innervation of the nose is mainly from the maxillary nerve and the ophthalmic nerve.Within the epithelium of the olfactory region lies the olfactory cells (neurons).

The peripheral processes of these cells terminate under the mucosa and are sensitive to odour molecules in the air.

The central processes forms the olfactory nerves (CN I).

Paranasal sinuses

Paranasal sinuses are air filled spaces lying within the bones around the nasal cavity.

The paranasal sinuses develop as outgrowths from the nasal cavities and erode into the surrounding bones. All are: lined by respiratory mucosa, which is ciliated and mucus

secreting; open into the nasal cavities; and innervated by branches of the trigeminal nerve [V].

Sinuses are named according to the bones they are located in:Frontal sinusesEthmoid sinusesSphenoid sinusesMaxillary sinuses

Frontal sinus

The frontal sinuses, one on each side, are variable in size and are the most superior of the sinuses.

The frontal sinus lies within the inner and outer plates of the frontal bone, posterior to the supercilliary arches and the root of the nose.

It drains into the middle nasal meatus.

Ethmoid sinusesSeveral ethmoid air cells (3-15) collectively are called the ethmoid sinuses.Ethmoid air cells form three groups: Anterior group Middle group Posterior group

Sphenoid sinus The sphenoid sinus is situated within the body of the

sphenoid bone. Sinuses of each side is seperated by a bony septum. It drains into the sphenoethmoidal recess.

Maxillary sinus The maxillary sinuses, one on each side, are the largest of the

paranasal sinuses and completely fill the bodies of the maxillae.

The maxillary opening drains into the middle nasal meatus.

Larynx Larnynx is the organ of phonation (vocalization).

It is formed of cartilage, muscles and connective tissue.

Larynx’s inner surface is covered by the respiratory mucosa.

The cavity of the larynx is continuous below with the trachea, and above opens into the pharynx (nasopharynx).

Skeleton of larynx is formed of 3 unpaired and 3 paired cartilagesUnpaired cartilages Thyroid cartilage (biggest) Cricoid cartilage Epiglottic cartilagePaired cartilages Arytenoid Corniculate Cuneiform

Thyroid cartilage The thyroid cartilage is the largest cartilage of the larynx.

It is formed of two laminae which fuse anteriorly at the thyroid angle to form laryngeal prominence (Adam’s apple).

Fibroelastic membrane of the larynx It lies under the mucosa of the larynx.

The fibroelastic membrane of the larynx has thickenings at certain regions and forms some of the ligaments between the cartilages.

It is formed of two parts:Quadrangular membraneConus elasticus

Conus elasticus (cricovocal membrane): Its free upper margin thickens to form the vocal ligament, which is covered by mucosa to form the vocal fold.

The opening between the two vocal folds is called rima glottis.

Vocal cord= Vocal fold

Each vocal ligament, converges anteriorly and attaches to the anterior part of the inner surface of the thyroid cartilage (thyroid angle).

Posteriorly, they individually attach to the vocal processes of the arytenoid cartilages.

Rima glottis widens during inspiration and two vocal folds are approximated during phonation.

Various changes of the vocal folds determine the color, pitch and the tones of sound.

Pitch increases with tensing, decreases by relaxation.

Intensity of expiration determines the loudness of sound.

Laryngeal Muscles Extrisic muscles These are the suprahyoid and infrahyoid muscles. They either depress or elavate the larynx and hyoid bone.

Intrinsic muscles: There are six intrinsic muscles in the larnyx. They move the laryngeal parts.

Vasculature of the larynxThe major blood supply to the larynx is by the superior and inferior laryngeal arteries.

Nerves of the larynxLarynx is innervated by the inferior and superior laryngeal nerves. Both the inferior and superior laryngeal nerves are branches of the vagus nerve (CN X).

Trachea

The trachea extends from the inferior end of larynx.

It terminates by dividing into right and left main bronchi.

Right main bronchus is wider, shorter, runs more vertically.

The main bronchi give branches inside the lungs that form the bronchial tree.Lobar bronchi (secondary bronchi)3 on the right, 2 on the leftSegmental bronchi (tertiary bronchi)Supply the bronchopulmonary segmentsTrachea is formed of tracheal rings which are incomplete posteriorly.

Trachea is formed of tracheal rings which are incomplete posteriorly.

Pleaura & the Lungs PleuraEach pulmonary cavity (right and left) is lined by a pleural membrane (pleura) that also reflects onto and covers the external surface of the lungs occupying the cavities.

Each lung is invested by and enclosed in a serous pleural sac that consists of two continuous membranes:

Visceral pleura (invests all surfaces of the lungs)

Parietal pleura (lines the pulmonary cavities and the inner surface of the thorax)

The pleural cavity—the potential space between the layers of pleura—contains a capillary layer of serous pleural fluid, which lubricates the pleural surfaces and allows the layers of pleura to slide smoothly over each other during respiration.

Lungs The two lungs are organs of respiration and lie on either side of

the mediastinum surrounded by the right and left pleural cavities.

Air enters and leaves the lungs via main bronchi, which are branches of the trachea.

Their main function is to oxygenate the blood by bringing the inspired air into close relation with the venous blood in the pulmonary capillaries.

The pulmonary arteries deliver deoxygenated blood to the lungs from the right ventricle of the heart.

Oxygenated blood returns to the left atrium via the pulmonary veins.

Each lung bears the following features:1. Apex (upper pole)2. Three surfaces (costal, mediastinal and diaphragmatic).3. Root of the lung is formed by the structures entering and

leaving the lung through its hilum.4. There are two lobes in the left lung seperated by the oblique

fissure.5. There are three lobes in the right lung seperated by horizontal

and oblique fissures.

Branching of the bronchial tree Trachea Principal bronchus Lobar bronchi (secondary bronchi) Segmental bronchi (tertiary bronchi) Terminal bronchiol Respiratory bronchiol Alveolar duct Alveolar sac Alveolus

Each lobar bronchus divides into several tertiary segmental bronchi that supply the bronchopulmonary segments.

The bronchopulmonary segments are the largest subdivisions of a lobe.

Vasculature of the pleaura and the lungs Each lung has a pulmonary artery (carries venous blood)

and two pulmonary veins (carries arterial blood).

Each lobe and segment has its own artery.

Branching of the arteries follow the bronchial tree and terminate as capillaries around the alveols.

Intersegmental part of the pulmonary veins run within the septa and drain the segments.

Veins of the parietal pleura drain into the systemic veins mainly through the intercostal veins.

Bronchial arteries The bronchial arterties supply blood to the tissues of the lung. Left bronchial arteries are paired and the right bronchial artery is one single artery.

Bronchial veinsRight bronchial vein drains into the azygos vein, whereas left bronchial vein drains into the accessory hemiazygos vein.

Nerves of the lungs and pleuraLungs are innervated by pulmonary plexuses, which contains both sympathetic and parasympathetic nerves.

The vagus nerve supplies parasympathetic innervation. (bronchoconstrictor, vasodilator to the lung vessels, secretomotor to the glands).

The sympathetic innervation comes from the sympathetic trunk (bronchodilator, vasoconstrictor to the lung vessels, inhibitor to the glands).

Lymph nodesLymphatics form a superficial and a deep plexus.