Respiratory Tract Anatomy

• Concerns the anatomy of the respiratory tract.

Learning Outcomes

• Will cover the respiratory tract's introduction and functions.
• Structural and functional divisions will be explored.
• Focus on the tract's innervation.
• Will address the structure and functions of the nose, pharynx, larynx, trachea, and their respective divisions.

Parts of the Upper Respiratory Tract

• Includes the nasal cavity, nasopharynx, oropharynx, laryngopharynx, and trachea.

Nose Parts

• The nose consists of the external nose and the nasal cavity.
• The external nose is shaped like a pyramid.
• The external nose apex (tip), root, and dorsum.
• Nostrils (nares) are a pair of piriform apertures
• The nasal septum is located medially
• Ala of the nose sits laterally.

Blood Supply and Innervation

• Arterial supply comes from the dorsal nasal branch (ophthalmic), infraorbital (maxillary), and alar and septal (facial) arteries.
• Sensory innervation is provided by the external nasal, infratrochlear (ophthalmic), and infraorbital (maxillary) nerves.
• Motor innervation comes from the facial nerve branches.

Nasal Cavity

• The nasal cavity is divided into two asymmetrical halves by a median nasal septum.
• It extends from the nostrils to the choanae.
• The vestibule is close to the nostrils.
• The vestibule is lined by skin with hairs and sebaceous glands.

Nasal Cavity Dimensions

• Subdivided into halves featuring a roof, floor, medial wall, and lateral wall.
• Each half measures about 5cm in height, 5-7cm in length, 1.5cm in width near the floor, and 1-2mm near the roof.

Nasal Cavity Roof

• The roof is part of the ethmoid bone and includes the cribriform plate.
• It measures 7cm long and 2mm wide.
• The roof slopes downwards both in front and behind.
• Its middle horizontal part is the cribriform plate of the ethmoid bone.
• The anterior slope is the nasal part of the frontal bone, nasal bone, and nasal cartilages.
• The posterior slope is the inferior surface of the body of the sphenoid bone.

Floor

• The floor measures 5cm long and 1.5cm wide.
• It is formed by the palatine process of the maxilla and the horizontal plate of the palatine bone.
• The floor is concave from side to side.

Nasal Septum (Medial Wall)

• The nasal septum is the median osseocartilaginous partition between the two halves.
• Each side is covered by a mucous membrane that forms the medial wall of both nasal cavities.
• The septum contains bony and cartilaginous parts.
• The bony formation includes the perpendicular plate of the ethmoid and vomer bones.
• The cartilaginous formation consists of the septal cartilage and inferior nasal cartilage.
• The cuticular formation includes fibro-fatty tissue and skin, the columella, and the vomero-nasal organ of Jacobson.

Nasal Septum: Arterial Supply

• Supplied by Kiesselbach's plexus, anterior and posterior ethmoid arteries, sphenopalatine artery, and greater palatine artery.

Venous Drainage

• Drains via the superior ophthalmic vein (anterior-superior), facial vein to IJV (mobile part of the septum), and pterygoid venous plexus (postero-inferior).
• Venous drainage involves the Kiesselbach's plexus, facial vein, sphenopalatine vein, and pterygoid venous plexus.

Nerve Supply

• The olfactory zone is supplied by the ant. ethmoidal N (ophthalmic).
• Long Sphenopalatine, Short Sphenopalatine and Greater palatine N.
• Supplied by the Pterygo palatine ganglion & Maxillary N.
• Nasal septum receives special sensory innervation, which is general sensory from the olfactory nerve.
• Medial internal nasal branch of the anterior ethmoidal nerve.

Lateral Wall

• The lateral wall can be subdivided into three parts.
• Small depressed area in the anterior part called the vestibule.
• The vestibule is lined by modified skin that contain short, stiff, curved hairs termed vibrissae and contain sweat and sebaceous glands.
• The middle part is known as the atrium of the middle meatus.
• The posterior part contains the concha and spaces separating the concha are called meatuses.

Nasal Conchae (Turbinate Bones)

• The inferior concha is a separate bone.
• It extends horizontally backwards, ending 1.25cm in front of the pharyngeal opening of the auditory tube, and is continuous anteriorly as the vestibule.
• The space under the concha covers the inferior meatus.
• The termination of the naso-lacrimal duct is involved.
• The middle meatus features the Bulla ethamoidalis- a bony bulging
• Middle ethmoidal air sinuses open into the meatus or above the bulla.
• Includes the Hiatus semilunaris- a Cresentric space below the bulla. Opening to the maxillary sinus.
• Includes a short Ethmoidal infundibulum with a short passage at the anterior end of the hiatus. Anterior ethmoidal and frontal sinus opens into it.

Superior Concha

• The shortest concha.
• Superior meatus- Posterior ethmoidal sinus opens.
• Supreme meatus lies between the superior concha and roof of the nasal cavity.
• Has a Sphenoethamoidal recess.
• Sphenoidal air sinuses opens into it.

Nasal Passage

• Inferior meatus opens to the nasolacrimal duct.
• Frontal Sinus, Maxillary Sinus, Anterior Ethmoidal cells, and Middle Ethmoidal cells are in the Middle Meatus.
• The superior Meatus opens into the Posterior ethmoidal cells.
• The Sphenoethmoidal Recess opens into the Sphenoidal Sinus.

Lateral Wall of Nose: Arterial Supply

• The arterial supply to the lateral wall of the nose comes from the anterior ethmoidal, posterior ethmoidal, facial, and sphenopalatine arteries.

Lateral Wall of Nose: Nerve Supply

• The lateral wall of the nose is supplied by the anterior ethmoidal (ophthalmic) nerve.
• Also has the Pterygopalatine ganglion (maxillary nerve), maxillary nerve, and Pterygopalatine ganglion (maxillary nerve).
• It receives special sensory innervation from the olfactory nerve.

Applied Anatomy: Spread of Infection

• Infections can spread to the middle cranial fossa via the cribriform plate and to the lacrimal apparatus via the nasolacrimal duct.
• Septal deviation causes congestion corrected by sub mucosal resection.
• Epistaxis refers to bleeding from the nose.
• Dangerous areas of the nose allow infections to spread along the olfactory nerves to the cranial cavity.
• Nasal Fracture is a break or crack in bone/cartilage occurring over the bridge/septum area dividing nostrils.

Applied Anatomy

• DNS stands for Deviated Nasal Septum.
• A nasal polyp is another type of condition.

Little's Area

• Represents the Kiesselbach's plexus area.
• It lies is in the anteroinferior aspect of the nasal septum.
• Region where four arteries anastomose to form a vascular plexus.
• It is also a common site of nosebleeds (epistaxis).

Applied Anatomy: Allergic Rhinitis

• Which causes Hypertrophy of mucosa over the inferior nasal concha.

Pharynx

• The pharynx measures 12–14 cm long.
• It's a musculomembranous tube shaped like an inverted cone.
• Stretching from cranial base to inferior cricoid cartilage border (C6).
• Communicates w/nasal, oral & laryngeal cavities via nasopharynx, oropharynx & laryngopharynx.
• Divisible into nasopharynx, oropharynx, & laryngopharynx. Also connects the oral cavity and pharynx through the oropharyngeal isthmus.

Nasopharynx

• Opening of the auditory tube.
• Tubal elevation
• Salpingopharyngeal & salpingopalatine fold
• Tubal tonsil & Pharyngeal tonsil
• Communication between naso & oropharynx is pharyngeal isthmus

Oropharynx

• Lies in front of C2 & upper part of C3 vertebra.
• Palatopharyngeal folds/arches
• Palatine tonsil & tonsillar sinus.

Laryngopharynx

• Lies in front of C3-C6 vertebra.
• The upper part is made of of inlet larynx.
• Has below and posterior surfaces by the arytenoid & cricoid cartilages.

Wall of Pharynx

• Wall is made of skeletal muscles & fascia.
• Made of Buccopharyngeal fascia coats outside of muscle wall and a Pharyngobasilar fascia that lines inside of muscle wall.

Constrictors

• The Superior middle & inferior constrictors, originate posterior to nasal, oral & laryngeal cavities.
• Fibers meet at midline raphe.

Longitudinal Muscles

• The Stylopharyngeus, palatopharyngeus & salpingopharyngeus.

Nerve Supply

• All constrictors & salpingopharyngeus are innervated by pharyngeal branch of vagus.
• Stylopharyngeus are innervated by the glossopharyngeal and palatopharyngeus by cranial part of accessory

Blood Vessels and Lymphatics

• Ascending pharyngeal, lingual, facial, maxillary arteries.
• Also, Venous plexus surrounding pharynx drains into internal jugular & facial veins as well as Lymph vessels draining into deep cervical lymph nodes.
• The Pharyngeal plexus is formed by branches of glossopharyngeal, vagus,& cranial accessory

Killian’s Dehiscence

• Triangular area in pharynx wall of the thyropharyngeal and cricopharyngeus (inferior constrictor) of the pharynx.
• Represents a weak spot where pharyngoesophageal diverticulum (Zenker's diverticulum) is likely to occur.

Paranasal Air Sinus

• Air filled spaces in bone around nasal cavity
• Named after bones they're located in.

Types of Sinuses

• There are four groups: the Maxillary sinuses (Antrum of Highmore) as well as Ethmoid, Frontal, and Sphenoid sinuses.

Paranasal Air Sinus Information

• These are cavities found in the interior of the maxilla, frontal, sphenoid, and ethmoid bones.
• They are lined with mucoperiosteum and filled with air and communicate with the nasal cavity through relatively small apertures. Lined by pseudostratified ciliated columnar epithelium too.
• Maxillary sinuses start being aerated at birth as the Frontal /sphenoidal sinuses develop at 6-7 years of age
• Ethmoid sinuses Develop during puberty and develop slowly until 17-18 years of age.

Functions

• Decrease skull bone weight, warm, moisten & filter incoming air as well as serve as a resonating chamber for voice.
• They are also shock absorbers and control and help control the Immune system
• Voice is altered when apertures are blocked or filled with fluid.

Applied Anatomy

• Sinusitis- is an inflammation of the tissue lining the sinus. Healthy sinuses are filled with air. When they become blocked and filled with fluid, infection germ grows.
• The types of sinusitis are acute, subacute, chronic and recurrent.
• Common cold, allergic rhinitis, nasal polyp and deviated nasal septum can cause sinusitis