Upper Respiratory Tract Anatomy

• The lecture covers the anatomy of the upper respiratory tract, focusing on the nose, pharynx, and larynx.

Nose

• Functions as the upper part of the respiratory tract.
• Contains olfactory receptors for smell.
• The nasal cavities are separated by a midline nasal septum.

Nose Relations

• The nasal cavities are related to the oral cavity inferiorly, the cranial cavity superiorly, and the orbits laterally.

External Nose

• The external nose is kept open by a skeletal framework of bone and cartilage.
• It has an apex (tip) anteriorly and an upper angle.
• The bones include the nasal, maxillary, and frontal bones.

Anterior Nasal Openings (Nares)

• These are kept open by nasal cartilages, the inferior nasal spine, and the maxillae.

Posterior Nasal Openings (Choanae)

• These form the openings between the nasal cavities and the nasopharynx.
• Choanae are rigid structures completely surrounded by bone.

Nasal Cavity Regions

• Nasal Vestibule: Lined by skin and hair to filter the respired air.
• Respiratory Region: Lined by respiratory epithelium with a rich neurovascular supply that warms the air.
• Olfactory Region: Lined by olfactory epithelium containing olfactory receptors for smell.

Boundaries of the Nasal Cavity

• The floor is formed by the hard palate.
• The medial wall consists of the nasal septum that separates the right and left nasal cavities and is covered by mucosa.
• The nasal septum is formed by the septal nasal cartilage, vomer, and the perpendicular plate of the ethmoid bone.
• The lateral wall consists of bone, cartilage, and soft tissues.
• There are three nasal conchae: superior, middle, and inferior.
• The conchae divide each nasal cavity into four air channels.
• Spheno-ethmoidal recess.
• Superior nasal meatus.
• Middle nasal meatus.
• Inferior nasal meatus.
• The lateral wall also contains the openings for the paranasal sinuses (frontal, ethmoid, sphenoid, maxillary) and the nasolacrimal duct.

Openings in the Lateral Nasal Wall

• Spheno-ethmoidal Recess: Contains the opening of the sphenoidal sinus.
• Superior Nasal Meatus: Contains the opening of posterior ethmoidal cells.
• Middle Nasal Meatus: Contains the opening of the frontal sinus, anterior and middle ethmoidal cells, and the maxillary sinus (semilunar hiatus).
• Inferior Nasal Meatus: Contains the opening of the nasolacrimal duct.

Blood Supply of the Nasal Cavity (Arteries)

• The arterial supply originates from both the internal and external carotid arteries.
• Anterior and Posterior Ethmoidal Arteries: Originate from the internal carotid artery (ophthalmic artery).
• Sphenopalatine Artery: Originates from the external carotid artery (maxillary artery).
• Greater Palatine Artery: Originates from the external carotid artery (maxillary artery).
• Superior Labial Artery: Originates from the external carotid artery (facial artery).
• Lateral Nasal Arteries: Originates from the external carotid artery (facial artery).
• The arteries anastomose at the anterior region of the medial wall.
• This area is highly vascular and is a common site for nosebleeds (epistaxis).

Nasal Cavity Drainage

• Drains into the pterygoid plexus of veins, facial vein, and superior ophthalmic vein.

Lymphatic Drainage of the Nasal Cavity

• Drains into the submandibular and upper deep cervical nodes.

Nasal Cavity Innervation

• Olfactory Nerve: Carries the sense of smell (olfaction).
• Trigeminal Nerve (T): Carries general sensation.
• Ophthalmic nerve.
• Maxillary nerve.
• Parasympathetic: Secretomotor for the glands.
• Sympathetic: Regulates blood flow in the nasal mucosa.

Pharynx

• Associated with both the digestive and respiratory tracts
• Consists of muscles and fascia

Pharynx Structure

• Attached to the skull base superiorly
• Continuous with the esophagus at the C6 vertebral level inferiorly

Pharynx Parts

• Nasopharynx: Located behind the nasal cavities.
• Oropharynx: Located behind the oral cavity.
• Laryngopharynx: Located behind the larynx.

Pharynx Cavity Features

• Pharyngotympanic Tube Opening is present along with tubal elevation.
• Pharyngeal Recess.
• Salpingopharyngeal Fold (formed by the Salpingopharyngeus muscle).
• Pharyngeal Tonsils (Adenoid).
• Palatine Tonsils.

Blood Supply and Lymphatic Drainage of the Pharynx

• Arterial supply comes from branches of the external carotid artery (ECA).
• Veins form a plexus that drains into the internal jugular vein (IJV).
• Lymphatics drain into the deep cervical nodes.

Nerve Supply of the Pharynx

• Motor: Vagus and Glossopharyngeal nerves.
• Sensory:
• Nasopharynx: Maxillary nerve.
• Oropharynx: Glossopharyngeal nerve.
• Laryngopharynx: Vagus nerve.
• Branches from cranial nerves 9 and 10, along with sympathetic nerves, form the pharyngeal plexus on the pharynx wall.

Larynx

• It is a hollow musculo-ligamentous structure with a cartilaginous framework.
• It is attached to the hyoid bone superiorly and extends to the top of the trachea inferiorly, at the level of C6.
• The upper opening, called the laryngeal inlet, is tilted posteriorly and opens into the pharynx.

Larynx Functions

• Functions as part of the respiratory tract.
• Is an organ of voice production.

Laryngeal Cartilages

• Large, Unpaired Cartilages: Thyroid, Cricoid, and Epiglottis.
• Paired Small Cartilages: Arytenoid, Corniculate, and Cuneiform.
• The cartilages are connected by synovial joints.
• Thyroid Cartilage: The largest laryngeal cartilage, formed by a right and left laminae which join to form the laryngeal prominence (Adam's apple).
• Epiglottis: A leaf-shaped cartilage that closes the laryngeal inlet during swallowing.

Ligaments of the Larynx

• Extrinsic:
• Thyrohyoid membrane.
• Hyo-epiglottic ligament.
• Cricotracheal ligament.
• Intrinsic:
• Cricothyroid ligament.
• Quadrangular membrane.

Laryngeal Ligaments

• Vestibular Fold: The free lower margin of the quadrangular ligament thickens.
• Forms the vestibular ligament under the vestibular fold which constitutes the false vocal cords.
• Vocal Fold: The free upper margin of the cricothyroid ligament thickens.
• Forms the vocal ligament under the vocal fold, which is the true vocal cord.

Laryngeal Cavity Regions

• Vestibule: Situated between the laryngeal inlet and the vestibular folds.
• Middle Part: Located between the vestibular and vocal folds.
• Infraglottic Space: Extends between the vocal folds and the inferior opening of the larynx.
• Rima Glottides: It is the opening between the two adjacent vocal folds (V).
• Rima Vestibuli: It is the opening between the two adjacent vestibular folds.

Intrinsic Muscles of the Larynx

• Cricothyroid
• Posterior cricoarytenoid
• Lateral crico-arytenoid
• Thyro-arytenoid
• Transverse arytenoid
• Oblique arytenoid
• Vocalis
• Sphincter of the laryngeal inlet (produced by the Thyro-arytenoid and Oblique arytenoid muscles).
• Length of the vocal folds is controlled by the Cricothyroid ligament.
• Vocal ligaments' tension is maintained by Vocalis.
• Closes the rima glottides (Adduction): Transverse and Lateral arytenoid muscles.
• The Posterior Cricoarytenoid is the only abductor of the vocal folds and the primary opener of the rima glottides.

Blood Supply of the Larynx

• Superior Laryngeal Artery: Originates from the superior thyroid branch of the external carotid artery.
• Inferior Laryngeal Artery: Originates from the inferior thyroid branch of the subclavian artery.
• Superior Laryngeal Veins: Drain into the superior thyroid vein, which drains into the internal jugular veins (IJV).
• Inferior Laryngeal Veins: Drain into the inferior thyroid vein, which drains into the left brachiocephalic vein.

Lymphatic Drainage of the Larynx

• Drains into the deep cervical nodes.

Nerve Supply of the Larynx

• Motor and sensory innervation originate from branches of the vagus nerve (X).
• Superior Laryngeal Nerves: Divide into internal and external branches.
  • The external laryngeal nerve supplies the cricothyroid muscle.
  • The internal laryngeal nerve supplies sensory innervation to the upper part of the laryngeal cavity, down to the level of the vocal folds.
• Recurrent Laryngeal Nerves: Supply motor innervation to all intrinsic muscles of the larynx, except for the cricothyroid, and sensory innervation to the laryngeal cavity below the vocal folds.