Anatomy of the Nose and Sinuses

Upper Airways

• The lecture was delivered on 25-11-2024, during Year 2, Semester 1, by Dr. Vijayalakshmi S B.
• The lecturer's email address is [email protected].
• The lecturer's department is Anatomy.
• The learning outcomes covered oral cavity, gingivae, tongue structure, blood vessels, nerves, pharynx, palate, tonsils, gag reflex, nose (turbinates, meatuses, and sinuses), nasal septum and its blood supply, external/middle ear including auditory canal & tympanic membrane's structure, ossicles, muscles & relations, cartilages, ligaments, and muscles of the larynx, anatomy and movements of vocal cords, nerve supply & injuries, comparing and contrasting laryngotomy and tracheostomy.

Oral Cavity

• The oral cavity proper is the space within the oral vestibule.
• Anatomical structures including the tongue, lingual gingivae, molar tooth, oral vestibule, buccinator muscles, bolus of food, buccal gingiva and mandible are part of the oral cavity
• The oral cavity skeleton includes the frontal, temporal, parietal, occipital, ethmoid, maxillary, sphenoid, palatine, zygomatic, and vomer bones. -Also, mandibular bones
• Bud development for permanent teeth occurs between 8-12 weeks.
• Permanent teeth erupt from 6 years of age onwards with 32 teeth total.
• Central and lateral incisors are included. There's 1 canine tooth.
• 2 premolar teeth.
• 3 molar teeth, with the third molar, or wisdom teeth erupting around age 20.

Oral Cavity Boundaries

• The oral cavity is bordered by the hard palate, soft palate, oropharynx and laryngopharynx.
• The visual cranium is bordered by structures including the frontal sinus, nasal cavity, hard palate, oral cavity proper, genioglossus, mylohyoid, nasopharynx, oropharynx, laryngopharynx, esophagus. -Visual cranium includes viscerocranium and the mandible and hyoid bone..

Oral Cavity - Palatine Tonsils

• The palatine tonsils are located within the oral cavity.
• The palatopharyngeal and palatoglossal arches surround the tonsils.

Oral Cavity - Tongue

• The tongue is the principal organ for taste, speech, and swallowing and is situated in the mouth floor.
• It curves around the body of the mandible.
• It comprises root, apex, inferior surface, and dorsum.
• Tongue is connected to the hyoid bone, mandible, epiglottis and soft palate.
• It includes hyoglossus, genioglossus and the glossoepiglottic fold which connect the root of the tongue to the epiglottis and 2 lateral glossoepiglottic folds (binding vallecula). There are palatoglossal folds which connect to the soft palate

Oral Cavity- Tongue - Surface

• Superior surface includes filiform, fungiform, foliate and vallate papillae.
• Foramen caecum, sulcus terminalis, lingual papillae and lingual tonsil are also related to the tongue. -Vallate papillae, filiform papillae, fungiform papillae, and foliate papillae.
• Inferior surface includes fimbriated fold, frenulum of tongue, sublingual fold, and sublingual caruncle, greater and lesser lingual ducts.

Tongue Muscles

• The extrinsic muscles of the tongue connect it to the skeleton.
• These include palatoglossus, hyoglossus, styloglossus, and genioglossus..
• All supplied by hypoglossal nerve (XII)
• Intrinsic muscles stay within the tongue and are supplied by the hypoglossal nerve (XII).
• Includes superior, inferior, transverse and vertical muscles.

Tongue Movements

• Protrusion is achieved by action of the genioglossus muscles.
• Retraction and depression are achieved by simultaneous action of the styloglossus and hyoglossus muscles.
• Elevation is achieved by simultaneous action of the styloglossus and palatoglossus.

Tongue Blood Supply

• The lingual branch of the external carotid is the primary artery supplying the tongue, but the tonsillar branch of the facial artery and ascending pharyngeal also contribute.
• Deep and dorsal lingual veins empty into the internal jugular vein.

Tongue Nerve Supply

• All the intrinsic muscles of the tongue are supplied by the hypoglossal nerve (CN XII), except the palatoglossus, which is supplied by the vagus nerve (CN X).
• The sensory nerves of the tongue include the lingual branch of the mandibular nerve (for the anterior 2/3), chorda tympani branch of the facial nerve (for taste in the anterior 2/3), and the glossopharyngeal nerve (for the posterior 1/3).
• The superior laryngeal branch of the vagus nerve contributes sensory input to the root of the tongue (and taste).

Lingual Nerve

• The lingual nerve originates from the mandibular nerve (CN V3).
• The lingual nerve is characterized by postganglionic parasympathetic fibers from the submandibular ganglion.
• The lingual nerve also contains chorda tympani (from facial nerve (VII)) fibers which carry taste sensation.
• The lingual artery branches into several smaller arteries.
  • The lingual nerve supplies sensory fibers to the tongue.
• The preganglionic secretomotor fibers originate from the superior salivatory nucleus in the pons. These fibers travel through sensory components of the chorda tympani and lingual nerve, and to reach submandibular ganglion. Postganglionic fibers supply directly the submandibular and sublingual glands through the lingual nerve

Oral Cavity - Innervation

• Motor nerves involved: Mandibular, Vagus, Hypoglossal, Anterior ramus of C1.
• Facial nerves carry taste to the anterior tongue, while glossopharyngeal nerves carry sensory and taste from most of the posterior tongue, and the vagus nerves carry these sensory functions from a small part of the posterior tongue.

External Nose

• Parts include: root, bridge, apex, ala, nostril.
• It has a skeletal framework of nasal, maxillary, and the nasal part of the frontal bone, with both bones and hyaline cartilage.
• The lateral, alar and septal cartilages are important anatomical component of the external nose.

Nasal Cavity

• Has 3 regions: vestible (internal to nostril, lined with skin, filters air), respiratory (main cavity, lined with pseudostratified ciliated columnar epithelium, with olfactory area), and olfactory (lined with olfactory epithelium allowing sense of smell)
• The medial wall/septum involves the perpendicular plate of the ethmoid and the vomer. The anterior part of the septum is cartilage.
  • The roof of the nasal cavity connects to the frontal bone, cribriform plate, and sphenoid bone.
• The floor is the hard palate.
• The lateral walls contain nasal conchae (turbinates).

Nasal Cavity Lateral Wall Openings

• The openings include superior, middle, and inferior meatuses.
• The superior meatus has groups of posterior ethmoidal openings.
• The middle meatus contains the middle ethmoidal groups, frontal sinus, and anterior ethmoidal group openings, and the maxillary sinus opening.
• The inferior meatus has the nasolacrimal duct opening.

Paranasal Sinuses

• Extensions of the nasal cavity.
• Lined with cilia epithelium.
• Communicate with the nasal cavity through channels.
• Located within the frontal, sphenoid, and ethmoid bones and within the maxilla.
• Functions include resonating sound, lightening the skull, warming and moistening inspired air.

Relevance to Clinical Practice

• Paranasal sinus infections (sinusitis) can be caused by nasal infections or dental abscesses.
• Ethmoid sinusitis can also spread to the orbit or affect the optic nerve.

Pharynx

• A funnel-shaped muscular organ.
• Covered by mucosa, forms a pathway for air and food.
• Divided into nasopharynx, oropharynx, and laryngopharynx.
• Three constrictor muscles (superior, middle, inferior) connect posteriorly to form raphe.
• Three elevator muscles (salpingopharyngeus, stylopharyngeus, palatopharyngeus) attach to the eustachian tube, styloid process, soft palate, and merge with the constrictor muscles.

Palatine

• Forms the roof of the oral cavity and floor of nasal cavities.
• The hard palate is anteriorly.
• The soft palate is posteriorly.
  • Covered with periosteum and oral mucosa (inferiorly).
  • Covered with respiratory mucosa (superiorly) -Contains two parts; hard and soft palate. -The hard palate is anteriorly, the soft palate posteriorly.

Ear

• The ear is comprised of external, middle, and internal portions.
• External ear parts - include the helix, antehelix, concha, tragus, antriagrus, lobule. They are made of elastic cartilage.
• Middle ear parts include malleus, incus, and stapes (auditory ossicles).
• Internal ear structures include cochlear duct, semicircular canals.

Ear Canal

• Adult canal is comprised of lateral 2/5 cartilaginous and medial 3/5 bone.
• Child canal is 2/5 cartilaginous and 3/5 bone.
• Lining includes the epithelium, ceruminous glands which secrete cerumen that prevents maceration of skin by water. Cerumen then migrates laterally in a spiral path.

Tympanic Membrane

• Consists of 3 layers including skin, fibrous tissue and respiratory epithelium.
  • It is circular about 1 cm in size, with the apex or umbo pointed medially and angled at approximately 55 degrees.

Auditory Ossicles

• Small bones (malleus, incus, stapes) form a mobile chain from the tympanic membrane to the oval window.

Middle Ear

• An air-filled cavity in the petrous temporal bone.
• Lined with mucous membrane - Respiratory epithelium.
• Connects to nasopharynx via eustachian tube for pressure relief (equalization).

Internal Ear

• A bony and membranous maze within the petrous temporal bone.
• Bony labyrinth has 3 semicircular canals, vestibule, and cochlea.
• Membranous labyrinth consists of cochlear duct and 3 semicircular ducts suspended in the bony labyrinth and contain saccule, utricle, and endolymphatic ducts).

Larynx

• A cartilaginous structure with a lining of mucosa.
• Located in the neck below the hyoid bone connecting to it through the hyoid ligament, and in front of the trachea via the cricotracheal ligament.
• Cartilages include the thyroid, cricoid, arytenoid and epiglottis.

Larynx Muscles

• Extrinsic (connect to the skeleton): Geniohyoid, stylohyoid, digastric, stylopharyngeus, salpingopharyngeus, palatopharyngeus.
• Intrinsic (within the larynx wall): Oblique arytenoid, transverse arytenoid, posterior cricoarytenoid, lateral cricoarytenoid, cricothyroid, thyroarytenoid, vocalis.
  • The posterior cricoarytenoid is a life saving muscle.

Larynx: Nerve Supply

• Sensory (mucous membrane): Internal and external laryngeal branches of the vagus nerve. (Sensory above the vocal cords supplied by the internal, below the vocal cords supplied by the recurrent laryngeal nerve)
• Motor (intrinsic muscles): Recurrent laryngeal nerve branch of the vagus nerve; external laryngeal branch of the superior laryngeal nerve (Critothyroid).

Larynx Blood Supply

• Branches of the Superior Laryngeal artery ( from superior thyroid artery ); Internal branch.
• Branches of the Inferior laryngeal artery (from inferior thyroid artery).
• The upper one-half of the larynx is supplied primarily by the superior thyroid arteries, and the lower one-half by the inferior thyroid arteries.

Larynx: Drains Lymphatically

• Lymph nodes above the vocal fold—upper deep cervical nodes.
• Lymph nodes below the vocal fold—lower deep cervical nodes.