Week 7 HUBS: Upper respiratory tract: Nasal cavity, Nasopharynx, Oral cavity

Nasal Cavity and Nasopharynx

  • Anatomy goal: describe organization from nares to chonae; include septum, lateral walls, and paranasal sinuses.
  • Nasal cavity parts:
    • External openings: Nares; posterior apertures: Choanae (chonae).
    • Medial wall: Nasal septum; potential Deviated septum.
    • Lateral wall: three curved shelves (conchae): Superior, Middle, Inferior.
    • Resulting air chambers: 44 air chambers – Spheno-ethmoidal recess, Superior meatus, Middle meatus, Inferior meatus.
  • Boundaries and openings:
    • Nasal vestibule: anterior region in contact with nares.
    • Nasal cavity communicates with nasopharynx via choanae.
  • Innervation and blood supply:
    • Innervation: Special sensory – Olfactory CN I. General sensation – Trigeminal (V2).
    • Parasympathetic innervation: Facial (CN VII) via pterygopalatine ganglion (to nasal mucosa).
    • Blood supply: Sphenopalatine artery (terminal branch of maxillary artery).
    • Venous drainage: via facial and maxillary veins; pathways include drainage to cavernous sinus via angular and deep facial veins; to pterygoid plexus; to internal jugular via common facial vein.
  • Paranasal sinuses (4):
    • Frontal – drains to middle meatus via frontonasal duct.
    • Ethmoidal – fills ethmoidal labyrinth; drains into frontonasal duct, ethmoidal bulla, superior meatus.
    • Sphenoid – located posterior to spheno-ethmoidal recess.
    • Maxillary – largest; drains to middle meatus.
  • Nasopharynx:
    • Boundaries: posterior to choanae; superior to soft palate.
    • Lateral wall features: opening of pharyngotympanic (auditory) tube; mucosal elevations/folds over openings and muscles.
  • Learning objectives (Nasal Cavity and Nasopharynx):
    • Describe nasal cavity organization from nares to chonae, including septum and lateral walls.
    • Name and describe nerves innervating the nasal cavity.
    • Indicate blood supply and venous drainage of the nasal cavity.
    • Name and identify the paranasal sinuses; describe boundaries of nasopharynx and openings in lateral wall of nasopharynx.

Paranasal Sinuses

  • Lined by respiratory mucosa (ciliated, mucus-secreting).
  • Open into nasal cavities; innervated by branches of CN V.
  • List:
    • Frontal — drains to middle meatus via frontonasal duct.
    • Ethmoidal — fills ethmoidal labyrinth; drains into frontonasal duct, ethmoidal bulla, superior nasal meatus.
    • Sphenoid — located posterior to spheno-ethmoidal recess.
    • Maxillary — largest; drains to middle nasal meatus.

Nasopharynx (anatomy)

  • Location: posterior to choanae; superior to soft palate.
  • Lateral wall: opening of pharyngotympanic tube; mucosal folds and muscles.

Oral Cavity

  • Two regions:
    • 22 regions: 1) Oral vestibule (between dental arches and lips/cheeks); 2) Oral cavity proper (within teeth).
  • Functions: inlet to digestive system; digestion begins with saliva; chewing; swallowing; speech.
  • Walls and floor:
    • Cheeks: formed by buccinator; presses cheek against teeth; holds food in oral cavity; attaches to pterygomandibular raphe and inserts with orbicularis oris.
    • Floor: mylohyoid and geniohyoid muscles.
  • Palate:
    • Hard palate (anterior): formed by palatine process of maxilla and horizontal plate of palatine bone; mucosa coverings: inferiorly oral; superiorly nasal.
    • Soft palate: muscular valve; muscles include Tensor veli palatini, Levator veli palatini, Palatopharyngeus, Palatoglossus, Musculus uvula.
  • Tongue:
    • Muscular organ for ingestion, swallowing, speech, taste, general sensation.
    • Extrinsic and intrinsic muscles; innervation pattern:
    • All extrinsic muscles innervated by XII (hypoglossal) except Palatoglossus, which is innervated by X (vagus).
    • Tongue motor actions by muscle fibers:
    • Longitudinal: shorten tongue and curl; Transverse: lengthen and narrow; Vertical: flatten and widen.
  • Innervation of tongue:
    • General sensation: V3 (mandibular branch).
    • Special sensation (taste): VII (glossary chorda tympani) and IX (glossopharyngeal).
    • Motor: XII for most muscles; Palatoglossus via X.

Salivary Glands

  • Three pairs of major glands:
    • Parotid — innervation: IX (glossopharyngeal). Note: Facial nerve pierces parotid but does NOT innervate it.
    • Submandibular — parasympathetic via VII.
    • Sublingual — parasympathetic via VII.
  • Parotid gland location and duct:
    • Exits anterior to masseter; parotid duct opens into the oral cavity near the second upper molar tooth.

## Muscles of Mastication

  • There are 44 muscles: Temporalis, Masseter, Medial Pterygoid, Lateral Pterygoid.
    • Functions:
  • Elevate, retract, and perform lateral movements of the mandible.
    • Attachments:
  • Temporalis: from temporal fossa to coronoid process of mandible.
  • Masseter: from zygomatic arch to lateral ramus of mandible.
  • Medial Pterygoid: from medial surface of pterygoid plate to medial mandible.
  • Lateral Pterygoid: from lateral plate of pterygoid process to TMJ capsule and neck of mandible.
    • Nerve supply:
  • All four muscles are innervated by the mandibular branch of the trigeminal nerve (V3).
    • Notes:
  • The pterygoid muscles attach to the sphenoid bone (pterygoid processes).
  • V3 exits the skull via foramen ovale.

Quick Reference Notes on Key Terms

  • Epistaxis: nosebleed; commonly from the sphenopalatine artery.
  • Frontonasal duct: drainage pathway for Frontal and Ethmoidal sinuses.
  • Ethmoidal bulla and superior meatus: drainage landmarks for ethmoidal air cells.
  • Pharyngotympanic (auditory) tube: connects middle ear to nasopharynx; opening on nasopharyngeal wall.
  • Chorda tympani: carries taste fibers (special sensation) from the anterior two-thirds of tongue (via VII).
  • Otic ganglion and lesser petrosal nerve: parasympathetic pathway to parotid gland.
  • Foramen ovale: exit point for V3 from the skull.

Summary for Last-Minute Review

  • Nasal cavity structure: nares → conchae → meatuses; major vessels and nerves; four sinuses and their drainage routes.
  • Nasopharynx: boundaries and lateral openings (pharyngotympanic tube).
  • Oral cavity: vestibule vs proper; palate anatomy; tongue muscles and innervation; saliva glands and their innervation; mastication muscles and V3 innervation.