nasal cavities

nasal cavities

• pyramidal shaped space

• divided into two equal halves by nasal septum

• open to outside at anterior and to nasopharynx at posterior

conchae (turbinates)

3 curved bony projections from lateral walls of each cavity, creating channels between them (meatuses)

bony boundaries of nasal cavities

• lacrimal and nasal → superior/anterior part of lateral wall

• maxilla and palatine → floor (hard palate) and lateral wall

• vomer and ethmoid → roof and medial wall (ethmoid also lateral wall)

• sphenoid → roof and posterior lateral wall (medial pterygoid plate)

• frontal → roof (anterior)

choanae

• openings at posterior of nasal cavity into nasopharynx

• bound within medial pterygoid plates of sphenoid bone

nasal septum

formed by perpendicular plate of ethmoid bone and vomer bone

roles of ethmoid bone in nasal cavities

• perpendicular plate → medial wall

• superior and middle conchae → lateral wall

• air cells (sinuses)

bones forming nasal conchae

• superior and middle conchae → ethmoid bone

• inferior concha → inferior nasal concha bones

nasal conchae and meatuses

• conchae create meatuses that channel air through nasal cavity from nares to choanae (posterior of nasal cavity)

• conchae act as baffles, restraining flow of air to warm and humidify it

  • increased surface area of mucosa

• sphenothmoidal recess superior to superior nasal concha

mucosal walls of nasal cavities and nasopharynx

• all inside surfaces are lined with mucosa → warm, humidify, and filter air

• opening (ostium) of pharyngotympanic (auditory/Eustachian) tube posterior to nasal conchae

pharyngotympanic tube

connects nasopharynx and middle ear, allowing pressure to be equalized on both sides of the tympanic membrane

paranasal sinuses

• four paired air-filled spaces lined with mucosa

• connected medially to nasal cavities

• grow within frontal, maxillary, sphenoid, and ethmoid bones

functions of paranasal sinuses

• immune (mucosa/mucus)

• warming/humidifying air

• altering/amplifying voice

• scaling skull size appropriately as we grow, while keeping it light

drainage pathways of the paranasal sinuses

• frontal, maxillary, and ethmoid sinuses drain into the middle meatus

• sphenoid sinus drains into sphenoethmoidal recess

• mucus accumulation from sinuses can enter nasal cavity, then into nasopharynx via choanae

sinusitis

• infections caused by inhaled air and pathogens entering sinuses

• sinuses are ideal environments for bacterial growth (warm, humid, moist, narrow)

• in maxillary sinus, can lead to referred pain to the upper teeth (via maxillary nerve)

structures of lacrimal apparatus

• lacrimal gland

• lacrimal puncta (openings)

• lacrimal sac

  • sits in fossa between lacrimal and maxilla bones

• nasolacrimal duct

  • drains into nasal cavity in inferior meatus (under inferior nasal concha)

  • when crying, tears overflow into nasal cavity → runny nose

carotid system

• begins at the common carotid (early branch of aorta)

• rises superiorly in the neck and bifurcating at the level of ~C4-C5 into internal an external carotid arteries

carotid arteries

supplies all organs and regions of the head with blood (with contributions from the vertebral arteries to the brain)

internal carotid artery

• enters the cranial cavity via the carotid canal and foramen lacerum

• gives off a large branch to the orbit and eye via the optic canal (ophthalmic artery)

• most branches supply blood to the brain

external carotid artery

main blood supply to structures of the neck, face, scalp, and oral and nasal cavities

maxillary artery

• terminal branch of external carotid artery

• passes medial to the mandible → gives branches to oral cavity

sphenopalatine artery

• terminal branch of maxillary artery

• enters nasal cavity at the sphenopalatine foramen

• nasal branch supplies lateral wall (conchae, etc.)

• septal branch supplies medial wall (septum)

blood supply to nasal cavities

• arterial supply comes mainly from sphenopalatine artery (nasal and septal branches) and ethmoidal artery (branches of ophthalmic artery)

• form lots of connections (anastomoses)

anastomoses

• direct connections between vessels

• pro: tissue in nasal cavity is especially well perfused

• con: nosebleeds are common, dense network of blood vessels located superficially in mucosa

sensory innervation of nasal cavity

• split between branches of ophthalmic and maxillary nerves

  • V₁ anterior, V₂ posterior

• anterior ethmoid nerve (branch of nasociliary from V₁) to anterior medial and lateral walls of nasal cavity and septal cartilage

• nasal nerves (branches of maxillary nerve) to posterior lateral and medial (as nasopalatine nerve, along vomer and septum) walls and septal cartilage

  • nasopalatine nerve also enters oral cavity via incisor foramen to palate

• olfactory nerve passes through cribriform plate, for olfaction only