NASAL CAVITIES

Paired chambers separated by a bony and cartilaginous septum

VESTIBULE

Function: communicates anteriorly with the external environment, filtrate out the large particulate matter before it is carried in the airstream

Composition: stratified squamous epithelium with hair and sebaceous glands

RESPIRATORY SEGMENT (MUCOSA)

Function: the turbinates (conchae) - the folds of lateral walls - by increasing surface area, provide efficiency in warming the inspired air and in its filtration by turbulent precipitation.

Composition:

• Ciliated pseudostratified columnar epithelium with basement membrane

Cells:

• Ciliated cells - the most numerous of the cell types, extend through the full thickness of the epithelium

Function: provide a coordinated sweeping motion of the mucus coat -"ciliary escalator" - that serves as an important protective mechanism for removing small inhaled particles

• Mucus (goblet) cells - are interspersed among the ciliated cells and also extend through the full thickness of the epithelium

Function: unicellular mucin-secreting glands

• Brush cells -columnar cells that bear microvilli. The basal surface is in synaptic contact with the afferent nerve endings that penetrate the basal lamina and form trigeminal nerve

Function: receptor cells of general sensation

• Small granule cells - their cytoplasm processes is sometimes observed extending to the lumen and cytoplasm contains numerous, membrane-bonded, dense-core granules

Function: release polypeptide hormones and/or catecholamines that are thought to function in reflexes regulating the airway or vascular caliber

• Basal cells

Function: serve as a reserve population by maintaining individual cell replacement in the epithelium

• Lamina propria

Function: conditioning (warming, moistening and removal of particulate materials) of the air, prevention the epithelium from dehydration by moving air.

Composition: loose connective tissue with rich vascular network - capillary loops, mucous glands

OLFACTORY SEGMENT (MUCOSA)

Location: lateral and medial nasal walls

Function: sense of smell

Composition:

• Olfactory epithelium - pseudostratified columnar epithelium with basement membrane

Cells:

• Olfactory cells - bipolar neurons. Apical pole is a dendritic process that project above the epithelial surface as olfactory vesicle bearing cilia. The basal pole of the cell gives rise to the axonal process that leaves the epithelium to enter the connective tissue, where it joints with axons from other olfactory cells to give rise to the olfactory nerve

• Supporting cells - the most numerous cells with microvilli on their apical surface

• Brush cells -columnar cells that bear microvilli. The basal surface is in synaptic contact with the afferent nerve endings that penetrate the basal lamina and form trigeminal nerve

• Basal cells

• Lamina propria is directly contiguous with the periosteum of the underlying bone

Composition: loose connective tissue with numerous blood and lymphatic vessels, unmyelinated olfactory nerves, myelinated nerves, and olfactory glands - branched tubuloacinar serous glands

SINUSES

Location: in the wall of the nasal bones (ethmoid, frontal, sphenoid, and maxillary). They communicate with nasal cavities via narrow opening onto the respiratory mucosa

Composition: thin, ciliated, pseudostratified columnar epithelium with numerous goblet cells