Non structural components
Structural components – Include epithelium, basement membrane and submucosal tissue.
Non-structural components – Include resident and Non resident cells of lymphoid and myeloid lineage.
Epithelium & Basement membrane:
anterior 2 cms of the nasal cavity is lined by skin comprising of
keratinized stratified squamous epithelium. It also contains
fibrocollagenous dermis and adnexal glands. The rest of the nasal
cavity is lined by respiratory type of epithelium which develops from
ectoderm. This mucous membrane is also known as Schneiderian membrane.
The Schneiderian membrane is composed of four cell types:
Ciliated columnar / cuboidal epithelial cells
Interspaced between these cells are goblet cells
Non ciliated columnar cells with microvilli
The ratio of columnar to goblet cells is roughly 5:1.
normal nasal epithelium may show metaplastic changes i.e. presence of
cuboidal / metaplastic squamous epithelium due to constant drying
effects of inspired air. Metaplastic changes are commonly seen at the
head of inferior turbinate. The columnar epithelium contains tight
junctions and they rest on the basement membrane.
basement membrane contains collagen fibres of types (I, III, IV, V, VI
and VII). Other constituents of basement membrane are:
Heparan sulfate proteoglycan
basement membrane is rather thin and delicate in the whole of the nasal
cavity. It is usually thick over the inferior turbinate area.
comparison the lining mucosa of the paranasal sinuses are rather thin
and less specialized in nature. This difference could be attributed to
their different embryological origin and functional differences.
superior turbinate, superior portion of nasal septum, roof of the nasal
cavity, and superior and medial portions of the middle turbinate are
lined by olfactory epithelium. The olfactory epithelium is also
pseudostratified ciliated columnar epithelium containing bipolar
olfactory cells, microvillar cells and supporting sustentacular cells.
Due to increasing age / infections the olfactory epithelium may be
replaced in patches by normal nasal mucous membrane.
lies under the basement membrane overlying the cartilage / bony frame
work of the nasal cavity. It is composed of loose fibrovascular
connective tissue, numerous seromucinous and minor salivary glands. It
also contains blood vessels, nerves, myeloid and lymphoid cells. The
blood vessels include extensive arterial and venous anastomosis. These
blood vessels communicate with venous erectile tissue. This erectile
tissue is more prominent over the turbinates.
Non structural components:
Lymphoid tissue in the nasal mucosa comprises of:
single lymphocytes scattered among the epithelial cells and lamina propria
NALT – Nasal associated lymphoid tissue resembling payer's patches of the gut. These are not encapsulated.
NALT is not well formed like Payer's patches of the gut. They become enlarged and pronounced during nasal infections.
The lymphoid cells include:
Natural killer cells
Conditions causing nasal polypi include:
Samter's triad – This include bronchial asthma, aspirin sensitivity and nasal polyposis
Eosinophilic mucous chronic rhinosinusitis (including AFRS)
Churg – Strauss disease
Macroscopic features of nasal polypi:
Pale smooth shining and oedematous
Soft in consistency when compared to surrounding nasal mucosa
Long standing nasal polypi can be firm and white due to metaplasia of lining mucosa and presence of extensive fibrosis
due to chronic rhinosinusitis does not show surface mucosal ulceration.
Presence of surface ulceration macroscopically in polyp tissue should
arise suspicion of other pathologies. Presence of thick dark tenaceous
secretions along with nasal polypi is caused due to Eosinophilicc
mucous chronic rhinosinusitis / AFRS etc.
Microscopic changes seen in polypoid tissue are:
Structural changes involving lining epithelium, submucosa and rarely underlying bone
Presence of inflammatory exudate
nasal polyp is lined by ciliated columnar epithelium. Their basement
membrane is of varying thickness. The stroma contains lymphocytes.
Histological classification of nasal polypi:
Oedematous / allergic nasal polypi
Chronic inflammatory nasal polypi
Seromucinous / glandular polypi
/ allergic nasal polypi: Is the commonest variety. This type is seen in
patients with allergy. The association between nasal allergy and
polyposis still remains controversial. These polypi are lined by
ciliated columnar epithelium with ulceration, mucositis, epithelial
hyperplasia, squamous metaplasia. The basement membrane is thickened
and the submucosa is oedematous. Mucous retention cysts may also be
seen. Inflammatory cell infiltrate include eosinophils, plasma cells
and lymphocytes. Polypi in patients with cystic fibrosis have thin
basement membrane with less stromal eosinophilia and predominantly
neutrophilic infiltrations. Hence cystic fibrosis polypi are termed as
neutrophilic polyp. Mucous secretions in patients with cystic fibrosis
are thick and densly eosinophilic in nature.
inflammatory polyp: This is also known as fibroinflammatory polyp. This
type of polypi are less common. This type of polypi may be caused when
oedematous polypi are traumatized. Thee stroma may undergo secondary
inflammatory change causing myofibroblastic proliferation. These polypi
may mimic soft tissue neoplasm. The surface epithelium shows squamous
metaplasia which is a manifestion of chronicity of the disease. The
submucosa characteristically show fibrosis. This is a classic feature
of this type of polyp.
Seomucinous polypi: Hyperplasia of seromucinous glands are rare. These are considered to be true neoplasm.
Underlying bone shows remodelling. This is all the more true in long standing disorders.