Wednesday, May 30, 2012

Histology and morphology of the nasal mucosa


Skin
The skin that covers the nasal vestibule is rich in pilous follicles, sebaceous glands and sweat glands.



Epithelium
The respiratory epithelium is comprised of four different cell types: ciliated cells, goblet cells, brush cells and basal cells. 



Ciliated cells: These cells derive their name from the celia they contain, which are extracellular
finger-like extensions 5 microns high and 0.3 microns thick. Their function is to remove inhaled particles.

Goblet cells: These cells perform secreting activity. They are surrounded by the ciliated cells or are clustered, forming veritable intraepithelial glands. The goblet cells, together with the exocrine glands, maintain and renew the mucosa covering that is required for ciliary movement.

Brush cells: These line the surface of the mucosa and have microvilli (cytoplasm prolongations in the apical pole) to increase the exchange surface of the nasal respiratory mucosa. They play an important role in the phenomena of secretion and reabsorption of the nasal mucosa.

Basal cells: These are replacement cells that may give rise to one of the other three cell types.


Basal membrane 
This membrane guarantees cohesion between epithelial cells as well as adhesion between epithelium and chorion and controls the relationship between epithelium and chorion.



Chorion
The mucosal chorion consists of three layers: lymphoid, glandular and vascular.


Lymphoid layer: Comprised of lymphoid cells such as lymphocytes, which are responsible for late allergic response. It also contains plasmocytes, the main source of immunoglobulin; histiocytes or macrophages that eliminate foreign elements by phagocytosis and are also responsible for the synthesis of collagen and mucopolysaccharides; and polynuclear cells which appear in inflammatory states.

Glandular layer or stratum: Three types of glands may be distinguished according to the cell constitution of the acinus (group of cells specialised in secretion, which form the glands): the mucous glands, which secrete mucus; the serous glands, which produce a clear, aqueous secretion poor in mucin and the mixed seromucous glands.
Myoepithelial cells, contractile cells that facilitate excretion, surround the glandular acini. 

Deep vascular layer: This is comprised of the blood vessels of the nasal mucosa. The arteries that enter the nasal fossae in contact with the periosteum. The capillaries that have endothelial pores and grooves and permit rapid exchange between blood and the mucosa at subepithelial, glandular and periosteal level. The venous network that also extends throughout the same three layers.

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