Abstract
The mucous membrane of the nose has a special function of warming and moistening the inspired air. The membrane reacts quickly to such exegenous stimuli as coldness, medicaments and allergic antigens. These physiological and pathological reactions are probably regulated by the adaptability of blood vessels of the nasal mucosa.
The specimens for this electron microscopic study were obtained from Little's area of the nasal septum and the anterior surface of the inferior turbinate of ten male and four female patients during surgery. They were fixed in 2.5% glutar aldehyde and 1% osmic acid, embedded in Epon 812 and stained with uranyl acetate and lead citrate.
The following results were obtained:
1) The muscular arteries possess a composite internal elastic membrane, very thin basement membrane and thick, filamentous smooth-muscle layers. Many cholinergic and a few adrenergic nerve endings are found in the adventitia of these arteries.
2) The arterioles are characterized by thick, dense smooth-muscle layers. They lack the internal elastic membrane. The endothelial cells are tall and have scanty cytoplasm.
3) The cavernous sinus lacks the internal elastic membrane. The tunica media of the wall is characterized by thick, irregular smooth-muscle layers, a large number of elastic fibers and collagen fibers.
4) The venules of the propria are characterized by large internal space and thin, poorly differentiated perivascular cells. The internal surface is continuously lined by five to ten endothelial cells, although the surrounding basement membrane is discontinuous. The endothelial cells show high pinocytotic activity and contain many dense bodies and fine filaments. The junction of each endothelial cell appears to be sealed by tight substances.
5) The capillaries are varied in their structure. The internal surface of capillaries in the tunica mucosa is lined by non-fenestrated endothelial cells and basement membrane, and usually surrounded by a pericyte. Fenestrated capillaries are occasionally found neighboring the nasal glands, but the fenestrations are rather few in number. The wall of capillary is thin at the side adjoining the nasal gland and many fenestrations are found over that side. The capillaries directly beneath the epithelial lining are characterized by very thin endothelial cells with many fenestrations which are mainly found on their epithelial side. The endothelial cells of all types of capillaries show relatively low pinocytotic activity.
6) The control mechanism of nasal blood flow seems to be of complexity. The fine structure of these blood vessels suggests that the muscular arteries and arterioles may supply rapid blood flow to the peripheral blood vessels by strong contraction of the wall. The veins, venules and capillaries may act as a capacity vessels by expanding of the wall.
7) The increase of vascular permeability of the nasal blood vessels may occur mainly through venules and the fenestrated capillaries. Especially rapid transport of fluid with such high molecular substances as serum proteins, may occur through an increased pinocytosis of venules.
8) The wall of venule-like capillaries immediately beneath the epithelial lining and venules in the superficial portion of the mucosa are thin and brittle, so that they are easily damaged by endogenous and exogenous forces. The structural features of these vessels are considered to explain the cause of nasal hemorrhage.
