Encapsulated nerve endings were found in both the subepidermal connective tissue and the lamina propria of a human tympanic membrane. The structure of the corpuscles was round or oval and contained a number of axon terminals with mitochondria and Schwann cell processes. Amorphous materials were present in the intercellular space. These features appear to be advantageous in transmitting mechanical forces on the capsule to the axon terminals and are comparable to the function of a mechanoreceptor. Resultant changes in the shape and stiffness of the tympanic membrane as the result of its dislocation indicate similar changes in the pressure on the corpuscle. The arrangement of the sensory corpuscles suggests that they may play a role in detecting pressure changes in the middle ear cavity.

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In our previous histological studies of the tympanic membrane, we reported the presence of encapsulated nerve corpuscles that are capable of detecting middle ear pressure. Based on these findings, the relation between sensory receptors in the tympanic membrane and tubal function was examined in a clinical study. Tubal function was tested during Valsalva maneuvers and its active equilibration. Function was recorded as a change of the static compliance of the tympanic membrane on an otoadmittance meter. To paralyze the sensory receptors in the tympanic membrane, iontophoresis was used to induce anesthesia of the drum. Forty ears of 20 subjects were tested. All ears were able to equalize positive middle ear pressure without or with a single swallowing. After anesthesia, 13 ears needed more than two swallows and 4 ears failed to equalize middle ear pressure in spite of repeated swallowings. As eustachian tube function changed following anesthesia of the tympanic membranes, a neural connection between sensory receptors in the tympanic membrane and tubal muscles is suggested.

Arteriovenous anastomosis (AVA) in nasal respiratory mucosa of humans and guinea pigs were studied with scanning electron microscopy (SEM) after removal of extracellular connective tissues by tryptic digestion and HCl hydrolysis. The shape of AVA in humans is different from that in guinea pigs. In guinea pigs, it is simple with no specific structure observed on the vessels. In humans, it is characterized by a spherical swelling at the intermediate segment. The Tunica media of the spherical body is formed by the aggregation of spindle-shaped cells and receives a rich nerve supply. These findings suggest powerful contractility of human AVA compared with guinea pigs. Arteriovenous anastomosis in human nasal respiratory mucosa may strongly influence arterial blood flow into the cavernosus sinusoid and determine the characteristic microcirculatory pattern in human nasal mucosa.

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