Structure Of Tympanic Membrane Research Articles

Epimorphic regeneration in the mammalian tympanic membrane

Adult mammals are generally believed to have limited ability to regenerate complex tissues and instead, repair wounds by forming scars. In humans and across mammalian species, the tympanic membrane (TM) rapidly repairs perforations without intervention. Using mouse models, we demonstrate that the TM repairs itself through a process that bears many hallmarks of epimorphic regeneration rather than typical wound healing. Following injury, the TM forms a wound epidermis characterized by EGFR ligand expression and signaling. After the expansion of the wound epidermis that emerges from known stem cell regions of the TM, a multi-lineage blastema-like cellular mass is recruited. After two weeks, the tissue architecture of the TM is largely restored, but with disorganized collagen. In the months that follow, the organized and patterned collagen framework of the TM is restored resulting in scar-free repair. Finally, we demonstrate that deletion of Egfr in the epidermis results in failure to expand the wound epidermis, recruit the blastema-like cells, and regenerate normal TM structure. This work establishes the TM as a model of mammalian complex tissue regeneration.

Rabbit tympanic membrane thickness distribution obtained via optical coherence tomography

Knowing the precise tympanic membrane (TM) thickness variation is crucial in understanding the functional properties of the TM and has a significant effect on the accuracy of computational models. Using optical coherence tomography, we imaged five left and five right TMs of domestic New Zealand rabbits. From these data, ten thickness distribution maps were computed. Although inter-specimen variability is present, similar features could be observed in all samples: The rabbit TM is thickest around the umbo, with values of 150 ± 32 µm. From the umbo towards the TM annulus, the thickness gradually decreases down to 38 ± 7 µm around the midway location, but increases up to 54 ± 19 µm at the TM annulus. The thickness values at the umbo are comparable to literature data for humans, but the rabbit TM is thinner at the TM annulus and in-between the umbo and annulus. Moreover, the rabbit TM thickness distribution is highly symmetrical, which is not the case for the human TM. The results improve our general understanding of TM structure in rabbits and may improve numerical models of TM dynamical behavior.

Localized vibrations incorporated thickness assessment of cadaveric tympanic membranes using Doppler-optical coherence tomography

Vibrations of the tympanic membrane (TM) play a key role in the diagnosis of the middle ear in hearing research. The thickness is one of the factors that determines performance analysis of the TM and plays an important role in forming vibration patterns. When the thickness of TM is changed for various reasons, the vibration pattern is also changed, which interferes with sound transmission. The previously reported studies of measuring TM obtained the response of the entire or at a single point to understand the characteristics of the TM, which is limited to providing detailed information for the region of interest. However, in terms of the clinical applications, the various medical care including TM reconstruction, treatment of perforation, and otitis media with effusion, were mainly performed on a specific part of the TM rather than the whole range. In recent studies, optical coherence tomography (OCT) technology has been employed to visualize whole TM structures with exceptional resolution, while Doppler-OCT has emphasized the appropriateness of this technology for the identification of TM functionality. Since anomalies in vibration patterns of TM can cause hearing loss, Doppler-OCT was incorporated in the proposed scheme to investigate the functionality of TM by localizing vibrations and assessing thickness information of specific vibrating region. However, we focused on analyzing the difference in the TM response according to the thickness and structural changes at each sound wave frequencies. These vibrations and their corresponding tomographic thickness measurements were obtained from ex vivo cadaveric TM specimen placed in a soundproof chamber and was exposed to pure-tone sound frequencies, such as 1, 2, 4, and 6 kHz, respectively. Subsequently, a laboratory-customized cross-sectional image segmentation method was employed to obtain precise correlation between localized vibrations and TM thickness. Since the hearing abnormalities were occurred due to changes of structural formation and functionality, the qualitative and quantitative results of this demonstration are able to simultaneously provide vibration and thickness information for the actual target region and it suggests a possibility to apply for clinical applications, which require a target region-based data.

Acoustic transmitted electrospun fibrous membranes for tympanic membrane regeneration

Scaffold with good acoustic transmission effect, high mechanical strength and good biocompatibility is a challenge for tympanic membrane (TM) regeneration. A new strategy using Tannic acid (TA) as the structural matrix crosslinked with Gelatin methacryloyl (Gelma) hydrogel, a new type of GelMA-TA double-cross-linked hydrogel acoustic transmitted electrospun fibrous membrane with good acoustic effect, strong mechanical properties and excellent cellular adhesion was constructed, implanted in situ to promote the TM regeneration. TA interacts with GelMA electrospun fibrous membrane to form N–H ···O = C and O-H···O = C intermolecular hydrogen bonds. By adjusting TA concentration, the mechanical strength of the GelMA-TA can be adjusted to improve the sound response sensitivity and reduce the sound loss. GelMA-TA has good porosity and biocompatibility, enabling the cells to adhere, penetrate and grow uniformly. Histological analysis and CD31 immunohistochemical analysis showed that GelMA-TA not only shortened the healing period of TM, but also improved the healing rate, forming a three-layer structure similar to the natural TM. GelMA-TA's excellent acoustic character were also confirmed by in vitro acoustic tests and in vivo objective audiological results. The GelMA-TA acoustic transmitted electrospun fibrous membranes proves to be efficient and versatile in TM structure and the function regeneration.

Can Tissue Engineering Bring Hope to the Development of Human Tympanic Membrane?

The tympanic membrane (TM), more commonly known as the eardrum, consists of a thin layer of tissue in the human ear that receives sound vibrations from outside of the body and transmits them to the auditory ossicles. The TM perforations (TMPs) are a common ontological condition, which in some cases can result in permanent hearing loss. Despite the spontaneous healing capacity of the TM to regenerate in the majority of cases of acute perforation, chronic perforations require surgical interventions. However, the disadvantages of the surgical procedure include infection, anesthetic risks, and high failure of graft patency. The tissue engineering strategy, which includes the applications of a three-dimensional (3D) scaffold, cells, and biomolecules or a combination of them for the closure of chronic perforation, has been considered as an emerging treatment. Using this approach, emerging products are currently under development to regenerate the TM structure and its properties. This research aimed to highlight the problems with the current methods of TMP treatment, and critically evaluate the tissue engineering approaches, which may overcome these drawbacks. The focus of this review is on recent literature to critically discuss the emerging advanced materials used as a 3D scaffold in the development of a TM with cellular engineering, biomolecules, cells, and the fabrications of the TM and its pathway to the clinical application. In this review, we discuss the properties of TM and the advantages and disadvantages of the current clinical products for repair and replacement of the TM. Furthermore, we provide an overview of the in vitro and preclinical studies of emerging products over the past 5 years. The results of recent preclinical studies suggest that the tissue engineering field holds significant promise.

Dynamic Properties of Microresonators with the Bionic Structure of Tympanic Membrane.

The structure of a microresonator will affect the vibration characteristics and the performance of the system. Inspired by the structural characteristics of the human tympanic membrane, this paper proposed a microresonator with the bionic structure of a tympanic membrane. The structure of a tympanic membrane was simplified to a regular shape with three structural parameters: diameter, height, and thickness. To imitate the tympanic membrane, the contour surface of the bionic structure was modeled based on the formula of transverse vibration mode of a circular thin plate. The geometric model of the bionic structure was established by using the three structural parameters and the contour surface equation. The dynamic properties of the bionic model were studied by the finite element method (FEM). We discuss the modal characteristics of the bionic structure and study the effect of structural parameters and scale on the dynamic properties. The advantages of the bionic structure were investigated by a comparison with circular plate microresonators. The results illustrate that the bionic structure can significantly improve the resonant frequency and have a much larger effective area of vibration displacement.

Application of Multispectral Imaging in the Human Tympanic Membrane.

Multispectral imaging has recently shown good performance in determining information about physiology, morphology, and composition of tissue. In the endoscopy field, many researches have shown the ability to apply multispectral or narrow-band images in surveying vascular structure based on the interaction of light wavelength with tissue composition. However, there has been no mention to assess the contrast between other components in the middle ear such as the tympanic membrane, malleus, and the surrounding area. Using CT, OCT, or ODT can clearly describe the tympanic membrane structure; nevertheless, these approaches are expensive, more complex, and time-consuming and are not suitable for most common middle ear diagnoses. Here, we show the potential of using the multispectral imaging technique to enhance the contrast of the tympanic membrane compared to the surrounding tissue. The optical absorption and scattering of biological tissues constituents are not the same at different wavelengths. In this pilot study, multiwavelength images of the tympanic membrane were captured by using the otoscope with LED light source at three distinct spectral regions: 450 nm, 530 nm, and 630 nm. Subsequently, analyses of the intensity images as well as the histogram of these images point out that the 630 nm illumination image features an evident contrast in the intensity of the tympanic membrane and malleus compared to the surrounding area. Analysis of such images could facilitate the boundary determination and segmentation of the tympanic membrane (TM) with high precision.

Dynamic Rabbit Model of Ear Barotrauma.

BACKGROUND: Establishing animal models of ear barotrauma (EB) to provide evaluation criteria for Eustachian tube dysfunction.METHODS: Using expansive sponges, 70 rabbits' right pharyngeal openings of the auditory tubes were blocked to cause dysfunction in the right Eustachian tubes. The right tympanic cavities of 65 rabbits were the Model Group (Subgroups 1-13) and these rabbits' left tympanic cavities were the Nonblockage Group. Hypobaric chamber tests (HCTs) at various vertical speeds (100 m · s-1, 75 m · s-1, 50 m · s-1, and 15 m · s-1) and altitudes (13,123 ft and 6562 ft) were conducted. The remaining five rabbits' right tympanic cavities were the Control Group and no HCTs were conducted. After HCTs, observations were made on rabbits' behavioral changes, oto-endoscope and tympanometry results, and pathological changes of the tympanic mucosae.RESULTS: 1) Rabbits in Subgroups 1-12 demonstrated EB, while Subgroup 13 and the Control Group did not. 2) Histopathology showed EB caused by rapid ascent/descent at 100 m · s-1 was more severe than that of 75 m · s-1 and 50 m · s-1 (P < 0.01), and that there were no significant differences in EB caused by rapid ascent/descent at 75 m · s-1 and 50 m · s-1 (P > 0.05). There were no significant differences in pathological injuries at the altitudes of 6562 ft and 13,123 ft (P > 0.05). 3) Based on tympanic membrane structures, tympanometry, and histopathological results, rabbits' EB can be classified into mild, moderate, and severe.DISCUSSION: EB's dynamic models could be established through HCTs on rabbits with Eustachian tube dysfunction.Wang B, Xu X, Lin J, Jin Z. Dynamic rabbit model of ear barotrauma. Aerosp Med Hum Perform. 2019; 90(8):696-702.

Pars tensa and tympanicomalleal joint: proposal for a new anatomic classification.

The tympanic membrane (TM) belongs to the ear. Despite its place in the ear anatomy, can we give it also a different anatomic classification? The main objective is to clarify the nature of TM, tympanic bone and malleus to propose a new anatomic classification. This cadaveric study was performed in two human heads and six fresh temporal bones. A study of the temporomandibular joint, external acoustic meatus (EAM), TM and middle ear structures was conducted. A medical literature review englobing anatomy, embryology, histology and phylogeny of the ear was performed and the results were compared with the results of the dissection. The external ear is constituted by the auricle and the EAM. This last segment is made by a cartilaginous and an osseous portion. The osseous portion of the EAM is constituted mainly by tympanic bone. The external ear is separated from the middle ear by the TM. Inside the middle ear, there are three ossicles: malleus, incus and stapes, which allow the conduction of sound to the cochlea. Based on the anatomic dissection and medical literature review of the tympanic bone, malleus and TM, we propose that these structures are interconnected like a joint, and named it "Tympanicomalleal joint". It seems that the TM can be part of a joint that evolved to improve sound transmission and middle ear protection. Thinking TM has part of a joint may help in the development of more efficient reconstructive surgical techniques.

Assessment and management of retraction pockets.

This manuscript intends to review types, pathogenesis, associated risk factors, and potential methods of prevention and treatment of the retraction pockets in adults and children. The importance of retraction pockets (RP) lies in loss of original histological and anatomical structure which is associated with development of ossicular chain erosion, cho¬lesteatoma formation and potentially life threatening complications of cholesteatoma. The trans-mucosal exchange each gas in the middle ear (ME) is towards equalizing its partial pressures with the partial pressure in the environ¬ment. MEs that have abnormalities in the volume and ventilation pathways in the epitympanic may be more suscep¬tible to retraction pockets. Sustained pressure differences and/or inflammation leads to destruction of collagen fibers in the lamina propria. Inflammatory mediators and cytokines lead to release of collagenases result in viscoelastic properties of the lamina propria. The process of changes in the tympanic membrane structure may evolve to the cho¬lesteatoma formation. There are many different staging systems that clinicians prioritize in their decision making in the management of RP. The authors discuss the management possibilities in different clinical situations: RP without and with ongoing or intermittent evidence of Eustachian Tube Dysfunction (ETD), presence of adenoid hypertrophy or re-growth of adenoids, presence or absence of effusion, invisible depth of RP without effusion. invisible depth of RP with effusion, ongoing RP after VT insertion, and finally suspicion of cholesteatoma in a deep RP with ME effusion. A decision algorithm regarding the management of TM retraction and retraction pockets is provided.

Effects of Negative Middle Ear Pressure on Wideband Acoustic Immittance in Normal-Hearing Adults.

Wideband acoustic immittance (WAI) measurements are capable of quantifying middle ear performance over a wide range of frequencies relevant to human hearing. Static pressure in the middle ear cavity affects sound transmission to the cochlea, but few datasets exist to quantify the relationship between middle ear transmission and the static pressure. In this study, WAI measurements of normal ears are analyzed in both negative middle ear pressure (NMEP) and ambient middle ear pressure (AMEP) conditions, with a focus on the effects of NMEP in individual ears. Eight subjects with normal middle ear function were trained to induce consistent NMEPs, quantified by the tympanic peak pressure (TPP) and WAI. The effects of NMEP on the wideband power absorbance level are analyzed for individual ears. Complex (magnitude and phase) WAI quantities at the tympanic membrane (TM) are studied by removing the delay due to the residual ear canal (REC) volume between the probe tip and the TM. WAI results are then analyzed using a simplified classical model of the middle ear. For the 8 ears presented here, NMEP has the largest and most significant effect across ears from 0.8 to 1.9 kHz, resulting in reduced power absorbance by the middle ear and cochlea. On average, NMEP causes a decrease in the power absorbance level for low- to mid-frequencies, and a small increase above about 4 kHz. The effects of NMEP on WAI quantities, including the absorbance level and TM impedance, vary considerably across ears. The complex WAI at the TM and fitted model parameters show that NMEP causes a decrease in the aggregate compliance at the TM. Estimated REC delays show little to no dependence on NMEP. In agreement with previous results, these data show that the power absorbance level is most sensitive to NMEP around 1 kHz. The REC effect is removed from WAI measurements, allowing for direct estimation of complex WAI at the TM. These estimates show NMEP effects consistent with an increased stiffness in the middle ear, which could originate from the TM, tensor tympani, annular ligament, or other middle ear structures. Model results quantify this nonlinear, stiffness-related change in a systematic way, that is not dependent on averaging WAI results in frequency bands. Given the variability of pressure effects, likely related to intersubject variability at AMEP, TPP is not a strong predictor of change in WAI at the TM. More data and modeling will be needed to better quantify the relationship between NMEP, WAI, and middle ear transmission.

Real-time imaging of in-vitro human middle ear using high frequency ultrasound

Imaging techniques currently used in the clinic to inspect ears in patients are generally limited to views terminating at the tympanic membrane (TM) surface. For imaging past the TM, methods such as computed tomography are typically used, but in addition to disadvantages such as being costly, time consuming, and causing radiation exposure, these often do not provide sufficient resolution of the middle ear structures of interest. This study presents an investigation into the capability of high frequency ultrasound to image the middle ear with high resolution in real-time, as well as measure vibrations of TM and middle ear structures in response to sound stimuli. In unfixed cadaver ears, the TM, ossicles, and ossicular support tissues were all readily identifiable, with capabilities demonstrated for real-time imaging and video capture, and vibrometry of middle ear structures. Based on these results, we conclude that high frequency ultrasonography is a relatively simple and minimally invasive technology with great potential to provide clinicians with new tools for diagnosing and monitoring middle ear pathologies.

The discordant eardrum

At frequencies above 3 kHz, the tympanic membrane vibrates chaotically. By having many resonances, the eardrum can transmit the broadest possible bandwidth of sound with optimal sensitivity. In essence, the eardrum works best through discord. The eardrum's success as an instrument of hearing can be directly explained through a combination of its shape, angular placement, and composition. The eardrum has a conical asymmetrical shape, lies at a steep angle with respect to the ear canal, and has organized radial and circumferential collagen fiber layers that provide the scaffolding. Understanding the role of each feature in hearing transduction will help direct future surgical reconstructions, lead to improved microphone and loudspeaker designs, and provide a basis for understanding the different tympanic membrane structures across species. To analyze the significance of each anatomical feature, a computer simulation of the ear canal, eardrum, and ossicles was developed. It is shown that a cone-shaped eardrum can transfer more force to the ossicles than a flat eardrum, especially at high frequencies. The tilted eardrum within the ear canal allows it to have a larger area for the same canal size, which increases sound transmission to the cochlea. The asymmetric eardrum with collagen fibers achieves optimal transmission at high frequencies by creating a multitude of deliberately mistuned resonances. The resonances are summed at the malleus attachment to produce a smooth transfer of pressure across all frequencies. In each case, the peculiar properties of the eardrum are directly responsible for the optimal sensitivity of this discordant drum.

In vivo measurement of human tympanic membrane structure

Problem: To noninvasively quantify the in vivo human tympanic membrane (TM) structure for further explaining some of the variability in long-term hearing improvement after tympanoplasty surgery for chronic otitis media. Methods: All MR images of 5 female and 5 male volunteers’ TM, semicircular canals, and cochlea were acquired by a 3-T MR system (Brucker S630) using a surface coil of 9 cm diameter and 3D SNAP sequences, aged 20 to 35 years. The pixel resolution of the acquired image for the volunteers’ right ears was 0.59 × 0.63 × 0.47 mm by 3D SNAP. A 3D solid model of in vivo TM, semicircular canals, and cochlea was then reconstructed based on the acquired MR images. The geometric characteristics of TM, semicircular canals, and cochlea were subsequently determined by 2 indices including surface area and volume. Results: The surface areas were 108.34, 152.94, and 108.15 square mm, and the volumes were 36.47, 46.02, and 30.18 cubic mm for TM structure of 3 volunteers, respectively. The preliminary data indicated that small surface area and large volume would obtain the thick TM. Variability of dimensional characteristics of 7 more volunteers’ TM was further analyzed. The number of volunteers did not reach a statistically significant level. Conclusion: The dimensional characteristics of in vivo human TM was quantified by using surface area and volume indices. The thickness of TM was then qualified by surface area and volume. Using the proposed measurement method, the spatial configuration of the in vivo TM can be tracked pre- and postoperation noninvasively. Significance: Knowledge of the structure of TM may help determine the cause of continued problems such as the age-related changes in the mechanics of the TM, and can explain part of the age-related hearing loss observed. Some patients with surgically repaired tympanic membrane perforation still have hearing loss. Support: None reported.

Myringotomy delays the tympanic membrane recovery in acute otitis media: a study in the rat model.

Acute otitis media is a major cause of visits to pediatric health care providers. Myringotomy in uncomplicated acute otitis media is debatable today. The study addressed this problem through the otomicroscopic and histopathological observations of the events occurring in the tympanic membrane during the first week after myringotomy. Randomized study in an experimental animal model. Under anesthesia, the left middle ear of 36 Sprague-Dawley rats was inoculated with Streptococcus pneumoniae type 3. Forty-eight hours later, at day 0, four animals were immediately killed and the remaining animals were randomly assigned into a myringotomy group (n = 16, myringotomy on the left ear) and a non-myringotomy group (n = 16, otomicroscopy without myringotomy). Otomicroscopy and killings were performed in series of four animals from each group at days 1, 2, 4, and 7 after myringotomy. Tympanic membranes were collected after fixation and processed for light and electron microscopy. All inoculated ears showed a manifest acute otitis media at day 0. An intense infiltration by inflammatory cells and edema distorted severely the tympanic membrane structure. These findings decreased the following days. However, inflammation as evaluated by the thickness and the cytoarchitecture of the tympanic membrane layers, recovered significantly faster in the membranes in the non-myringotomy group. At day 7, all tympanic membranes in the myringotomy group were closed by a hypertrophic keratinizing epithelium and a remodeling connective tissue layer, whereas the animals in the non-myringotomy group had a residual edema in the lamina propria. The present infectious model induced an intense inflammatory reaction within the entire structure of the tympanic membrane. Myringotomy provoked a delayed recovery from the inflammatory process within the tympanic membrane. Therefore, if applicable to human conditions, the use of myringotomy in the management of acute otitis media should be restricted to selected cases of acute otitis media.

The attachment structure of the guinea pig tympanic membrane

Objective: The attachment structure between the tympanic membrane and the surrounding structures, the annular ring and the manubrial part, has not been described fully. We examined the relationship between the tympanic membrane and the tympanic annulus or the handle of the malleus in guinea pigs using light microscopy as well as transmission and scanning electron microscopy (SEM). Methods: We used the temporal bone of the guinea pig and examined the relationship between the tympanic membrane and the surrounding structures using light microscopy and transmission electron microscopy. In the examination of scanning electron microscopy, we used the special method such as alkali–water maceration/SEM method. Results: The results showed that the radial fibers of the tympanic membrane continued directly into the annular ring and the manubrial part. The histological structure of the annular ring was amorphous and collagen fibers were seen in the amorphous matrix. The manubrial part histologically resembled the annular ring. These structures were associated with the cartilage structure. Our observations indicated that the collagen fibers of the tympanic membrane are a special type of cartilage collagen fibers. Conclusion: In conclusion, we propose that the surrounding structures of the tympanic membrane such as the tympanic annulus and manubrial part play an important role in the maintenance and the vibration of the tympanic membrane.

Effect of topical hyaluronic acid on experimental cholesteatoma

Purpose: Inflammation and connective tissue hyperplasia are believed to be important etiological factors in cholesteatoma pathogenesis. Previous work has shown that topically applied hyaluronic acid can reduce connective tissue proliferation in healing wounds and accelerate healing of tympanic membrane perforations. This study was undertaken to determine whether the anti proliferative effect of hyaluronic acid may inhibit propylene glycol-induced cholesteatoma in an animal model. Materials and Methods: A 60% propylene glycol solution was injected bilaterally into the middle ear cavities of 20 adult chinchillas. The control group (N = 10) received propylene glycol alone. In addition to propylene glycol injections, the experimental group (N = 10) received repeated bilateral topical applications of 1.5% hyaluronic acid onto the tympanic membranes. Animals were killed at 4 weeks for gross and light microscopic examination. Results: Seven control and 10 experimental animals survived the full 1-month study period. At the end of that time, cholesteatoma was found in 71% (10/14) of control ears and 70% (14/20) of experimental ears. Tympanic membrane structure did not differ significantly between groups by light microscopy and, in all animals, cholesteatomas originated by migration of hyperplastic epidermis through the tympanic membrane, as has been observed in previous studies using this animal model. Conclusion: Under the conditions of this study, topical hyaluronic acid had no significant effect on cholesteatoma formation.

Phenol anesthesia of the tympanic membrane in purulent otitis media: a structural analysis in the rat.

In the present study, local anesthetics were applied to the tympanic membrane (TM) of rats following experimentally evoked purulent otitis media (POM). The structure of the TM was evaluated 24 h, 2 weeks and 3 months after application of phenol to a discrete are of the right TM. The left ear was used as a control. POM induced swelling of all tissue layers of the pears tensa. The tissues were invaded by inflammatory cells and disintegrated. The fibrous layer also dissolved, leaving spontaneous perforations. However, phenol on inflamed TMs did not further alter the TM structure. These findings infer that the injurious effect of topical anesthesia on the intact TM is more or less negligible when applied to diseased TMs.

Tympanic membrane structure during a Staphylococcus aureus-induced middle ear infection. A study in the rat middle ear.

In response to a Staphylococcus aureus-induced middle ear infection the tympanic membrane showed infiltration of polymorphonuclear granulocytes, lymphocytes, and macrophages and increased areas covered by ciliary and secretory epithelium. These reactions, which were comparable to the cellular and mucociliary responses seen in the middle ear mucosa during infection, were restricted to the pars flaccida and to predominantly the annular and manubrial regions of the pars tensa. This showed that the greater part of the tympanic membrane, where the lamina propria is composed of collagenous bundles and only very thin layers of loose connective tissue, is hardly affected by or barely responds to the inflammatory stimulus.

Microvascular networks in tympanic membrane, malleus periosteum, and annulus perichondrium of neonatal mongrel dog: a vasculoanatomic model for surgical considerations.

India-ink-imaged blood-vessel networks in cleared tympanic membranes and adnexa from ten neonatal dogs were examined microscopically and photographed. The major significance of the study lies in documentation of a dual source of arterial supply, a bilaminar relationship of arterial and venous plexuses intrinsic to the tympanic membrane, and a consistent major venous pathway relative to a definite locus (pars flaccida of the membrane). Illustration of all three types of blood pathways (arteries, veins, and capillaries) provides new vasculoanatomic data that are essential to ear surgery, specifically--to myringotomies and myringoplasties. A comparison was made between dog and human tympanic membrane structures and their arterial supplies. Close similarities suggested that dog tympanic membrane might serve as a suitable model for development of innovative surgical procedures and as a model for rehearsal of difficult techniques. The results of this investigation provide a valuable caveat to otologists.