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Purpose Clarify the composition of the Posterior wall of the Inguinal Canal(PWIC), the location and composition of the Transverse Fascia(TF), and the tissue origin of the Cremaster(C) by observing the anatomy of the inguinal region of the cadaver. Methods 30 cadavers were dissected to observe the alignment of the muscles and fascia of the inguinal canal and the anterior peritoneal space. the anatomical levels of the posterior wall of the inguinal canal and the alignment of the Spermatic Cord(SC) were observed. Results (1) The posterior wall of the inguinal canal was white, bright, and tough tendon membrane-like tissue; (2) the transverse fascia was a thin fascial tissue with only one layer of membranous structure located in the abdominal wall under the abdominal wall on the side of the blood vessels of the peritoneal cavity; (3) the internal oblique muscle and its tendon membrane, and the transversus abdominis muscle and its tendon membrane extended on the surface of the spermatic cord, and fused and continued to the cremaster on the surface of the spermatic cord. Conclusions 1. PWIC is mainly composed of Internal oblique muscle of abdomen (IOMA), Aponeurosis of internal oblique muscle of abdomen (AIOMA), Transverse abdominal muscle (TAM), and Transverse abdominal aponeurosis(TAA) as the following four types: (1) TAM and AIOMA fused to form a tendinous layer; (2) IOMA and TAM form the posterior wall of the muscle in the PWIC; (3) IOMA and AIOMA continue in the PWIC; 4) TAM and TAA continue in the PWIC. 2.TF is a thin fascial tissue with only one layer of membrane structure, TF is not involved in the composition of PWIC, so this fascia has nothing to do with resisting the occurrence of inguinal hernia. 3. The spermatic cord that travels in the inguinal canal is fixed to the lower wall of the inguinal canal by the tendon membrane of the cremaster, which is organized from the internal oblique and transversus abdominis muscles and their tendon membranes, The inguinal canal is a musculotendinous canal.

The vestibular system maintains the body's sense of balance and, therefore, was probably subject to strong selection during evolutionary transitions in locomotion. Among mammals, bats possess unique traits that place unusual demands on their vestibular systems. First, bats are capable of powered flight, which in birds is associated with enlarged semicircular canals. Second, many bats have enlarged cochleae associated with echolocation, and both cochleae and semicircular canals share a space within the petrosal bone. To determine how bat vestibular systems have evolved in the face of these pressures, we used micro-CT scans to compare canal morphology across species with contrasting flight and echolocation capabilities. We found no increase in canal radius in bats associated with the acquisition of powered flight, but canal radius did correlate with body mass in bat species from the suborder Yangochiroptera, and also in non-echolocating Old World fruit bats from the suborder Yinpterochiroptera. No such trend was seen in members of the Yinpterochiroptera that use laryngeal echolocation, although canal radius was associated with wing-tip roundedness in this group. We also found that the vestibular system scaled with cochlea size, although the relationship differed in species that use constant frequency echolocation. Across all bats, the shape of the anterior and lateral canals was associated with large cochlea size and small body size respectively, suggesting differential spatial constraints on each canal depending on its orientation within the skull. Thus in many echolocating bats, it seems that the combination of small body size and enlarged cochlea together act as a principal force on the vestibular system. The two main groups of echolocating bats displayed different canal morphologies, in terms of size and shape in relation to body mass and cochlear size, thus suggesting independent evolutionary pathways and offering tentative support for multiple acquisitions of echolocation.

This study provides a comprehensive analysis of ear canal geometry from 0.7 to 91 years, based on high-resolution computed tomography scans of 221 ears. Quantified features include cross-sectional areas along the canal’s length, total canal length, curvature, and key anatomical landmarks such as the first and second bends and the cartilage-to-bone transition. Significant developmental changes occur during the first 10 years of life, with adult-like characteristics emerging between ages 10 and 15 years, likely coinciding with puberty. Substantial interindividual variability is observed across all ages, particularly in the canal area. The canal becomes fully cartilaginous at and lateral to the second bend by 0.7 years, with further growth occurring only in the bony segment thereafter. These anatomical findings have important implications for audiologic threshold assessments, wideband acoustic immitance measures, age-appropriate hearing aid fitting schedules, and surgical planning, particularly in pediatric populations where anatomical variation is greatest.

Objectives. The objectives of the study include the following: (i) to assess the presence of accessory canals and foramina in the body of the mandible using cone-beam computed tomography (CBCT), (ii) to evaluate the location, number, diameter, and length of accessory canals in the body of the mandible, and (iii) to propose a new classification for mandibular accessory canals based on the location. Methods. A total of 50 (25 males and 25 females) CBCT scans were analyzed in three anatomical planes and three-dimensional (3D) reconstructions for the exact number, location, diameter, and accessory length canals and accessory foramina in the body of the mandible. The statistical analysis used was an independent t-test. Results. Out of 50 CBCT scans, a total of 243 accessory canals and 245 accessory foramina were found. About 53% of accessory canals and foramina were found in males, while 47% were observed in females; 89% were evident in the anterior region, and only 11% were in the posterior region. The majority (64%) of the medial lingual canals had a diameter greater than or equal to 1 mm, while only 32% of accessory canals had a diameter of less than 1 mm (p<0.05). The mean length of median lingual canals in females was 1.2910±0.2582 mm and 2.6438±0.5288 mm in male subjects. Mandibular accessory canals are classified broadly into anterior and posterior accessory canals, which have further subdivisions. Conclusion. CBCT plays a dynamic role in determining the mandible location of various neurovascular structures, including accessory canals and foramina. Female subjects were observed with more accessory canals and foramina and more common in the anterior region than in the posterior region.

Two early Late Pleistocene (~105,000- to 125,000-year-old) crania from Lingjing, Xuchang, China, exhibit a morphological mosaic with differences from and similarities to their western contemporaries. They share pan–Old World trends in encephalization and in supraorbital, neurocranial vault, and nuchal gracilization. They reflect eastern Eurasian ancestry in having low, sagittally flat, and inferiorly broad neurocrania. They share occipital (suprainiac and nuchal torus) and temporal labyrinthine (semicircular canal) morphology with the Neandertals. This morphological combination reflects Pleistocene human evolutionary patterns in general biology, as well as both regional continuity and interregional population dynamics.

Jawed vertebrates have inner ears with three semicircular canals, the presence of which has been used as a key to understanding evolutionary relationships. Ostracoderms, the jawless stem gnathostomes, had only two canals and lacked the lateral canal 1 – 3 . Lampreys, which are modern cyclostomes, are generally thought to possess two semicircular canals whereas the hagfishes—which are also cyclostomes—have only a single canal, which used to be regarded as a more primitive trait 1 , 4 . However, recent molecular and developmental analyses have strongly supported the monophyly of cyclostomes 5 – 7 , which has left the evolutionary trajectory of the vertebrate inner ear unclear 8 . Here we show the differentiation of the otic vesicle of the lamprey Lethenteron camtschaticum and inshore hagfish Eptatretus burgeri . This is the first time, to our knowledge, that the development of the hagfish inner ear is reported. We found that canal development in the lamprey starts with two depressions—which is reminiscent of the early developmental pattern of the inner ear in modern gnathostomes. These cyclostome otic vesicles show a pattern of expression of regulatory genes, including OTX genes, that is comparable to that of gnathosomes. Although two depressions appear in the lamprey vesicle, they subsequently fuse to form a single canal that is similar to that of hagfishes. Complete separation of the depressions results in anterior and posterior canals in gnathostomes. The single depression of the vesicle in hagfishes thus appears to be a secondarily derived trait. Furthermore, the lateral canal in crown gnathostomes was acquired secondarily—not by de novo acquisition of an OTX expression domain, but by the evolution of a developmental program downstream of the OTX genes. The differentiation of the inner ear in the lamprey Lethenteron camtschaticum and hagfish Eptatretus burgeri sheds light on the evolution of the semicircular canals of jawed vertebrates.

Historically, research on jellyfish anatomy has been viewed as secondary in importance and has not benefited from technical advances that could improve the quality of the results when compared to other disciplines. The most notable example is the anatomical research on jellyfish, which has been done using conventional methods for many years. Thus far, recent studies have shown that X-ray microtomography (µCT) and resin endocasts can yield outputs with remarkably high detail quality. The application of a similar protocol to Cotylorhiza tuberculata has allowed us to redescribe the anatomy of this species’ gastrovascular system, providing numerous additional details, among them the double constricted canal structure present in the oral arms, which was absent in previous descriptions. Additionally, functional anatomy experiments have revealed a double circulation system within these canals, featuring specialized oral arms’ openings for intake and outflow, as previously observed in Rhizostoma pulmo . These findings challenge the theory of a simple digestive system in scyphozoans featuring openings that acts both as mouths and anuses. Given the genetic distance between Cotylorhiza tuberculata and Rhizostoma pulmo , which belong to different suborders (Kolpophorae and Dactyliophorae, respectively), we propose that this complex gastrovascular circulation pattern may be more widespread among the Rhizostomeae.

The current study shows in a close-up view anatomical relationship between the subarcuate canal and the osseous labyrinth. For this purpose we used micro-computed tomography which allowed performing three-dimensional reconstruction of the subarcuate canal and gave adequate data for estimation its diameter across its course. The diameter of the middle part (the most uniform) of the subarcuate canal varied from 0.28 mm to 0.46 mm. Hence, we calculated the centre of mass for each cross-section of the separated subarcuate canal. This procedure helped us to visualise trajectory of the subarcuate canal and its spatial orientation within the petrous bone. From our data we concluded that subarcuate canals revealed not well defined trajectories and their spatial orientation varied across the studied temporal bones.

Colombia’s diverse ecosystems are home to various marsupial species known for its distinctive reproductive traits. Limited research has explored the reproductive anatomy of Didelphis marsupialis , particularly regarding variations associated with reproductive phase. This study aimed to characterize the reproductive anatomy of female D. marsupialis and assess its relationship with reproductive phases. We analyzed 57 female opossum cadavers using dissection, histology, and biometry. Specimens were classified by life stage based on dental chronology and by reproductive phase—interestrus, proliferative, and diestrus—based on ovarian features. Among the specimens, 79% lacked pouch young, while 21% carried young with an average of 3 individuals (range = 1–7). Uterine dimensions varied with the reproductive phase, with the pregnant female displaying the largest measurements. Five teats were commonly observed in adults (range = 0–10), while subadults exhibited the highest mean teat count (eleven), suggesting an adaptability to the reproductive demands. We identify six distinct anatomical variations in the vaginal complex, including the inconstant presence of a vaginal sinus septum and diverse cul-de-sac configurations. These variations allow us to reconstruct the temporary formation and subsequent regression of the birth canal, characterized by an invagination of the vaginal sinus and epithelial lining during pregnancy, followed by a postpartum involution. Additionally, we propose to use the term “urogenital canal” over “urogenital sinus” as it is more accurate anatomically. Future research should address the timing of the birth canal formation and regression and its relationship with the mammary gland development in living individuals.

The cause of the elevated outflow resistance and consequent ocular hypertension characteristic of glaucoma is unknown. To investigate possible causes for this flow resistance, we used atomic force microscopy (AFM) with 10-μm spherical tips to probe the stiffness of the inner wall of Schlemm’s canal as a function of distance from the tissue surface in normal and glaucomatous postmortem human eyes, and 1-μm spherical AFM tips to probe the region immediately below the tissue surface. To localize flow resistance, perfusion and imaging methods were used to characterize the pressure drop in the immediate vicinity of the inner wall using giant vacuoles that form in Schlemm’s canal cells as micropressure sensors. Tissue stiffness increased with increasing AFM indentation depth. Tissues from glaucomatous eyes were stiffer compared with normal eyes, with greatly increased stiffness residing within ∼1 μm of the inner-wall surface. Giant vacuole size and density were similar in normal and glaucomatous eyes despite lower flow rate through the latter due to their higher flow resistance. This implied that the elevated flow resistance found in the glaucomatous eyes was localized to the same region as the increased tissue stiffness. Our findings implicate pathological changes to biophysical characteristics of Schlemm’s canal endothelia and/or their immediate underlying extracellular matrix as cause for ocular hypertension in glaucoma.