Developmental changes in the retrorectal region of the human fetus

Visualization of the dentogingival junction using micro-plastination technique

Plastination has revolutionized the field of anatomy and research by providing biosecurity and enabling the long-term preservation of biological material, ranging from entire bodies to individual organs and even micron sections. The dentogingival junction (DGJ) consists of both epithelial and connective tissues that are closely related to the tooth's mineralized tissues. Cutting-grinding techniques are commonly used to visualize DGJ histology. These techniques exclude enamel from preparations and focus on visualizing hard or soft tissues. To improve the micro-anatomical and histological study of this region, we applied micro-plastination technique to obtain micro-thin slices below 150 μm thick from human and animal samples. The DGJ microanatomy was visualized by applying histological stains to the micro-plastinated slices, highlighting the technique's endogenous autofluorescence capacity identifying periodontal tissues, including dentin, enamel, cementoenamel junction, dentinal tubules, connective tissue, and collagen. Based on our results, we confirm that micro-plastination is a useful technique for visualizing anatomical regions that are difficult to access, such as the DGJ. Micro-plastination can be used as an alternative technique, providing a new approach for its application in anatomical and morphological research protocols.

OUP accepted manuscript

Background

The relative anatomical understanding of the perirectal fasciae is of paramount importance for the proper performance of total mesorectal excision (TME). This study was to demonstrate the planes of TME and validates the intraoperative findings using cadaveric observations.

Methods

In this combined retrospective and prospective study, bilateral attachment of the rectosacral fascia (RSF) was observed in 28 cadaveric specimens (male, n = 14; female, n = 14). From January 2018 to December 2019, surgical videos of 67 patients who underwent laparoscopic TME at the Affiliated Union Hospital of Fujian Medical University (Fuzhou, China) were reviewed and interpreted with the cadaveric findings.

Results

The RSF (synonym: Waldeyer's fascia) is the end of the pre-hypogastric fascia at the level of S4 and comprises two layers (upper and lower). These two layers provide double fascial protection for the venous sacral plexus. It inserts into the fascia propria of the rectum along a broad horizontal arc that merges anterolaterally in an oblique downward direction until it meets the posterolateral merge of Denonvilliers' fascia at the lateral rectal ligament (LRL). This ligament does not look like a true ligament but is more likely to be a fascial combination that cushions the rectal innervation and middle rectal vessels.

Conclusions

Understanding the lateral attachment of RSF and its contribution to LRL provides invaluable surgical guidance to dissect this critical area. Therefore, lateral dissection is proposed from the anterior to the posterior direction to find the correct plane that guarantees an intact mesorectal envelope to protect the important nearby nerve structures.

Extrinsic innervation of the pelvic organs in the lesser pelvis of human embryos

Realistic models to understand the developmental appearance of the pelvic nervous system in mammals are scarce. We visualized the development of the inferior hypogastric plexus and its preganglionic connections in human embryos at 4-8 weeks post-fertilization, using Amira 3D reconstruction and Cinema 4D-remodelling software. We defined the embryonic lesser pelvis as the pelvic area caudal to both umbilical arteries and containing the hindgut. Neural crest cells (NCCs) appeared dorsolateral to the median sacral artery near vertebra S1 at ~5 weeks and had extended to vertebra S5 1 day later. Once para-arterial, NCCs either formed sympathetic ganglia or continued to migrate ventrally to the pre-arterial region, where they formed large bilateral inferior hypogastric ganglionic cell clusters (IHGCs). Unlike more cranial pre-aortic plexuses, both IHGCs did not merge because the 'pelvic pouch', a temporary caudal extension of the peritoneal cavity, interposed. Although NCCs in the sacral area started to migrate later, they reached their pre-arterial position simultaneously with the NCCs in the thoracolumbar regions. Accordingly, the superior hypogastric nerve, a caudal extension of the lumbar splanchnic nerves along the superior rectal artery, contacted the IHGCs only 1 day later than the lumbar splanchnic nerves contacted the inferior mesenteric ganglion. The superior hypogastric nerve subsequently splits to become the superior hypogastric plexus. The IHGCs had two additional sources of preganglionic innervation, of which the pelvic splanchnic nerves arrived at ~6.5 weeks and the sacral splanchnic nerves only at ~8 weeks. After all preganglionic connections had formed, separate parts of the inferior hypogastric plexus formed at the bladder neck and distal hindgut.

Presacral masses and sacrococcygeal teratomas in patients with and without anorectal malformations: A single institution comparative study

BACKGROUND

Despite variability at presentation, presacral masses in patients with and without anorectal malformations (ARM) appear histologically similar. The purpose of this study was to identify differences in oncologic outcomes between these two groups.

METHODS

A retrospective review was performed utilizing our institutional cancer and colorectal and pelvic reconstruction databases for patients with presacral masses and sacrococcygeal teratomas between 1990 and 2017. Data captured included age at surgical resection, type of ARM, tumor location within the pelvis, tumor histopathology, tumor size, adjuvant chemotherapy, recurrence, and follow-up.

RESULTS

Forty-six patients comprised our cohort, of whom 12 had an ARM. The median age was older at resection for those with an ARM (1.4 years; range 1 day to 29.4 years) compared to those without an ARM (9 days; range 0 days to 6.9 years) (p = 0.01). The mean tumor size was 2.5 cm in patients with an ARM compared to 6.0 cm in patients without an ARM (p = 0.036). All patients with ARM had exclusively intrapelvic tumors, and histopathology included mature teratoma (8), yolk sac tumor (1), lipoma (1), and unknown (2). Tumor location for patients with sacral and presacral masses without ARM included exclusively extrapelvic (10), primarily extrapelvic with large intrapelvic component (7), primarily intrapelvic with extrapelvic component (1), exclusively intrapelvic (8), and unknown (8). Histopathology for patients with presacral masses without ARM included mature teratoma (20), immature teratoma (7), yolk sac tumor (3), ganglioneuroma (1), neuroblastoma (1), benign epithelial cyst (1), and unknown (1). Tumor recurrence rate was similar between patients with ARM (n = 3, 25%) and those without an ARM (n = 5, 15%) (p = 0.41). The 5-year event free survival was 65% (95% CI: 25%-87%) in the group with ARM and 81% (95% CI: 60%-92%) in the group without ARM (p = 0.44).

CONCLUSION

Sacral and presacral masses in patients with ARM are resected at a later age and are more likely to be intrapelvic. They appear histologically similar and have similar rates of recurrence and malignancy when compared to patients without ARM.

LEVEL OF EVIDENCE

III TYPE OF STUDY: Retrospective comparative study.

The development of the cloaca in the human embryo

Subdivision of cloaca into urogenital and anorectal passages has remained controversial because of disagreements about the identity and role of the septum developing between both passages. This study aimed to clarify the development of the cloaca using a quantitative 3D morphological approach in human embryos of 4–10 post‐fertilisation weeks. Embryos were visualised with Amira 3D‐reconstruction and Cinema 4D‐remodelling software. Distances between landmarks were computed with Amira3D software. Our main finding was a pronounced difference in growth between rapidly expanding central and ventral parts, and slowly or non‐growing cranial and dorsal parts. The entrance of the Wolffian duct into the cloaca proved a stable landmark that remained linked to the position of vertebra S3. Suppressed growth in the cranial cloaca resulted in an apparent craniodorsal migration of the entrance of the Wolffian duct, while suppressed growth in the dorsal cloaca changed the entrance of the hindgut from cranial to dorsal on the cloaca. Transformation of this ‘end‐to‐end’ into an ‘end‐to‐side’ junction produced temporary ‘lateral (Rathke's) folds’. The persistent difference in dorsoventral growth straightened the embryonic caudal body axis and concomitantly extended the frontally oriented ‘urorectal (Tourneux's) septum’ caudally between the ventral urogenital and dorsal anorectal parts of the cloaca. The dorsoventral growth difference also divided the cloacal membrane into a well‐developed ventral urethral plate and a thin dorsal cloacal membrane proper, which ruptured at 6.5 weeks. The expansion of the pericloacal mesenchyme followed the dorsoventral growth difference and produced the genital tubercle. Dysregulation of dorsal cloacal development is probably an important cause of anorectal malformations: too little regressive development may result in anorectal agenesis, and too much regression in stenosis or atresia of the remaining part of the dorsal cloaca.

The development of the dorsal mesentery in human embryos and fetuses

The vertebrate intestine has a continuous dorsal mesentery between pharynx and anus that facilitates intestinal mobility. Based on width and fate the dorsal mesentery can be subdivided into that of the caudal foregut, midgut, and hindgut. The dorsal mesentery of stomach and duodenum is wide and topographically complex due to strong and asymmetric growth of the stomach. The associated formation of the lesser sac partitions the dorsal mesentery into the right-sided "caval fold" that serves as conduit for the inferior caval vein and the left-sided mesogastrium. The thin dorsal mesentery of the midgut originates between the base of the superior and inferior mesenteric arteries, and follows the transient increase in intestinal growth that results in small-intestinal looping, intestinal herniation and, subsequently, return. The following fixation of a large portion of the abdominal dorsal mesentery to the dorsal peritoneal wall by adhesion and fusion is only seen in primates and is often incomplete. Adhesion and fusion of mesothelial surfaces in the lesser pelvis results in the formation of the "mesorectum". Whether Toldt's and Denonvilliers' "fasciae of fusion" identify the location of the original mesothelial surfaces or, alternatively, represent the effects of postnatal wear and tear due to intestinal motility and intra-abdominal pressure changes, remains to be shown. "Malrotations" are characterized by growth defects of the intestinal loops with an ischemic origin and a narrow mesenteric root due to insufficient adhesion and fusion.

Fetal median sacral artery anatomy study by micro-CT imaging

PURPOSE

The median sacral artery (MSA) is the termination of the dorsal aorta, which undergoes a complex regression and remodeling process during embryo and fetal development. The MSA contributes to the pelvic vascularization and may be injured during pelvic surgery. The embryological steps of MSA development, anastomosis formation and anatomical variations are linked, but not fully understood.

METHODS

The pelvic vascularization and more precisely the MSA of a human fetus at 22 weeks of gestation (GW) were studied using micro-CT imaging. Image treatment included arterial segmentations and 3D visualization.

RESULTS

At 22 GW, the MSA was a well-developed straight artery in front of the sacrum and was longer than the abdominal aorta. Anastomoses between the MSA and the internal pudendal arteries and the superior rectal artery were detected. No evidence was found for the existence of a coccygeal glomus with arteriovenous anastomosis.

CONCLUSIONS

Micro-CT imaging and 3D visualization helped us understand the MSA central role in pelvic vascularization through the ilio-aortic anastomotic system. It is essential to know this anastomotic network to treat pathological conditions, such as sacrococcygeal teratomas and parasitic ischiopagus twins (for instance, fetus in fetu and twin-reversed arterial perfusion sequence).

Periodic acid-Schiff (PAS) reaction and plastination in whole body slices. A novel technique to identify fascial tissue structures

Since collagen rich fascial tissue is often very delicate and difficult to discern on native tissue slices, we have developed a method for staining full-body slices using the periodic acid-Schiff (PAS) reaction with subsequent plastination. Since the PAS reaction primarily stains carbohydrates, we could exploit the circumstance that different collagen types vary in carbohydrate content. Contrary to fasciae, tissues such as muscle, bone, nerves and blood vessels exhibit significantly less staining or remain unstained. We have validated the whole-body slice staining results in microscopic tissue slides which were stained with standard extracellular matrix stains such as Masson-Goldner trichrome stain and van-Gieson stain. Furthermore, we have performed immunofluorescence imaging to confirm the presence of collagen in the stained tissue. We achieved very good staining and plastination results and were able to clearly identify even very thin fascia in transversal body slices. This technique may prove useful in advancing our knowledge on the complex topography of fascial structures.

Coccygeal body revisited: An immunohistochemical study using donated elderly cadavers

To describe the normal anatomy and histology of the adult coccygeal body (CB) and to discuss about the origin and function, using immunohistochemistry, we examined 29 CBs found in 32 elderly donated cadavers without macroscopic pathology in the pelvis. The CB was usually located in or near the anococcygeal ligaments. It was almost always composed of multiple masses or nodules of round glomus cells (smooth muscle actin or SMA++). However, the CB sometimes contained abundant dilated veins with scattered glomus cells. Thus, the CBs varied from the glomus cell nodule-dominant type, through an intermediate morphology with a mixture of nodules and veins, to the vein-dominant type. Each glomus cell mass was surrounded by abundant sympathetic nerves. In all specimens, we found multiple abnormal arteries, each of which carried a glomus-like cell layer around the almost -obliterated vascular lumen; as well as an SMA-negative thick arterial wall containing abundant sympathetic nerves. The ligaments around the CB are known to be under strong mechanical stress from the pelvic floor. We considered abnormal arteries containing the unique internal layer as an intermediate between a normal muscular artery and a glomus cell mass of CB. Under long-termed mechanical stress, a muscular artery seems to lose smooth muscles with increased sympathetic nerve fibers, to compensate for the lack of muscle function. Taken together with fetal morphology (our recent report), some or most of the CBs might not be an arteriovenous shunt but a result of stress-induced acquired transformation of pericytes. Anat Rec, 2017. © 2017 Wiley Periodicals, Inc. Anat Rec, 300:1826-1837, 2017. © 2017 Wiley Periodicals, Inc.

The Filum Terminale Revisited: A Histological Study in Human Fetuses

Previous studies have suggested that secondary neurulation provides no functional neurons but only the filum terminale. However, no studies have confirmed that the coccygeal and lower sacral nerves do not originate from the secondary neural tube but only from the primary tube. To obtain a better understanding of these relationships, we examined sagittal or frontal sections from 20 embryonic and fetal specimens ranging from 6 to 14 weeks of gestation. During the growth of the vertebral column as well as the subsequent upward migration of the caudal end of the dural sac, the secondary neural tube was stretched to maintain the original attachment to the coccyx or the lower sacral vertebra. The filum-like structure showed much individual variability but in all cases appeared to be derived from the stretched neural tube. Intermediate age morphology revealed that the secondary neural tube itself provided an initial filum terminale before the ascent of the dural sac. Given that the coccygeal and lower sacral nerves are likely to originate from the secondary neural tube, these parts of the tube persisted and differentiated into spinal neurons to form the anococcygeal nerves. Likewise, the filum terminale was also most likely to contain some neurons that persisted postnatally. Depending on the timing and site of degeneration of the secondary neural tube, individual variations could occur in proportion to the amount of sensory and motor elements in the anococcygeal nerve supply.

Anatomical considerations for transanal minimal-invasive surgery: the caudal to cephalic approach

AIM

Nerve-sparing surgery during laparoscopic rectal mobilization is still limited by anatomical constraints such as obesity, the narrowness of the male pelvis, an ultra low rectal cancer or all of these. The transanal approach for total mesorectal excision has overcome the shortcomings of limited access to the rectal 'no-man's land' close to the pelvic floor. The aim of this anatomical study was to define a roadmap of anatomical landmarks for the caudal to cephalic approach so as to standardize nerve-sparing rectal mobilization procedures.

METHOD

Macroscopic dissections of the pelvis in a caudal to cephalic direction were performed in eight alcohol-glycerol embalmed cadavers. A roadmap of anatomical landmarks was created at different levels of section to demonstrate the sites of nerve injury.

RESULTS

Extrinsic autonomic nerves to the urogenital organs and the internal sphincter muscle are closely adjacent to the lowest portion of the rectum above the pelvic diaphragm.

CONCLUSION

This anatomical guide for the pelvic surgeon should facilitate a safe and nerve-sparing dissection of the mesorectal plane with a meticulous overview of the lowest autonomic nerve fibres. New anatomical insights by a 'caudal to cephalic' approach to the 'no-man's land' should help overcome anatomical constraints of a narrow, obese and male pelvis during rectal mobilization procedures.

Anococcygeal raphe revisited: a histological study using mid-term human fetuses and elderly cadavers

PURPOSE

We recently demonstrated the morphology of the anococcygeal ligament. As the anococcygeal ligament and raphe are often confused, the concept of the anococcygeal raphe needs to be re-examined from the perspective of fetal development, as well as in terms of adult morphology.

MATERIALS AND METHODS

We examined the horizontal sections of 15 fetuses as well as adult histology. From cadavers, we obtained an almost cubic tissue mass containing the dorsal wall of the anorectum, the coccyx and the covering skin. Most sections were stained with hematoxylin and eosin or Masson-trichrome solution.

RESULTS

The adult ligament contained both smooth and striated muscle fibers. A similar band-like structure was seen in fetuses, containing: 1) smooth muscle fibers originating from the longitudinal muscle coat of the anal canal and 2) striated muscle fibers from the external anal sphincter (EAS). However, in fetuses, the levator ani muscle did not attach to either the band or the coccyx. Along and around the anococcygeal ligament, we did not find any aponeurotic tissue with transversely oriented fibers connecting bilateral levator ani slings. Instead, in adults, a fibrous tissue mass was located at a gap between bilateral levator ani slings; this site corresponded to the dorsal side of the ligament and the EAS in the immediately deep side of the natal skin cleft.

CONCLUSION

We hypothesize that a classically described raphe corresponds to the specific subcutaneous tissue on the superficial or dorsal side of the anococcygeal ligament.

Waldeyer's fascia: anatomical location and relationship to neighboring fasciae in retrorectal space

PURPOSE

The term Waldeyer's fascia has caused confusion in surgery for rectal cancer. We have therefore dissected endopelvic fasciae to clarify the structure and location of Waldeyer's fascia, and to determine its anatomical relationships with adjacent fasciae.

METHODS

Twenty cadavers (13 males and 7 females) were dissected. Each specimen was sectioned in the sagittal plane and both hemipelvises were examined.

RESULTS

Waldeyer's fascia was observed in all specimens originating from the presacral fascia at the S2-S4 level and fusing with the posterior leaf of the mesorectal parietal fascia. Waldeyer's fascia divided the retrorectal space (RRS) into inferior and superior compartments, with the upper leaf constituting the floor of the superior compartment and the lower leaf constituting the dome of the inferior compartment. There were no nerves, blood vessels or lymphatic vessels within the two leaves.

CONCLUSION

Waldeyer's fascia was located between the mesorectal parietal and presacral fasciae. Waldeyer's fascia included two leaves, which jointly divided the RRS into inferior and superior compartments. Waldeyer's fascia is a pivotal anatomical structure in the surgical treatment of rectal cancer.

Development of the human hypogastric nerve sheath with special reference to the topohistology between the nerve sheath and other prevertebral fascial structures

Semi-serial sections from the lumbosacral region of nine fetuses (8-25 weeks gestation) were examined to clarify the lumbar prevertebral fascial arrangement. The prevertebral fasciae became evident after 12 weeks of age. After 20 weeks of age, the hypogastric nerve (HGN) was sandwiched by two fascial structures; the ventral fascia which seemed to correspond to the mesorectal fascia, whereas the dorsal fascia corresponded to the presacral fascia. These fasciae or the HGN sheaths extended laterally along the ventral aspects of the great vessels and associated lymph follicles. The ventral fascia is, to some extent, fused with the mesocolon descendens on the left side of the body. Notably, the lateral continuation of these two fasciae also sandwiches the left ureter, but not the right ureter, presumably due to modifications by the left-sided fusion fascia. A hypothetical common sheath for the HGN and ureter (i.e., the ureterohypogastric or vesicohypogastric fascia) might thus be an oversimplification. Before retroperitoneal fixation, the morphology of the peritoneal recess along the mesocolon descendens and mesosigmoid suggested interindividual differences in location, shape, and size. Therefore, in adults the ease of surgical separation of the rectum and left-sided colon from the HGN seems to depend on interindividual differences in the development of the embryonic peritoneal recess. On the caudal side of the second sacral segment, fascial structures were restricted along and around the HGN, pelvic splanchnic nerve, and pelvic plexus. The rectal lateral ligament thus seems to represent a kind of migration fascia formed by mechanical stress.

Review of the anatomic concepts in relation to the retrorectal space and endopelvic fascia: Waldeyer's fascia and the rectosacral fascia

OBJECTIVE

A precise anatomical study of the fascias within the retrorectal space is reported, analyzing and clarifying the anatomical concepts previously employed to describe Waldeyer's and the rectosacral fascia.

METHOD

The pelvis was dissected in 15 cadavers (10 males and five females). All specimens were divided in the median sagittal plane including the middle axis of the anal canal, to allow a correct visualization of and access to the retrorectal space.

RESULTS

The retrorectal space was limited anteriorly by the rectum and posterior mesorectum covered by a fine visceral fascia, and posteriorly by the sacrum covered by the parietal presacral fascia. The rectosacral fascia divided the retrorectal space into inferior and superior portions in 80% of the male and 100% of the female specimens. It originated from the presacral parietal fascia at the level of S2 in 15%, S3 in 38% and S4 in 46% of specimens. In all cases it passed caudally to join the rectal visceral fascia 3-5 cm above the anorectal junction. As described by Waldeyer, the floor of the retrorectal space is formed by the fusion of the presacral parietal fascia and the rectal visceral fascia and lies above the levator ani muscle at the level of the anorectal junction.

CONCLUSION

The rectosacral fascia divides the retrorectal space into inferior and superior portions. This must be differentiated from Waldeyer's description of the fascia lying in the inferior limit of the retrorectal space, formed by the fusion of the rectal visceral and parietal fascias.

What are the supportive structures of the female urethra?

AIMS

Female stress urinary incontinence is thought to result from impairment of the connective tissue "ligaments" of the urethra. Surgical repair of female incontinence mainly involves fixation of the urethra to the pubic bone or other surrounding structures. In the present anatomical-radiological study, the anatomy of the connective tissue structures around the female urethra was investigated to determine the anatomical structures that support the urethra and the rhabdosphincter.

MATERIALS AND METHODS

The topography of the anterior compartment of the female pelvis was studied in serial sections and one anatomical preparation of 30 female fetuses and of six adult females. The pelves of 29 female fetuses were processed according to plastination histology technique. The pelves of the six adult specimens were processed according to sheet plastination technique. In addition, the anatomical findings were compared with MR images of 41 adult female volunteers.

RESULTS

The ventro-lateral aspect of the urethra remains free of fixating ligaments throughout its pelvic course. Ventro-laterally the urethra is enclosed by the ventral parts of the levator ani, its fasciae and a ventral urethral connective tissue bridge connecting both sides. Dorsally, the urethra is intimately connected to the wall of the vagina.

CONCLUSIONS

The female urethra has no direct ligamentous fixation to the pubic bone. Urethral continence after pregnancy and childbirth may be explained by a widening of the hiatus of the levator ani or the anterior vaginal wall, resulting in overstretching of the ventral urethral connective tissue bridge or the disruption of the fixation between urethra and vagina.

AN EMBRYOLOGICAL STUDY OF FETAL DEVELOPMENT OF THE RECTOURETHRALIS MUSCLE—DOES IT REALLY EXIST?

PURPOSE

The so-called rectourethralis muscle is widely described in the urological literature. However, its description is subject to variations concerning extent and morphology. Moreover, little is known about its fetal development, which would allow a better understanding of the adult anatomy. The aim of this study was to investigate the morphology, extent and development of the rectourethralis muscle in fetal specimens.

MATERIALS AND METHODS

A total of 15 normal human male fetuses were included in the study. Age ranged from 13th week of gestation to term. The histological study used plastination and standard and immunohistochemical techniques to identify the developing muscular structures in serial sections of the rectourethral space. Investigations in all 3 planes (coronal, sagittal and transverse) were performed.

RESULTS

In all sections of the proximal aspect of the rectourethral space no developing muscle fibers could be identified leaving the anterior wall of the rectum to join the rhabdosphincter or the apical prostate. In the distal aspect of the rectourethral space an independent muscular structure located between the external muscular layer of the anorectal canal and the dorsal bundles of the rhabdosphincter could be clearly demonstrated. This structure consisted of connective, smooth and striated muscle tissue, and was deeply anchored to the apical perineal body.

CONCLUSIONS

This study suggests that the so-called rectourethralis muscle is a misnomer in the urological literature. In the fetal period a developing muscular structure could be clearly identified as a part of the apical perineal body, which would correspond to the rectoperinealis muscle in the adult.

Histotopographic study of the rectourethralis muscle

Radical perineal prostatectomy, relative to retropubic prostatectomy, has become an increasingly used surgical technique for prostate cancer, following advances in laparoscopic methods for pelvic lymph node dissection. Recent protocols of risk stratification may even obviate the need for lymph node dissection. Section of the rectourethralis muscle (RUM) is necessary for access to the retroprostatic space, however, during this procedure rectal injuries may be produced. In this work, we studied the topography and morphology of the RUM, which, despite its importance in perineal surgery, has not been univocally described in the literature. After in situ formalin fixation, the pelvic viscera were removed from 16 male cadavers (age: 54-72 years) and from 4 full-term infants (gestational age: 37-38 weeks). Serial macrosections of the bladder base, prostate gland, and lower rectum cut in horizontal (6 adults and 2 infants) and sagittal (6 adults and 2 infants) planes underwent histological (hematoxylin and eosin, azan-Mallory, and Weigert's staining) and immunohistochemical (anti-smooth muscle actin and anti-sarcomeric actin) study. The remaining 4 adult specimens were cut in horizontal and sagittal planes and plastinated using the epoxy resin E12 sheet procedure. RUM was identified in 10 of 12 (83%) adult specimens and in 4 of 4 (100%) infant specimens. In both sagittal and transverse sections, it showed a triangular-shaped configuration. In all cases, at the level of its posterior portion, fibers continuing with the longitudinal muscular layer of the rectum were visible. In the majority of adult and infant cases, attachment of muscle fibers into the anterior wall of the anal canal was also observed. Anteriorly, the mean (+/-SD) distance between the RUM and the membranous urethra was 5.3 (+/-1.25) mm in adults and 1.0 (+/-0.41) mm in infants. Location of RUM in the prerectal space and the absence of urethral attachment makes the original name of this muscle, "prerectal," by Henle, more correct. In 7 of 10 (70%) adult cases and in 1 of 4 (25%) infant cases, muscle fibers were densely packed along the lateral portions of the RUM, while in its central portion connective tissue was prevalent, with sparse numbers of smooth muscle fibers. Immunohistochemical staining showed that this muscle consists almost entirely of smooth fibers. In all the infant specimens, the RUM was clearly separated from the levator ani, while in 8 of 10 (80%) adult cases, striated fibers of the levator ani and smooth fibers of the RUM intermingled. These structural associations suggest a functional cooperation between the two muscles, particularly in determining the anorectal flexure.

Plastinationshistologische Untersuchungen zur Insertion der Sehne des Musculus extensor pollicis brevis an der Daumengrundphalanx

By help of thick transparent cross-sections of 10 thumbs, manufactured by plastination histology, it has been shown that the most fibres of the extensor pollicis brevis tendon insert on a special tubercle of the basis of the proximal phalanx. Our studies prove that the shape of this tubercle is configurated in the phalanx proximalis longitudinally between the first and second fifth part and in the wideness of the base, seen from radial to ulnar between the forth and fifth tenth part.

Does a superficial musculoaponeurotic system exist in the face and neck? An anatomical study by the tissue plastination technique

An exact knowledge of the subcutaneous layers in the different regions of the face and neck is important in several surgical disciplines. In the parotid region, a superficial musculoaponeurotic system (SMAS) has been described. The existence of a SMAS as a guiding structure for the surgeon in the other regions of the face and neck has been discussed but is controversial. Therefore, the authors investigated the development of the subcutaneous connective-tissue layers in the different facial regions and in the neck. They studied these regions in 22 human fetuses using the technique of plastination histology and in three newborn and three adult specimens using sheet plastination. In addition, they dissected the neck and face in 10 fresh adult cadavers to identify the SMAS as in the surgical situation. The results show that no SMAS could be detected in any facial regions other than the parotid region. In the parotid region, it is thick and attached to the parotid sheath. However, it becomes very thin, discontinuous, and undissectable in the cheek area. No SMAS can be found in the neck, in which the authors are the first to describe a fascia covering both sides of the platysma. This fascia has close topographical connections to the subcutaneous layers of the adjoining regions. On the basis of these findings, the surgical pathways have to be defined regionally in the face. A "platysma fascia" can be considered as a surgical landmark in the neck. Therefore, the authors conclude that it is not justified to generalize a SMAS as a surgical guiding structure.

Ossification in the human calcaneus: a model for spatial bone development and ossification

Perichondral bone, the circumferential grooves of Ranvier and cartilage canals are features of endochondral bone development. Cartilage canals containing connective tissue and blood vessels are found in the epiphysis of long bones and in cartilaginous anlagen of small and irregular bones. The pattern of cartilage canals seems to be integral to bone development and ossification. The canals may be concerned with the nourishment of large masses of cartilage, but neither their role in the formation of ossification centres nor their interaction with the circumferential grooves of Ranvier has been established. The relationships between cartilage canals, perichondral bone and the ossification centre were studied in the calcaneus of 9 to 38-wk-old human fetuses, by use of epoxy resin embedding, three-dimensional computer reconstructions and immunhistochemistry on paraffin sections. We found that cartilage canals are regularly arranged in shells surrounding the ossification centre. Whereas most of the shell canals might be involved in the nourishment of the cartilage, the inner shell is directly connected with the perichondral ossification groove of Ranvier and with large vessels from outside. In this way the inner shell canal imports extracellular matrix, cells and vessels into the cartilage. With the so-called communicating canals it is also connected to the endochondral ossification centre to which it delivers extracellular matrix, cells and vessels. The communicating canals can be considered as inverted 'internal' ossification grooves. They seem to be responsible for both build up intramembranous osteoid and for the direction of growth and thereby for orientation of the ossication centre.

The different growth zones of the fetal foot

Previous publications revealed no reliable data or models concerning the three-dimensional ontogenesis of the lower extremity. Using the method of plastination-histology in combination with 3D-computer-reconstructions we were able to produce exact, virtual 3D-specimens of 19 healthy fetal feet. The fetuses were aged between 9 to 38 weeks of gestation and age-dependently related to four defined age-groups. We compared these feet with the help of a new geometrical method. Thus, we obtained a kind of "slow-motion-picture" of the undisturbed three-dimensional development of the fetal foot. Our results show that the human fetal foot has a desultory mode of growth and that growth priorities within the foot-skeleton change dependent upon age and region. Though the growth of the fetal foot-skeleton is desultory, it is not disconnected. The result of this peculiar mode of growth is to create the foot arches and thus seems to be functionally-oriented toward the human foot's specific purposes.

Tomographical anatomy of the pelvis, pelvic floor, and related structures

The sectional anatomy of the pelvic floor was studied in plastinated sections of adult pelves by computed tomography and by magnetic resonance imaging. In sectional anatomy, the levator ani is composed of three portions that can be clearly distinguished by their planes of cleavage and by the course of their fiber bundles. No muscular connections are found between the levator ani portions and the pelvic organs. The fascia of the levator ani in always interposed between the muscle and the pelvic organs. The sectional anatomy of the sphincter ani externus reveals a subdivision into a subcutaneous and a deep portion. Although the puborectalis portion of the levator ani and the deep portion of the sphincter ani externus are more or less continuous, in sectional anatomy they can be distinguished due to their different origins and attachments.

Subglottic region: normal topography and possible clinical implications

A precise definition of clinically important laryngeal regions and compartments is still a matter of controversy. The often neglected subglottic area was reinvestigated in plastinated serial sections of 21 human adult specimens. The superior border of the subglottic region is defined by the transition of squamous stratified epithelium covering the vocal cords into the respiratory epithelium of the caudal airways. It is found at the inferior margin of the vocal fold at variable distance from the free edge of the vocal cord and bears a high risk of carcinogenesis. The anterior border of the subglottic region is the cricothyroid space between the thyroid cartilage and cricoid arch. Medially, it is bridged by the median cricothyroid ligament. Laterally, the gap between thyroid and cricoid cartilage is filled by adipose tissue in most cases. This provides a broad connection of intra- and extralaryngeal connective tissue. There, cancer may escape the larynx. The conus elasticus is often regarded as a firm fibroelastic membrane within the subglottic region, but its structure may be disturbed by piercing blood vessels or age-related changes, facilitating cancerous spread. The cricoid lamina representing the dorsal border of the subglottic space ossifies preferentially in its superior part, which is often attacked by tumor invasion. The inferior border of the subglottic region is defined at the inferior rim of the cricoid cartilage. At this level, the endocricoid submucosal tissue contains loosely arranged collagenous fibers, which probably do not act as an anatomic barrier.

[Plastination histologic investigations on the inserting pars terminalis aponeurosis dorsalis of three-sectioned fingers]

With the help of thick transparent cross-sections of fingers, manufactured by plastination histology, it has been shown that fibres of the extensor aponeurosis insert not only the way described in current textbook on the basis phalangis distalis and on the capsule of the distal interphalangeal joint. Our studies prove that parts of the dorsal extension plate insert dorsally to the nail matrix and others run over the edge of the basis phalangis to the proximal part of the diaphysis where they intermingle with the periost of the phalanx.

Aryepiglottic fold: normal topography and clinical implications

The aryepiglottic folds extend between the arytenoid cartilage and the lateral margin of the epiglottis on each side and constitute the lateral borders of the laryngeal inlet. They are involved in physiologic closure mechanisms of the larynx and in pathologic conditions such as inspiratory stridor. Information on the normal topography of the aryepiglottic folds is poor and controversial. Therefore, this region was reinvestigated in serial whole-organ sections of 25 plastinated normal adult human larynges. Dorsally, the right and the left aryepiglottic folds are separated by the interarytenoid notch and comprise the corniculate and cuneiform cartilages, as well as numerous groups of mucous glands. Ventrally, the aryepiglottic folds are adjacent to the peri-epiglottic adipose tissue. Both regions are clearly separated by several layers of transversely oriented collagenous fiber layers. The muscular constituent of the aryepiglottic folds is only poorly developed, and no muscle fibers insert at the epiglottis. A coherent quadrangular membrane representing a ligamentous "skeleton" of the aryepiglottic folds is absent. A conspicuous collagenous fiber layer is found only to strengthen the free dorsal margin of the fold. Both muscular and ligamentous components may render the aryepiglottic folds sufficiently tense as to resist inspiratory inward suction in normal cases. However, pliability must be preserved to guarantee adequate folding in approximation of the aryepiglottic folds during deglutition. Thereby, the posterior part of the laryngeal inlet is closed, whereas the anterior part is probably closed by independent inward bulging of the peri-epiglottic adipose tissue.

Tomographical anatomy of the pelvis, pelvic floor, and related structures

The sectional anatomy of the pelvic floor was studied in plastinated sections of adult pelves by computed tomography and by magnetic resonance imaging. In sectional anatomy, the levator ani is composed of three portions that can be clearly distinguished by their planes of cleavage and by the course of their fiber bundles. No muscular connections are found between the levator ani portions and the pelvic organs. The fascia of the levator ani in always interposed between the muscle and the pelvic organs. The sectional anatomy of the sphincter ani externus reveals a subdivision into a subcutaneous and a deep portion. Although the puborectalis portion of the levator ani and the deep portion of the sphincter ani externus are more or less continuous, in sectional anatomy they can be distinguished due to their different origins and attachments.

Borders and topographic relationships of the paraglottic space

The precise topographic relationships of the paraglottic space (PGS) were investigated in serial plastinated or frozen whole-organ sections of 46 normal adult larynges. Laterally, the PGS was bordered by the thyroid cartilage. Superomedially, the PGS in some specimens was only separated from the periepiglottic space by a coherent collagenous fiber septum. The paraglottic adipose tissue extended between the caudal fibers of the thyroarytenoid muscle. Inferomedially, the PGS was bordered by the conus elasticus. The anteroinferior portion of the PGS extended beyond the larynx beneath the inferior rim of the thyroid cartilage. Posteroinferiorly, the paraglottic adipose tissue extended towards the cricoarytenoid joint. Dorsally, the PGS was bordered by the mucosal lining of the piriform sinus. Due to the intimate topographic and histologic relationships present, cancer involving the PGS may rapidly infiltrate all adjacent anatomic structures.

The ossification centre of the talus

The ossification of the talus was studied in plastinated and histological preparations of normal feet of eight newborn children. Quantitative data on the newborn talus were obtained with the IBAS image analysis system and by point counting methods. In the newborn talus up to 24 percent of the talar anlage already consists of bony tissue. The ossification centre is situated in the neck, which includes the non-articulating surfaces of the talus. Periosteal bone joins the endochondral centre below and, in well-differentiated specimens also above. The basal periosteal collar forms the surfaces of the sinus and canalis tarsi, whereas the cranial bony collar is included in the tibiotalar joint. The histological architecture of these periosteal collars differs. Four arteries contribute to the blood supply of the talar ossification centre.

Sectional anatomy of connective tissue structures in the hindfoot of the newborn child and the adult

BACKGROUND

The knowledge of the normal anatomy of the newborn hindfoot is essential for the understanding of foot deformities. In the present study, we investigated tendons, ligaments, and soft tissue structures in the newborn foot.

METHODS

The sectional anatomy of eight newborn feet was studied in 300-500-microns-thick sections processed by plastination histology. For comparison, 3-5-mm-thick plastinated sheets of adult feet were investigated.

RESULTS

Our specimens show obvious differences of the newborn compared with the adult foot. In the subcutaneous adipose tissue, the heel pad and the fat pad of the Achilles tendon and the relative size and topography of adipose tissue pads are different. Moreover, the course of the flexor hallucis tendon and the insertion pattern of the Achilles tendon are distinct. Finally, there are differences in the course and in the relative length of some plantar ligaments.

CONCLUSIONS

Our data reveal that the differences between the newborn foot and the adult foot result mainly from the different shape and position of the tarsal bones. Our findings are of clinical importance for the evaluation of magnetic resonance imaging in the normal infant's foot and in foot deformities.

Anatomical basis of autonomic nerve-preserving total mesorectal excision for rectal cancer

Total mesorectal excision with autonomic nerve preservation for rectal cancer is based on the anatomy of the mesorectum and of the pelvic autonomic nerves. Cadaver dissections were performed to describe the relationship between these structures. Between the rectum and the sacrum a retrorectal space can be developed, lined anteriorly by the visceral leaf and posteriorly by the parietal leaf of the pelvic fascia. The hypogastric nerve runs anterior to the visceral fascia, from the sacral promontory in a laterocaudad direction. The splanchnic sacral nerves originate from the sacral foramina, posterior to the parietal fascia, and run caudad, laterally and anteriorly. After piercing the parietal layer of the pelvic fascia, approximately 4 cm from the midline, the sacral nerves run between a double layer of the visceral part of the pelvic fascia. The relationship between the hypogastric nerves, the splanchnic nerves and the pelvic fascia was comparable in all six specimens examined.

[Development and clinical anatomy of the rectal adventitia. significance for radical operation of rectal carcinoma]

The development, topography and clinical anatomy of the adventitia recti were studied in 300- to 600-microns-thick sections through the pelves of human fetuses and newborn children and 5-mm sections through the pelves of adults. The adventitia recti constitutes a continuous compartment bordered laterally by the fascia recti. In the adult the adventitia recti consists mainly of adipose tissue. The extent of the adventitia recti differs in different parts of the rectal wall. The branches of the vasa rectalia superiora and the visceral lymph nodes of the rectum are situated within the adventitia recti. Our findings suggest that it is necessary to remove the adipose tissue of the adventitia recti and the adjoining lymph nodes individually during resection of the rectum in order to minimize the risk of tumor recurrence.

The paraglottic space and transglottic cancer: anatomical considerations

Transglottic cancer of the larynx crosses the laryngeal ventricle and involves both the vestibular and vocal folds. It has been described to spread within the paraglottic space (PGS). This region of adipose tissue, containing blood vessels and nerves, immediately adjacent to the thyroid laminae, was originally defined by Tucker and Smith (1962). However, the precise topographic relationships of this clinically important space are still controversely discussed. Therefore, a reinvestigation was done in serial sections of 19 plastinated adult human larynges. Laterally, the PGS is bordered by the thyroid cartilage. Superomedially, the PGS is continuous with the preepiglottic space (PES) in most specimens. In some cases, the PGS and the PES are completely separated from each other by a conspicuous collagenous fiber septum. Small projections of the paraglottic adipose tissue extend between the fibers of the thyroarytenoid muscle. Inferomedially, the PGS is bordered by the conus elasticus. Anteroinferior extensions of the PGS escape the larynx beneath the inferior rim of the thyroid cartilage. Posteroinferiorly, the paraglottic adipose tissue extends between the intrinsic laryngeal muscles and towards the cricoarytenoid joint. Dorsally, the PGS is bordered by the mucosal lining of the piriform sinus. A precise knowledge of the topography of the PGS can explain typical symptoms and routes of spread of tumorous growth: extension toward the hypopharynx, extension into the anterior extralaryngeal tissues, invasion of the thyroid cartilage, impairment of vocal cord movements due to infiltration of laryngeal muscles or immobilization of the cricoarytenoid joint.

The attachments of the conus elasticus to the laryngeal skeleton: physiologic and clinical implications

The attachments of the inferior and dorsal extensions of the lateral parts of the conus elasticus (CE) are not fully understood. A re-investigation was done in plastinated serial sections of 20 adult human larynges. The CE consists of a coherent sheet of connective tissue fibers dividing into two layers toward the inferior anchorage to the cricoid arch, and the posterior anchorage to the cricoid lamina. Caudally, the medial fiber layer is continuous with the submucous fibroelastic membrane of the trachea and is not connected to the cricoid cartilage. The lateral caudal fiber layer is attached to the superior rim of the cricoid arch. Dorsally, both layers of the CE are fixed to the cricoid lamina, the lateral sheet to the lateral edge of the cartilage, the medial sheet to its anterior perichondrium near the midline. Towards the cricoarytenoid joint, the dorsal extension of the CE divides into a caudal and a cranial sheet including a fold of adipose tissue at the base of the arytenoid cartilage. The cranial layer extends towards the vocal process, the caudal layer radiates into the joint capsule and may therefore influence the complicated joint mechanics. The firm attachments of the CE to the cricoid cartilage probably counteract deformations of the CE during phonation. An insufficient fixation of the CE may contribute to an obstruction of the airways causing sleep apnea.

The cricoarytenoid ligament: its morphology and possible implications for vocal cord movements

The cricoarytenoid ligament was studied in sections of ten plastinated adult human larynges. The collagenous fibres forming the ligament originate from a small area at the upper rim of the cricoid lamina and from the adjacent dorsal cricoid perichondrium. The fibres strengthen the dorsal and medial part of the capsule of the cricoarytenoid joint. They are arranged in several layers separated by adipose tissue. The most medial layer of the collagenous fibres is attached to the medial aspect of the vocal process, whereas the vocal cord is anchored more laterally. Contrary to the descriptions in the literature, no fibres of the cricoarytenoid ligament join the vocal cord. Especially, the medial part of the ligament is important for controlling abduction and abduction of the vocal cords. Voice disturbance may result from structural asymmetry of the cricoarytenoid ligament.

Normal topography of the conus elasticus. Anatomical bases for the spread of laryngeal cancer

The topographic relations of the conus elasticus were studied with special regard to the local spread of laryngeal cancer. Sections of twelve plastinated adult human larynges were investigated. Lateral from the median cricothyroid ligament, the conus elasticus reveals two broad gaps containing adipose tissue and blood vessels. Along these routes, tumors of the larynx may easily extend into the ventral extralaryngeal tissues by continuous growth. Fibres of the conus elasticus cover the entire cranial surface of the vocalis muscle near the muscle's insertion at the thyroid cartilage. This part of the conus elasticus has been termed "thyroglottic ligament" in the fetus [22]. In the adult, this ligament prevents early cancer of the anterior vocal cords from invading adjacent structures. Other collagenous fibres continuous with the conus elasticus provide only an incomplete layer separating the lateral cricoarytenoid and the thyroarytenoid muscle. These fibres do not constitute an effective barrier against cancer growth.

Autonomic nerves cross the posterior plane of rectal dissection

This investigation was an anatomical study to determine whether branches of the pre-sacral autonomic plexus cross the posterior plane of surgical dissection to supply the rectum. Initially four cadaver hemi-pelves were dissected. Twelve patients undergoing full rectal mobilization were then studied at operation. In all subjects the pre-sacral nerves were arranged as a plexus below the sacral promontory, rather than as individual left and right nerve trunks. Structures thought to be nerves were identified crossing the plane of posterior mobilization of the rectum. They were traced towards their origin and destination, photographed and representative fibres biopsied. A total of 42 such structures were biopsied (16 in cadavers, 26 in operative cases) and 40 were confirmed to be nerves. These nerves connect the pre-sacral autonomic plexus with the posterior aspect of the rectum and were found at all sacral levels. In the operative cases the level of the positive biopsies were S1-six, S2-six, S3-five, S4-four, S5-three. The posterior plane of rectal dissection is therefore crossed by autonomic nerves that innervate the rectum. The pre-sacral nerves have been found to form a plexus in all subjects.

Tomographical anatomy of the pelvis, visceral pelvic connective tissue, and its compartments

The sectional anatomy of the pelvic connective tissue was studied in plastinated sections of fetal and adult pelves, by computed tomography and by magnetic resonance imaging. The comparative study of the different specimens shows that the pelvic connective tissue consists of three compartments: a presacral compartment, a perirectal compartment, and a paravisceral compartment. The content and the borders of the compartments are described. Furthermore the pelvic fasciae and the pelvic ligaments are studied within the different specimens. A thin pelvic visceral fascia can only be found around the perirectal compartment. In tomographical anatomy the so called supportive ligaments of the uterus are only composed of the round ligaments and the sacrouterine ligaments.

Topographical relations between the posterior cricothyroid ligament and the inferior laryngeal nerve

The posterior cricothyroid ligament and its topographic relation to the inferior laryngeal nerve were studied in 54 human adult male and female larynges. Fourteen specimens were impregnated with curable polymers and cut into 600-800 microns sections along different planes. Forty formalin-fixed hemi-larynges were dissected and various measurements were made. The posterior cricothyroid ligament provides a dorsal strengthening for the joint capsule of the cricothyroid joint. Its fibers spread in a fan-like manner from a small area of origin at the cricoid cartilage to a more extended area of attachment at the inferior thyroid cornu. The ligament consists of one (7.5%) to four (12.5%), in most cases of three (45.0%) or two (35.0%), individual parts oriented from mediocranial to latero-caudal. The inferior laryngeal nerve courses immediately dorsal to the ligament. In 60% it is covered by fibers of the posterior cricoarytenoid muscle, in the remaining 40% it is not. In this latter topographic situation there is almost no soft tissue interposed between the nerve and the hypopharynx. Therefore, the nerve may be exposed to pressure forces exerted from dorsally. It may be pushed against the unyielding posterior cricothyroid ligament and suffer functional or structural impairment. Probably, this mechanism may explain some of the laryngeal nerve lesions described in the literature after insertion of gastric tubes.

Anatomical aspects of postintubational subglottic stenosis

The subglottic regions of 54 human adult male and female larynges were studied with regard to anatomical aspects of postintubational stenosis. Fourteen specimens were impregnated with curable polymers and cut into 600-800 microns sections along different planes. Forty formalin-fixed hemilarynges were dissected. Measurements of the upper cricoid lamina and the thickness of the endocricoid soft tissues were taken for statistical analysis. Immediately beneath the glottis, the upper part of the cricoid lamina consists of two lateral plates with an average angle of 110 degrees. Distally, the cricoid adopts a more and more rounded lumen. At the level of the cricothyroid joint, the definite airway lumen is always laterally narrowed by a prominent thickening of the endocricoid soft tissue. Large amounts of loose connective tissue facilitate the development of edema in case of injury in this region. Dorsally, the submucous stratum is smaller and consists mainly of dense connective tissue. The blood vessels are fixed to the cricoid perichondrium by collagenous fibers. Any pressure applied from the airway lumen will force the vessels against the nonresilient cartilage, resulting in occlusion and ischemia. These pathophysiologic mechanisms are important for the development of early laryngeal damage during endotracheal intubation, possibly resulting in posterior stenosis due to scarring later on.

Topography and subdivision of the pelvic connective tissue in human fetuses and in the adult

We investigated epoxy resin impregnated sections through the pelves of 9 to 37-week-old fetuses, of newborn infants, and of adults to study the topography and subdivision of the pelvic connective tissue. Fetal and adult preparations show that the pelvic connective tissue can be subdivided into a presacral, a perirectal and a paravisceral compartment. Whereas the presacral and the perirectal compartment contain connective tissue, adipose tissue and supplying structures, the paravisceral compartment is mainly composed of adipose tissue. While only a very thin rectal fascia was found at the border of the perirectal compartment, no further visceral pelvic fascia can be seen in the impregnated sections. Moreover it is shown that the ligaments of the pelvic cavity are only composed of the sacrouterine ligaments and the pubovesical ligaments in the female and the puboprostatic ligaments in the male. Our data show that sectional anatomy provides new insights into the organization of the pelvic connective tissue, that may be of clinical importance.

Vascularization of the fetal elbow joint

Unlike the adult tissue, prenatal cartilage may be well vascularized. We studied the prenatal development of vascular channels within the epiphyses of the human elbow joint. Plastinated 200-1000 microns thick sections through the right and left arms of 12 fetuses with a crown-rump-length of 90-360 mm and of a newborn infant were investigated. Cartilage canals first develop within the distal humeral epiphysis, later on within the olecranon process and the radial head. With advancing age, the canals reveal an increasingly complex pattern of distribution. However, a constant basic pattern can be recognized at every developmental stage. The cartilage canals take their origin from the perichondrium. At their point of entrance into the cartilaginous tissue, their walls are often ill-defined and consist of several fibrous layers which gradually irradiate into the cartilage. At the opposite tip, the channel wall is more clearly demarcated. Many cartilage canals contain several vessels forming loops or branching into bunch-like structures at the tip of the canals. The vessels mostly lie adjacent to the canal walls, grouped around a core of loose connective tissue. As a rule different channels run towards the centre of the cartilage and do not form any anastomoses. The vascularization of the epiphyses of the human elbow joint takes place a long time before the secondary centres of ossification develop, which normally appear after birth. Thus, a direct causal relationship seems unlikely.

Topographical anatomy of the posterior elbow region during fetal development

We studied the topography of the elbow region with special regard to the ulnar nerve during fetal life. Plastinated 600 microns thick sections through the right and left arms of ten fetuses with a crown-rump length (CRL) of 105 to 360 mm and of a newborn infant were investigated. The ulnar groove does not appear on the dorsal side of the medial humeral epicondyle earlier than at a crown-rump length of 130 mm. It provides the entrance into a formerly described fibro-osseous tunnel called the cubital tunnel. Its floor is formed by the posterior bundle of the ulnar collateral ligament, which bulges medially on flexion of the elbow joint. Up to 270 mm CRL it is composed of rather loosely arranged connective tissue fibres. Later on, its fibres are densely packed and show a parallel orientation. The ulnar nerve is pushed medially but remains behind the medial epicondyle. None of the specimens showed displacement to the anterior site of the elbow joint. An aponeurotic arch bridging the humerus and ulna and covering the ulnar nerve medially could not be identified. The findings in the newborn infant did not reveal any significant differences compared to the fetal specimens.

Development of the levator ani muscle in human fetuses

The development of the levator ani muscle was studied in 300- to 700-microns thick sections through the pelves of 9- to 37-week-old fetuses and newborn children. During early fetal development, the anlage of the levator ani muscle can already be subdivided into three portions. The planes of cleavage between them become clearly evident in fetuses during the middle trimester when all points of origin and insertion of the levator ani muscle can be recognized. The tendinous arch of the pelvic fascia plays an important role in the differentiation between the pubococcygeus and the iliococcygeus parts of the levator ani muscle. The funnel-shaped form of the pelvic diaphragm is completed by about the 14th week of fetal development. Differences between the male and female levator ani muscles are already marked before birth.

Development and organization of the pelvic connective tissue in the human fetus

The developmental changes in the pelvic connective tissue were studied in 200-600 microns sections through the pelves of human fetuses and newborn children, plastinated with an epoxy resin. Three periods are important for the differentiation of the pelvic connective tissue in fetuses. During a first or mesenchymal period (9-12-week-old fetuses), all pelvic regions identical with the so-called pelvic spaces in the adult are filled with loose undifferentiated mesenchyme. Some pelvic organs are covered by a layer of condensed mesenchyme which later constitutes the connective tissue sheath of these organs. During a second or fibrous period (13-20-week-old fetuses), dense connective tissue predominates. It is arranged in circular and semicircular systems covering the rectum, the bladder and the urethra as well as the peritoneal pouches. The arrangement of dense connective tissue is the same in the male and in the female fetus. No ligaments were found within the pelvic cavity apart from the pubovesical and the puboprostatic ligaments. The connective tissue sheaths of the pelvic organs differ from one another. At the level of the pelvic floor only some of them are directly connected with the parietal pelvic fascia. The pelvic spaces are filled by loose connective tissue. During a third or adipose period (21-38-week-old fetuses) adipose tissue develops within the different compartments of the pelvic cavity so that the clear organization found during the second period is abolished.