The morphogenesis of the renal plexus: Renal artery and sympathetic fibers.

To examine the origin and development of the renal plexus and its relationship to the renal vessels in embryos and early human fetuses. Serial sections of 34 human embryos (stages 16 to 23 of Carnegie, 4 or 5-8 weeks) and 38 fetuses (9-19 weeks) were analyzed. Throughout the embryonic period, the kidney was not innervated by the renal plexus. Those nerves appeared at the beginning of the early fetal period (9 weeks) as branches given off by the immature autonomic abdominal plexus. The renal nerves started to approach to the kidney during the early fetal period at 9-10 weeks of development. They were distributed in close proximity to the renal arteries and their branches. They were observed first with the settlement of the renal veins. The renal artery is present as a branch of the abdominal aorta at stage 19 (between 6 and 7 weeks) prior to development of the renal plexus. The renal veins were not present during the embryonic period but appeared at the start of the fetal period, along with the renal nerves that emerged from segmented sympathetic para-aortic bodies (SPBs). Clin. Anat. 32:272-276, 2019. © 2018 Wiley Periodicals, Inc.

Anatomical variations of the renal arteries: Cadaveric and radiologic study, review of the literature, and proposal of a new classification of clinical interest.

PURPOSE: To analyse the variations of the renal arteries in two samples, cadaveric and computerized tomographic (CT) images, as well as to propose a simple classification of such variations based on the obtained results and an extensive review of the literature on the topic. MATERIAL AND METHODS: Sixty human dissected kidneys and their vessels, and 583 abdominal CT were studied. RESULTS: A total of 86 arteries were described in the cadaveric sample, whereas 1223 were analysed in the radiological one. Five types (a-e) and patterns (I-V) have been stablished in the classification. Type a, aortic hilar artery, incidences were 79% in cadavers and 95% in CT; Type b, hilar upper polar artery, incidences were 10% in cadavers and 2% in CT; Type c, aortic upper polar artery, incidences were 5% in cadavers and 2% in CT; Type d, aortic lower polar artery, incidences were 3% in cadavers and 1% in CT; Type e, hilar lower polar artery, incidences were 2% in cadaver and less than 0.1% in CT. The pattern represents the number of arteries reaching one kidney. Patterns I-IV were found in cadavers (I: 78%; II: 19%; III and IV: 2%); in CT sample only patterns I (88%) and II (12%). Pattern V was added because it has been described in the reviewed literature. CONCLUSIONS: Type a and pattern I are the most prevalent, both in the cadaveric and the CT samples. Also in the consulted literature. There are no differences in the types and pattern incidences by side or sex. A simple, comprehensive and useful classification is proposed.

Understanding the anatomy of the larynx from the era of Gimbernat to the present day moving towards laryngeal transplantation

Knowledge of the gross anatomy of the larynx in Spain throughout the period when Gimbernat was working as a surgeon and anatomist was considerable; very much comparable to our present understanding. However, the lack of aseptic surgical technique, anaesthesia, and antibiotics limited the ability to undertake complex surgery. Nevertheless, it was during that period when for first time it became possible to diagnose some laryngeal pathologies, thanks to the invention, by a Spanishsinger, Manuel Garcia (1805-1906), of a primitive laryngoscope that made it possible to see the laryngeal interior. Only in 1873 was the first major surgery of the larynx was reported when Billroth undertook the first laryngectomy to treat surgically laryngeal carcinoma. It was more than a hundred years later, before the first laryngeal transplantation was attempted by Strome and his team (1998), and though initially meeting with some success, that transplanted larynx had to be removed 14 years later. Based on our current understanding of laryngeal anatomy and surgical technique, we argue that there are four factors that must be addressed if satisfactory transplantation of the larynx to be achieved: 1) psycho-social and ethicolegal aspects; 2) tissue viability vs. rejection; 3) restoration of a vascular, and 4) selective reinnervation of the larynx has to be achieved. The three first factors are being addressed, however, the selective reinnervation remains challenging because the nerve supply of the larynx is now known to be much more complex than many accounts imply. This is because: 1) each laryngeal muscle may receive a variable number of nerve branches; 2) there are multiple connections between the different laryngeal nerves; 3) many laryngeal nerves and connections are mixed conveying both motor and sensory fibres; and 4) the laryngeal muscles may receive a dual nerve supply, from both the recurrent laryngeal and superior laryngeal nerves (AU)

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Are the interarytenoid muscles supplied by branches of both the recurrent and superior laryngeal nerves?

OBJECTIVES/HYPOTHESIS: It has been generally accepted that the branches of the internal branch of the superior laryngeal nerve to the interarytenoid muscle are exclusively sensory. However, some experimental studies have suggested that these branches may contain motor axons, and therefore that the interarytenoid muscle is supplied by both the superior and recurrent laryngeal nerves. The aim of this work was to determine whether motor axons to the interarytenoid muscles are present in both laryngeal nerves. STUDY DESIGN: Basic research. METHODS: Twelve human internal branches of the superior laryngeal nerve were dissected, and its branches to the interarytenoid muscle were removed and processed for choline-acetyltransferase immunohistochemistry, a method not used previously in studying the nerve fiber composition of the laryngeal nerves. RESULTS: The internal branch of the superior laryngeal nerve divided into two to five branches to the interarytenoid muscle. All branches contained motor axons, with the proportion of motor axons varying from 6% to 31%. CONCLUSION: The present study confirms that the internal branch of the superior laryngeal nerve provides a motor innervation to the interarytenoid muscles. LEVEL OF EVIDENCE: N/A. Laryngoscope, 126:1117-1122, 2016.

Somatotopic changes in the nucleus ambiguus after section and regeneration of the recurrent laryngeal nerve of the rat.

Changes in motoneurons innervating laryngeal muscles after section and regeneration of the recurrent laryngeal nerve (RLN) are far from being understood. Here, we report the somatotopic changes within the nucleus ambiguus (Amb) after the nerve injury and relates it to the resulting laryngeal fold impairment. The left RLN of each animal was transected and the stumps were glued together using surgical fibrin glue. After several survival periods (1, 2, 4, 8, 12, 16 weeks; at least six rats at each time point) the posterior cricoarytenoid (PCA) and thyroarytenoid (TA) muscles were injected with fluorescent-conjugated cholera toxin and the motility of the vocal folds evaluated. After section and subsequent repair of the RLN, no movement of the vocal folds could be detected at any of the survival times studied and the somatotopy and the number of labeled motoneurons changed. From 4 wpi award, the somatotopy was significantly disorganized, with the PCA motoneurons being located rostrally relative to their normal location. A rostrocaudal overlap between the two pools of motoneurons supplying the PCA and TA muscles was observed from 2 wpi onwards. Hardly any labeled neurons were found in the contralateral Amb in any of the experimental groups. An injury of the RLN leads to a reinnervation of the denervated motor endplates of PCA and TA. However, misdirected axons sprout and regrowth from the proximal stump to the larynx. As a result, misplaced innervation of muscles results in a lack of functional recovery of the laryngeal folds movement following a RLN injury.

Somatotopy of the neurons innervating the cricothyroid, posterior cricoarytenoid, and thyroarytenoid muscles of the rat's larynx.

Neurons innervating the intrinsic muscles of the larynx are located within the nucleus ambiguus but the precise distribution of the neurons for each muscle is still a matter for debate. The purpose of this study was to finely determine the position and the number of the neurons innervating the intrinsic laryngeal muscles cricothyroid, posterior cricoarytenoid, and thyroarytenoid in the rat. The study was carried out in a total of 28 Sprague Dawley rats. The B subunit of the cholera toxin was employed as a retrograde tracer to determine the locations, within the nucleus ambiguus, of the neurons of these intrinsic laryngeal muscles following intramuscular injection. The labelled neurons were found ipsilaterally in the nucleus ambiguus grouped in discrete populations with reproducible rostrocaudal and dorsoventral locations among the sample of animals. Neurons innervating the cricothyroid muscle were located the most rostral of the three populations, neurons innervating the posterior cricoarytenoid were found more caudal, though there was a region of rostrocaudal overlap between these two populations. The most caudal were the neurons innervating the thyroarytenoid muscle, presenting a variable degree of overlap with the posterior cricoarytenoid muscle. The mean number (±SD) of labelled neurons was found to be 41 ± 9 for the cricothyroid, 39 ± 10 for the posterior cricoarytenoid and 33 ± 12 for the thyroarytenoid.

Ulnar nerve innervation of the triceps muscle: real or apparent? An anatomic study.

BACKGROUND: Since the 18th century, the existence of ulnar nerve innervation of the medial head of the triceps brachii muscle has been controversial. The evidence for or against such innervation has been based on macroscopic dissection, an unsuitable method for studying intraneural topography or intramuscular branching. The study of smaller specimens (embryos or fetuses) by means of serial histologic sections may resolve the controversy. QUESTIONS/PURPOSES: Using fetal specimens and histology we determined the contributions of the ulnar and radial nerves to innervation of the triceps brachii muscle. METHODS: We histologically examined 15 embryonic and fetal arms. Radial nerve branches obtained from six adult arms were analyzed immunohistochemically to determine motor fiber content. RESULTS: The medial head of the triceps brachii muscle was always innervated by the radial nerve (ulnar collateral branch). The branches seeming to leave the ulnar nerve at elbow level were the continuation of the radial nerve that had joined the ulnar nerve sheath via a connection in the axillary region. Immunohistochemistry revealed motor and nonmotor fibers in this radial nerve branch. CONCLUSIONS: A connection between the radial and ulnar nerves sometimes may exist, resulting in an apparent ulnar nerve origin of muscular branches to the medial head of the triceps, even though in all our specimens the fibers could be traced back to the radial nerve. CLINICAL RELEVANCE: Before performing or suggesting new muscle and nerve transpositions using this apparent ulnar innervation, the real origin should be confirmed to avoid failure.

Morphogenesis of the human laryngeal ventricles.

BACKGROUND: Two theories explain the origin of human laryngeal ventricles: (1) ventricles derive from the fifth pharyngeal pouches; (2) development independent from the pouches. METHODS: In all, there were 21 serially sectioned human embryos from stages 15 to 23, and 11 fetuses of 9 to 18 weeks. Computer-aided 3-dimentional reconstructions were made. RESULTS: The cranial part of the laryngeal sulcus and future vestibule expands from the pharyngeal floor between the third and fourth pharyngeal pouches during stages 15 and 16 (33-37 days). The primordia of the ventricles appeared at stage 18 (44 days) as 2 lateral swellings in the caudal end of the future vestibule, limited by the third pharyngeal pouches. Active epithelial expansion and subsequent canalization during late embryonic and early fetal periods finalizes their development. CONCLUSIONS: The laryngeal ventricles do not derive from the pharyngeal pouches but the median region of the pharyngeal floor between the third and fourth pharyngeal pouches and arches at the caudal end of the future vestibule.

A new straight proximal humeral nail: a cadaveric study of itsanatomical relationships

New humeral nailing systems appear constantly in the market, but few anatomical studies assessing the potential risks of neurovascular injury, exist. The aim of this study is to determine the potential risk of neurovascular injury during proximal and distal locking. An anatomical analysis was carried out in cadavers where a new straight proximal humeral nail had been inserted. The nail entry point was always located medially to the myotendinous junction of the supraspinatus muscle, therefore affecting only muscle fibres. The nail entry point was surrounded by articular cartilage of the humeral head. The axillary nerve and the posterior humeral circumflex artery were at safe distances (>2cm) from all proximal and distal locking screws. The radial nerve and its accompanying artery, the profunda brachii artery, were at risk whenever medial cortex violation happened, as they were located within 1cm of the exit point of the most distal locking screw. The straight humeral nail analysed in the current study seems to be more secure in relation to the neurovascular injury potential when compared to previously reported ones. Only the incorrect selection of the length of the most distal locking screw may lead to injury of the radial nerve and/or profunda brachii artery; therefore, close monitorisation during the insertion of this distal locking screw is recommended (AU)

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Obturator artery revisited.

INTRODUCTION AND HYPOTHESIS: The aim of this work is to analyse the variability of the obturator artery (oa), unify previous criteria and propose a simple classification for clinical use. METHODS: A sample of 119 adult human embalmed cadavers was used. Origin and course of the oa in relation with the external iliac artery, internal iliac artery and inferior epigastric artery were studied. Chi-squared and t test were used for statistical comparison, and p < 0.05 was considered significant. RESULTS: Based on the number of roots of origin, three different situations were observed. The oa shows a single origin (96.55%). The oa presents a double origin (3.02%), or the oa arises from three roots (0.43%). The first situation was subclassified into six types according to the oa origin. Equal vascular pattern in both hemi-pelvises was observed in 58.93%. CONCLUSIONS: Almost 31% of oa passes over the superior pubic ramus implying an increased risk during some procedures.

Potential structures that could be confused with a nonrecurrent inferior laryngeal nerve: an anatomic study.

OBJECTIVES: Study and detailed description of the large connections between the normally recurrent inferior laryngeal nerve (RILN) and the sympathetic trunk (ST) because these may be mistaken for a nonrecurrent inferior laryngeal nerve (NRILN). STUDY DESIGN: Morphologic study of adult human necks. METHODS: The necks of 144 human, adult, embalmed cadavers were examined (68 males, 76 females). They had been partially dissected by Cambridge preclinical medical students and then further dissected by the authors using magnification. The RILN, the ST, and their branches were identified and dissected. A total of 277 RILNs and STs (137 rights, 140 lefts) were observed. RESULTS: A communicating branch (CB) with a similar diameter to the RILN occurred between the ST and the RILN in 48 of the 277 (17.3%) dissections, 24 from the 137 (17.5%) right dissections, and 24 from the 140 (17%) left dissections. In 12 cases, the CB was bilateral. The CB arose from the superior cervical sympathetic ganglion in 3 of the 48 (6.25%) cases, from the middle ganglion in 10 (21%) cases, from the stellate ganglion in 3 (6.25%) cases, and from the ST in 32 (66.6%) cases. One (0.36%) NRILN associated with a right retro-esophageal subclavian artery (arteria lusoria) was found. CONCLUSIONS: 1) The CB between the RILN and the ST may have a diameter and course similar to an NRILN and may be confused with it. 2) The occurrence of the CB is greater than the occurrence referred to in previous studies. 3) The occurrence of the CB is similar by side and sex. 4) The CB may arise at different levels from the cervical ST and ganglia and end in the thyroid area. 5) Other neural elements may also be confused with an RILN, such as the cardiac nerves and the collateral branches from an NRILN to the trachea and esophagus.

Variability in nerve patterns of the adductor muscle group supplied by the recurrent laryngeal nerve.

INTRODUCTION: Accurate knowledge of the nerve supply of each individual muscle is needed to achieve a successful selective reinnervation of the larynx. The aim of the present work was to study the nerve supply of the adductor laryngeal muscles supplied by the recurrent laryngeal nerve. STUDY DESIGN: Morphologic study of human larynges. METHODS: The muscular nerve supply was studied in a total sample of 75 human larynges obtained from necropsies (47 males and 28 females, age range from 41-95 years) and examined by careful dissection using a surgical microscope. RESULTS: The arytenoid muscle received one branch from each recurrent nerve. In 88% of cases, this branch arose in a common trunk with the upper branch of the posterior cricoarytenoid muscle. In 8% of cases, the nerve for the arytenoid muscle also had a branch going to the lateral cricoarytenoid muscle. The arytenoid muscle also received from one to three pairs of branches from the posterior division of the internal laryngeal nerve; these were interconnected ipsi- and contralaterally and were also connected to the two branches coming from the recurrent laryngeal nerve. The lateral cricoarytenoid muscle received from one to six branches from the recurrent nerve, but in 5.8% of cases, it also received a twig from a connecting branch between the recurrent nerve and the external (5.6%) or the internal laryngeal nerves (0.2%). The thyroarytenoid muscle received from one to four branches from the recurrent nerve, but in 5.6% of cases, it also received a twig from a connecting branch between the recurrent nerve with the external (4.6%) or the internal (1%) laryngeal nerves. CONCLUSION: No abductor or adductor division of the recurrent laryngeal nerve was found in the present study. In 88% of cases, the nerve supply to the arytenoid muscle (adductor) and the posterior cricoarytenoid muscle (abductor) arose from a common trunk, which in 8% of cases, also had a branch to the lateral cricoarytenoid muscle. Furthermore, the high incidence of branches innervating the adductor muscles from connections between the recurrent laryngeal nerve and the internal and external laryngeal nerves led us to reconsider the contribution of these nerves in the supply to this muscle group.

Supernumerary humeral heads of the biceps brachii muscle revisited.

Supernumerary humeral heads of the biceps brachii muscle were found in 27 (15.4%) of 175 cadavers. They were bilateral in five cadavers and unilateral in 22 (8 left, 14 right), giving a total of 32 examples in 350 arms (9.1%). Depending on their origin and location, the supernumerary heads were classified as superior, infero-medial, and infero-lateral humeral heads. Previous studies were reviewed using this classification. The infero-medial humeral head was observed in 31 of 350 (9%) arms and was therefore the most common variation. The superior humeral head was observed in five (1.5%). The infero-lateral humeral head was the least common variation, observed only in one (0.3%) of 350 arms. A biceps brachii with three heads was observed in 27 of 350 (7.7%) arms and with four heads in five (1.4%) arms.

Coexistence of a pectoralis quartus muscle and an unusual axillary arch: case report and review.

A pectoralis quartus muscle and an unusual axillary arch were found on the left side of a female cadaver. The axillary arch was a musculoaponeurotic complex continuous with the iliacal fibers of the latissimus dorsi. The muscular part, together with the tendon of pectoralis major, inserted into the lateral lip of the bicipital groove of the humerus, whereas the aponeurotic part was formed by a fibrous band that extended deep to the pectoralis major to insert into the coracoid process between the attachments of the coracobrachialis and pectoralis minor. The pectoralis quartus originated from the rectus sheath, and joined the inferior medial border of the fibrous band of the axillary arch, at the lateral edge of the pectoralis major. The axillary arch muscle crossed anteriorly the axillary vessels and the brachial plexus. The clinical importance of these muscles is reviewed.

Intramuscular Martin-Gruber anastomosis.

The incidence and morphology of the intramuscular Martin-Gruber anastomosis are presented based on the study of 118 human cadavers (55 male, 63 female). The Martin-Gruber anastomosis was found in 25 (21.2%) of the 118 cadavers. It occurred in 11 (20%) of the 55 male cadavers (4 bilateral, 7 unilateral; 5 left and 2 right) and in 14 (22.2%) of the 63 female cadavers (2 bilateral, 12 unilateral; 8 left and 4 right). Therefore, the Martin-Gruber anastomosis was found in 31 (13.1%) of the 236 upper limbs. According to a recent classification (Rodríguez-Niedenführ et al., 2000), pattern I was found in 29 cases (93.5%), corresponding to Type A in 13 (41.9%), Type B in 3 (9.7%) and Type C in 13 (41.9%), whereas pattern II was found in 2 cases (6.5%), both being a duplication of Type IC. Intramuscular Martin-Gruber anastomosis was a single anastomosis that originated in all cases from the anterior interosseous nerve (pattern IC) and then passed through a muscle bundle of the flexor digitorum profundus and behind the ulnar artery to join the ulnar nerve as a single connecting branch. It did not send branches to the flexor digitorum profundus. This intramuscular course was observed in 3 of the 13 cases of Type C anastomosis (23.1%) or 3 cases out of 31 Martin-Gruber anastomoses (10%).

Martin-Gruber anastomosis revisited.

Based on a study of 70 human cadavers (31 male, 39 female) and on cases described previously, we propose a new classification of the Martin-Gruber anastomosis, a neural connection between the median and ulnar nerves in the forearm. The anastomosis was found in 16 (22.9%) cadavers, being bilateral in three (18.7%) and unilateral in 13 (81.3%), five right and eight left. It occurred in eight (25.8%) of the 31 male cadavers and in eight (20.5%) of the 39 females. Therefore, the anastomosis was found in 19 (13.6%) of the 140 forearms. In Pattern I (89.5%) the anastomosis was made by only one branch, whereas in Pattern II (10.5%) it was made by two. The individual branches were classified as Types a, b, and c based on the nature of their origin from the median nerve. Type a (47.3%) arose from the branch to the superficial forearm flexor muscles, Type b (10.6%) from the common trunk, and Type c (31.6%) from the anterior interosseous nerve. Pattern II was a duplication of Type c (10.5%). The anastomotic branch took an oblique or arched course before joining the ulnar nerve, undivided in 15 cases, but divided into two branches in four cases. The anastomosis passed in front of the ulnar artery in four cases, behind it in six, and in nine cases it was related to the anterior ulnar recurrent artery.

Patterns of connections between the musculocutaneous and median nerves in the axilla and arm.

Variations in connections between the musculocutaneous and median nerves in the arm are not as uncommon as was once thought. This opinion led us to perform a study in 138 cadavers (66 male, 72 female). These variations were seen in 64 cadavers (46.4%), 9 bilaterally and 55 unilaterally (26 right and 29 left); in total, therefore, variations were observed in 73 out of 276 arms (26.4%), 42 male and 31 female. No statistically significant differences by gender and side were observed. We classify the variations in three main patterns: Pattern 1, fusion of both nerves (14 arms, 19.2%); Pattern 2, presence of one supplementary branch between both nerves (53 arms, 72.6%); and Pattern 3, two branches (5 arms, 6.8%). Pattern 2 was further subdivided into a sub-group 2a when a single root from the musculocutaneous nerve contributed to the connection (51 arms, 69.9%), and 2b when there were two roots from the musculocutaneous nerve (2 arms, 2.7%). A combination of Patterns 1 and 2a was observed in one case (1.4%). Further variations are described, published classification systems are reviewed and a meta-analysis of previous results is presented. An overall incidence of 33% of variant arms was observed. Of these variant arms, Pattern 1 represented 13.1%, Pattern 2 represented 75.4%, and Pattern 3, 8.5%, similar to our figures.