Morphological analysis of cementoenamel junction in premolars of Sri Lankans

Anatomical Science International - Cementoenamel junction is an anatomical landmark which indicates the meeting point of enamel of the crown and the cementum of the root. It is an important...     

Nerve fiber analysis of ansa cervicalis-vagus communications

Communications between the ansa cervicalis and the vagus nerve, although described only as variations in many textbooks, can be observed frequently in the dissection room. Following macroscopic observation, some of such cases were subsequently dissected under surgical microscope to determine the nature of such communications. As a result, two broad categories of communications between the ansa cervicalis complex and the vagus nerve could be recognized: (i) false (pseudo) communications, where the two nerves were attached only by the connective tissue with no fiber exchange; and (ii) true communications, with nerve fiber involvement. Fiber analysis showed that the majority of the ansa–vagal communications observed during gross dissection were of the first category. True communications, when present, were only scanty contributions and always directed towards the side of the vagus. In addition, the vagus (region of the inferior ganglion) and hypoglossal nerves were found to be in close contact at the base of the skull and usually could not be separated by gross dissection. But such attachments, too, were shown to be almost entirely of false nature except for the possible presence of a few fine nerve filaments. It seems that the ansa–vagal communications are merely a result of the close physical relationship between the two structures and serve no significant functional purpose, but at the same time may hinder the prospects of using ansa cervicalis in surgical procedures such as re-innervation of laryngeal and facial muscles, following damage to recurrent laryngeal and facial nerves, respectively.     

Middle thymothyroid artery arising from the common carotid artery: case report of a rare variation

A middle thymothyroid artery, arising from the anterior aspect of the right common carotid as an anomalous branch was observed in a 71-year-old Japanese male cadaver. It soon divided into a thyroidea ima artery, a branch supplying the sternoclavicular joints, and a thymic branch. In addition, twigs from these three main branches supplied the sternohyoid and sternothyroid muscles, right inferior parathyroid gland and also some deep cervical lymph nodes. Anatomical features, clinical implications and a brief account of the developmental aspects of this rare variation are included in this report.     

Nerve communication between the glossopharyngeal nerve,external carotid plexus and the superficial cervical ansa: human autopsy case

The authors encountered a very rare human autopsy case in which the supernumerary branch of the glossopharyngeal nerve and a nerve branch arising from the external carotid plexus communicated with the superficial cervical ansa. This anomaly was observed on the left side of a 71-year-old male cadaver during the gross anatomical seminar at Niigata University in 2004. The nerve fascicle and fiber analyses indicated that the supernumerary branch of the glossopharyngeal nerve separated cranial to the branches to the pharyngeal constrictor muscles, carotid sinus and stylopharyngeal muscle and sent the nerve fibers to the muscular branches to the platysma and the cutaneous branches to the cervical region. Additionally, it was shown that the branch arising from the external carotid plexus sent the nerve fibers to the cutaneous branch to the cervical region. Although the external carotid plexus is primarily postganglionic sympathetic fibers originating from the superior cervical ganglion, the vagus and glossopharyngeal nerves gave off branches connecting to the plexus, and therefore it was not possible to determine the origins of this branch of the external carotid plexus. The present nerve fascicle analysis demonstrates that the supernumerary branch of the glossopharyngeal nerve, which innervated the platysma, did not share any nerve components with the branches to the pharyngeal constrictor muscles, carotid sinus and stylopharyngeal muscle, suggesting that this supernumerary branch may be categorized into the different group from these well-known branches.     

Reexamination of the communicating branch between the sural and tibial nerves

Reexamination of communicating branches between the sural and tibial nerves ventral to the calcanean tendon was carried out on 52 legs of 26 Japanese cadavers which were used for ordinary dissection practices at the Niigata University School of Medicine. Communicating branches were found in 7 out of 52 dissections (13.5% of cases). In three of the 7 specimens, the communicating branch, the sural nerve and the tibial nerve with the deep crural fascia were removed from the legs and demonstrated by a modified Sihler's staining technique. Three types of communicating branches, Y, U and N, were distinguished on the basis of their shapes. In type Y, a medial branch from the sural nerve and a branch from the tibial nerve joined in Y-shape and become one terminal branch. In type U, the both branches formed a loop between the sural and tibial nerves. The type N communicating branch ran obliquely and medially to reach the tibial nerve distally. Only the Y type appeared in 5 specimens. Both the Y and U type and the Y and N types occurred in one specimen each. We assume that the communicating branch of the N type contains motor fibers which are derived from the sural nerve and innervate some plantar muscles, because this type is correspond to the communication type of some animals in which motor fibers have been demonstrated. Therefore, if the sural nerve biopsy is performed to examine a pure sensory nerve, removal of the more distal part of the sural nerve than a diverging point of a communicating branch is recommended. This study also indicated that the modified Sihler's staining technique is useful to examine distributions of cadaveric peripheral nerves after medical students' dissection course.     

Morphological study of the ansa cervicalis and the phrenic nerve

Morphological features of ansa cervicalis and phrenic nerve were studied in 106 cadavers. Ansa cervicalis was located medial to the internal jugular vein in 63% (medial type) and lateral to the vein in 33.7% (lateral type). Ansa cervicalis was derived from a combination of C1-C4 spinal segments, with C1-C3 being the most frequent pattern (87.5%). In >60% the ansa was bilaterally symmetrical. The distribution of medial and lateral types was equal on left and right sides of the body. The segmental composition of the inferior root was higher in the medial type and also on the left side of the body. In the lateral type the branches that formed the inferior root frequently (75%) formed a common trunk before joining the superior root, but in 74.8% of the medial type they joined the superior root independently. The phrenic nerve was derived from C4 and C5 in 52%. The C4 segment was present in the phrenic nerve in all cases except one. Additional phrenic components that pass anterior to the subclavian vein were defined as accessory phrenic nerves and found in 28.7%, while those passing posterior to the same vein were defined as secondary phrenic nerves (19.8%). Most of the accessory phrenic nerves contained a C5 segment and the nerve to subclavius was the commonest source. Various relationships between the ansa cervicalis and the phrenic nerve are investigated and, based on these findings, two separate classifications for the two nerves are suggested.