Ganglion cardiacum or juxtaductal body of human fetuses

The differences in the anatomy of the thoracolumbar and sacral autonomic outflow are quantitative

PURPOSE

We have re-evaluated the anatomical arguments that underlie the division of the spinal visceral outflow into sympathetic and parasympathetic divisions.

METHODOLOGY

Using a systematic literature search, we mapped the location of catecholaminergic neurons throughout the mammalian peripheral nervous system. Subsequently, a narrative method was employed to characterize segment-dependent differences in the location of preganglionic cell bodies and the composition of white and gray rami communicantes.

RESULTS AND CONCLUSION

One hundred seventy studies were included in the systematic review, providing information on 389 anatomical structures. Catecholaminergic nerve fibers are present in most spinal and all cranial nerves and ganglia, including those that are known for their parasympathetic function. Along the entire spinal autonomic outflow pathways, proximal and distal catecholaminergic cell bodies are common in the head, thoracic, and abdominal and pelvic region, which invalidates the "short-versus-long preganglionic neuron" argument. Contrary to the classically confined outflow levels T1-L2 and S2-S4, preganglionic neurons have been found in the resulting lumbar gap. Preganglionic cell bodies that are located in the intermediolateral zone of the thoracolumbar spinal cord gradually nest more ventrally within the ventral motor nuclei at the lumbar and sacral levels, and their fibers bypass the white ramus communicans and sympathetic trunk to emerge directly from the spinal roots. Bypassing the sympathetic trunk, therefore, is not exclusive for the sacral outflow. We conclude that the autonomic outflow displays a conserved architecture along the entire spinal axis, and that the perceived differences in the anatomy of the autonomic thoracolumbar and sacral outflow are quantitative.

The so-called absorption process of the pulmonary vein into the left atrium of the heart: a histological study using human embryos and fetuses

BACKGROUND

Embryonic pulmonary veins (PVs) are believed to be absorbed into the left atrium (LA) to provide an adult morphology in which "four" veins drain separately into the atrium.

MATERIALS AND METHODS

Serial histological sections were obtained from 27 human embryos and fetuses.

RESULTS

Between 5 and 6 weeks, the four PVs joined together to form a trunk-like structure (initial spatium pulmonalis) that was larger than the initial LA (two-ostia pattern). The cardiac nerves ran inferiorly along the posterior aspect of the four veins, as well as the spatium. At and until 7 weeks, the cardiac nerves were concentrated to elongate the nerve fold, and the latter separated the left PV trunk from the expanding LA (left spatium). Similarly, the right PV opened to a thick and deep LA recess (right spatium). At 8-12 weeks, depending on the growth of the LA, the opening of the left and right PVs became distant, and the spatium was elongated transversely. The left spatium was enlarged to open widely to the proper left atrium in contrast to the right spatium pushed anteriorly by the right atrium. The three-ostia pattern was transiently observed because of the lost delimitation between the left spatium and proper atrium. The myocardium was thin in the left spatium behind the left atrial nerve fold, whereas the right spatium was tube-like with a thick myocardium.

CONCLUSIONS

The four-ostia pattern seemed to be established at birth due to a drastically increased venous return from the lung, resulting in a flat smooth left atrial posterior wall.

Nervus terminalis and nerves to the vomeronasal organ: a study using human fetal specimens

The human nervus terminalis (terminal nerve) and the nerves to the vomeronasal organ (VNON) are both associated with the olfactory nerves and are of major interest to embryologists. However, there is still limited knowledge on their topographical anatomy in the nasal septum and on the number and distribution of ganglion cells along and near the cribriform plate of the ethmoid bone. We observed serial or semiserial sections of 30 fetuses at 7-18 weeks (crown rump length [CRL], 25-160 mm). Calretinin and S100 protein staining demonstrated not only the terminal nerve along the anterior edge of the perpendicular lamina of the ethmoid, but also the VNON along the posterior edge of the lamina. The terminal nerve was composed of 1-2 nerve bundles that passed through the anterior end of the cribriform plate, whereas the VNON consisted of 2-3 bundles behind the olfactory nerves. The terminal nerve ran along and crossed the posterior side of the nasal branch of the anterior ethmoidal nerve. Multiple clusters of small ganglion cells were found on the lateral surfaces of the ethmoid's crista galli, which are likely the origin of both the terminal nerve and VNON. The ganglions along the crista galli were ball-like and 15-20 µm in diameter and, ranged from 40-153 in unilateral number according to our counting at 21-µm-interval except for one specimen (480 neurons; CRL, 137 mm). An effect of nerve degeneration with increasing age seemed to be masked by a remarkable individual difference.

Ganglia in the Human Fetal Lung

Although pulmonary ganglia were considered to be an analogue of the myenteric ganglia of intestines in embryos, there seemed to be no morphological evaluation in the later stage of development. We conducted immunostainings of intrapulmonary nerves using 17 human fetuses at 14-18 and 28-34 weeks. The ganglion cells were small (15-20 μm in diameter) in the earlier group, but they increased in size (20-30 μm) in the late group. One ganglion, containing 5-30 cell bodies, was usually located "outside" of the bronchial smooth muscle or cartilage. In addition, a few ganglion was found beneath the mucosa of the trachea and principal bronchi. The highest density of ganglia (5-15 ganglia per section with 50 μm interval) was found at the origin of the subsegmental bronchi, but ganglia were absent along more peripheral bronchi those are responsible for contraction and obstruction of the airway. Therefore, in topographical relation between smooth muscle and nerve, intrapulmonary intrinsic neurons were different from intestinal myenteric neurons. Consequently, a previous hypothesis of "embryonic intramuscular bronchial ganglia" seemed not to be based on observations of the peripheral bronchus but on the central bronchus than the sub-subsegmental level. An extrinsic migration and redistribution of ganglia might occur at midterm to provide the final location outside of airway smooth muscles. Finally, no ganglion cell bodies were positive either for neuronal nitric oxide synthase or tyrosine hydroxylase. Instead of the classical entity of autonomic nerves, nonadrenergic noncholinergic (NANC) innervation might be dominant even in fetuses. Anat Rec, 302:2233-2244, 2019. © 2019 American Association for Anatomy.

Nerve distribution in myocardium including the atrial and ventricular septa in late stage human fetuses

Few information had been reported on deep intracardiac nerves in the myocardium of late human fetuses such as nerves at the atrial-pulmonary vein junction and in the atrial and ventricular septa. We examined histological sections of the heart obtained from 12 human fetuses at 25–33 weeks. A high density of intracardiac nerves was evident around the mitral valve annulus in contrast to few nerves around the tricuspid annulus. To the crux at the atrioventricular sulcus, the degenerating left common cardinal vein brought abundant nerve bundles coming from cardiac nerves descending along the anterior aspect of the pulmonary trunk. Likewise, nerve bundles in the left atrial nerve fold came from cardiac nerves between the ascending aorta and pulmonary artery. Conversely, another nerves from the venous pole to the atrium seemed to be much limited in number. Moreover, the primary atrial septum contained much fewer nerves than the secondary septum. Therefore, nerve density in the atrial wall varied considerably between sites. As ventricular muscles were degenerated from the luminal side for sculpturing of papillary muscles and trabeculae, deep nerves became exposed to the ventricular endothelium. Likewise, as pectineal muscles were sculptured, nerves were exposed in the atrial endothelium. Consequently, a myocardial assembly or sculpture seemed to be associated with degeneration and reconstruction of early-developed nerves. A failure in reconstruction during further expansion of the left atrium might be connected with an individual variation in anatomical substrates of atrial fibrillation.