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Crinoid genus Ammonicrinus is represented by two species, A. sulcatus Kongiel and A. kongieli sp.n., in the Grzegorzowice - Skały and Świętomarz - Śniadka profiles of the Middle Devonian in the Holy Cross Mts. The presence of barrel-like columnals of a limited mobility in distal part of stems and the development of wide tuberculated external cover indicate that both species represent sessile benthos. In A. sulcatus stem was connected with crown through modified columnalium. The crown was equipped with short arms which could take food in a space limited to the interior of coiled part of the stem. The food was supplied by current parallel to the bottom. The structure of crown and stem suggests that all Ammonicrinus species represent the same evolutionary stage.
The formation of the myelin sheath of the human hypogastric nerves was studied by electron microscopy in a foetus of 23 weeks of postovulatory age (220 mm C-R length). In the investigated foetus the hypogastric nerves were mainly composed of bundles of unmyelinated fibres. The myelinated fibres were seen to be at different stages of myelination. Well myelinated fibres had thick compact laminated myelin. The number of myelin lamellae on a single fibre was 22.
A study was performed on 12 human embryos at developmental stages 16 and 17 (6th week). In the investigated embryos the primary palate is formed from medial nasal, lateral nasal, and maxillary processes. The medial and lateral nasal processes merge and form the nasal fin at stage 16. This fin regresses and at stage 17 and persists as the oronasal membrane. The primordia of the secondary palate appear at stage 17. (Folia Morphol 2011; 70, 1: 29–32)
In three human foetuses aged 15, 17, and 23 weeks the number of axons surrounded by single Schwann cells was counted. These Schwann cell/axon complexes form the Schwann units. The largest Schwann units in the foetus aged 15 weeks contained 232 axons, in the foetus of 17 weeks the number was 140 and in the foetus of 23 weeks the largest units contained 65 axons.
A CT study was performed on 8 foetuses aged between 20 and 38 weeks. In foetuses at the 20th week the semicircular canals, the spiral canal of the cochlea and the initial (labyrinthine) part of the facial canal are visible. At week 24 the tympanic part of the facial canal is observed. In the 31st week the cochlea is divided into 2 compartments, and in the 38th week the vestibular aqueduct and osseous labyrinth are seen.
A study was made on 18 embryos of developmental stages 13–15 (5th week). Serial sections made in horizontal, frontal, and sagittal planes were stained with routine histological methods and some of them were treated with silver. In embryos of stage 13, the otic vesicle is at the rhombomere 5, and close to the vesicle is the facial-vestibulocochlear ganglionic complex in which the geniculate, vestibular, and cochlear ganglion may be discerned. These ganglia are well demarcated in embryos of stage 14. In the last investigated stage (15th) the nerve fibres of the ganglia reach the common afferent tract. (Folia Morphol 2009; 68, 3: 167–173)
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