The hypogastric nerves of a human foetus of 220 mm C-R length (23rd week)
were investigated with an electron microscope. These nerves were composed
mainly of bundles of unmyelinated fibres and single myelinated fibres. Small
ganglia and single ganglion cells were observed in the hypogastric nerves. Light
and dark cells were found among the nerve cells. The two types of cell differed
in the number of ribosomes and the amount rough endoplasmic reticulum. In
the period of development investigated protosynapses and mature synapses
were observed in the hypogastric nerves

Bruska, Małgorzata

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Folia Morphol. Vol. 64, No. 3, pp. 199–211Copyright © 2005 Via MedicaISSN 0015–5659www.fm.viamedica.plO R I G I N A L  A R T I C L E199Address for correspondence: Prof. Małgorzata Bruska, Department of Anatomy, University School of Medical Sciences, ul. Święcickiego 6,60–781 Poznań, Poland, tel: +48 61 854 65 67, fax: +48 61 854 65 68, e-mail: mbruska@amp.edu.plNerve cells and synapses in the human foetalhypogastric nervesMałgorzata BruskaDepartment of Anatomy, University School of Medical Sciences, Poznań, Poland[Received 27 June 2005; Accepted 27 July 2005]The hypogastric nerves of a human foetus of 220 mm C-R length (23rd week)were investigated with an electron microscope. These nerves were composedmainly of bundles of unmyelinated fibres and single myelinated fibres. Smallganglia and single ganglion cells were observed in the hypogastric nerves. Lightand dark cells were found among the nerve cells. The two types of cell differedin the number of ribosomes and the amount rough endoplasmic reticulum. Inthe period of development investigated protosynapses and mature synapseswere observed in the hypogastric nerves.Key words: human neuroembryology, hypogastric nerves, nerve cells,synapsesINTRODUCTIONThe hypogastric nerves are formed by the bifurca-tion of the lower part of the intermesenteric plexus [28].This lower part of the intermesenteric plexus isoften described as the “superior hypogastric plexus”,located anterior to the bifurcation of the aorta and5th lumbar vertebral body and sacral promontory. Itis also termed the “presacral” nerve.However, its sympathetic and parasympatheticsources are the same as the other parts of the inter-mesenteric plexus. The hypogastric nerves diverge,curving outwards, downwards, and backwards intothe pelvis, at first lying medial and almost parallel tothe internal iliac vessels and then medial to its bran-ches [17]. The angle between the diverging nerves isoften bridged by delicate interlacing fibres. The hy-pogastric nerves may be single or may consist of2 or 3 nerve bundles interconnected by oblique anas-tomosing strands to form a narrow elongatedplexus [17, 28].These interconnecting rami are important in dis-tributing preganglionic fibres to both pelvic plex-uses, enabling bilateral control of the pelvic or-gans [12].Each nerve terminates in the corresponding pel-vic plexus and provides its chief complement of sym-pathetic fibres. In addition to sympathetic fibres, thehypogastric nerves also contain parasympatheticfibres from the pelvic nerves.Visceral afferent fibres from the pelvic visceraand blood vessels also pass along the hypogastricnerves, as has been shown with HRP tracing tech-niques [19] and electrophysiological studies [19, 20].They may contribute branches to the distal colon,the testis or ovary, the ureter, and the iliac arteriesor their branches.The composition of nerve fibres in the hypogas-tric nerves and their range of innervation is evidenceof their important role in several important reflexfunctions of the urinary and genital organs [2, 5, 6,15, 22, 23, 25, 29].The aim of the present study is to investigate thestructure of neurons in the hypogastric nerves in thehuman foetus.200Folia Morphol., 2005, Vol. 64, No. 3MATERIAL AND METHODSExamination was made of the hypogastric nervesof a human foetus of 220 mm C-R length, aged23 weeks. The hypogastric nerves were removed im-mediately after surgery and immersed in 1.2% chilledglutaraldehyde for 1 h. The material was then placedfor 2 h in 2% glutaraldehyde buffered to pH 7.4 withcacodylate. After being washed in cacodylate bufferfor 24 h, parts of the hypogastric nerves were fixedin 1% osmium tetroxide. Thin and semi-thin sectionswere made on Reichert ultramicrotome. The semi-thin sections were contrasted with uranyl acetateand lead citrate. The thin sections were examined inJEM-7A and Philips electron microscopes.RESULTSIn the foetus investigated the hypogastric nerveswere composed mainly of bundles of unmyelinatedfibres and single myelinated fibres at different phas-es of myelination (Fig. 1).Endoneural spaces containing collagenous fibres,fibroblasts and blood vessels were observed betweenthe bundles of axons (Fig. 2). Small ganglia and scat-tered nerve cells were observed in the hypogastricnerves. Among the nerve cells two types are found,viz. light and dark cells (Fig. 3). The two types of cellvary in the number of ribosomes and the amount ofrough endoplasmic reticulum. The ganglion cellswere separated by lemmocytes and nerve fibres, andthey were also observed on the periphery of bloodvessels (Fig. 4). The cells had irregular contours andhad oval or irregular nuclei with dispersed chroma-tin and nucleoli. The nucleoli had light spaces, theso-called “nucleolar vacuoles” (Fig. 5, 6). The cyto-plasm of the light cells contained dispersed ribo-somes and channels of the rough endoplasmic retic-ulum, which were also located at the periphery ofthe cell, forming Nissl’s substance (Fig. 6, 7). Clus-ters of polyribosomes, a very few mitochondria andlysosomes, smooth endoplasmic reticulum and largeareas of neurofilaments were also present.The dark cells were smaller than the light cellsand had irregular contours. In the nucleus smallclumps of heterochromatin were found (Fig. 1, 3, 8).The structure of the nucleoli was the same as in thelight cells. The cytoplasm of the dark cells containeda large number of ribosomes, which formed rosettes.The rough endoplasmic reticulum was more abun-dant, especially on the periphery of the cell. The largenumber of ribosomes and the amount of rough en-doplasmic reticulum resulted in a dense and darkcytoplasm.The ganglion cells were surrounded by the pro-cesses of satellite cells (Fig. 2–5). The single nervecells found in the hypogastric nerves located closeto the blood vessels may be regarded as SIF cells.Small ganglia and single ganglion cells presentin the hypogastric nerves may be relay stations forpreganglionic fibres which make synaptic contactswithin the nerve. This was also confirmed by the pres-ence of synapses in the nerves investigated. Primi-tive synapses (protosynapses) and mature synapseswere observed in these nerves (Fig. 9, 10). The pro-tosynapses are characterised by the density of thepresynaptic and postsynaptic membranes, sphericalsynaptic vesicles, and differences in the thickness ofthe synaptic membranes, the presynaptic membranebeing thicker.Synaptic junctions were found between axon anddendrite. Mature synapses contain spherical synap-tic vesicles on the presynaptic side.DISCUSSIONThe hypogastric nerves are composed predomi-nantly of thin myelinated and unmyelinated fibres.This was shown in our previous study as well as byother researchers [4, 20, 28]. Preganglionic sympa-thetic fibres pass along these nerves from the lum-bar ganglia of the sympathetic trunks to the pelvicplexuses and the plexuses of the pelvic viscera.Scattered nerve cells and small ganglia in thenerves form an important link in the reflexes fromthe pelvic organs.The hypogastric nerves, which arise from the in-termesenteric plexus to the pelvic plexuses, form animportant centre regulating the function of the pel-vic viscera [12–14, 18, 26]. The light and dark cellshave been described by several authors in the sen-sory ganglia of the cranial and spinal nerves [1, 7,16, 21]. They are observed during prenatal develop-ment [3]. Tennyson [24] observed both types of cellin the spinal ganglia of the foetal rabbit. She notedthat a larger amount of the rough endoplasmic retic-ulum is characteristic of more mature cells [24]. Alt-man and Bayer [1] found that the light cells appearfirst during development. Forbes and Welt [11] dis-tinguished 3 types of cell in the trigeminal ganglionof the rat. These differ in the amount of Nissl’s sub-stance, which may point to functional differences inthe cells.The synaptic junctions described within the hy-pogastric nerves prove that the nerves are the relaystation [8–10, 27] in sympathetic fibres to the pelvicviscera.201Małgorzata Bruska, Human foetal hypogastric nervesFigure 1. The hypogastric nerve of a human foetus at 23 weeks. Magn. × 3320. Ax — axon, D — dark cell.202Folia Morphol., 2005, Vol. 64, No. 3Figure 2. The hypogastric nerve of a human foetus at 23 weeks. Magn. × 7300. Ax — axon, Col — collagenous fibres, L — light cell, Lm — lem-mocyte, Sc — satellite cell.203Małgorzata Bruska, Human foetal hypogastric nervesFigure 3. The hypogastric nerve of a human foetus at 23 weeks. Magn. × 3600. D — dark cell, L — light cell.204Folia Morphol., 2005, Vol. 64, No. 3Figure 4. The hypogastric nerve of a human foetus at 23 weeks. Magn. × 5950. Ax — axon, Bv — blood vessel, Lm — lemmocyte, N — nucleus,Sc — satellite cell.205Małgorzata Bruska, Human foetal hypogastric nervesFigure 5. The hypogastric nerve of a human foetus at 23 weeks. Magn. × 8400. Er — rough endoplasmic reticulum, Mt — mitochondrium,N — nucleus, Nc — nucleolus, Sc — satellite cell, Sr — smooth endoplasmic reticulum.206Folia Morphol., 2005, Vol. 64, No. 3Figure 6. The hypogastric nerve of a human foetus at 23 weeks. Magn. × 8400. Ax — axon, Er — rough endoplasmic reticulum, Nc — nucleolus,Sr — smooth endoplasmic reticulum.207Małgorzata Bruska, Human foetal hypogastric nervesFigure 7. The hypogastric nerve of a human foetus at 23 weeks. Magn. × 15500. Ax — axon, Er — rough endoplasmic reticulum, L — light cell,My — myelin sheath.208Folia Morphol., 2005, Vol. 64, No. 3Figure 8. The hypogastric nerve of a human foetus at 23 weeks. Magn. × 5250. D — dark cell, L — light cell.209Małgorzata Bruska, Human foetal hypogastric nervesFigure 9. The hypogastric nerve of a human foetus at 23 weeks. Magn. × 66500. P — protosynapse, S — synaptic junction.210Folia Morphol., 2005, Vol. 64, No. 3Figure 10. The hypogastric nerve of a human foetus at 23 weeks. Magn. × 58000. S — synaptic junction.211Małgorzata Bruska, Human foetal hypogastric nervesREFERENCES1. Altman J, Bayer S (1982) Development of the cranialnerve ganglia and related nuclei in the rat. Adv AnatEmbryol Cell Biol, 74: 4–23.2. Appenzeller O (1976) The autonomic nervous sys-tem. An introduction to basic and clinical concepts.North-Holland Publ. Co. Amsterdam, Oxford.3. Bruska M (1986) Light and dark cells in the humanembryonic trigeminal ganglion. Folia Morphol, 55:307–315.4. Bruska M, Piotrowski A (2004) Development of themyelin sheath of the hypogastric nerves in a humanfoetus aged 23 weeks. Folia Morphol, 63: 289–301.5. Creed KE (1979) The role of the hypogastric nerve inbladder and urethral activity of the dog. Br J Phar-macol, 65: 367–375.6. 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Nerve cells and synapses in the human foetal hypogastric nerves

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Nerve cells and synapses in the human foetal hypogastric nerves

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