THE INNERVATION AND ARTERIAL BLOOD SUPPLY OF PIG'S STOMACH IN FOETAL PERIOD

Aleksander Chrószcz
Department of Anatomy and Histology, Wrocław Univesity of Environmental and Life Sciences, Poland

ABSTRACT

The investigations were carried out on 138 pig foetuses coming from sows in standard husbandry. Whole material was divided into six age groups. The sympathetic and parasympathetic innervation, coming from the sympathetic trunk and vagal nerve, was described, according to its prenatal development. It develops the most rapidly between the 70^th – 97^th day of gestation in isometric phase of the stomach growth. The arterial blood supply was observed in corrosion casts and in latex filled vessels. The arterial blood supply in the 3^rd and 6^th age group was similar to angioarchitecture observed postnatally. Sex and the uterus horn location have not significant influence on innervation and arterial blood supply development.

Key words: embryology, foetus, pig, stomach, innervation, blood supply.

INTRODUCTION

The prenatal life can be divided into two subsequent periods: embrional and foetal period. According to the gestation of pig, the first period starts after tubulation (12^th – 35^th day of prenatal life) and the second, the foetal period, which starts in 36^th day of gestation and finishes at birth [13]. According to the lack of wider studies in accesible literature aiming on the foetal period, I devoted this work to the precise anatomical analysis of stomach nerve and blood supply. The postnatal morphology of vegetative innervation of pig's stomach is well known [7,8,16]. The neuroanatomical studies on other domestic mammals in prenatal life are also common carried out [10,11,14,20,21,22,23,24,25,26,29,32].

The morphology and development of gastric vessels in adult pig was frequently described in literature [16,28,31]. The microarchitecture of gastric mucosa blood supply inspires the greatest interrest of scientists [3,4,5,6,15,31].

The work is devoted to the morphological analysis of pig' stomach innervation and arterial blood supply during the foetal period.

MATERIAL AND METHODS

The investigations were carried out on 138 pig foetuses, 68 male and 70 female. Whole material was coming from 13 sows, between the 35^th – 114^th day of gestation (Table1). All animals were breeding in standard husbandry and they are genetic homogenous [30].

The foetus age was estimated on the base of methods introduced by Marrable [13] and Latshaw [9]. According to Bożiłow and Sawicki [1], whole investigated material was divided into six age groups:

• 1^st group – the 35^th day of gestation

• 2^nd group – the 56^th – 61^st day of gestation

• 3^rd group – the 70^th – 76^th day of gestation

• 4^th group – the 82^nd – 86^th day of gestation

• 5^th group – the 92^nd – 97^th day of gestation

• 6^th group – the 107^th – 114^th day of gestation.

During the anatomical preparation was used 2 – 3% acetic acid solution and 70% ethanol solution were used in order to make nerve fibres more visible. The investigation was made using the stereoscopic microscope with enlargement 2.5x – 100x. The arterial blood vessles were filled with latex (LBSK 5545). It allows for correct neuroanatomical and angiological interpretation of observed structures. The author used NAV [18] and NEV [19] in the descriptive part of this work. The results were displayed as photographies.

RESULTS AND DISCUSSION

The sympathetic innervation of stomach in pig foetuses derives from the sumpathetic trunk (truncus sympathicus) and the parasympathetic supply of investgated organ is provided by the vagal nerves (nervi vagi). The same situation was observed in adult animals [7,17]. In all investigated groups, the vagal nerve forms the dorsal and ventral vagal trunk (truncus vagalis dorsalis et ventralis) and it was proved by other mammals investigations authors [20,21,22,23,25].

In the first age group, the ventral vagal trunk forms the parietal gastric plexus (plexus gastricus parietalis) in the parietal surface of stomach. From this structure emerge some parietal gastric branches (rami gastrici pareitalis), which supply the body of stomach (corpus ventriculi) and its cardiac part (pars cardiaca) (Fig. 1). The parietal gastric plexus is also the source of pyloric branch (ramus pyloricus), which goes along the lesser curvature of stomach (curvatura minor ventriculi) to the pyloric part (pars pylorica). The hepatic braches (rami hepatici) of ventral vagal trunk were observed. The dorsal vagal trunk forms the visceral gastric plexus (plexus gastricus visceralis) with following branches: celiac branches (rami coeliaci), traveling along left gastric artery (arteria gastrica sinistra) to the celiac plexus (plexus coeliacus) and 2 – 3 visceral gastric branches (rami gastrici viscerales) to the body of stomach (Fig. 2). The above mentioned results are also proved by other authors [25,33].

In the second group, the morphology of ventral vagal trunk was similar to observed in the first group. The parietal gastric branches were subsequent divided, but the number of branches was still low (Fig. 3). The innervation area of visceral gastric branches was wider and its developed towards the greater curvature of stomach (curvatura major ventriculi) (Fig.4). The splanchnic nerves (nervi splanchnici) were clearly visible. They emerge the sympathetic trunk and travel caudally and ventrally, in the neighbourhood of suprarenal gland (glandula suprarenale), they reach the celiac plexus and gastric wall along the branches of celiac artery (arteria coeliaca) (Fig.5).

The observations carried out in the 3^rd, 4^th and 5^th age group proved the subsequent divisions of dorsal and ventral vagal trunk. The innervation area of ventral vagal trunk was biger as in earlier age groups (Fig. 6). Similar situation was observed in the dorsal vagal trunk and the sympathetic branches (Fig. 7 and 8). Both innervation areas developed towards the greater curvature of stomach. These embryological observations were also proved by Pospieszny [25].

In the 6^th age group, the architecture and morphological structure of vagal trunk and sympathetic trunk derivatives is similar to observed in postnatal life (Figs. 9, 10 and 11) [17,24,27]. The proof of fast secondary division of neuroanatomical structures of stomach in pigs were found in literature [14,24,25,27]. The most visible division process was seen in ruminants, according to the development of complex stomach [14,20,21,22,23,26]. The development of vegetal innervation is the complex problem of embryology and it depends on some chemical substances, for example neurorophic growth factor (NGF) [7]. It seems to have low modulating influences on the parasympathetic neuvous system [2]. The hypothetic existence of modulating factors in parasympathetic nervous system development is common stated by many authors [7,12,29].

The arterial blood supply of stomach in the 3^rd age group was provided by branches of the celiac artery (arteria coeliaca) (Fig. 12). The same situation was observed postnatally [17,28,31]. The first branch of celiac artery was the phrenic caudal artery (arteria phrenica caudalis), the second branch forms the splenic artery (arteria lienalis) and the third was represented by the hepatic artery (arteria hepatica) (Fig. 13). The left gastric artery (arteria gastrica sinistra) for the visceral surface of stomach was the first branch of lienal artery (Fig. 12). Further arterial branch is formed by diverticular artery (arteria diverticuli), which supplies the cranial part of the ventricular diverticulum and the fornix ventriculi. Next branches of the lienal artery are short and form the short gastric arteries (arteriae gastricae breves) for caudal wall of the gastric diverticle (Fig. 14) and the splenic branches, which built the short common trunk, gastrolienal branch (ramus gastrolienalis). The lienal artery lies in the splenic hilus (hilus lienalis) in order to supply spleen (lien). It forms the left gastroepiploic artery (arteria gastroepiplioca sinistra), which proximal part lies within the gastrolienal ligament (ligamentum gastrolienale) and reach the greater curvature of stomach (Fig. 15). It gives a strong branch located dorsally and cranialy within the greater curvature. The left gastroepiploic artery travels ventrally and caudally along the greater curvature. Both vessels form the great number of tranverse branches for the wall of stomach. The hepatic artery (arteria hepatica) form the main source of nutritional blood supply for liver (hepar). They derivatives, by the gastroduodenal artery (arteria gastroduodenalis), the pancreaticoduodenal artery (arteria pancreaticoduodenalis), the right gasroepilpoic artery (arteria gastroepiploica dextra) and the right gastric artery (arteria gastrica dextra) (Fig. 16) took part in blood supply of stomach wall. The above mentioned blood vessels architecture of foetal stomach is similar to the adult animals angiology.

Macroscopically, any anastomoses were not observed between the left and right gasroepiploic artery, which are very common in adult animals [16,28,31]. The structure of angioarchitecture in 114th day of gestation was similar to observed earlier. The division pattern of the splenic and hepatic artery resembles the postnatal gastric supply (Figs. 17 and 18). The same observations were carried out due to the left gastric artery and the diverticular artery (Figs. 19 and 20). The above mentioned results are similar to the angiological observation carried out postnatally. The microarchitecture of vascularisation of stomach walls is complex and it plays important role in stomach functions, especially in gastric gland and gastric resorption [16,28,31].

CONCLUSIONS

1. The gastric innervation coming from the vagal nerves and sympathetic trunk develops the most rapidly between the 70^th – 97^th day of gestation in isometric phase of the stomach growth.
2. The arterial blood supply in the 3^rd and 6^th age group was similar to angioarchitecture observed postnatally.
3. Sex and the uterus horn location have not significant influence on innervation and blood supply in foetal pig stomach.
4. The most dynamic development of stomach innervation was observed between the 70^th and 97^th day of prenatal life.

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Accepted for print: 19.09.2008

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