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vol.17 número2ANALISIS DEL PRINCIPAL COMPONENTE DEL CRECIMIENTO METATARSAL FETAL HUMANO EN EL SEGUNDO TRIMESTRE GESTIONALESTUDIO SOBRE LA RAMIFICACION DE LA ARTERIA SACRAL MEDIANA Y LA TEMPERATURA CORPORAL DEL ARMADILLO (Dasypus novemcinctus) índice de autoresíndice de materiabúsqueda de artículos
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Revista chilena de anatomía

versión impresa ISSN 0716-9868

Rev. chil. anat. v.17 n.2 Temuco  

http://dx.doi.org/10.4067/S0716-98681999000200003 

ORIGIN AND DISTRIBUTION OF THE BASILAR ARTERY IN THE
ENCEPHALON OF ZEBUINE BOVINE FETUSES

ORIGEN Y DISTRIBUCION DE LA ARTERIA BASILAR EN EL ENCEFALO DE
FETOS DE BOVINOS ACEBUADOS

* Alan Peres Ferraz de Melo
** Maria Angelica Miglino
*** Márcia Rita Fernandes Machado
**

Rosângela Felipe Rodrigues

* Anatomia dos Animais Domésticos, Centro Universitario de Rio Pretense, São José do Rio Preto. São Paulo, SP, Brasil.
** Faculdade de Medicina Veterinária e Zootecnia da Universidade de São Paulo, Brasil.
*** Faculdade de Medicina Veterinaria - UNESP - Jaboticabal, SP., Brasil

SUMMARY: In this research we used 30 encephalon of zebuine bovine fetuses, previously injected with colored latex and fixed in formalin solution of 20%, followed by careful dissections. The basilar artery has its origin off the convergence of the caudal branch of the carotid artery of the encephalon (both right and left sides) in a hundred per cent of the cases, showing progressively a smaller caliber a facial-caudal way, which suggests that maybe the blood flow goes along in this way, where there are some collateral branches of the basilar artery, as it follows: caudal cerebellar artery, arteries to the bridge and to the medulla oblongata.

KEY WORDS: 1. Basilar artery; 2. Bovine fetuses; 3. Anatomy.

INTRODUCTION

In the never-ending progress of sciences, among these Anatomy, knowledge as it was never known is what we look for.

The Nervous System, a common query to incessant researches, has been the object of deep studying, both in human and animal species. The great interest over matters such as this has given the 90's the "Brain Decade" status. It has been tried to figure out how the encephalon organizes itself over the different species and what is the practical meaning for each part of the puzzle.

In the particular case of ruminants, we question about the reasons, more in a practical way, related to the presence of this admirable web in between the path of great arteries, those responsible on blood supply for the brain and for the involution which happens to the internal carotid artery in the fetal period.

Researching over the literature available to us, specially in Textbooks, all information related is, more generally, to large and small ruminants in adult age and not making it very clear about how certain structures are displayed during the evolution of the fetus.

Therefore, we become interested in a systemized anatomical study of the arteries in the basis of brain from zebuine bovine fetuses, with the objective of better understanding these vessel's behavior in those animals, as well as to contribute to the discussions around this matter, in a comparative way.

MATERIAL AND METHOD

We used in the present study 30 encephalon from zebuine bovine fetuses, 18 males and 12 females, collected at the Suinofrigo Slaughterhouse, Birigüi, State of São Paulo, Brazil. The fetuses were in different periods of development.

We accessed the right common carotid artery and the left jugular vein, obliterating the left common carotid artery and the right jugular vein, and then we continuously injected mild water intending to remove every blood disposal that still could be in the circulatory system. We then obliterated the left jugular vein, right after the system has been washed off. After this, we injected a latex Neoprene 650, through the right common carotid artery.

In these heads, after the latex substance had been injected, it was applied a formaldehyde solution of 10%; and then with the use of a syringe all the muscle tissues were injected, as well as the soft tissues left, while carefully removing part of the cranial cover (frontal and parietal areas) and after incising the dura-mater, we sunk the pieces in a tank with a formaldehyde solution of 20% up to not less than 10 days, before the dissections.

RESULTS

1. Basilar artery
  1.2 - Arteries who begin at the basilar artery
    1.2.1 - arteries to the cerebellum
      1.2.1.1-caudal cerebellar artery
      1.2.1.2-other arteries to the cerebellum
       
  1.3 - Arteries to the bridge
  1.4 - Arteries to the oblonge medule

1. Basilar artery

The basilar artery begins at the convergence of the caudal branches of the carotid artery of the encephalon (right and left parts). In its first section, relative to the oblonga medule, the vessel maintains its caliber mostly uniform; although, after the emergency of the caudal cerebellar arteries (right and left), it shows an evident and progressive reduction of this caliber, in the facial-caudal way.

This artery has its origin in the median line, over the ventral mesencephalic surface, the bridge, the oblonge medule and over the adjacent part of the spinal cord, giving off several collateral branches during its path. It has appeared as a single vessel in all preparations, and in 1 of these (3,3%) due the a variation in the path of the carotid's artery caudal branch of the encephalon in the right direction, it became a direct continuation of the carotid's artery caudal branch of the encephalon in the left side. It also exhibits, in another of the observations (3,3%) two island-shape formations during its path. (Fig. 1).



Figure 1 - Encephalon of a zebuine bovine fetus; increased zoom of 10x. It is noticed "island"shape formations in the basilar artery (n). Encephalic carotid artery (a), with its facial branch (b) and caudal branch (c); facial choroidei artery (e); caudal cerebri artery (j); mesencephalic (l); rostral cerebellar artery (m); other arteries destinated to the cerebellum (o); arteries to the bridge (p); caudal cerebellar artery (q); arteries to the medulla oblongata (r); hipofisary infundibulum (3); mamilar body (4); piriform lobe (5); bridge (6), trigeminal nerv (7); medulla oblongata (9).

Figure 2 - A, B and C - schemes of the encephalon of zebuine bovine fetuses, where we observe the encephalic carotid artery (a) with its rostral branch (b) and caudal branch (c); hipofisary artery (d); rostral choroidei artery (e); median cerebral artery (f); rostral cerebral artery (g); intercomunicating artery (h); marginal artery (i); caudal cerebral artery (j); mesencephalic artery (l); rostral cerebellar artery (m); basilar artery (n); other arteries to the cerebellum (o); arteries to the bridge (p); caudal cerebellar artery (q); arteries to the medulla oblongata (r); olfatory bulb (1); optical chiasma (2); hipofisary infundibulum (3); mamilar body (4); piriform lobe (5); bridge (6), cerebellar hemisphere (7); medulla oblongata (8) and spinal medulla (9).

1.2. Arteries who begin at the basilar artery.

Along with the basilar artery the following vessels are originated; in the right and left sides: arteries to the cerebellum, arteries to the bridge and arteries to the oblonge medule.

1.2.1. Arteries to the cerebellum.

From all the arteries going to the cerebellum, the caudal cerebellar artery is the most significant vessel.

1.2.1.1. Caudal cerebellar artery (right and left).

This artery always begins at the basilar artery, most generally relating to the bridge-bulb depression. It has its path in a caudal-lateral way, circling the oblonge medule ventral-dorsally to the caudal portion of the cerebellum, and appearing as a single vessel in all preparations. We observed, concerning the level of their origin in both sides, that in 7 observations (23,3%) they seem to be symmetric (Fig. 1); in 17 preparations (56,7%) the position of the focused artery is more facial in the right side (A and C schemes) and, in 6 preparations (20,0%) it is more facial in the left side (B scheme).

1.2.1.2. Other arteries to the cerebellum.

These arteries direct to the cerebellum in a lateral-caudal way towards the facial portion of such structure. They vary in number and have smaller caliber than caudal cerebellar arteries. (Fig.1)

1.3. Arteries to the bridge.

These are very fine branches when compared to the other vessels here described and always originate from the basilar artery, since its first path to the level where the caudal cerebellar artery begins (right and left), going laterally over the bridge, where it distributes itself always in a non symmetric way in both sides.

1.4. Arteries to the oblonge medule

These branches, with a small caliber either, begin caudal to the emergency of the caudal cerebellar artery (right and left); they also exhibit, generally, non symmetric distribution in both sides.

DISCUSSION

Concerning the formation of the basilar artery, all the authors researched relate that this artery begins at the union of the caudal branches of the carotid artery of the encephalon; we found in our material the basilar artery being formed by those caudal branches of the carotid artery of the encephalon, confirming what the authors related had described. CROSBY & SCHNITZLEIN (1982) write that this union is quite variable, and there might be small vessels connecting them, as we could observe in our preparations. In our material, we also observed the basilar artery reducing its caliber in the facial-caudal way (100%), confirming the affirmatives of TANDLER (1898) apud DE VRIESE (1905), DE VRIESE (1905), BALDWIN (1964), DANIEL et al. (1953) apud BALDWIN (1964), BALDWIN & BELL (1963 a, b, c), CHOMIAK & WELENTO (1967), NANDA (1981) and CROSBY & SCHNITZLEIN. Some authors, as CROSBY & SCHNITZLEIN and BALDWIN explain that the basilar artery is resumed to the condition of minor branch at the arterial brain circuit. This information cannot be taken in a one-way basis, when interpreting our results, once that the basilar artery, at its origin by the convergence of the caudal branches of the carotid artery of the encephalon, show non-smaller caliber than the facial and caudal branches of the carotid artery of the encephalon. From the other side, the basilar artery gives off branches that irrigate specially the bridge and the oblonge medule and yet the caudal cerebellar artery, a very important vessel, besides some other vessels to the cerebellum. Even though, if we look to the caliber variation of the basilar artery in the facial-caudal way by observing the figures, an interesting fact is presented, that is the fact that the artery maintains its caliber since the origin until it gives off the caudal cerebellar arteries (right and left), when then the vessel begins to show reducing in its caliber. In some cases, the origin of these two arteries and its continuing trunk actually seems to be as a triple splitting of the basilar artery. This behavior observed founds its basis in the description of TESTUT (1911), which writes that the basilar is divided in two parts, a superior one which corresponds to the bridge (basilar artery itself) and in our material, corresponds to the first section of this artery, with a uniform caliber. The other part of the basilar artery is the inferior one which relates to the oblonge medule and medulla, constituting the anterior spinal trunk which makes anastomosis to the right and the left with the segmental arteries. This relate of TESTUT also matches with another aspect noted upon the basilar artery's behavior, more properly of its collateral branches; therefore we observed the more facial ones showing a pronounced inclination concerning its originating trunk and constituting among these an acute angle faced caudal. But, as long as we go the caudal way this angles increase intending to become straight angles, meanwhile, pari passu, these collateral branches turn to be more delicate. The affirmative of CROSBY & SCHNITZLEIN and BALDWIN & BELL that the basilar artery is the minor branch of the brain circuit, might be more likely, comparing to our material, as the final part (caudal) of the basilar artery, which shows to be actually very reduced as we have just considered about.

GILLILAN (1974) relates the presence of "arterial circles" at the basilar arteries. We observed, in our preparations, island-shape formations during the path of the basilar artery, what seem us some suggestion of vestiges from early stages of the phylogenetic development process of this artery, along with the considerations of TESTUT. Referring to this author, at the first stage of such development it occurs the presence of two arteries (right and left) that continue in caudal way after the caudal branch of the internal carotid artery; in the next stage, these two arteries become as one in a single median trunk, constituting the basilar trunk or basilar artery. Seem to us, more likely, that these island-shape formations which we described might represent vestiges from the evolution process from the fusion of these two arteries.

RESUMEN: En el presente trabajo utilizamos 30 encéfalos de fetos de bovinos cruzados con cebú, inyectados con látex coloreado rojo y fijados en solución de formaldehido al 20%, seguido de una minuciosa disección. La arteria basilar tiene origen a partir de la convergencia del ramo caudal de la arteria carótida del encéfalo (antímeros derecho e izquierdo), en el 100% de los casos, evidenciando una disminución progresiva de su calibre rostro-caudal. Esto sugiere que el flujo sanguíneo se produciría en tal sentido, donde existen algunas ramas colaterales de la arteria basilar: arteria cerebelar caudal y arterias que se dirigen al puente y a la médula oblonga.

Palabras Clave: 1. Arteria basilar; 2. Fetos de bovinos; 3. Anatomía.

REFERENCES

BALDWIN, B. A. & BELL, F. R. Blood flow in the carotid and vertebral arteries of the sheep and calf. J. Phsiol., 167(3):448-62, 1963a.         [ Links ]

BALDWIN, B. A. & BELL, F. R. The effect on blood pressure in the sheep and calf of clamping some of the arteries contributing to the cephalic circulation. J. Phsiol., 167(3):463-76, 1963b.         [ Links ]

BALDWIN, B. A. & BELL, F. R. The anatomy of the cerebral circulation of the sheep and ox. The dynamic distribution of the blood supplied by the carotid and vertebralarteries to cranial regions. J. Anat., London, 97(2):203-15, 1963c.         [ Links ]

BALDWIN, B. A. The anatomy of the arterial supply to the cranial regions of the sheep and ox. Am. J. Anat., 115: 101-18, 1964.         [ Links ]

BLACKMAN, N. L.; CHEETHANI, K. & BLACKMORE, D. K. Differencesin blood supply to the cerebral cortex between sheep and calves during shaughter. Res. Vet. Sci., 40:252-4, 1986.         [ Links ]

CHOMIAK, M. & WELENTO, J. Tetnice Mózgowia Cielaka. Polsk. Arch. Weter., 11(1):186-94, 1967.         [ Links ]

CROSBY, E.C. & SCHNITZLEIN, H. N. Blood supply to brains of some ungulates and the horse. Comparative correlative neuroanatomy of the vertebrate telencephalon. N. Y. Macmillan. 1982. pp 301-9.         [ Links ]

DANIEL, B. et al. (1953) apud BALDWIN, B.A. The anatomy of the arterial supply to the cranial regions of the sheep and ox. Am. J. Anat., 115:101-18, 1964.         [ Links ]

DE VRIESE, B. Sur la significtion morfologique des artéres cérébrales. Arch. Biol., Liège, 21:357-457, 1905.         [ Links ]

GILLILAN, L. A. Blood supply to brains of ungulates with and without a rete mirbile caroticum. J. Comp. Neurol., 153:275-90, 1974.         [ Links ]

INTERNATIONAL COMMITTEE ON VETERINARY GROSS ANATOMICAL NOMENCLATURE. Nomina Anatomica Veterinaria. 4. ed. New York, 1994. pp 70-2.         [ Links ]

NANDA, B. S. Suprimento sangüíneo para o cérebro. In: GETTY, R. SISSON/GROSSMAN Anatomia dos animais domésticos. 5.ed. Rio de Janeiro, Interamericana, 1981. V.1. pp 910-4.         [ Links ]

TANDLER, J. (1898) apud DE VRIESE, B. Sur la significtion morfologique des artéres cérébrales. Arch. Biol., Liège, 21:357-457, 1905.         [ Links ]

TESTUT, L. Traité d'anatomie humaine. 6. ed. Paris, Octave Doin, 1911. V. 2. pp 917-20.         [ Links ]

Dirección para correspondencia:
Prof. Dr. Alan Peres Ferraz de Melo
Rua Barroso Neto, 328, apto 24
CEP 05585-010.
São Paulo, SP,
BRASIL
E-mail: alanmelo@unirpnet.com.br.

Recibido : 01-10-1999
Aceptado: 16-11-1999

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