SciELO - Scientific Electronic Library Online

 
vol.16 número1DIAMETROS DE LAS ARTERIAS CEREBELAR SUPERIOR Y CEREBELAR ANTERIOR-INFERIOR EN EL SEGMENTO PONTINO-ANTERIORCARACTERISTICAS DE LA MUCOSA PALATINA DEL Calomys callosus: ESTUDIO A LOS MICROSCOPIOS DE LUZ Y ELECTRONICO DE BARRIDO índice de autoresíndice de materiabúsqueda de artículos
Home Pagelista alfabética de revistas  

Servicios Personalizados

Revista

Articulo

Indicadores

Links relacionados

Compartir


Revista chilena de anatomía

versión impresa ISSN 0716-9868

Rev. chil. anat. v.16 n.1 Temuco  1998

http://dx.doi.org/10.4067/S0716-98681998000100005 

DESCRIPTION OF NODAL FIBERS IN THE CRANIAL VEIN CAVA WALLS OF THE BOVINE (Bos indicus)

DESCRIPCION DE FIBRAS NODALES EN LAS PAREDES DE LA CAVA CRANEAL DE BOVINO (Bos indicus)

* Maria Lúcia Eleutério
** Carlos Roberto Piffer
* Antonio de Castro Rodrigues
*** Josiane Medeiros de Mello

* Department of Anatomy, IB, UNESP, Botucatu, SP, Brazil
** Department of Anatomy, UNIMAR, Marília, SP, Brazil
*** Department of Biological Ciencies, UNIOESTE, PR, Brazil
Financial Support: CNPq (Proc. 830331/93-0)

SUMMARY: Several authors have studied the presence of cardiac striated muscle fibers, with characteristics of nodal fibers on the wall of the vein cava and coronary sinus of mammals. However, there is not consensus about the exact localization of these fibers. The aim of this paper is to identify the possible presence of these fibers on the cranial vein cava walls of the bovine. For this purpose we have used 10 bovine hearts with its base vessels fixed in a solution of formol 10%. After the fixation, the intrapericardiac segment was harvested and included in paraplastic. It was obtained cross and longitudinal sections, which were submitted to stain by trichromic by Masson and Mallory, cloridic orcein by Unna-Taenzer and Calleja. The microscopic results reveal that the nodal fibers are placed on the ventral and left walls of the cranial vein cava, at level of its flow into the right atrium. We conclude that the presence of these fibers on the cranial vein cava walls transmit the electrical stimulus arised in the sinu-atrial node to whole atrial musculature and venous walls, promotting the constriccion of the vein ostium to avoid the venous deflux during the atrial systole.

KEY WORDS: 1. Nodal fibers; 2. Muscle cardiac fibers; 3. Vein cava; 4. Heart; 5. Bovine.

INTRODUCTION

Bovines are animals of great economical value and great interest in the medical-veterinary area. Even this way, anatomical studies related to the cardiovascular system that specifically treat morphofunctional characteristics of the venous walls are scarse, mainly those related to the cranial vena cava. Some authors were concerned about only describing the location of muscle fibers with nodal characteristics on the walls of this vein. BORTOLOMI & PALMIERI (1962), mentioned by PINTO E SILVA& BORELLI (1969), described that, in man and other mammals, the sinu-atrial node is always located on the superior and cranial vein cava walls, respectively, probably in an area corresponding to the terminal grove. BRUNI & ZIMMERL (1951) showed that the sinu-atrial node, in the ruminants, is arranged at level or in the area next to the terminal grove and its rising fibers are placed between the right and the former walls of the cranial vein cava.

TANDLER (1929) found fibers of the sinu-atrial node on the side-ventral wall of the human vena cava superior. The purpose of these fascicles of nodal fibers would be to permit that the impulses, triggered at the level of the sinuatrial node, reach, at the same time, both atrial muscles and vascular wall.

MATERIAL AND METHOD

The anatomical material used in the present research was obtained from zebus, necropsed cows, of both sexes, with different ages and weights. The base and supra-aortic vessels were fixed in a solution of 10% formol (100 ml formaldehyde 40% / 900 ml distilled water) for three weeks.

After fixing, we did the dissection and the ressection of the cranial vein cava, separating it in three distinct parts, allowing the study of its walls on the following levels of the intrapericardiac segment: distal part, proximal part and at level of flow into the right atrium.

Venous segments, this way identified and isolated, were included in "Paraplast plus", from whose blocks 10µm thick longitudinal and transversal serial cross were made.

For the anatomomicroscopic study of the walls of the cranial vein cava the following methods of staining were used (according to Ganter & Jolles's histological techniques, 1970): trichromic by Masson and Mallory, cloridic orcein by Unna-Taenzer, Calleja and, as a background coloration, Van Gieson's Picro-Fuchsin, besides other specific techniques for the study of functional anatomy of the blood vascular walls.

Photomicrographs were obtained from the histological preparations, with the help of a Zeiss photomicroscope with a 10X ocular and 2,5 X to 40 X objectives.

RESULTS

For better description and comprehension of the venous structure and the conjunctive-muscular behaviour, we divided the intrapericardiac segment of the cranial vein cava into three parts: distal, in the region of insertion and reflexion of the pericardium; proximal in the region near to the right atrium; and at level of the flow into in the right atrium.



Fig. 1. Photomicrograph of the ventral wall at level of the flow into the right atrium, showing a thin subendothelial elastic network (arrows) and the medium tunic (MT), made up with fascicles of collagen and muscle striated cardiac round oblique fibers (arrow heads). Observe on the internal layer of the adventitious tunic the presence of fascicles of muscle fibers with characteristics of nodal fibers (*). Trichromic by Mallory (1250X). Longitudinal section.



Fig. 2. Photomicrograph of the medium tunic of the left wall, at level of the flow into the right atrium. Observe the presence of muscle fibers with characteristics of nodal fibers (arrows). Trichromic by Mallory (1250X). Longitudinal section.

The distal, proximal and mouth parts of the intrapericardiac segment of the cranial vein cava have four distinct walls: ventral, dorsal, right and left, presenting constitution, thickness and behaviour of the conjunctive-muscular component completely different, with characteristics of propelling vein. The intima tunic shows a thick subendothelial elastic net with longitudinally extended frames in relation to the vascular lumen, probably meaning an internal elastic lamina. The medium tunic is made up with thick fascicles of longitudinal and oblique collagen fibers interconnected by fascicles of longitudinal elastic fibers (Fig.1). Fasciculi of striated cardiac muscle fibers and smooth muscle fibers are also present in some walls (Fig.1 e 2). At the level of the mouth, the medium tunic is reduced. The adventitiuos tunic of the wall of the vein is made up with thick fascicles of cardiac striated muscle fibers arranged longitudinal and obliquely in the distal and proximal parts of the intrapericardiac segment and in the round direction next to the flow into the right atrium. Fascicles are originating from an expansion of the atrial myocardium. Fascicles of cardiac striated muscle fibers with histological and structural characteristics of nodal fibers are located on the ventral (Fig.1) and left (Fig.2) walls of the cranial vein cava of the bovine. Such structures are showed as masses of specialized, small, poor in miofibrilae, whitened cardiac cells, involved by a fibroelastic capsule, continuous with the sinuatrial node.

DISCUSSION

Our microscopic results of the structure of the cranial vein cava of the bovine along the intrapericardiac segment, in the proximal and distal parts and in its flow into the right atrium, showed that ventral, dorsal, right and left walls present completely distinct constitution and behaviour of the conjunctive-muscular component, mainly in relation to the adventitious tunic.

However, the presence of fascicles of cardiac muscle fibers with histological and structural characteristics of nodal fibers on the ventral (Fig.1) and left (Fig.2) walls of this vein was important for the authors, so that they could compare their results with other researchers. PIFFER et al. (1993a,b), during detailed studies about the structure of the human vein cava superior, at the level of the intrapericardiac segment, showed the heart conduction system (pacemaker), arranged in form of a plexus of fine differentiated muscle fibers, noticed all over the right wall of the human vein cava. Differently from this found, TESTUY & LATARJET (1960), HAM (1967), BARGMANN (1968) and CHIARUGI & BUCCIANTE (1971) described, in man, the sinu-atrial node placed in the region of the terminal grove, at the level of the angle placed at level flow into the right atrium, extending by the upper 2/3 of the terminal grove. BRUNI & ZIMMERL(1951) showed, in ruminants, that, besides the sinuatrial node is present next to the terminal grove, its fibers ascend to the right and anterior cranial vein cava walls. TANDLER (1929) observed the sinu-atrial nodal fibers on the ventro-lateral wall in man. In our results, thick fascicles of striated cardiac muscle fibers were found with morphologic and histological characteristics of nodal fibers on the ventral and left walls of the cranial vein cava only at the level of the flow into the right atrium. Such results suggest these fibers are continuous with sinuatrial node and they stablish a communication by itself.

In a study among the relationship of the walls muscle of the walls of the coronary sinus, of the oblique vein of the left atrium and of the inferior vein cava in mammals, including man, carried up by COAKLEY & KING (1959), it was noticed that many fibers of the cardiac muscle, found on the walls of these vessels, are histologically similar to the fibers of the sinu-atrial and atrioventricular nodes. The authors explain that these nodal fibers may be related to the temporary appearance of a left atrioventricular nodal in calf and human embryos, being considered as a persistence of that structure in adult. However, the fact of these muscle fibers being, in all vessels, directly continuous with the ones of the normal atrioventricular node, it is possible that these fibers are just an extension of the nodal structure for the walls of the vessels in the basis of the heart.

Thus, we think that the expansion of fascicles of nodal fibers until the ventral and left walls of the cranial vein cava of the bovine, as well as until the right wall of the intrapericardiac segment of the human superior vein cava (PIFFER et al.,1993a,b, 1996) has the purpose of allowing electric stimuli, generated at level of the sinu-atrial node, reach, at the same time, both the atrial muscle and the vascular wall, providing, during the atrial systole, the contraction of the vascular wall, as well. We believe that during the atrial systole the contraction of the oblique and longitudinal fascicles of cardiac striated muscle fibers could also happen, leading to shortening and enlargement of the caliber of the vascular segment and, consequently, to conduction of the venous blood into the atrial chamber. Besides, the contraction of the round fascicles of cardiac striated muscle fibers, in a subsequent stage, would cause the venous caliber to get narrower, obstructing blood ebb. Our conclusion agrees with the descriptions of GOERTTLER (1934, 1951), BUCCIANTE (1940), KUGELGEN (1956) and PIFFER (1996) for the human superior vein cava.

RESUMEN: Muchas investigaciones han estudiado la presencia de fibras musculares estriadas cardíacas, con características de fibras nodales en las paredes de la vena cava y del seno coronario de mamíferos. Sin embargo no hay un consenso sobre la localización exacta de estas fibras. El objetivo de este trabajo fue identificar estas fibras en la vena cava craneal de bovino. Para este propósito, utilizamos 10 corazones bovinos con los vasos de la base, fijados en formol 10%. Después de la fijación, el segmento intrapericárdico fue aislado e incluido en paraplástico. Se obtuvieron cortes transversales y longitudinales los que fueron sometidos a coloración con tricrómicos de Masson y Mallory, orceína clorhídrica de Unna-Taenzer y Calleja. Los resultados microscópicos revelaron que estas fibras nodales están localizadas en las paredes ventral e izquierda de la vena cava craneal a nivel de la desembocadura en el atrio derecho. Concluimos que estas fibras presentes en las paredes de la vena cava craneal, transmiten el estímulo eléctrico originado en el nodo sinoatrial para toda musculatura atrial, hasta las paredes venosas, causando la constricción del ostio venoso impidiendo el reflujo venoso durante la sístole atrial.

PALABRAS CLAVE: 1. Fibras nodales; 2. Fibras musculares cardíacas; 3. Vena cava; 4. Corazón; 5. Bovino.

REFERENCES

BARGMANN, W. Histologia e anatomia microscópica humana. 3a. ed. Labor, Barcelona, 1968.         [ Links ]

BORTOLOMI, R. & PALMIERI, G. Osservazioni sul nodo del seno di Ovis aries, Capra hircus, Bos taurus ed Equus caballus. Riv. Biol.(Perugia), 55:281-319,1962.         [ Links ]

BRUNI, A.C. & ZIMMERL, U. Anatomia degli animali domestici. Milano, 2:297-8, 1951.         [ Links ]

BUCCIANTE, L. Architettura e struttura della guaina mio-cardica delle vene cave, pulmonari e del seno coronario dell'uomo. Arch. Ital. Med. Sper., 5:273-94, l940.         [ Links ]

CHIARUGI, B. & BUCCIANTE, L. Istituzione di anatomia dell'uomo. l0. ed. Vallardi, Milano, 2:452-4, V.2. 1971.         [ Links ]

COAKLEY, J. B. & KING, T.S. Cardiac muscle relations of the coronary sinus, the oblique vein of the left atrium and the left precaval vein in mammals. J. Anat., 93:32-5, 1959.         [ Links ]

GOERTTLER, K. Die Konstruktion der Wand des Menschlichen Samenenleiters Undihre Funktionelle Bedeutung. Morphol. Jahrb.,74:550-80, 1934.         [ Links ]

GOERTTLER, K. Die Bedeutung der Funktion elle Struktur der Gefasswand. Undersuchungen and der Nabelschmurarterie des Menschen. Morphol. Jahr., 91:127-39, 1951.         [ Links ]

HAM, A.W. Histologia. 3a. ed. Guanabara Koogan, p.563, Rio de Janeiro, 1967.         [ Links ]

KUGELGEN, A. V. Weitere mitteilungen uber den wandbau der grossen venen des menschen under besenderer berucksichfigung ihrer kollagens-trukturen. Z. Zellforsch., 44:121-74, 1956.         [ Links ]

PIFFER, C. R., PIFFER, M. I. S. & SANTI, F.P. et al. Característica estrutural das paredes da veia cava superior ao nível do segmento intrapericárdico e da desembocadura no átrio direito de indivíduos adultos e idosos. In: VIII Congresso Luso-Brasileiro, p. 126, São Paulo SP, 1993a.         [ Links ]

PIFFER, C.R.; PIFFER, M. I. S. & SANTI, F. P. et al. Estudo morfológico do nodo sinuatrial ao nível do segmento intrapericárdico da veia cava cava superior humana. In: Jornada Científica da Associação dos Docentes, p.94, Botucatu SP, 1993b.         [ Links ]

PIFFER, C. R.; PIFFER, M.I.S.; SANTI, F.P. et al. Strutuctural characteristics of the superior venae caval at the intrapericardiac segment in adults and aging individuals. Okajimas Folia Anat. Jpn., 73(2-3):89-100, 1996.         [ Links ]

PINTO E SILVA, P. & BORELLI,V. Contribuição ao estudo da irrigação do nodo sinu-atrial em bovinos de raça holandesa, preta e branca. Arq. Inst. Biol., 36:67-84, 1969.         [ Links ]

TANDLER, J. Tratado de anatomía sistemática. Angiología. Salvat, Barcelona, 1929. V. 3. p.78.         [ Links ]

TESTUT, L. & LATARJET, A. Tratado de anatomía humana. 9a. ed. Salvat. Barcelona, 1960.V. 2. pp l08-l3.         [ Links ]

Dirección para correspondencia:
Prof. Dra. Maria Lúcia Eleutério
Universidade Estadual Paulista
Campus Botucatu
Instituto de Biociências
Departamento de Anatomía
Botucatu, SP
Rubião Junior CEP 18618-000
BRASIL

Fax: 55-149-213744

Recibido : 12-08-1997
Aceptado : 24-02-1998

Creative Commons License Todo el contenido de esta revista, excepto dónde está identificado, está bajo una Licencia Creative Commons