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vol.19 issue1MORPHOLOGICAL STUDY OF THE FEMALE EXTERNAL GENITALIA OF THE MYOCASTOR COYPUS (COYPU)MACRO AND MICROSCOPIC CHARACTERISTICS OF THE HEART AND GREAT VESSELS OF THE COYPU (Myocastor coypus, Molina) OF DIFFERENT AGES author indexsubject indexarticles search
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Revista chilena de anatomía

Print version ISSN 0716-9868

Rev. chil. anat. vol.19 n.1 Temuco Apr. 2001

http://dx.doi.org/10.4067/S0716-98682001000100004 

STUDY OF THE COMPOSITION OF THE DIAGONAL ARTERY WALL IN
PIG'S HEART

ESTUDIO DE LA CONSTITUCIÓN DE LA PARED DE LA ARTERIA DIAGONAL
EN CORAZONES DE SUINOS

Sônia Maria Marques Gomes Bertolini* ; Maria Tereza Jordão* * ; José Henrique dos Santos Areas Júnior* * * ;
Nadir Eunice Valverde Barbato de Prates* * * * ; Fabrício Augusto Stocco* *

SUMMARY: This work was carried out aiming at studying at the light microscope the diagonal artery of the pig's heart to analyse the composition of the arterial wall and the morphometry of its tunicas as well. The hearts of twelve pigs of both sexs were used. From those 12 hearts, six had diagonal artery and other six tacked it. From those with the artery 18 blocks of 1cm2 were removed from the intimal segment of the arteries, six blocks bling form the diagonal artery, six from the anterior interventricular arteries and six from the circunflex arteries. From another 6 hearts without diagonal artery 12 blocks of the 1 cm2 were removed, six blocks bling from the anterior interventricular arteries and six from the circunflex arteries. In each arterial segment 20µm thick histological sections were made. The laminal obtained were stained by the following methods: resorcine-fucsine of Weigert counter-stained with picrofucsine of van Gieson; method of Verhoef; method of Azan . It was observed that the diagonal arteries belonged to the groups of muscular, or medium diameter arteries. As for the histomorphometric analysis, considering the tickness of the wall of the anterior interventricular, circunflex and diagonal arteries, it was observed that a larger thickness occured at the epicardial wall, followed by the miocardial wall. It was demonstrated a larger wall in the anterior interventricular artery, followed by the circunflex and then the diagonal arteries. Comparing the mean thickness of the wall of the anterior interventricular artery in the hearts with or without diagonal artery, it was observed that in the former it was thinner than in the latter. This finding was also made for the mean thickness of the wall of the circunflex artery in the hearts with ou without diagonal artery, showing that presence of the diagonal artery determns a change in the initial thicness of the walls of the two arteries.

KEY WORDS: 1. Heart; 2. Coronary artery; 3. Pig.

INTRODUCTION

The left coronary artery, soon after its origin at the aortic sinus, sends septal branches and then bifurcates in the anterior interventricular and circumflex branches. Nevertheless, there are reports that the trunk of the left coronary artery trifurcates, giving rise to the anterior interventricular, circumflex and diagonal branches (Banchi, 1904; Crainicianu, 1922; Loscano, 1942).

The diagonal artery was observed by Rocha-Lagôa (1928) in 36.6% of the studied cases, rarely exhibiting a diameter similar to that of the anterior interventricular and circumflex arteries.

Titus( 1972) reports that at the site of division of the left coronary artery one or more ventricular diagonal arteries can arise.

According to Baptista (1987) in humans this artery is found in 6% of the cases. As for the race, Paula (1970) detects that in white humans the diagonal artery is present in 33% of the cases and in negroes in 81% of the cases.

Baptista et al. (1991), referring to the investigations of Geiringer (1951), who believes that the myocardial bridge is a protecting factor against atherosclerosis, relates the presence of diagonal arteries of short and medium length to the reduced risk of coronary atherosclerosis.

Considering the importance of the diagonal artery for heart blood flow, this work was carried out aiming at studying at the light microscope the diagonal artery of the pig's heart to analyze the composition of the arterial wall and the morphometry of its tunicas as well.

MATERIAL AND METHOD

The hearts of twelve pigs of both sexes, resulting from the breeding of Landrace and Large White, were used. The weight of the animals was approximately 180 days. These animals were obtained at the Experimental Farm of Iguatemi, from the State University of Maringá, Pr.

Histological Analysis. From these 12 hearts, six had diagonal artery and the other six lacked it. From those with the artery 18 blocks of 1 cm2 were removed from the initial segment of the arteries, six blocks being from the diagonal artery, six from the anterior interventricular arteries and six from the circumflex arteries.

These pieces were dehydrated in ascending series of alcohol, starting at 70% through the absolute, diaphanized in xilene and included in paraffin.

In each arterial segment 20µm-thick histological sections were made, oriented according to the transverse and longitudinal planes relative to the longest axis of the vessel. The laminae obtained were stained alternately and sequentially by the following methods: resorcine-fucsine of Weigert with previous oxidation in potassium permanganate according to Lillie & Fulmer (1976), counter-stained with picrofucsine of Van Gieson (Weigert-Van Gieson); method of Verhoef; and method of Azan modified by Ferraz de Carvalho (1968).

After mounting, the laminae were examined in an Olympus CBB light microscope to allow analysis of the composition of the wall of the diagonal artery and then photographed in photomicroscope BX50 using photographic equipment PM 10AK.

Morphometric analysis. To assess the thickness of the tunicas the sections subjected to histological treatment were used.

The tunicas were measured in four equidistant points (myocardial wall, epicardial wall, left wall and right wall) with the aid of an Olympus CBB light microscope equiped with 10X lens coupled to micrometer disc and 40X objective.

RESULTS AND DISCUSSION

When analyzing the behaviour of the diagonal arteries of short and medium length from their origin at the left coronary artery until they became intramyocardial, it was verified that the short ones were found in a myocardial sulcus (Fig. 1), while in those classified as of medium length this sulcus was not present.


Fig. 1. Photomi-crograph of the diagonal artery of a heart of pig showing the diagonal artery (AD); periadventitial connective tissue (P); myocardial sulcus (S); and myocardium (MI). Weigert-Van Gieson. 50X.

The diagonal artery of the heart of pigs, in its subepicardial course, was surrounded by periadventitial connective tissue composed of large numbers of collagens fibers and smaller amounts of bundles of elastic fibers.

It was possible to identify the three tunicas of the vessel: intima, media and adventitia (Fig. 2).


Fig. 2. Photomicrograph of the diagonal artery of a heart of pig. Observe: tunica intima (I); tunica media (M); tunica adventitia (A); periadventitial connective tissue (P); myocardial sulcus (S); bundles of nerve fibers (F). Weigert-Van Gieson. 125X.

The tunica intima had a continuous inner elastic lamina around its whole circumference. This lamina lacked thickenings (Figs. 2 and 3).


Fig. 3. Photomicrograph of the diagonal artery of a heart of pig. Observe: tunica intima (I); tunica media (M); tunica adventitia (A); bundles of elastic fibers (E); bundles of collagen fibers (C). Weigert-Van Gieson. 125X.

The tunica media was composed mainly of bundles of smooth muscle fibers, which were present in large amounts; bundles of elastic and collagen fibers were also seen in similar proportions (Fig. 3).

The adventitia was composed of elastic and collagen fibers, with a predominance of the former (Fig. 4).


Fig. 4. Photomicrograph of the diagonal artery of a heart of pig. Note: tunica intima (I); tunica media (M); bundles of collagen fibers (C); bundles of elastic fibers (E); bundles of smooth muscle fibers (L); tunica adventitia (A). Verhoef. 250X.

In trying to classify the diagonal arteries according to their structure it was observed that they belonged to the group of muscular, or medium-diameter arteries (Dangelo & Fatini, 1988). This is because their tunica media is formed mainly by bundles of smooth muscle fibers (Junqueira, 1990) and it is also the most developed, when compared with the other tunicas.

As for the histomorphometric analysis, considering the thickness of the walls of the anterior interventricular, circumflex and diagonal arteries, it was observed that a larger thickness occured at the epicardial wall, followed by the myocardial wall. The left and right walls of these vessels had similar thicknesses (Fig. 5).


Fig. 5. Histomorphometric study (µm) of the diagonal artery of hearts of pigs at its initial segment (C1, C2, C3, C4, C5 y C6)

Comparing the mean thicknesses (mean of the four walls of a given vessel) of the walls of the anterior interventricular, circumflex and diagonal arteries it was demonstrated a larger wall in the anterior interventricular artery, followed by the circumflex and then the diagonal arteries (Fig. 6).


Fig. 6. Histomorphometric comparison (µm) of the mean thicknesses of the walls of the anterior interventricular (IVA) , circumflex and diagonal arteries in six hearts of pigs (C1, C2, C3, C4, C5 y C6).

In those hearts lacking a diagonal wall, it was noted that the wall of the anterior interventricular artery was also thicker than that of the circumflex artery (Fig. 7).


Fig. 7. Histomorphometric comparison (µm) of the mean thicknesses of the walls of the anterior interventricular (IVA) and circumflex arteries in six hearts of pigs lacking diagonal artery (C1, C2, C3, C4, C5 y C6).

Comparing the mean thickness of the wall of the anterior interventricular artery in the hearts with or without diagonal artery, it was observed that in the former it was thinner than in the latter. This finding was also made for the mean thickness of the wall of the circumflex artery in the hearts with or without diagonal artery, showing that the presence of the diagonal artery determines a change in the initial thickness of the walls of the other two arteries (Figs. 8 and 9).


Fig. 8. Comparison of the mean thickness (µm) of the walls of the anterior interventricular (IVA) of hearts with ou without diagonal artery.


Fig. 9. Comparison of the mean thickness (µm) of the walls of the circumflex arteries of hearts with or without diagonal artery.

* Universidade Estadual de Maringá e Universidade Paranaense, Paraná, Brasil.
** Universidade Paranaense, Paraná, Brasil.
*** Bolsista CAPES, Brasil.
**** Instituto de Ciências Biomédicas da Universidade de São Paulo, Paraná, Brasil.

RESUMEN: Se realizó este trabajo con el objetivo de estudiar al microscopio la luz de la arteria diagonal en los corazones de los suinos para analizar la constitución de la pared arterial y la morfometria de las túnicas. Se utilizaron 12 corazones de suinos, de ellos 6 poseían la arteria diagonal mientras que en otros 6 corazones el referido vaso no estaba presente. De los corazones con arteria diagonal, se obtuvieron 18 bloques de 1 cm2 del seguimiento inicial de las arterias, siendo 6 de arterias diagonales, 6 de arterias interventriculares anteriores y 6 de arterias circunflejas. De los otros 6 corazones sin arteria diagonal fueron retirados 12 bloques de 1 cm2, 6 del seguimiento inicial de las arterias interventriculares anteriores y 6 del seguimiento inicial de las arterias circunflejas. Estas piezas fueron sometidas a rutinas histológicas obteniéndose cortes transversales y logintudinales de 20µm de grosor. Las láminas obtenidas fueron teñidas por los métodos de Weigert - Van Gieson, Verhoef y Azan. La arteria diagonal del corazón del suino puede ser clasificada como una arteria muscular; siendo posible diferenciar las tres túnicas. De éstas, la túnica media es la más diferenciada; mostrando mayor grosor la pared de la arteria interventricular anterior, seguida de la arteria circunfleja y, finalmente, de la diagonal; en todas las arterias (IVA, circunfleja y diagonal) se observó que la pared miocárdica era la más fina, comparada con la epicárdica. Se concluye que la longitud del vaso influye en el grosor de la pared. Cuanto mayor es la extensión del vaso, mayor el grosor inicial de la pared y que la presencia de la arteria diagonal determina un menor grosor de la pared de las arterias IVA y circunfleja, comparadas a los corazones que no presentan arteria diagonal.

PALABRAS CLAVE: 1. Corazón; 2. Arteria coronaria; 3. Suinos.

REFERENCES

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Dirección para correspondencia:
Sônia Maria Marques Gomes Bertolini
Rua Clementina Basseto, 318 - Ap. 204
CEP: 87030-110
Maringá - PR
BRASIL

Recibido : 07-12-2000
Aceptado: 29-01-2201

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