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Keywords:

  • cerebral arteries;
  • Bovini;
  • Bos;
  • Bison

ABSTRACT

  1. Top of page
  2. ABSTRACT
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. CONCLUSIONS
  7. LITERATURE CITED

Studies were conducted on 78 preparations of head and brain arteries in four species of Bos genus, that is in domestic cattle (N = 59), including 22 foetuses (CRL 36.5–78.5 cm), in banteng (Bos javanicus, N = 3), yak (Bos mutus f. grunniens, N = 2), American bison (Bison bison, N = 4), and European bison (Bison bonasus, N = 10). The comparative analysis permitted to demonstrate a similar pattern of brain base arteries in the studied animals. In the studied species, blood vessels of the arterial circle of the brain were found to form by bifurcation of intracranial segments of inner carotid arteries, which protruded from the paired rostral epidural rete mirabile. In Bovidae arterial circle of the brain was supplied with blood mainly by maxillary artery through the blood vessels of the paired rostral epidural rete mirabile. The unpaired caudal epidural rete mirabile was participating in blood supply to the arterial circle of the brain from vertebral and occipital arteries. It manifested character of a taxonomic trait for species of Bos and Bison genera. Basilar artery in all the examined animals manifested a variable diameter, with preliminary portion markedly narrowed, which prevented its participation in blood supply to the arterial circle of the brain. The results and taxonomic position of the species made the authors to suggest a hypothesis that a similar arterial pattern on the brain base might be present also in other species, not included in this analysis. Anat Rec, 296:1677–1682, 2013. © 2013 Wiley Periodicals, Inc.

Arteries of cerebral base in domestic cattle (Bos taurus), in taxonomy of species (Simpson 1945) included, within subfamily of Bovinae, to the Bovini were described by Jenke (1919), Barone and Schafer (1952–1953), Baldwin (1964), Baldwin and Bell (1960a, 1960b, 1963), Uehara et al. (1978), and König (1979). Moreover, the pattern of cerebral base arteries in domestic cattle was compared with those in yak (Wang et al., 2012b), in zebu cattle, and buffalo (Rao et al., 1968). In the prenatal ontogenesis of cattle, the blood vessels were analyzed by König (1979), Brudnicki and Gielecki (1996), and Ocal and Aslan (1994).

In species belonging to the above mentioned taxons, the arteries were described by Ding et al. (2007) and Wang et al. (2012a) in yak (Bos gruniens), Węgrzyn et al. (1983) in European bison (Bison bonasus) of the Bison genus and by Bamel et al. (1975) in water buffalo (Bubalus bubalis) of the Bubalus genus.

This study aimed at an anatomic comparative analysis of cerebral base arteries in domestic cattle, their adult and foetal representatives, and in other species of Bovinae subfamily, in representatives of Bos and Bison genera. Apart from their cognitive anatomic aspects, results of such studies may provide data of general biological significance. Taking example from studies of Bugge (1971a-1971c, 1974, 1978) and Wible (1986) it may be assumed that the results may supply data useful as accessory arguments in discussion on taxonomy and phylogenesis of species. Results of our own investigations and their comparison with those obtained in the other studies permit to verify the presented research hypothesis that the pattern of cerebral base arteries carries specific traits for Bos, Bison, and Bubalus species of genera which in species taxonomy of Simpson (1945) belong to tribe of Bovini.

MATERIALS AND METHODS

  1. Top of page
  2. ABSTRACT
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. CONCLUSIONS
  7. LITERATURE CITED

The studies were conducted on 78 preparations of head and cerebral arteries in four species of Bos genus, that ise. in domestic cattle (N = 59: 18 adults, 1 calf 3 months of age, 18 newborns, and 22 foetuses [crown rump length (CRL) 36.5–78.5 cm]), as well as in banteng (Bos javanicus, N = 3 adults), yak (Bos mutus f. grunniens, N = 2 adults), and in representatives of Bison genus, that is in American bison (Bison bison, N = 4: 2 adults, 2 newborns) and European bison (B. bonasus, N = 10: 5 adult, 5 newborn).

The studies were conducted on preparations collected in our Department of Animal Anatomy, made of the material obtained from animal slaughter-houses and post-autopsy material obtained from national zoological gardens. Preparations of arteries were made by injecting them with stained acetone solution of vinyl superchloride, introduced bilaterally to common carotid arteries at the pressure of 60–80 kP (Godynicki, 1970). Because of its density, the solution was not able to penetrate the capillaries what prevented the filling of the venous system.

Following hardening of the plastic material which was filling the blood vessels, the preparations were subjected to biological liquid maceration in water containing enzymatic washing powder (temperature 40°C–45°C for one month) which yielded casts of the vessels on an osseous scaffold, in which course and anastomoses of the vessels were examined, paying attention also to their variability and asymmetry. Moreover, 20 preparations of cerebral base arteries were prepared using foetuses and calves of domestic cattle and stained LBS 3060 latex which, following fixing in 10% formalin solution, were manually prepared to examine respective arterial courses as related to cerebral structures.

Arterial nomenclature followed the examples given in Nomina Anatomica Veterinaria (2012) and the illustrated nomenclature prepared by Simoens et al. (1978–1979). An advantage was taken of the classical mammalian taxonomy based on morphological traits of animals (Simpson, 1945) and the Mammal species of the World (Wilson and Reeder, 2005) publication.

RESULTS

  1. Top of page
  2. ABSTRACT
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. CONCLUSIONS
  7. LITERATURE CITED

Arterial circle of the brain (circulus arteriosus cerebri) is positioned on the cerebral base of cranial cavity, consisting of rostral cerebral arteries (aa. cerebri rostrales) on the rostral and lateral sides and caudal communicating arteries (aa. communicans caudales) on the caudal and lateral sides (Fig. 1).

image

Figure 1. Brain base arteries of the calf (cattle) with a vascular variety of a left caudal communicating artery.

  1. A. carotis interna pars intracranialis
  2. A. cerebri rostralis
  3. A. communicans caudalis
  4. A. basilaris
  5. A. cerebri media
  6. A. choroidea rostralis
  7. A. cerebri caudalis
  8. A. cerebelli rostralis
  9. A. cerebelli caudalis

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Both components of the arterial circle of the brain in the studied animals represented branches of terminal divisions in intracranial segments of internal carotid arteries. Internal carotid artery (a. carotis interna) arises together with external carotid artery (a. carotis externa) in terminal division of the common carotid artery (a. carotis communis), with which in the course of ontogeny it loses contact since its extracranial part undergoes obliteration. A complete internal carotid artery was observed in foetuses and newborn cattle (Fig. 2) while in the adult individuals only its intracranial portion was preserved, which protruded from rostral epidural rete mirabile. In adult animals due to these developmental vascular alterations (obliteration of the extracranial part of internal carotid artery) maxillary artery took up the function of the principal source of blood for the arterial circle of the brain. This develops through the rostral branches (rami rostrales) and the caudal branch (ramus caudalis) joining rostral epidural rete mirabile (rete mirabile epidurale rostrale), from which finally the intracranial segment of internal carotid artery emerges, representing the parental blood vessel in the arterial circle of the brain.

image

Figure 2. The terminal division and connections of the common carotid artery.

  1. A. carotis interna
  2. A. carotis externa
  3. Rete mirabile epidurale rostrale
  4. A. carotis communis
  5. A. occipitalis

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In the rostral cerebral artery (a. cerebri rostralis), considering its course, a preliminary segment can be distinguished, which originates at the site of terminal division of internal carotid artery and terminates at the site of branching off of the middle cerebral artery. The second segment reaches optic chiasm and the third segment is positioned rostrally in the longitudinal fissure of the brain, bends on the genu of corpus callosum and continues its course on the medial surface of cerebral hemispheres.

The rostral cerebral artery in calf foetuses may exhibit on short fragments fissure-resembling loops, situated close to its origin from internal carotid artery or closer to branching off of the middle cerebral artery.

The second segment of rostral cerebral artery is positioned next to optic chiasm and forms an anastomosis with optic chiasm rete through a fine branch. In the region of ethmoidal fossa, the terminal segment of rostral cerebral artery anastomoses with internal ethmoidal artery. This artery is an extension of the external ethmoidal artery (positioned in the orbit), which branches off the external ophthalmic artery.

The communicating rostral artery (a. communicans rostralis) anastomoses bilateral segments of rostral cerebral arteries at the level of optic chiasm. The rostral communicating artery was noted in 50 cattle individuals, including 18 foetuses, 3 bantengs, 2 yaks, 3 American bisons, and 8 European bisons.

The first segment of rostral cerebral artery yields rostral choroidal artery (a. choroidea rostralis) and middle cerebral artery (a. cerebri media). In vascular varieties, the rostral choroid artery originated from caudal communicating artery or at the place of terminal division of internal carotid artery into rostral cerebral artery and caudal communicating artery. Moreover, an asymmetry was noted in the manner of its separation and in the number of its branches. The middle cerebral artery represented the largest branch of arterial circle of the brain, it ran toward the side and on the surface of cerebral hemispheres. Bilateral origin of two middle cerebral arteries was detected in five foetuses of cattle and in a single adult animal on the left hand side three branches of the middle cerebral artery were demonstrated, originating on the left hand side from the rostral cerebral artery.

The caudal communicating artery (a. communicans caudalis) yields caudal cerebral artery (a. cerebri caudalis) and rostral cerebellar artery (a. cerebelli rostralis). In banteng, the two caudal communicating arteries resembled in shape the ν letter, in contrast to the remaining species in which the arteries formed more round figures. The caudal communicating artery manifested a variable diameter, up to the site of origin of caudal cerebral artery higher than diameter of the remaining fragment, reaching the basilar artery. In cattle foetuses also the caudal communicating artery manifested the presence of vascular loops.

The caudal cerebral artery (a. cerebri caudalis), the most pronounced branch of caudal communicating artery in vascular varieties, manifested asymmetry in the stemming manner and in the number of branches. Two caudal cerebral arteries were noted on one side in one European bison, one banteng, and in seven specimens of domestic cattle. Moreover, in domestic cattle two caudal cerebral arteries were demonstrated bilaterally in three animals.

The rostral cerebellar artery (a. cerebelli rostralis) represented a single or multiple arteries, stemming at the half of the length from the caudal communicating artery. In vascular varieties, the rostral cerebellar artery originated from the rostral segment of basilar artery. On both sides, caudal communicating arteries anastomosed with the basilar artery. Basilar artery (a. basilaris) originates from fusion of bilateral vertebral arteries and rostrally anastomoses with left and right caudal communicating arteries. In studied animals it manifested a variable diameter, clearly narrowing toward junction with vertebral arteries. In vascular varieties in a newborn calf and in a single foetus of cattle a segmental slit-like splitting of basilar artery was noted before origins of cerebellar caudal arteries with re-union of the formed parallel blood vessels into a single artery. This variety was positioned caudally from origins of caudal cerebellar arteries. The basilar artery yielded caudal cerebellar arteries and numerous branches to the pons.

Caudal cerebellar artery (a. cerebelli caudalis) branched off the basilar artery perpendicularly, at half of its length, close to the caudal edge of the pons. In vascular varieties in two foetuses of CRL 40.5 cm and in a single newborn calf the right caudal cerebellar artery originated close to the site of junction between basilar artery and the right caudal communicating artery, ran in parallel to basilar artery and, then, after reaching the levels of the left caudal cerebellar artery and turning to the right it directed itself toward cerebellar hemisphere.

The rostral epidural rete mirabile (rete mirabile epidurale rostrale) was binate (Fig. 3). It was formed by numerous dense, reciprocally anastomosed arteries. In cranial cavity it was positioned on both sides of hypophyseal fossa. The rostral branches and caudal branch to rostral epidural rete mirabile connect this rete to maxillary artery. Moreover, external ophthalmic artery might direct to it thin branches. Rostral epidural rete mirabile anastomosed also with caudal epidural rete mirabile and optic chiasm rete.

image

Figure 3. Arterial retia mirabile in cranial cavity of the cattle.

  1. A. ophtalmica externa
  2. Rete chiasmaticum
  3. Rete mirabile epidurale rostrale
  4. A. carotis interna
  5. Rete mirabile epidurale caudale
  6. Aa. condylares
  7. Rami spinales

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Caudal epidural rete mirabile (rete mirabile epidurale caudale) was uneven and positioned in cranial cavity on the basilar part of occipital bone. It was formed by anastomosing arteries, the number and density of which were much lower than in rostral epidural rete mirabile. The caudal epidural rete mirabile was anastomosed with vertebral and condylar arteries, which after branching off the occipital arteries bilaterally pass through hypoglossal canal and enter the cranial fossa.

Due to connections between both retia mirabile, that is the paired rostral epidural rete mirabile and uneven caudal epidural rete mirabile the arterial circle of the brain reached an additional blood supply from vertebral and occipital arteries.

Rete of the optic chiasm (rete chiasmaticum) was formed from thin and delicate blood vessels, positioned in the groove of optic chiasm and in optic canals in front of optic chiasm. It manifests junctions with rostral cerebral artery and rostral epidural rete mirabile. The rete of optic chiasm yielded also a thin internal ophthalmic artery.

DISCUSSION

  1. Top of page
  2. ABSTRACT
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. CONCLUSIONS
  7. LITERATURE CITED

Comparative studies on cerebral base arteries, conducted in animal species from Bovidae subfamily and Bos and Bison genera have demonstrated a general similarity of the blood vessels.

The rostral cerebral artery and caudal communicating artery or principal elements of arterial circle of the brain in studied Bovidae represent branches of terminal intracranial division of internal carotid artery, branches which emerge from rostral epidural rete mirabile (rete mirabile epidurale rostrale). In ontogenesis of the studied species, similarly to other ruminants, the internal carotid artery manifests extensive alterations (Godynicki and Frąckowiak, 1979). In our own studies, the fully preserved internal carotid artery with its extracranial segment was detected only in bovine foetuses and newborns. In adult individuals of all the studied species, an obliteration was noted of the extracranial segment of internal carotid artery and the phenomenon was confirmed in Bovidae by König (1979) and Godynicki and Frąckowiak (1979). A specific exception from the pattern in head arteries in ruminants was a fully preserved internal carotid artery in musk deers (Godynicki and Frąckowiak, 1979) and in chevrotains, Tragulidae, also known as mouse deers (Tandler, 1902). Moreover, a fully preserved internal carotid artery was found also in even-toed ungulates (Artiodactyla) and in Camelidae (Godynicki and Frąckowiak, 1979; Ocal et al., 1998).

A nomenclature related to rostral cerebral artery has not been standardized, not only in the earlier studies (Barone and Schafer, 1952–1953; Jenke, 1919) but also in some publications of recent years (Ding et al., 2007) and it diverges from the nomenclature sanctioned by Nomina Anatomica Veterinaria (2012).

The rostral communicating artery which completes the arterial circle of the brain was detected in most of studied animals. The arterial circle of the brain anastomosed by the rostral communicating artery was disclosed by Brudnicki and Gielecki (1996) in 86% of studied bovine foetuses. An opposite opinion was expressed by König (1979), who found that in bovine foetuses an open arterial circle of the brain prevails.

In studied animals, the rostral cerebral arteries manifested vascular varieties, the extent of which has been particularly pronounced in bovine foetuses. The varieties have involved vascular loops or fragmentary fenestration of the rostral cerebral artery in bovine foetuses in preliminary segment of the artery or above the origin of the middle cerebral artery. Brudnicki and Gielecki (1996) in their studies on bovine foetuses also detected such vascular loops in preliminary segments of bilateral rostral cerebral arteries. The caudal communicating artery, forming the caudal/lateral segment of the arterial circle of the brain, anastomosed with basilar artery. Simoens et al. (1978–1979) found that the communicating caudal artery creates a connection between internal carotid artery and basilar artery. A similar position, consistent with Nomina Anatomica Veterinaria (2012) has been taken in this study.

Some rodents lack the bilateral communicating caudal arteries and their arterial circle of the brain remains open on the caudal side (Künzel, 1985; Kuchinka et al., 2008). In vascular varieties of the analyzed bovine foetuses, the caudal communicating artery manifested slit-resembling vascular loops, similar to those detected by Brudnicki and Gielecki (1996).

The rostral choroidal artery represents the first branch of the arterial circle of the brain. The origin and number of branches in the rostral choroidal artery in the examined Bovidae manifested vascular varieties. Brudnicki and Gielecki (1996) in 48% of the bovine foetuses detected bilateral origin of the rostral choroidal artery at the sites of terminal branching of internal carotid arteries and in 10% of the foetuses their bilateral origin at caudal communicating arteries. In 34% of bovine foetuses, the authors detected asymmetry of the arterial origin, which on one side branched off the rostral cerebral artery and on the other originated from the caudal communicating artery.

The middle cerebral artery, that is the most pronounced branch of the rostral cerebral artery, in vascular varieties in the cattle was represented by multiple arteries originating from rostral cerebral artery, which were formed by fusion of three branches in a single adult individual and by fusion of two branches in bovine foetuses. In the past vascular varieties involving multiple middle cerebral artery were described by Jenke (1919) and Rösslein (1987) in the horse and by Gillilan (1974) in other species.

The caudal cerebral artery, representing the most pronounced branch yielded by the posterior part of the arterial circle of the brain, was a single blood vessel and in vascular varieties noted in cattle and banteng it was found to originate by two branches on one side of the arterial circle. Bilateral paired caudal cerebral arteries were detected in the cattle.

According to Brown (1966), the bilateral caudal cerebral arteries arise by bifurcation of the middle cerebral artery which in this manner participates in formation of the arterial circle of the brain. Jenke (1919) included the caudal cerebral artery to branches of the basilar artery.

The basilar artery in studied Bovidae anastomosed with bilateral caudal communicating arteries and in this way, similarly to other animals, took part in completing the caudal part of the arterial circle of the brain.

In the studied animals, a preliminary part of the basilar artery was significantly narrowed. Baldwin and Bell (1960a, 1960b, 1963) noted the decrease in diameter of the artery in cattle and sheep and demonstrated experimentally that in the animals the basilar artery did not mediate in blood supply from vertebral arteries to the brain.

However, the basilar artery is well expressed and provides the main passage of blood to the brain in those species of rodents in which the inner carotid artery undergoes obliteration (Brown, 1966; Bugge, 1978; Firbas et al., 1973).

In the studied representatives of Bovidae the arterial circle of the brain was supplied in blood mainly by maxillary artery, which with mediation of rostral branches and the caudal branch anastomosed with rostral epidural rete mirabile while the stemming from it intracranial part of internal carotid artery extended into blood vessels of the arterial circle of the brain.

In all the examined animals belonging to Bison and Bos genera as well as in animals of Bubalus genus (Rao et al., 1968; Bamel et al., 1975), the rostral epidural rete mirabile anastomosed with the unpaired caudal epidural rete mirabile, which in this manner gained communication with bilateral condylar arteries and vertebral arteries.

The presence of the caudal epidural rete mirabile distinguished the cranial arterial pattern in Bovidae representatives belonging to Bison, Bos, and Bubalus genera (Rao et al., 1968; Bamel et al., 1975) from that noted in the remaining representatives of the subfamily (Godynicki and Frąckowiak, 1979).

The paired rostral epidural rete mirabile and the unpaired caudal epidural rete mirabile were described in the cattle by König (1979), Simoens et al. (1987), Uehara et al. (1978), in yak by Ding et al. (2007), Wang et al. (2012a, 2012b), in buffalo by Rao et al. (1968), Bamel et al. (1975), while in the other species of Bovidae the rete were analyzed by Godynicki and Frąckowiak (1979). The caudal epidural rete mirabile represents a specific discriminant feature of brain base arterial system present only in the cattle, other species of Bison and Bos genera and in water buffalo (Rao et al., 1968; Bamel et al., 1975).

Considering taxonomic position of species and following works of Bugge (1974, 1978) and Wible (1986), the hypothesis can be advanced that an identical cerebral vascular pattern represents a universal trait of also the remaining, not studied here, species of Bison and Bos genera and, recalling publications of Rao et al. (1968) and those of Bamel et al. (1975), also in animals of Bubalus genus. However, the presence of the caudal epidural rete mirabile in the brain base arterial pattern represents a discriminant trait of the taxonomic trait character in species of Bison, Bos, and Bubalus genera. The presence of the trait in animals of the mentioned taxa provides another proof justifying separation of Bovini within the subfamily of Bovinae in the classical system of mammal's classification, based on morphological traits (Simpson, 1945). Contemporary taxonomy of mammalian species, suggested by Wilson and Reeder (2005) fails to take into account the taxonomic unit of the genus. The caudal epidural rete mirabile, demonstrated in the system of cerebral base arteries in the studied species of Bos and Bison genera and described also in Bubalus (Bamel et al., 1975), represents a structure specific for species included by Simpson (1945) to the tribe of Bovini, which corroborates the research hypothesis put forward in this study.

Mitchell and Lust (2008) in their analysis of publications documenting involvement of carotid rete or epidural rete mirabile in cerebral thermal control in Artiodactyla concluded that the arterial network within the arterial pattern of the head provided the animals with broad adaptive abilities of living in variable environments and, by doing so, to spread throughout the Earth. For comparison, species of Perissodactyla order, devoid of such an arterial system in their heads and, thus, devoid of such thermal control mechanism, are definitely less numerous and inhabit a much more restricted area of our planet.

CONCLUSIONS

  1. Top of page
  2. ABSTRACT
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. CONCLUSIONS
  7. LITERATURE CITED
  1. The studied animals of Bovini manifest a similar pattern of brain base arteries.
  2. Brain base arteries in Bovini include rete mirabile while the extracranial segment of internal carotid artery undergoes obliteration.
  3. Arterial circle of the brain in studied animals is supplied with blood first of all by maxillary artery and also by vertebral artery and occipital artery with mediation of rete mirabile.
  4. A specific discriminant trait in the system of brain base arteries in species of Bovini involves the presence of caudal epidural rete mirabile.
  5. The specific traits of brain base arterial pattern in the animals extend the list of morphological similarities between the species classified within the taxon of Bovini.

LITERATURE CITED

  1. Top of page
  2. ABSTRACT
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. CONCLUSIONS
  7. LITERATURE CITED
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  • Wang XR, Liu Y, Zhang LP, Wang XJ, Wu JP. 2012b. Comparative anatomical study of the epidural retia mirabile in the yak and cattle. Asian J Anim Vet Adv 7:884890.
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