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Cranial arterial patterns of the alpaca (Camelidae: Vicugna pacos )

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ABSTRACT

Artiodactyl cranial arterial patterns deviate significantly from the standard mammalian pattern, most notably in the possession of a structure called the carotid rete (CR)—a subdural arterial meshwork that is housed within the cavernous venous sinus, replacing the internal carotid artery (ICA). This relationship between the CR and the cavernous sinus facilitates a suite of unique physiologies, including selective brain cooling. The CR has been studied in a number of artiodactyls; however, to my knowledge, only a single study to date documents a subset of the cranial arteries of New World camelids (llamas, alpacas, vicugñas and guanacoes). This study is the first complete description of the cranial arteries of a New World camelid species, the alpaca (Vicugna pacos), and the first description of near-parturition cranial arterial morphology within New World camelids. This study finds that the carotid arterial system is conserved between developmental stages in the alpaca, and differs significantly from the pattern emphasized in other long-necked ruminant artiodactyls in that a patent, homologous ICA persists through the animal's life.

No MeSH data available.


Sagittal section of the skull and arteries of the alpaca, Vicugna pacos. CAC, cerebral arterial circle; CMA, ‘common’ auricular artery; CON, condylar artery; CR, carotid rete; DLA, deep lingual artery; ECA, external carotid artery; gPAL, greater palatine artery; iAL, inferior alveolar artery; ICA, internal carotid artery; IOB, infraorbital artery; LA, lingual artery; MA, maxillary artery; OC, occipital artery; OPR, ophthalmic rete; SLA, sublingual artery; sPAL, sphenopalatine artery.
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RSOS160967F3: Sagittal section of the skull and arteries of the alpaca, Vicugna pacos. CAC, cerebral arterial circle; CMA, ‘common’ auricular artery; CON, condylar artery; CR, carotid rete; DLA, deep lingual artery; ECA, external carotid artery; gPAL, greater palatine artery; iAL, inferior alveolar artery; ICA, internal carotid artery; IOB, infraorbital artery; LA, lingual artery; MA, maxillary artery; OC, occipital artery; OPR, ophthalmic rete; SLA, sublingual artery; sPAL, sphenopalatine artery.

Mentions: Overall, the branching patterns of cranial arteries were conserved among adult specimens. The branches of the external carotid artery (ECA) of the alpaca are summarized in the electronic supplementary material, table S1 and visualized in figures 1–4. The ECA (arteria [a.] carotis externa) begins to branch extensively deep to the condylar process of the mandible. The first major branch of the ECA is the occipital artery (a. occipitalis; figure 1). From the superior surface of the ECA, the occipital artery shares a short trunk with the ICA (a. carotis interna) and the condylar artery (figures 1–3). The trunk uniting these arteries is variable—the vessels may arise in close proximity to each other or from a common trunk, as described (figures 1–3). As the occipital artery ascends, it scours the deep surface of the jugular process and the posterior surface of the temporal crest (mastoid contribution; crista supramastoidea). The artery terminates by splitting into smaller branches that permeate the occipital region (nuchal ligament (ligamentum nuchae) and muscles) and a larger caudal meningeal artery (figures 1 and 2). The latter enters the cranium via a large mastoid foramen (foramen mastoideum) before radiating across the caudal half of the meninges. The ICA itself is reduced in calibre, and the vessel does not leave a medial bullar groove as it ascends to the basicranium as in other artiodactyls with a homologous ICA (figures 2 and 3; see e.g. Moschiola [42]; Tragulus [51]). As the ICA enters the basicranium, it traverses the promontorial foramen, coursing within a carotid canal in close association with the promontorium of the petrosal. The ventral surface of the petrosal is scoured by a slight transpromontorial sulcus. This sulcus corresponds to direct contact by the ICA of non-artiodactylan mammals [52–57]; however, in the adult alpaca, the ICA does not make direct contact with the petrosal. The presence of a transpromontorial sulcus in adult alpacas may be an effect of arterial reduction during ontogeny (see below). Upon entering the cranium, the ICA leaves a notch at the rostral-most extent of the epitympanic wing (sensu [55,57]; this structure is also referred to as the ‘pole of the promontorium’ sensu [58] and the ‘anteromedial flange’ sensu [59]). Once inside the brain case, the ICA communicates with the CR (figures 2–4; also illustrated for other Lamini by Kiełtyka-Kurc et al. [9]).Figure 1.


Cranial arterial patterns of the alpaca (Camelidae: Vicugna pacos )
Sagittal section of the skull and arteries of the alpaca, Vicugna pacos. CAC, cerebral arterial circle; CMA, ‘common’ auricular artery; CON, condylar artery; CR, carotid rete; DLA, deep lingual artery; ECA, external carotid artery; gPAL, greater palatine artery; iAL, inferior alveolar artery; ICA, internal carotid artery; IOB, infraorbital artery; LA, lingual artery; MA, maxillary artery; OC, occipital artery; OPR, ophthalmic rete; SLA, sublingual artery; sPAL, sphenopalatine artery.
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Related In: Results  -  Collection

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RSOS160967F3: Sagittal section of the skull and arteries of the alpaca, Vicugna pacos. CAC, cerebral arterial circle; CMA, ‘common’ auricular artery; CON, condylar artery; CR, carotid rete; DLA, deep lingual artery; ECA, external carotid artery; gPAL, greater palatine artery; iAL, inferior alveolar artery; ICA, internal carotid artery; IOB, infraorbital artery; LA, lingual artery; MA, maxillary artery; OC, occipital artery; OPR, ophthalmic rete; SLA, sublingual artery; sPAL, sphenopalatine artery.
Mentions: Overall, the branching patterns of cranial arteries were conserved among adult specimens. The branches of the external carotid artery (ECA) of the alpaca are summarized in the electronic supplementary material, table S1 and visualized in figures 1–4. The ECA (arteria [a.] carotis externa) begins to branch extensively deep to the condylar process of the mandible. The first major branch of the ECA is the occipital artery (a. occipitalis; figure 1). From the superior surface of the ECA, the occipital artery shares a short trunk with the ICA (a. carotis interna) and the condylar artery (figures 1–3). The trunk uniting these arteries is variable—the vessels may arise in close proximity to each other or from a common trunk, as described (figures 1–3). As the occipital artery ascends, it scours the deep surface of the jugular process and the posterior surface of the temporal crest (mastoid contribution; crista supramastoidea). The artery terminates by splitting into smaller branches that permeate the occipital region (nuchal ligament (ligamentum nuchae) and muscles) and a larger caudal meningeal artery (figures 1 and 2). The latter enters the cranium via a large mastoid foramen (foramen mastoideum) before radiating across the caudal half of the meninges. The ICA itself is reduced in calibre, and the vessel does not leave a medial bullar groove as it ascends to the basicranium as in other artiodactyls with a homologous ICA (figures 2 and 3; see e.g. Moschiola [42]; Tragulus [51]). As the ICA enters the basicranium, it traverses the promontorial foramen, coursing within a carotid canal in close association with the promontorium of the petrosal. The ventral surface of the petrosal is scoured by a slight transpromontorial sulcus. This sulcus corresponds to direct contact by the ICA of non-artiodactylan mammals [52–57]; however, in the adult alpaca, the ICA does not make direct contact with the petrosal. The presence of a transpromontorial sulcus in adult alpacas may be an effect of arterial reduction during ontogeny (see below). Upon entering the cranium, the ICA leaves a notch at the rostral-most extent of the epitympanic wing (sensu [55,57]; this structure is also referred to as the ‘pole of the promontorium’ sensu [58] and the ‘anteromedial flange’ sensu [59]). Once inside the brain case, the ICA communicates with the CR (figures 2–4; also illustrated for other Lamini by Kiełtyka-Kurc et al. [9]).Figure 1.

View Article: PubMed Central - PubMed

ABSTRACT

Artiodactyl cranial arterial patterns deviate significantly from the standard mammalian pattern, most notably in the possession of a structure called the carotid rete (CR)—a subdural arterial meshwork that is housed within the cavernous venous sinus, replacing the internal carotid artery (ICA). This relationship between the CR and the cavernous sinus facilitates a suite of unique physiologies, including selective brain cooling. The CR has been studied in a number of artiodactyls; however, to my knowledge, only a single study to date documents a subset of the cranial arteries of New World camelids (llamas, alpacas, vicugñas and guanacoes). This study is the first complete description of the cranial arteries of a New World camelid species, the alpaca (Vicugna pacos), and the first description of near-parturition cranial arterial morphology within New World camelids. This study finds that the carotid arterial system is conserved between developmental stages in the alpaca, and differs significantly from the pattern emphasized in other long-necked ruminant artiodactyls in that a patent, homologous ICA persists through the animal's life.

No MeSH data available.