Structure and sympathetic innervation of the intracranial arteries in the giraffe (Giraffa camelopardalis)

Fluorescence histochemistry discloses that the carotid rete mirabile in the giraffe has a poor sympathetic innervation. In contrast, the efferent artery of the rete (internal carotid artery) and the cerebral arteries show moderate sympathetic innervation. A certain degree of regional variability was noted in which the rostral arteries (anterior and middle cerebral) receive more sympathetic nerves than the caudal (posterior communicating and basilar) arteries. The sympathetic nerves on the giraffe cerebral vessels may constitute part of a host of mechanisms by which regional blood flow to the brain is regulated. Conversely, the paucity of sympathetic innervation of the carotid rete mirabile may indicate that this structure does not play an active role in vasoconstrictor responses during postural changes of the head.     

Anatomy of the arteries of the head in the domestic fowl

The anatomy of the cephalic arterial system in the fowl was studied in 24 specimens by means of latex-injected preparations and by dissection. Branches of the external carotid artery supply the extracranial regions. The vertebral arteries unite with the occipitals and have no major communications with the encephalic system. Blood can reach the brain directly from the internal carotid artery and indirectly by way of the extensive cerebral-extracranial anastomoses; especially prominent are those to the palatine and sphenomaxillary arteries from the maxillary and facial branches of the external carotid artery. A large external ophthalmic artery supplies the temporal rete and eye musculature, and an internal ophthalmic artery links the rete and the cerebral vessels. The circle of Willis is incomplete both anteriorly and posteriorly; the anterior cerebral arteries do not unite and the basilar artery is generally asymmetrical in origin. The basilar artery tapers caudally and is continued as the ventral spinal artery.     

Individual variability of the projection line of the common carotid artery

The investigation has been performed on 87 corpses of persons of both sex, that died after 60 years of age from the pathology not connected with any diseases in the neck organs. Individual variability in the common carotid artery projection line has been revealed; it conforms, to a certain extent, with the value of the neck index. When the neck is short and thick, the artery position corresponds to the line that runs across the following points: the superior--0.5 cm forward from the mandibular angle, the inferior--0.5 cm medially from the sternoclavicular joint. When the neck index is within the limits 1.71-1.88, it is expedient to draw the classical projection line. When the neck index is within the limits 1.57-1.69, it is possible to determine the projection zone as an elongated rectangle. At the bottom of every side the border of this zone is a straight line drawn between the sternoclavicular joint and the point situating 0.6 cm laterally from the joint, and at the top--the line connecting the top of the mastoid process with the point 1.0 cm behind the mandibular angle.     

Homeobox gene hoxa3 is essential for the formation of the carotid body in the mouse embryos

Homeobox gene Hoxa3 is strongly expressed in the third pharyngeal arch and pouch. We found that Hoxa3 homozygous null mutant mice had the lack of the carotid body. In all late-term mutant embryos examined (n = 10), no carotid body was present. The carotid body rudiment is formed in the wall of the third branchial artery, which develops into the common carotid artery and the first part of the internal carotid artery. The symmetrical patterns of the third, fourth, and sixth arch arteries were observed in wild-type littermates at embryonic day (E) 10.5-12.5. In Hoxa3 homozygous mutant embryos, however, the third arch artery began to degenerate at E10.5 and almost disappeared at E11.5. Furthermore, the bifurcation of the common carotid artery at the normal position, i.e., at the upper end of the larynx, was never detected in the mutant embryos at E16.5-E18.5. The common carotid artery of the homozygous mutants was separated into the internal and external carotid arteries immediately after its origin. Thus, the present study evidenced that the absence of the carotid body in Hoxa3 homozygous mutants is due to the defect of development of the third arch artery, resulting in malformation of the carotid artery system. During fetal development, the carotid body of mice is in close association with the superior cervical ganglion of the sympathetic trunk. The superior cervical ganglion rather showed hypertrophic features in Hoxa3 homozygous mutants lacking the carotid body.     

Diagnosis and treatment of carotid body paraganglioma: 21 years of experience at a clinical center of Serbia

BACKGROUND: The carotid body paraganglioma (chemodectoma) is a relatively rare neoplasm of obscure origin. These are usually benign and commonly present as asymptomatic cervical mass. PATIENTS AND METHODS: Records of 12 patients (9 female and 3 male) with carotid body tumors treated between 1982 and 2003, treated at our center were retrospectively reviewed. Data on classification, clinical presentation, and surgical treatment were extracted from the case records. Surgical complications and treatment outcome were noted and survival was calculated by actuarial method. The literature on carotid body paraganglioma was reviewed. RESULTS: The average age of the patients was 52 years (range 30-78 years). Eight of these cases presented as a large asymptomatic non-tender neck mass, and two each presented with dysphagia, and hoarseness of voice. As per Shamblin classification seven of tumors were type II and 5 were types III. In 7 cases subadventitial tumor excision was performed, while in 5 associated resection of both external and internal carotid arteries was carried out. The artery was repaired by end-to-end anastomosis in one case, with Dacron graft in one case, and with saphenous vein graft in 3 cases. There was no operative mortality. After a mean follow-up of 6.2 years (range 6 months to 20 years), there were no signs of tumor recurrence in any of the cases. CONCLUSIONS: Surgical excision is the treatment of choice for carotid body paragangliomas although radiation therapy is an option for patients who are not ideal candidates for surgery. For the tumors that are in intimate contact with carotid arteries, the treatment by vascular surgeon is recommended.     

Comparative anatomical studies of thyroid and thymic arteries: I. Rat (Rattus norvegicus albinus)

The thyroid and thymic arteries were investigated in 50 male and 50 female rats. In more than 70% of the animals, on both sides the cranial thyroid artery forms a common trunk with the ascending pharyngeal artery. The caudal thyroid artery arises not from the deep cervical but from the pericardiacophrenic artery. It may be replaced, however, by a branch of some other artery, such as the brachiocephalic, subclavian, vertebral, or ascending cervical, suggesting a shift of its origin from the internal thoracic artery to the thyrocervical trunk as in man. All the thoracic lobes of the thymus are supplied directly by a thymic branch of the internal thoracic artery or indirectly by a branch of the pericardiacophrenic artery. More than half of the specimens have a cervical thymic lobe of variable size, which is supplied by a branch of the cranial thyroid, external carotid, and/or occipital arteries. Some of these thymic arteries, except those from the external carotid and occipital arteries, reach the thoracic lobe. The thoracic lobes lacking a cervical lobe may be supplied by the thymic branch arising only from the cranial thyroid artery. Other anomalous arteries supplying the thoracic lobe are derived from the superficial cervical and/or the right common carotid arteries. These results show that the thymic arteries of rats are basically similar to those of man, although they display a clear difference in their frequency and origin.     

The variability of the circulus arteriosus (Willisii): order or anarchy?

The variation of the circulus arteriosus is studied using multivariate methods. The data which form the basis of this study are 19 measurements of half the circumference of the arteries that form the circle of Willis and its afferent and efferent branches; 100 circles of Willis were measured for this purpose. Since the number of variables per individual is large, multivariate statistical techniques are the most appropriate method to gain insight in the relations of vessel sizes that exist within the circle of Willis. So a principal component analysis was performed on the data. The results clearly show a number of relations between vessel sizes. In general, inverse relationships were found of vessels that have (at least partially) an identical irrigation area: both internal carotid arteries and the ipsilateral posterior communicating artery show an intimate relationship and are together inversely related to the basilar artery and the precommunicating part of the posterior cerebral artery. Inverse relationships are also found for both vertebral arteries and both precommunicating parts of the anterior cerebral arteries. The homonymous efferent arteries appear to be closely related and show an independent variation. Together the first six principal components explain 69% of the variance. These results support a haemodynamical hypothesis on the explanation of the variability of the circle of Willis. Moreover, the differential growth in the head-neck region during the first two decades of life is postulated to be the origin of a part of the variation.     

A rare origin of the superior thyroid artery

In the course of a classroom dissection of a negro male (height: 167 cm; weight: 56.8 kg), and anomalous right superior thyroid artery was noted. It arose from the common carotid artery 27 mm proximal to the bifurcation into external and internal carotids. Previous reports indicate that the incidence of origin of the superior thyroid from the common carotid or its bifurcation varies from 5 to 45%, depending on the population sampled. Moreover, a low origin is more common in females than males, and appears approximately twice as often on the left as on the right. Previous reports also indicate that the origin is only very rarely more than 1 cm proximal to the bifurcation, only one case having been reported of an origin 25 mm proximal. The present case appears to be the most proximal origin so far recorded, and the first far proximal origin in negroes. The implications of such a low origin for surgical approach to the thyroid are considerable.     

A morphometric study of age-related changes in the elastic systems of the common carotid artery and internal carotid artery in humans

The present study aims to quantify the distribution of the elastic fiber system in the walls of the common carotid artery and the internal carotid artery in humans. In order to identify specific fibers, segments of carotid arteries were stained using the Verhoeff (for elastic fibers), Weigert (for elastic and elauninic fibers) and Weigert-oxone (for elauninic and oxytalanic fibers) methods. A histomorphometric study was undertaken in order to estimate the linear density (LV) of the fibrous components present in the elastic system and determine the total length of these components in each segment. Microscopic fields were sampled using a test system in which the colors and bands defined in the current study were superimposed on the histological preparations. Data were analyzed through linear regression using first-order rate equations and computer software. The internal carotid artery can be loosely defined as muscular in nature. In order to classify common carotid arteries, it is necessary to consider subject age. From 0 to 30 years of age, the LV of mature elastic fibers does not change significantly in either (left or right) common carotid artery, although a significant reduction in the LV of this type of fiber occurs in the right internal carotid artery. The most marked reduction in oxytalanic and elauninic fibers occurs between 0 and 10 years of age, becoming less intense between the ages of 10 and 30.     

Arterial monoaminocytes of the base of the brain in vertebrates

By Falck's method monoaminocytes of the arteries in the encephalon base were studied in Teleostei (Anarhichas lupus, Eleginus navaga, Leuciscus brandti Liza soiuy in amphibians (Rana temporaria, Rana semiplicata, Bufo bufo), in reptiles (Testudo horsfiedli, Trionyx chinensis) and in birds (blue rock pigeon, hen). Specific and individual peculiarities in chromaffinocyte, labrocyte and melanophore distribution were revealed in the vertebrate cranial arteries. In all the animals studied chromaffin cells are more frequent in the lateral olfactory artery. Their concentration decreases towards cranial, caudal branches of the internal carotid artery, the main and internal carotid arteries. The greatest amount of chromaffinocytes was found in the cranial arteries of Anarhichas lupus, then comes Eleginus navaga, Leuciscus brandti and Liza soiny Concentration of melanophores in fishes increases with enlargement of the vascular diameter; these cells are more abundant in the arteries of Anarhichas lupus and in less amount in Eleginus navaga, Leuciscus brandti and Liza. Pigmented cells are more abundant in the internal carotid artery and its cranial and caudal branches than in lateral, olfactory and main arteries of fishes. On the contrary, in amphibians, the main artery contains a maximal concentration of melanophores. In the tortoise cranial arteries, there are only single cells of this type, and birds have no such cells. Labrocytes occur in the greatest concentration in the tortoise cranial arteries and in other vertebrates they are scarce or absent. As a whole, the role of the local endocrine link in regulation of the brain arteries mobility decreases in the following way: fishes--amphibians--reptiles--birds.     

A histochemical study of the innervation of the cerebral blood vessels in the domestic fowl

Summary Adrenergic and cholinergic nerves innervating the cerebral arteries of the domestic fowl were examined by specific histochemical techniques.The adrenergic nerve plexuses of the cerebral carotid system are markedly denser than those of other vertebrates observed by similar techniques. They form longitudinally elongated meshworks of fine fibres in the vascular wall of the arterial branches. Those innervating the vertebro-basilar system are less dense and more elongated, and, as the size of the artery diminishes, the fibres of the plexus become coarser. In the small pial and parenchymal arteries they are reduced to a few fibres running parallel to, or spiralling around the vascular axis.The cholinergic nerve plexuses are not as dense as the adrenergic system. The acetylcholinesterase activity is very weak, except in the plexuses innervating the cerebral carotid artery and the proximal portion of the anterior and posterior rami. In the vertebro-basilar system, a few thick nerve bundles run alongside the blood vessels of the vertebral and basilar arteries. Cholinergic nerves enter the cranial cavity along the internal carotid, the vertebral and possibly the cerebro-ethmoidal arteries.Intracerebral capillaries and some arterioles are not innervated with cholinergic and adrenergic fibres of peripheral origin, but with ones arising from parenchymal nerve cells.     

Meningeal arterial patterns in great apes: Implications for hominid vascular evolution

Arterial meningeal patterns were observed for 100 hemispheres from great ape endocasts (Pan paniscus, Pan troglodytes, Gorilla gorilla, and Pongo pygmaeus). Eight patterns emerged based on the relative contributions to the walls and dura mater of the middle part of the braincase of meningeal arteries that stem from two sources. These arteries enter the braincase through either the orbit (delivering blood from the internal carotid artery) or through the base of the middle cranial fossa (via the middle meningeal artery whose blood comes from the external carotid artery). The three genera of apes manifest different frequencies of the eight, patterns, with orangutans highly dependent on orbital meningeal arteries at one extreme, and chimpanzees showing the greatest reliance on the middle meningeal artery at the other. As was the case in an earlier study of rhesus monkeys, there is a trend across the two genera of African apes for increased mean cranial capacity to be associated with increased reliance on the internal carotid artery for supplying the middle portion of the braincase. However, unlike the case for macaques, this trend does not reach statistical significance in African apes. Because it is rare for humans to manifest significant arterial contributions from the orbit to the middle cranial fossa, the comparative data on monkeys, apes, and humans suggest that, during the course of vascular evolution in Homo, the middle meningeal artery eventually took over supply of the entire middle cranial fossa. This hypothesis should be tested in the hominid fossil record. Earlier work on meningeal arterial patterns in apes has traditionally relied on Adachi's system that was determined from humans and focuses on the origin of the middle branch of the middle meningeal artery. As a result, the extensive orbital contributions to the middle portion of the braincase that characterize apes were not recognized and the eight patterns described in this paper were often erroneously assigned to the three patterns that adequately describe only humans. Adachi's system should therefore be abandoned for nonhuman primates and early hominids. A correct understanding of meningeal arterial evolution cannot be achieved until the orbital contributions to the meningeal arteries are recognized and incorporated into an evolutionary study that spans from apes to fossil hominids to living people. © 1993 Wiley-Liss, Inc.     

Carotid bifurcation position and branching angle in patients with atherosclerotic carotid disease

Carotid artery bifurcation (CB) is the preferred site for development of atherosclerosis (AS) in extracranial cerebral arteries; internal carotid artery stenosis is the most common cause of ischemic stroke. The frequent atherosclerotic disease of CB may best be explained by the hemodynamic influence of complex blood flow that results from the unique geometry of the bifurcation. Few papers analyze all possible geometric structural characteristics of this bifurcation. While performing many carotid endarterectomies, we noticed that a certain correlation between CB height in the neck and its angle existed, that a larger angle is accompanied with increased frequency of elongation and kinking and that CB shape influences distribution of atherosclerosis. The purpose of this paper is to quantify and evaluate these clinical observations. Radiogrametric analysis of 154 bi-plane orthogonal aortic arch arteriograms of patients with symptomatic atherosclerotic carotid artery disease was performed and a total of 289 CBs were analyzed. The CB height in relation to cervical spine segments was measured and real angles of each bifurcation were calculated. A positive linear correlation between CB height and angle exists: the CB angle increases /decreases 3.34 degrees for each third of the cervical vertebral body height or intervertebral space height. The CB is positioned a little higher on the left side. The proximal border of the atherosclerotic process is found at the level of intersection of the axes of the common carotid artery branches in 92.6% of examined CBs. In lower CBs (with smaller angles) the proximal border was located in the last segment of the common carotid artery, while in high bifurcations (wider angles) the proximal border of the AS process is more distally in the blood flow, in the beginning of the internal carotid artery, and the process was more extensive. High CBs are more suitable for eversion endarterectomy while normal and low CBs are more suitable for open (classic) carotid endarterectomy. The influence of the geometric risk factor demands further investigation.     

Comparative studies on the vascular organization of carotid labyrinths of anurans and caudates

The three-dimensional structures of the carotid labyrinth in five species of anurans representing four families (Rana nigromaculata, Rana catesbeiana, Bufo japonicus, Hyla arborea, and Xenopus laevis), and three species of caudates representing three families (Cynops pyrrhogaster, Hynobius nebulosus, Ambystoma mexicanum) were compared using vascular corrosion castings and scanning electron microscopy (SEM). Anuran carotid labyrinths are spherical in shape and are classified into two groups according to the origin of the external and internal carotid arteries. One group, which included Rana, Hyla, and Bufo, is characterized by the presence of a vascular ring at the proximal end and some vascular routes at the distal end of the labyrinth. The external and internal carotid arteries originate from these structures. The other group, which includes only Xenopus, is characterized by the external carotid artery opening directly from the central chamber or the common carotid artery, and by the internal carotid artery originating from within the vascular maze. The vascular maze is most complex in Xenopus, less so in Rana and Bufo, and simplest in Hyla. The carotid labyrinths in Cynops and Hynobius are oblong in shape. The fundamental organization in salamanders is similar to that in anurans. The vascular maze, however, is much simpler than in Hyla. There is no specialized swelling in Ambystoma mexicanum. The present findings suggest that most amphibian carotid labyrinths have the appropriate architecture for controlling vascular tone.     

Atherosclerotic lesions of supra-aortic arteries in diabetic patients

The aim of this prospective study was to determine the prevalence and localization of stenotic atherosclerotic lesions of supra-aortic arteries in diabetic patients according to age and sex. Angiograms obtained by digital subtraction angiography were analyzed in 150 diabetic patients (study group) and 150 non-diabetic patients (control group) with symptoms of cerebral ischemia. Diabetic patients were found to have a significantly higher prevalence of stenotic atherosclerotic lesions of the internal carotid artery. Lesions of the large supra-aortic arteries were significantly more common in the left than in the right side of the neck (p < 0.001), but the difference between the diabetic and the non-diabetic group did not reach statistical significance. Hemodynamic conditions were found to be more important than diabetes for the occurrence of atherosclerotic lesions in these arteries. Changes in the proximal segment of the left common carotid artery were the most common finding in diabetic patients, hence attention should be paid to this localization on control examinations.     

The homologies of the lorisoid internal carotid artery system

The development of the “internal carotid” arterial system of the lesser galago (Galago senegalensis senegalensis)is described. The first artery to be formed is a typical promontory artery which runs through the middle-ear cavity and gives off the stapedial artery. It terminates in the cranial cavity by dividing into the middle cerebral, anterior cerebral, and two ophthalmic arteries. It is accompanied by the internal carotid nerve. A medially directed artery to the external carotid rete arises from the commencement of the promontory artery and joins the caudal end of the rete, whose cranial end lies in the foramen lacerum. As the promontory artery enters the cranial cavity, it communicates with the cranial end of the rete. The promontory artery, between the origin of the artery to the rete and its connection with the rete, becomes narrowed and eventually disappears. Thus the internal carotid artery is formed from the commencement of the promontory artery, the artery to the rete, the external carotid rete, and the terminal intracranial part of the promontory artery. The relationships of the artery to the rete indicate that it is the homologue of the human ascending pharyngeal artery.     

Time-dependent potentiation of contractile response to norepinephrine in canine isolated cerebral arteries.

The time course of contractile responses to alpha-adrenoceptor agonists was investigated using various arteries isolated from dogs and monkeys. The contractile response to norepinephrine was increased during the time course of the experiment in canine basilar and internal carotid arteries, whereas the response of isolated canine external carotid arteries and monkey internal carotid arteries did not change significantly. Treatment with 10(-7) M propranolol, 5 x 10(-6) M cocaine plus 10(-5) M hydrocortisone, or 5 x 10(-5) M acetylsalicylic acid did not significantly affect the time-dependent potentiation of the norepinephrine-induced contraction in canine internal carotid arteries. The time-dependent enhancement in the response to norepinephrine was also observed in the arterial preparations from which the endothelial cells were removed. The contractile response of canine internal carotid arteries to phenylephrine did not alter significantly throughout the experiments. On the other hand, the responses to clonidine and xylazine were markedly enhanced with time. Significant potentiation of the norepinephrine-induced contraction was observed in canine internal carotid arteries treated with 10(-8) M prazosin, whereas 10(-8) M yohimbine attenuated the time-dependent potentiation. These results suggest that the contractile responses of isolated canine basilar and internal carotid arteries to norepinephrine are potentiated during the course of the experiment, which is likely to be related, in part, to an enhancement in alpha 2-adrenoceptor mediated contraction.     

The carotid sinus in lizards with an anatomical survey of the ventral neck region

The anatomy of the ventral neck region of the scincid lizards Chalcides ocellatus and Scincus scincus is presented and is found to be similar to that of other lizards as described in the literature. The internal carotid artery arises by 3-5 roots from the dorsal side of the ascending limb of the carotid arch. During its first part, the internal carotid artery is completely divided into two nearly equal channels. The carotid sinus is more complicated in Chalcides than in Scincus. In lizards, it may be homologous to the carotid labyrinth of fishes and amphibians. Around the origin of the internal carotid artery are two kinds of epithelioid cells scattered in the adventitial connective tissue: a- large cells with rounded, faintly stained nuclei, and little, clear cytoplasm; b- cells with small darkly stained nuclei. Both kinds of cells appear to represent different levels of secretory activity. The number of the large cells increases with greater complexity of the carotid sinus. The cells also increase in size and number during summer (sexual period); this is especially true in younger animals. The epithelioid cells are considered to be homologous to the carotid body of higher vertebrates. The carotid sinus and epithelioid cells together form a closely interrelated system which may be intermediate between the carotid labyrinth of fishes and amphibians, and the carotid body of birds and mammals.     

The primitive course of the internal carotid artery in mammals.

In all recent mammals the internal carotid artery at the level of the auditory capsule is derived from the embryonic dorsal aorta. In adults of various groups, the artery lies in positions which are classified as medial or promontory. It is shown that these character states arise by a process of differential growth affecting the relative positions of the dorsal aorta and the cochlear promontory. There is no evidence for separate vessels in the embryo which could give rise to non-homologous internal carotid arteries in the two positions. It follows that the concept of a primitive mammalian morphotype with both a medial and a promontory internal carotid artery in the same individual presents a formidable embryological problem. It is recommended that, in the absence of supporting evidence, the widespread current taxonomic and palaeontological use of this hypothetical morphotype should be regarded with suspicion.     

Disruption of the Hoxa3 homeobox gene results in anomalies of the carotid artery system and the arterial baroreceptors

Homeobox gene Hoxa3 is expressed in the third pharyngeal arch and pouch and is required for development of the third arch artery in addition to the thymus, parathyroid gland and carotid body. We therefore statistically analyzed malformations of the carotid artery system in Hoxa3 homozygous mutant mice, in comparison with wild-type and heterozygous littermates. To identify the carotid artery system, red carbon ink was injected, or vascular casts were made by injection of Mercox resin and observed by scanning electron microscopy. Furthermore, innervation of the carotid sinus and baroreceptor regions in the aortic arch and right subclavian artery were studied in the Hoxa3 null mutants having an abnormal carotid artery system by immunohistochemistry with TuJ1 and protein gene product (PGP) 9.5 antibodies, which recognize nerve fibers and neurons. The common carotid artery of Hoxa3 homozygous mutants was absent or very short and therefore the internal and external carotid artery arose from a more proximal level than those of wild types. The baroreceptor innervation, however, persisted in the mutants, although vascular targets were changed. These results indicate that Hoxa3 gene is crucial for the formation of the common carotid artery and the null mutant mice are the first useful animal models to show that the third arch arteries on both sides specifically degenerate but the fourth and sixth arch arteries are normal.