Congenital Aplasia of the Common Carotid Artery: A Comprehensive Review.

In an attempt to describe the morphofunctional consequences of uni- and bilateral aplasia of the common carotid artery (CCA), which is usually a vascular source of the external carotid (ECA) and internal carotid (ICA) arteries, we investigated online databases of anatomical and clinical papers published from the 18th century to the present day. We found 87 recorded cases of uni- and bilateral CCA aplasia in subjects from the first hours to the eighth decade of life, which had been discovered in 14 (known) countries. Four crucial parameters were described: the embryology of the carotid arteries, morphophysiology of the carotid arteries, CCA aplasia, and unilateral versus bilateral CCA aplasia, including history, general data, diagnosing, vascular sources, caliber, course of the separated ECA and ICA, associated vascular variants, and pathological disorders. To complete the knowledge of the morphofunctional consequences of the absence of some artery of the carotid system, and risking the possibility of repeating some words, as "carotid artery", or "carotid aplasia" and the headings from our previous article about bilateral ICA absence, this review is the first in the literature that recorded all cases of the CCA aplasia published and/or cited for the past 233 years. Main characteristic of the CCA absence is its association with 21 different diseases, among which the aneurysms were in 13.69% of cases, and 17.80% of cases were without pathology.

Arterial supply to the thyroid gland and the relationship between the recurrent laryngeal nerve and the inferior thyroid artery in human fetal cadavers.

The aim of this study was to identify the arterial supply to the thyroid gland and the relationship between the inferior thyroid artery (ITA) and the recurrent laryngeal nerve (RLN) in fetal cadavers using anatomical dissection. The anterior necks of 200 fetuses were dissected. The origins of the superior thyroid artery (STA) and the ITA and location of the ITA in relation to the entrance of the thyroid lobe were examined. The relationship between the ITA and the RLN was determined. The origins of the STA were classified as: external carotid artery, common carotid artery (CCA), and the thyrolingual trunk. The origins of the ITA were the thyrocervical trunk and the CCA. The ITA was absent on the left side in two cases. The relationship of the RLN to the ITA fell into seven different types. Type 1: the RLN lay posterior to the artery; right (42.5%), left (65%). Type 2: the RLN lay anterior to the artery; right (40.5%), left (22.5%). Type 3: the RLN lay parallel to the artery; right (11.5%), left (7%). Type 4: the RLN lay between the two branches of the artery; right (1%), left (3.5%). Type 5: The extralaryngeal branch of the RLN was detected before it crossed the ITA; right (4.5%), left (0%). Type 6: the ITA lay between the two branches of the RLN; right (0%), left (0.5%). Type 7: the branches of the RLN lay among the branches of the ITA; right (0%), left (0.5%). The results from this study would be useful in future thyroid surgeries.

Maximal stimulation-induced in situ myosin light chain kinase activity is upregulated in fetal compared with adult ovine carotid arteries.

Postnatal decreases in vascular reactivity involve decreases in the thick filament component of myofilament calcium sensitivity, which is measured as the relationship between cytosolic calcium concentration and myosin light chain (MLC20) phosphorylation. The present study tests the hypothesis that downregulation of thick filament reactivity is due to downregulation of myosin light chain kinase (MLCK) activity in adult compared with fetal arteries. Total MLCK activity, calculated as %MLC20 phosphorylated per second in intact arteries during optimal inhibition of myosin light chain phosphatase activity, was significantly less in adult (6.56+/-0.29%) than in fetal preparations (7.39+/-0.53%). In situ MLC20 concentrations (microM) in adult (198+/-28) and fetal arteries (236+/-44) did not differ significantly. In situ MLCK concentrations (microM), however, were significantly greater in adult (8.21+/-0.59) than in fetal arteries (1.83+/-0.13). In situ MLCK activities (ng MLC20 phosphorylated.s(-1).ng MLCK(-1)) were significantly less in adult (0.26+/-0.01) than in fetal arteries (1.52+/-0.11). In contrast, MLCK activities in adult (15.8+/-1.5) and fetal artery homogenates (17.3+/-1.3) were not significantly different. When in situ fractional activation was calculated, adult values (1.72+/-0.17%) were significantly less than fetal values (9.08+/-0.83%). Together, these results indicate that decreased thick filament reactivity in adult compared with fetal ovine carotid arteries is due at least in part to greater MLCK activity in fetal arteries, which in turn cannot be explained by differences in MLCK, MLC20, or calmodulin concentrations. Instead, this difference appears to involve age-related differences in fractional activation of the MLCK enzyme.

Digital-image analysis of the left common carotid artery in human foetuses.

The rate of growth of the left common carotid artery during gestation has not been sufficiently evaluated. The present study was performed on 128 spontaneously aborted human foetuses aged 15-34 weeks to compile normative data for the dimensions of the left common carotid artery at varying gestational ages. Using anatomical dissection, digital image analysis (system of Leica Q Win Pro 16) and statistical analysis (ANOVA, regression analysis), a range of measurements (length, original external diameter and volume) for the left common carotid artery during gestation was examined. No significant gender differences were found (p > 0.05). The growth curves of the best fit for the plot of each morphometric parameter against gestational age were generated. The lengths ranged from 14.82 +/- 2.22 to 42.84 +/- 4.32 mm, according to the linear model y = -9.6918 + 1.5963 x +/- 3.1706 (r = 0.95; p < 0.001). The original external diameter increased from 0.72 +/- 0.18 to 3.28 +/- 0.40 mm, according to the linear function y = -1.5228 + 0.1428 x +/- 0.2749 (r = 0.95; p < 0.001). The left common carotid artery-to-aortic root diameter ratio increased from 0.356 +/- 0.062 to 0.480 +/- 0.101. The left common carotid artery-to-aortic arch diameter ratio increased from 0.447 +/- 0.079 to 0.535 +/- +/- 0.113. The volume ranged from 6.73 +/- 4.06 to 369.30 +/- 107.42 mm3 in accordance with the quadratic function y = 344.8 - 41.001 x + 1.254 x2 +/- +/- 46.955 (R2 = 0.87). The parameters examined have clinical application in the early recognition of arterial abnormalities, especially aortic coarctation.

FRS2 alpha 2F/2F mice lack carotid body and exhibit abnormalities of the superior cervical sympathetic ganglion and carotid sinus nerve.

The docking protein FRS2 alpha is an important mediator of fibroblast growth factor (FGF)-induced signal transduction, and functions by linking FGF receptors (FGFRs) to a variety of intracellular signaling pathways. We show that the carotid body is absent in FRS2 alpha(2F/2F) mice, in which the Shp2-binding sites of FRS2 alpha are disrupted. We also show that the carotid body rudiment is not formed in the wall of the third arch artery in mutant embryos. In wild-type mice, the superior cervical ganglion of the sympathetic trunk connects to the carotid body in the carotid bifurcation region, and extends thick nerve bundles into the carotid body. In FRS2 alpha(2F/2F) mice, the superior cervical ganglion was present in the lower cervical region as an elongated feature, but failed to undergo cranio-ventral migration. In addition, few neuronal processes extended from the ganglion into the carotid bifurcation region. The number of carotid sinus nerve fibers that reached the carotid bifurcation region was markedly decreased, and baroreceptor fibers belonging to the glossopharyngeal nerve were absent from the basal part of the internal carotid artery in FRS2 alpha(2F/2F) mutant mice. In some of the mutant mice (5 out of 14), baroreceptors and some glomus cells were distributed in the wall of the common carotid artery, onto which the sympathetic ganglion abutted. We propose that the sympathetic ganglion provides glomus cell precursors into the third arch artery derivative in the presence of sensory fibers of the glossopharyngeal nerve.

Morphometric study of the brachiobicarotid trunk in human fetuses.

The study was conducted to define a normal range for the length, external diameter and volume of the brachiobicarotid trunk during gestation. The material examined consisted of 128 human fetuses of both sexes (63 male, 65 female) aged from 15 to 34 weeks, from spontaneous abortions or stillbirths. The arterial bed was filled with white Latex LBS 3060, specimens were fixed in a 10% formalin, and then branches of the aortic arch were dissected, recorded using a camera, and digitalized to JPEG images. Afterwards, the brachiobicarotid trunks underwent morphometric analysis with the digital image analysis system of Leica QWin Pro16. Regression analysis was used to investigate the growth of the brachiobicarotid trunk during gestation. The brachiobicarotid trunk was observed in 27 of the 128 fetuses studied (21.09%). The results showed the brachiobicarotid trunk length as a function of fetal age, which could be expressed by y = -1.250+0.1433x+/- 0.7682, and the brachiobicarotid trunk diameter by y = -3.034+0.2845+/-0.4253. The volumetric growth of the brachiobicarotid trunk followed the quadratic function y = 178.5-19.69x+0.545x2+/-20.112. The correlation coefficients between arterial length or external diameter and fetal age, and the coefficient of determination between arterial volume and fetal age were as follows: r = 0.76 for length, r = 0.97 for external diameter, and R2 = 0.84 for volume (P<0.001). The relative diameter of the brachiobicarotid trunk increased from 0.738+/-0.089 to 0.916+/-0.088 during the study period.

Investigation of the bifurcation level of the common carotid artery and variations of the branches of the external carotid artery in human fetuses.

Variations in the position of the bifurcation of the common carotid artery (CCA) and the origin or branching pattern of the external carotid artery (ECA) are well known and documented. In this study, the bifurcation levels of the CCA and origin variations of the branches of the ECA have been extensively investigated in human fetuses. Bilaterally, 40 carotid bifurcations and 40 ECA and their branches have been examined. A latex solution, which had been diluted with water at a ratio of 25% and colored with red India ink, was injected into the aortic arch. Fetuses were kept at room temperature for 24 h before the ECA and its branches were dissected under the microsurgery microscope. Cases of variation were determined and photographed. The bifurcation level of the CCA was determined to be 55% at the C3 level, 35% at the C4 level, 10% at the C5 level on the right side and 60% at the C3 level, 40% at the C4 level on left side. The distribution of the ECA trunks was determined as follows: A linguofacial trunk was present in 20% of the cases, a thyrolingual trunk in 2.5%, a thyrolinguofacial trunk in 2.5% and an occipitoauricular trunk in 12.5%. Beyond this the ascending pharyngeal artery (APA) was observed in one fetus to originate from the internal carotid artery (ICA). Knowledge of variations in the origin and course of the ECA and its branches is of great importance in surgery and radiological examinations.

Mophometric study of the aortic arch and its major branches in rat fetuses on the 21st day of gestation.

The anatomy and embryology of the aortic arch and its branching tributaries (brachiocephalic trunk, left common carotid artery and left subclavian artery) in man and animals are well substantiated. However, the anatomical variations and morphometry of the aortic arch and its branching tributaries in rat fetus at the 21st gestation day have not been studied. Pregnant rats were hysterectomized and the arterial systems of 114 fetuses were injected with a polymerisable resin through the umbilical artery. After maceration, the vascular casts were dissected out and prepared for observations under a scanning electron microscope (SEM). The resulting SEM pictures were studied with a picture analyser and different vessel parameters (diameters, lengths and angles) were measured. The success rate of the microvascular cast injection was 46.5%. Out of the 53 observed aortic arch casts, 98.1% showed the classical branching pattern and one (1.9%) had no brachiocephalic trunk. Morphological analysis showed many differences, which were not linked to the litter. The statistical processing of the measurements enabled us to determine that the aorta diameter after the branching of the left subclavian artery was the most replicable parameter. Moreover, the results revealed some strong correlations between different parameters. There are probably no discrete categories among the various observed parameters as diameters and angles. Some parameters show very little variability and can thus be used as reference points for further studies such as the comparison of a control population with a population treated with a relevant xenobiotic.

Changes in blood vessels in fetuses 4 to 9 months intrauterine life old by postmortem angiography method.

We monitored changes in caliber, position and branching of blood vessels in fetuses of 4 - 9 months of intrauterine life. By precise dissection we prepared starting parts of common carotid artery and internal jugular vein in 40 cadaver fetuses. The vessels were injected with Telebrix and subjected to postmortem angiography at the Institute of Radiology Clinics Center in Sarajevo. Thereafter, arteries obtained were compared and analyzed. In preparations of few months old fetal material we observed arteries of fairly straight course, low caliber and with no observable ramification. When preparations of more mature stillborn infants were examined, we detected arteries of undulating course, more expressed ramification and higher caliber. In stillborn babies, all three arteries are of high caliber with rich branching. Considering that in this phase of brain development sulcuses are relatively wide, we can say that course of arteries is partially tortuous. Analysis of venous vessels shows good distinction of venous sinuses and subarachnoidal cisterns. We can conclude with great certainty that the changes occur in position, caliber and relationship among vessels in fetus during the period of brain sulci and gyri formation.

Absence of the common carotid artery: a rare vascular anomaly.

Although absence of the common carotid artery (CCA) is a rare anomaly, the specific configuration in our case makes it extremely rare. Clinical, angiographic, ultrasonographic, and embryologic correlations of this anomaly are discussed after the case report.

Superior bronchial artery arising from the left common carotid artery: embryology and clinical considerations.

A bronchial artery arising from the left common carotid artery was incidentally documented during cerebral angiography in a 64-year-old patient. This variant can be understood as the adult persistence of a primitive bronchial branch arising from the third branchial arch. It represents a potential pitfall for the identification and treatment of the bleeding source in patients with hemoptysis.

Effects of maturation and acute hypoxia on receptor-IP(3) coupling in ovine common carotid arteries.

Whereas previous studies have established that many mechanisms mediating pharmacomechanical coupling are subject to regulation, evidence of physiological regulation of the coupling efficiency between receptor activation and second-messenger production is scarce. The present studies address the hypothesis that acute hypoxia and maturation can influence the mass of second-messenger production for each activated agonist-bound receptor ("receptor gain"). For this assessment, receptor density and agonist affinity values were used to calculate 5-hydroxytryptamine (5-HT) concentrations that would produce standardized numbers of bound receptors (8.5 fmol/mg protein) in each experimental group and thus minimize effects of age or hypoxia on receptor density or agonist affinity. After 3 min of exposure to these 5-HT concentrations, normoxic magnitudes of contraction were similar (as %potassium maxima) in fetal (50 +/- 14%) and adult (40 +/- 9%) arteries, but hypoxia (PO(2) approximately 9--12 Torr for 30 min) depressed contractile tensions with a significantly different time course and magnitude in fetal (30 +/- 10%) and adult (17 +/- 11%) arteries (P < 0.05). Basal inositol 1,4,5-trisphosphate (IP(3)) values (in pmol/mg protein) were significantly greater in fetal (94 +/- 16) than in adult (44 +/- 6) arteries, and integrated areas above baseline for the IP(3) time courses (in nmol-s/mg protein) were significantly greater in fetal than in adult arteries both in normoxic (14.3 +/- 1.8 vs. 9.1 +/- 1.6) and hypoxic (15.0 +/- 2.1 vs. 8.6 +/- 1.2) conditions (P < 0.05). Hypoxia altered the IP(3) time courses both in the fetus and the adult but had no significant effect on IP(3 )mobilization or receptor gain. These data demonstrate that for the 5-HT(2a) receptor predominant in this preparation, receptor gain can be experimentally determined, is not influenced by acute hypoxia, but is greater in fetal than in adult ovine carotid arteries.

Skeletopy of the brachiocephalic trunk and the common carotid arteries in human fetuses.

By means of anatomical and radiological methods and with help of the Computer Digital Image Analysis System the brachiocephalic trunk and the common carotid arteries in relation to the vertebral column were studied in 60 human fetuses. The vessels were found to be between the upper borders: of the third thoracic vertebra and the first cervical vertebra (Th3s-C1s). In the 6th month of the ontogenetic development the vessels descended by one vertebra and established their location in the next prenatal compartment (8-9) between the lower borders: of these same vertebra (Th3i-C1i). We have counted the skeletopie age correlation coefficients of these vessels and found the diminuation of their values. Sexual skeletopic dimorphism have not been observed. These investigations have clinical implications.

Intracranial arteries of human fetuses are more resistant to hypercholesterolemia-induced fatty streak formation than extracranial arteries.

BACKGROUND: Atherosclerotic lesions in intracranial arteries occur later and are less extensive than in extracranial arteries. To investigate potential mechanisms responsible for this difference, in particular the atherogenic response to hypercholesterolemia and LDL oxidation, we compared the extent of fatty streak formation and the composition of these very early lesions in intracranial arteries of human fetuses from normocholesterolemic and hypercholesterolemic mothers with those in extracranial arteries. METHODS AND RESULTS: Lesions were quantified by computer-assisted image analysis of 30 oil red O-stained sections, each from the middle cerebral, basilar, and common carotid arteries and the abdominal aorta of human fetuses (spontaneous abortions and premature newborns who died within 12 hours of birth; both of fetal age 6.2+/-1.3 months) from 43 hypercholesterolemic mothers and 34 normocholesterolemic mothers. Macrophages, apolipoprotein B, and 2 epitopes of oxidized LDL in lesions were determined immunocytochemically. Activities of superoxide dismutase, catalase, and glutathione peroxidase in the arterial wall were also determined. Lesion numbers and sizes were dramatically greater in the abdominal aorta (area of the largest lesion per section: 66.5+/-10.9 x10(3) microm2) and the carotid (11. 6+/-5.3 x10(3) microm2) than in the basilar and middle cerebral artery (0.4+/-0.1 and 0.8+/-0.2 x10(3) microm2, respectively; P<0. 0001). Hypercholesterolemia resulted in a significant increase of lesion size in extracranial arteries but only a marginal increase in intracranial arteries. In analogy, hypercholesterolemia induced a much greater increase in the intimal presence of macrophages, apolipoprotein B, and oxidized LDL (oxidation-specific epitopes) in extracranial than in intracranial arteries. Immunocytochemistry did not indicate that lesions of intracranial arteries contain relatively less oxidized LDL than similar-size lesions of extracranial arteries. Activities of Mn-superoxide dismutase but not of Zn-superoxide dismutase, catalase, or glutathione peroxidase were significantly higher in both intracranial arteries. CONCLUSIONS: Exposure to hypercholesterolemia during fetal development results in extensive formation of fatty streaks in extracranial but not intracranial arteries. The fact that such a difference in lesion formation occurs in the absence of many other atherogenic risk factors found later in life suggests that differences in the atherogenic response to hypercholesterolemia are an important contributor to the slower onset of the disease in intracranial vessels in adults. Fetal arteries may allow elucidation of the mechanisms responsible, for example, better protection of intracranial arteries against free radical-mediated atherogenic processes.

Effects of maturation, artery size, and chronic hypoxia on 5-HT receptor type in ovine cranial arteries.

To test the hypothesis that variations in cerebrovascular reactivity to 5-HT among arteries of different size or type, during maturation, or during acclimatization to high altitude involve differences in serotonergic receptor subtype, we determined relative agonist potency orders and antagonist affinities in common carotid (Com), main branch middle cerebral (Main), and second branch middle cerebral (2BR) arteries from term fetal lambs and nonpregnant adult sheep acclimatized at sea level or at an altitude of 3,820 m for approximately 110 days. In normoxic adult Com segments, agonist potency order was 5-hydroxytryptamine (5-HT) > 5-carboxamidotryptamine (5-CT) >/= 8-hydroxy-2(di-n-propylamino)tetraline (8-OH-DPAT); sumatriptan (Suma) produced no contractile response; and antagonist dissociation constant (pKb) values were 9.4 and 9.5 for ketanserin against 5-HT and 5-CT, 7.5 for GR-127935 against 5-HT, and 7.2 for SB-206553 against 5-HT. In normoxic adult Main segments, agonist potency order was 5-HT > 5-CT >/= Suma >/= DPAT, and pKb values were 9.1 and 9.2 for ketanserin against 5-HT and 5-CT and 7.4 and 8.5 for GR-127935 against 5-HT and Suma, respectively. In the 2BR segments from normoxic adults, agonist potency order was 5-CT > 5-HT > Suma > DPAT and pKb values were 7.4 and 7.2 for ketanserin against 5-HT and 5-CT and 10.0 and 8.7 for GR-127935 against 5-HT and Suma, respectively. Compared with normoxic adults, none of these values were significantly different in hypoxic adults and in fetuses only the pKb values for ketanserin against 5-HT in the 2BR segments (8.8) were greater. From these results we propose that the ratio of 5-HT2 to 5-HT1 receptors is greatest in the Com and decreases progressively to its smallest values in 2BR or smaller segments. Because this gradient appears stable and relatively resistant to the effects of maturation and chronic hypoxia, changes in reactivity associated with these perturbations may involve alterations in receptor density and/or coupling efficiency for 5-HT in ovine cranial arteries.

Doppler ultrasonography of canine maternal and fetal arteries during normal gestation.

Two-dimensional ultrasonography was used in combination with colour-flow imaging and pulsed wave Doppler ultrasonography to study the maternal circulation and the development of fetal vascularization in six Beagles during normal gestation. For the first time, the development of the circulation was demonstrated in the bitch and her fetuses intra vitam. The bloodstream was examined in small uteroplacental arteries, the umbilical artery, the fetal aorta and the common carotid artery. The duration of the study was from week 3 after insemination until birth. Relatively large vessels were detected by cross-sectional ultrasonography, and small vessels were detected by colour-flow imaging. In pulsed wave Doppler ultrasonography, the blood flow was measured and described using the parameters of systolic peak velocity, diastolic peak velocity, end-diastolic velocity, pulsatility index, resistance index, A:B ratio (systolic peak velocity:end-diastolic velocity) and S:D parameter (systolic peak velocity:diastolic peak velocity). The development of the measured parameters is typical and similar to that in humans. The systolic peak velocity of the canine maternal uteroplacental arteries shows important differences in comparison with humans. The pulsatility index, resistance index and A:B ratio decrease in nearly all vessels. Only the fetal common carotid artery has constant pulsatility and resistance indices during gestation. For the first time, the quality and quantity of the normal blood flow have been monitored during the whole of gestation. A normal circulation is fundamental for supplying the fetus adequately with oxygen and nutrients and thus for physiological development. These ultrasonographic results are the basis for further clinical studies.

Persistent primitive hypoglossal artery complicated by atrial septal defect and congenital intrahepatic shunts.

During early embryogenesis, anastomoses are formed between the carotid artery and the basilar or the vertebral artery, and subsequently, these anastomoses regress. In some cases, these anastomoses remain as persistent carotid-basilar or carotid-vertebral anastomoses. Atrial septal defect (ASD), a communication between the atria at the septal level, is a congenital heart anomaly. Intrahepatic venous shunts between the portal and hepatic veins are very rare and only some are considered congenital. We present the first case report of a patient with an ASD, a persistent primitive hypoglossal artery, and congenital portahepatic shunts.

Prediction of cerebral blood flow in fetal lambs by carotid artery ultrasonic flow transducer.

To determine whether common carotid artery blood flow measured with an ultrasonic flow transducer would predict brain blood flow in fetal sheep, we measured unilateral common carotid artery blood flow and compared this to simultaneous measurements of total brain blood flows made by radioisotope-labelled microsphere techniques. We studied anaesthetized, exteriorized fetal sheep with intact umbilical circulation after ligation of extracranial, extracerebral arteries and placement of a common carotid artery flow transducer; five fetuses at 120 d gestation had 19 total comparison measurements. As measured by microsphere technique, mean basal blood flow during undisturbed conditions to regional brain areas were similar to normal values reported for the exteriorized ovine fetus; these flows were highly correlated to fetal PaCO2 and successfully varied over a wide range (total brain 9.1-200.4 ml/min/100g and total cortex 6.1-153.1 ml/min/100g) in subsequent experimental conditions of hypercapnia or occluded blood flow. Blood flow as measured by flow transducer significantly correlated (P < or = 0.01) with microsphere measurements of blood flow to total brain (r = 0.56) and total cortex (r = 0.62); regional flow to cerebellum (r = 0.70) and thalamus (r = 0.60) also correlated to transducer measurements. Stronger correlations were observed at low-flow conditions to total brain (r = 0.83) and to total cortex (r = 0.90). As measured by microsphere technique, right and left cortical blood flows were highly correlated (P = 0.0001, r = 0.97), indicating that the flow transducer or surgical manipulation did not disturb the distribution of cerebral blood flow. The mean values for zero flow reference of the transducer were < 1.5% of mean basal flow values. It is concluded that the common carotid artery flow transducer technique developed in this study provides an accurate prediction of blood flow to total brain and total cortex over a wide range of values in fetal sheep. This technique provides a methodologic advantage to sequential experimental interventions and may prove advantageous to studies of fetal sheep cerebral circulation.

Electron microscopic study on the development of the carotid body and glomus cell groups distributed in the wall of the common carotid artery and its branches in the chicken.

Development of the carotid body and the glomus cell groups in the wall of the common carotid artery and its branches was studied in chickens at various developmental stages by electron microscopy. At 8 days of incubation, the carotid body anlage consisted of mesenchyme-like cells, whereas the clusters of epithelial cells, which occasionally contained a few dense-cored vesicles and were accompanied by unmyelinated nerve fibers, were located in the region surrounding the carotid body anlage and in the wall of the common carotid artery. Subsequently, the granule-containing cells together with nerve fibers were detected in the periphery of the carotid body anlage. At 12 days of incubation, a large number of granule-containing cells (glomus cells) were dispersed throughout the carotid body parenchyma and were also widely distributed along the common carotid artery and its branches. The cells frequently extended long cytoplasmic processes that made contact with other glomus cells and nerve fibers. Synaptic junctions which showed desmosome-like thickening of pre- and postsynaptic membranes and accumulations of small clear vesicles (around 50 nm in diameter) were first detected along the contact between the long axons and glomus cells at 12 days of incubation. In the wall of the common carotid artery, interdigitations between the cytoplasmic processes of glomus cells and smooth muscle cells began to form. Sustentacular cells investing partly the glomus cells were also discerned both in the carotid body and around the arteries at this stage. At 14 days of incubation, the glomus cells expressed most of the characteristics of the mature cells, and the synaptic junctions displaying afferent morphology appeared; the secretory granules of glomus cells were accumulated near and attached to the desmosome-like thickening of apposed membranes.

[A rare variation in the zone of the carotid artery]. / Eine seltene Variation im Bereich der Arteria carotis.

An extremely rare variation in the angioarchitecture of the carotid arteries consists in the complete missing of the right common carotid artery. The brachiocephalic trunc (innominate artery), forming a bulbus-like extension, branches out into three major stems: internal carotid artery, external carotid artery and the right subclavian artery. The variation is embryologically explainable: The aortic arches III and IV arise together (without ventral aortic root between them) from the persisting initial segment of the right ventral aorta.