Craniofacial growth under the influence of blood supply. 9. Skull and mandibular growth after carotid ligation

Unilateral ligature of the common carotid artery leads to a reduction in the size of the zygomatic arch complex in rats aged 8 and 12 months. Skull growth is accelerated during the 4th and 12th month in operated animals, so that these animals have large skulls than the controls at maturity. Comparison with the literature suggests that this is a result of over-compensation of the blood supply after the ligature. Increased availability of arterial blood also leads to greater axial growth of tubular bones. The lack of skull growth during the 8th month is discussed. The biomathematical methods of analysis used for these studies are of only limited validity for the observation of skull growth.     

Craniofacial growth under the influence of the blood supply. 12. Regulation of bone remodeling

Growth is controlled by phylogenetic and ontogenetic factors. Regulation of bone growth can be regarded as taking place at 3 levels, a high, general level at which genetics and hormones represent the main regulators, a middle, regional level where the vascular influence predominates, and a low, local level dominated by mechanical factors. Stresses within the bone, which under physiological conditions are in a state of dynamic equilibrium, play a significant role in the shaping of bony structures. The apposition or resorption of bony material is accelerated if such stresses exceed or drop below certain limits. Biophysically, bone is comparable to technical materials consisting mainly of hydroxyl apatite and collagen. Deformation of the hydroxyl apatite is associated with piezoelectric effects which induce changes in bone structure.     

Craniofacial growth under the influence of blood supply. 10. Arthrosis of the temporomandibular joint

Unilateral and bilateral deformation of the temporomandibular joint was observed in young rats after unilateral ligature of the common carotid artery. They involved both the mandibular condyle and the mandibular fossa and were usually associated with a reduction in the dry weight of the masticatory muscles on the ligated side. This leads to the assumption that muscular atrophy is causally related to arthropathy of the temporomandibular joint. The methodological approach to induce changes in the temporomandibular joint may be used as a model of arthrosis of that joint.     

Craniofacial growth under the influence of the blood supply. 6. Metric studies of the skull

Cephalometric data show that the distances spanning several skull bones also have the highest growth rates. No sexual dimorphism can be observed in the skulls of animals that are six weeks old; such differences do not appear until after the fourth month of life. Allometric studies reveal a relative narrowing of the neurocranium and a relative broadening of the rostrum and zygomatic arch. The broadening of the zygomatic arch complex is related to the postnatal development of the masseter muscle. Vector analysis is used to demonstrate the growth activities of the different parts of the skull. Local changes in the bone during growth was observed in the regions of muscle origin and attachment.     

Craniofacial growth under the influence of the blood supply. 14. Theoretical deductions and clinical conclusion

After eliminating the masticatory muscles as a growth factor in our animal model is was possible to analyze the blood supply to the skull in sufficient detail. The animal organism and its parts may be regarded as self-regulating, self-optimizing and self-adapting systems. Open systems exchange energy and material with their surroundings. This is typical of all organisms and, since growth is one of their properties, to growth. The processes of ossification and growth of the rat skull are therefore comparable in principle with those taking place in the human. The specific features of the chewing mechanism, in contrast, are not comparable. The clinical conclusions drawn from our model studies illustrate the importance of the blood supply for craniofacial growth while simultaneously demonstrating the compensation ability and adaptability of arteries and bones.     

Craniofacial growth under the influence of blood supply. 13. Local biomechanical aspects of bone morphogenesis

The origin of formative forces is to be sought in genetically controlled growth processes. The forces generated by various system components are analyzed. The forces acting in mutual opposition can be illustrated by considering the brain as an intracranial force factor and the temporalis muscle as an external force factor. Apposition and resorption of bone is governed by the interaction between the stresses. The skull's primary growth centres such as the basicranial synchondroses must, like epiphyses of tubular bones, exert growth forces to overcome the restraining forces stemming from surrounding tissues. Growth can be suppressed by excessive counter-pressure, diverted by asymmetrically acting forces, and encouraged by the removal of suppressive forces.     

Craniofacial growth under the influence of blood supply. 5. Brain weight after unilateral interruption of the common carotid artery

After unilateral ligature of the common carotid artery in rats aged 42 d, the fresh weight of the brain does not deviate from that associated with normal growth in the course of subsequent postnatal development. This is believed to be due to the age at which the ligature was applied and to arterial compensatory mechanisms. The sensitive phases of cerebral development have already come to an end 42 d post partum. Ligature of the right common carotid artery can be fully compensated by circulus arteriosus (Willis), which provides hemodynamic pressure compensation.     

Craniofacial growth modified by blood supply. 2. Changes in arterial cross sections and arterial blood supply

The cross sectional areas of arteries were calculated from their measured thicknesses. The monthly increase in size of the cross sectional area of the aorta is higher in both the controls and the operated animals between the 6th week and 4th month of life than during the subsequent period. The rate at which the cross sectional area of the aorta increased in operated animals was about twice that observed in the controls. The left common carotid artery increased its cross section in the operated animals most rapidly up to the fourth month. The cross sectional areas of all anastomoses increased five-fold by the 12th month of life. The quantities of blood flowing correlated closely with the angiometric values.     

Craniofacial growth modified by blood supply. 8. Discussion of normal cranial growth of the rat

The dimensions of the skull and the dry weight of the skull bones show definite sexual dimorphism. The dynamics of the growth in the skull dimensions and their vectorial presentation show that skull growth in Rattus norvegicus BERKENHOUT is most rapid between the 42nd d and the 4th month of life. This phase is followed by a phase of localized bone growth, which persists up to an age of 300 d. The faster growth of the viscerocranium leads to changes in the proportions of the skull. The relative positions of viscerocranium and mandible and the higher relative position of the dentures are similar to principle to those seen in man. Finally, the morphogenetic effect of the temporalis muscle together with that of the brain in the shaping of the skull are discussed.     

Craniofacial growth modified by the blood supply. 7. Dry weight of the skull and growth of the mandible

The dry weight of the skull and jaw bone increases faster in operated rats than in the controls during the fourth and 12 months, but their rates of growth do not differ in the 8th month. The distances measured on the mandible reveal definite sexual dimorphism in the development of the different lengths and heights, these distance being greater in the male rats. Growth in the length of the processes predominated over the growth of the body of the mandible. Local changes in the bone were observed at the points of origin and attachment of muscles.     

Craniofacial growth influenced by blood supply. 1. Collaterals and anastomoses following unilateral ligation of the common carotid artery

The influence of the blood supply on craniofacial growth was investigated in 396 albino rats (Rattus norvegicus Berkenhout). This was done by blocking the right common carotid artery of animals aged 42 d. The rats were slaughtered at previously specified intervals after the operation. The ligature led to dilation of the other major arteries of the neck. Numerous collaterals and anastomoses were also formed. These occurred on the ligature side in the flow region between the proximal and distal stumps of the right common carotid artery, between the flow regions of the right external carotid artery and the right vertebral artery and between the flow regions of the right subclavian artery and the right external carotid artery. Further anastomoses arose between the arteries of the other side, i.e. the rostral thyroid artery, lingual artery, submental artery and labial mandibular artery.     

The influence of blood supply on craniofacial growth. 4. Reactions of the jaw musculature

The dry weight of the chewing muscles differ distinctly between male and female. In rats aged 8 to 12 months the dry weight of the chewing muscles after ligature of the carotid artery was lower on the side of the ligature. Necrotic fibres were occasionally found in the masseter muscle on the ligature side. Morphometric investigation of the masseter muscle fibres revealed no significant differences between the 2 sides in the operated rats. Since the rats were relatively young when the commune carotid artery was ligatured unilaterally, the consequences of the initially reduced blood supply to the chewing muscles on the right side could be compensated for rather well, mainly by the enlargement of previously existing anastomoses. Our quantitative and histological studies nevertheless show that muscular dysbalance of the masticatory apparatus was severe.     

The effect of a modified blood supply on the craniofacial growth of the rabbit. 4. Skull and lower jaw asymmetry

Using a microscopic measuring method we were able to detect minor regions of asymmetry in the zygomatic arches of rabbits in which the common carotid artery had been ligated. These are considered in connection with the (also slight) asymmetric gains in the dry weight of the muscles of mastication in the ligated animals (see 2nd Bulletin).     

The effect of a modified blood supply on the craniofacial growth of rabbits. 3. Skull and mandible: general size development

This report deals with the growth of the skull and lower jaw after unilateral ligation of the common carotid artery in juvenile rabbits. No differences that could be attributed to the operation were found between the animals with ligated carotids and the control animals.     

Craniofacial growth modified by blood supply. 3. Adaptation of the cranial arteries following unilateral ligation of the common carotid artery. Discussion of findings of the 1st and 2d communication

Ligature of the right common carotid artery induces compensatory dilatation of the arteries of the head and neck, and particularly of the left common carotid artery. Functional mechanisms also caused dilatation of the arterioles. The enlargement of previously formed anastomoses and collaterals was also observed. Angiophysical effects and histochemical phenomena are implicated in the modification of previously existing anastomoses. The transport capacity of the collaterals increases as the area of the summated lumena increases and as the length of the vascular pathways decreases. The time factor, finally, also plays an important in role the formation of anastomoses, which continues even after an observation period of 12 months in the rat.     

Avian cerebral blood flow: influence of the Bohr effect on oxygen supply.

To clarify the problems of altitude tolerance in birds, we studied the combined effect of hypocapnia and hypoxia on cerebral blood flow (CBF) in ducks. CBF was measured by the xenon clearance method. Normocapnic hypoxia causes CBF to increase when the arterial O2 tension (PaO2) falls below 60--70 mmHg. Hypocapnic hypoxia significantly shifts the blood flow curve so that blood flow does not increase until a lower PaO2 (50--60 mmHg) is reached. This gives the appearance that hypocapnia suppresses the hypoxia-induced increase in CBF. However, due to the Bohr effect, the hypocapnic blood contains significantly more O2 than does the normocapnic blood at the same PaO2. Therefore, when CBF is expressed as a function of O2 content, rather than PO2, CBF in the hypocapnic group does not differ significantly from the CBF in the normocapnic group. We interpret this to mean that because of the significantly greater oxygen content of the hypocapnic blood at a given PaO2, the degree of hypoxia experienced by these brains is not as severe as that experienced by the normocapnic brains.     

The blood supply of the brain under conditions of craniocerebral hypothermia

Summary Investigations were conducted on adult mongrel dogs. Hypothermia was created by chilling the brain through the surface coverings of the head, using a freon hypothermic apparatus. A pump-flow meter was used to record the amount of blood flowing out of the brain.The cerebral blood supply dropped with reduction of the temperature of the animals. This reduction was more manifest (19 ml/min per degree, on the average) with decrease of the brain temperature to 31–30°C. Further changes in the jugular vein circulation were less significant (averaging 3.1 ml/min per degree). At a temperature of 23–22°C, the average volume of the blood flow constituted 30% of the initial value.With normalization of the animals' temperature, the blood supply of the brain was restored.(Presented by Active Member of the Academy of Medical Sciences USSR, V. V. Parin) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 57, No. 2, pp. 41–44, February, 1964     

The effect of a modified blood supply on the craniofacial growth of rabbits. 2. Masticatory muscles

After ligation of the right common carotid artery, the dry weight of the muscles of mastication on the ligated side did not differ from that of the control animals between the 45th and 225th d of life. On the opposite side, however, the muscles were in some cases significantly heavier than those of the control animals, particularly in male rabbits with ligated common carotid arteries. The methodical application of these results is proposed.     

Arterial blood supply of the maxillary sinus.

Knowledge of the arterial supply of the maxillary sinus region is essential for surgical treatment in this area (e.g., implantation of grafting materials, repair of injuries, sinus floor elevation). The goal of this study was to describe the arterial architecture of the maxillary sinus region in respect to sinus lift procedures. In 18 unfixed human cadavers, the arterial vessels of the head were injected with a mixture of latex and barium sulfate. Afterward, the arteries entering the maxilla were prepared. The number and calibers as well as anastomoses were carefully documented. In addition, we measured the distance between the alveolar ridge and the lower main branches. The arterial supply of the maxilla originated from the posterior superior alveolar artery as well as from the infraorbital artery. In all specimens we found an intraosseous anastomosis between these two vessels. The oral mucosa in the area of interest is supplied by the posterior superior alveolar artery and the infraorbital artery, and an extraosseous anastomosis was found in 44% of our cases. The two anastomoses build up a double arterial arcade, supplying the lateral wall of the antrum and parts of the alveolar process.