Measurements on the grade of the human skull base and angle determinations]

1. The angle between the Os sphenoidale and the Clivus has been determined on 106 skulls. The mean was 117.68 degrees. 2. The altitude of the Foramen magnum with respect to the Frankfort plane was determined at -1.96 cm on the average. 3. The angle of inclination of the Foramen magnum to the Frankfort plane was determined from the altitude of the Basion and Opisthion and from the length of the Foramen magnum. The mean was -13.71 degrees. 4. In the inner base of the skull the altitudes of following structures have been determined: Planum sphenoidale (mean 2.34 cm), ground of the Fossa hypophysialis (1.32 cm), ground of the middle cranial fossa (-0.03 cm), ground of the posterior cranial fossa (-2.30 cm), upper edge of the Os petrosum (1.12 cm), Tuberculum jugulare (-0.21 cm), ground of the Meatus acusticus internus (0.45 cm). 5. In order to provide numerical data for the step-like building of the inner base of the skull, the differences between the altitudes of important structures from the inner base have been determined: Margo superior partis petrosae - Tuberculum jugulare (mean 1.35 cm). Opisthion - ground of the posterior cranial fossa (0.11 cm), Planum sphenoidale - ground of the middle cranial fossa (2.38 cm), ground of the middle cranial fossa - ground of the posterior cranial fossa (2.27 cm), Margo superior partis petrosae - ground of the posterior cranial fossa (3.35 cm), Margo superior partis petrosae - ground of the middle cranial fossa (1.15 cm).     

The significance of sesamoids and retro-articular processes for the mechanics of joints

Extensor muscles may insert by means of flexible tendons that wrap round the joint, through rigid sesamoids, or on to retro-articular processes. The three types of joint are examined, and equations are derived relating the force required in the muscle to the force exerted on the environment. A selection of mammalian joints are analysed to illustrate the theoretical conclusions.     

Function-dependent shape characteristics of the human skull

Using the FEM-program ANSYS 5.4, we have shaped a model of the human skull in which the flow of forces and the relative location and magnitudes of stresses are investigated. Forces are applied from below through the tooth row of the upper jaw. An ample volume is provided for the transmission of these bite forces upward to the roof of the braincase, where bearings counteract the forces from below. Within this volume, no other morphological features are considered than two cone-shaped orbits and a nasal channel which has a rounded, triangular cross section, extending upward between the orbits. Under loads (= bite forces) acting simultaneously in the directions and relative sizes of realistic bite- and chewing forces, there occurred stress concentrations inside the model which resemble closely the morphological characteristics of the human skull. The most remarkable pathways of stresses correspond to Toldt's and Benninghoff's nasal, zygomatic and pterygoid pillars. Aside from these stress concentrations, stress-free regions become visible at places, where the skull shows excavations: the vaulted palate with canalis incisivus, the canine fossa, superior and inferior orbital fissure, or cavities like the maxillary sinuses and cavum cranii. Behind the posterior molars and the pterygoid, the stresses disappear abruptly, and in the side wall of the nasal cavity a maxillary hiatus remains without stresses. A flow of forces comparable to, but not at the exact position of the zygomatic arch extends from the highly stressed zygomatic bone rearward and upward. In a later step of simulation, somewhat deeper, at the place of the really existing zygomatic arch, a series of small forces was applied, which correspond to the resultant force that is created by the redirection of the pull of the m. masseter into the temporal fascia. This--biologically reasonable--manipulation of the model leads to a reduction of the forces in the zygomatic bone, and to a downward shift of the zygomatic arch and its isolation from the skull's side wall by a deep, stress-free temporal fossa. The similarity between the stress flow in the model and the shape of the skull seems to indicate that the skull, like the bones of the postcranial skeleton, develops its shape in dependence from the mechanic stressing through the process of causal histogenesis. In view of experimental results, the possibility cannot be ruled out, that the safety factors in the skull deviate from those in the postcranial skeleton.     

Further study of the model of a human skull as a cupola with a plane base]

An experimental study of the base deformation of isolated human scull under conditions of scull collision with an obstacle has been carried out. The findings are compared with human cerebrospinal traums phenomena. An earlier suggested continuous scull model is modified on the basis of the data obtained. It is shown that the modified model (a part of spherical shell with the flat base) resembles scull behaviour in statics and dynamics better than the scull model in the form of spherical shell.     

Modulating effects of adenosine on the process of human platelet activation]

The inhibitory effect of adenosine on aggregation of human platelets activated by platelet activating factor (PAF), ADP and serotonin (5-HT) were examined using native platelets from blood of volunteers. Platelet aggregation was determined by Born's method. Effective adenosine concentrations (IC50) which had inhibited platelet aggregation were found to be 0.63 +/- 0.11, 1.47 +/- 0.31 and 0.64 +/- 0.18 microM, respectively. It was shown that 10 microM adenosine inhibited PAF-induced platelet aggregation completely. The same adenosine concentration blocked ADP- and 5-HT-induced aggregation only partially. Adenosine is physiological inhibitor of human platelet aggregation in administration of PAF, ADP and 5-HT. Specific characteristics of adenosine modulating effect on these ligands was elicited.     

Morphometric analysis of Cartesian coordinates of the human skull

A method for locating the three dimensional coordinates of cranial landmarks with respect to the Frankfort, midsagittal, and coronal planes is presented. Sliding calipers were used to obtain the distances from left and right porion and apex to each landmark, except for a few points where spreading calipers are required. In the present example, 35 landmarks (for a total of 105 measurements) were located for each of 35 Peruvian precolumbian skulls. These distances were entered into a program (SKULL) which calculates the Cartesian coordinates of each landmark. The XYZ coordinates of each landmark contain all the information necessary for calculation of the distances between any two landmarks, and these distances may also be obtained as output from program SKULL, if desired (595 distances if all 35 landmarks are used). Reliability of the location of coordinates was determined by comparing computed distances among selected landmarks from program SKULL with traditional anthropometric measurements. Satisfactory agreements were found. Direct multivariate analysis of the coordinates of the landmarks produced insights not available in traditional multivariate analysis of conventional anthropometric measurements.     

The osteogenic role of the dura mater in adult rabbits during regeneration of the skull]

It was shown in experiments with adult rabbits that the regeneration of skull vault bones after artificial trauma proceeds, mainly, at the expense of osteogenic activity of dura mater, rather than by means of outgrowth of bone from the defect margins. During regeneration, dura mater connects with the granulation tissue which fills the area of defect. The first bone islets are formed by the surface layer of dura mater near the defect margins and then all over the defect area. During regeneration bone islets merge with each other and with the old bone at the defect margins. In experiments with separation of the defect margins from dura mater by millipore filter, regeneration is insignificant over the filter near the old bone margins (bone trabeculae form which close destructed bone marrow cavities); the bone forms intensively under the filter on dura mater. In experiments with the removal of a piece of skull bone together with the adjacent region of dura mater, no bone regeneration occurs, the defect area is filled by the scar tissue.     

Hormonal stimulation of the reparative process in the skin or fats with vitamin A deficiency]

The effect of thyroid hormone on the regeneration of skin of A-deficient rats was studied. It was established that the reparative process in such animals was considerably retarded due to disturbances of the intensity and the character of the reaction. Under these conditions the succession of main stages of the regenerative process was maintained but there occurred a number of important qualitative and quantitative morphological disorders which substantially changed the course of healing of skin wounds. An additional injection of the thyroid hormone against this background had a favourable effect upon the skin regeneration but failed to produce a typical stimulating effect, characteristic of the hormonal agent in normality.     

The skull of Morganucodon

Morganucodon is a triconodont (atherian) mammal from the Lower Jurassic. Two species are described: M. oehleri from China and M. watsoni from Wales. The skull in M. walsoni is 26 mm long; M. oehleri is slightly larger. The dentition is differentiated functionally into incisors, canines, premolars and molars. The pineal foramen is closed. The prefrontals, postfrontals and postorbitals are lost. Septomaxilla, quadratojugal, tabular and pterygoid flanges are retained. The bony external nares are unpaired. The nasal cavity had the mammalian complement of turbinals. The posterior palate has ridges and troughs similar to those in tritylodonts, triconodonts and multituberculates. The alisphenoid ascending process is narrow and is not in contact with the anterior lamina of the petrosal, lying lateral to it. There is a cavum epiptericum, as in late therapsids. The anterior lamina forms the lateral braincase wall, perforated by the foramina pseudovale and pseudorotundum. There is a squamosal-dentary articulation, but the reptilian jaw joint is retained. The ear resembles that in later therapsids, with the tympanum in the lower jaw. The small quadrate was moveable, buttressed medially be a large stapes. Sound conduction from the tympanum was via articular, quadrate and stapes. The systematic position of Morganucodon is discussed.