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Per Erik Ahlberg - One of the best experts on this subject based on the ideXlab platform.
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Endocranial cavity of the braincase of Romundina stellina [7], specimen MNHN.F.CPW1.
2017Co-Authors: Vincent Dupret, Sophie Sanchez, Daniel Goujet, Per Erik AhlbergAbstract:A1-2. Perichondral bone of the neurocranium and the endocranial cavity (A1) with inner ears and right endolymphatic duct (A2) in dorsal view; the Perichondral bone underlying the paranuchal plates has been digitally removed for clarity. A3-4. Dermal bone of the skull roof and Perichondral bone of the endocranial cavity (A3) with the inner ears and right endolymphatic duct (A4) in ventral view. B-C. Endocranial cavity and cranial nerve canals in dorsal (B) and ventral (C) views. The endocranial cavity has been digitally filled in black in order to clarify the lace pattern of the Perichondral bone (otherwise obscured by the visual interaction between the dorsal and ventral sides of the cavity). Scale bars are 2 mm in length.
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The internal cranial anatomy of Romundina stellina Ørvig, 1975 (Vertebrata, Placodermi, Acanthothoraci) and the origin of jawed vertebrates—Anatomical atlas of a primitive gnathostome - Fig 15
2017Co-Authors: Vincent Dupret, Sophie Sanchez, Daniel Goujet, Per Erik AhlbergAbstract:Virtual X-ray slide in the otic (A) and occipital (B) areas of Romundina stellina [7], specimen MNHN.F.CPW1. The lace pattern observed in the internal Perichondral bone structures is not related to the distance to the dermal bone. White arrows indicate vascular canals at the boundary between dermal and Perichondral bone layers.
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Skull roof and external aspect of the braincase of Romundina stellina [7], specimen MNHN.F.CPW1.
2017Co-Authors: Vincent Dupret, Sophie Sanchez, Daniel Goujet, Per Erik AhlbergAbstract:A1-2. Skull roof (orange) and Perichondral bone cover of the braincase (EPB in the text; light pink) in dorsal (A1) and ventral (A2) views. A3-4. Perichondral bone cover of the braincase in dorsal (A3) and ventral views (A4), with emphasis on the different areas of the neurocranium. The Perichondral bone underlying the paranuchal plates has been removed. Notice the oblique crack (that also provoked the collapse of the medial wall of the right orbit), and the incompleteness of the braincase floor. B. Neurocranium in ventral view (the Perichondral bone underlying the paranuchal plates has been removed). C. Skull roof and neurocranium (premedian-ethmoid and orbital areas) in anterior view, slightly dorsal (the lateral semicircular canal is horizontal). D. Skull roof and neurocranium (premedian-ethmoid and orbital areas) in left anterodorsolateral view. E. Skull roof and neurocranium (premedian-ethmoid and orbital areas) in left anterolateral view. F. Skull roof and neurocranium (premedian-ethmoid, orbital and partly otic areas) in right lateral view. Scale bars are 2 mm in length.
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Dermal skull roof and blood vessels of Romundina stellina [7], specimen MNHN.F.CPW1. and occipital area of the braincase.
2017Co-Authors: Vincent Dupret, Sophie Sanchez, Daniel Goujet, Per Erik AhlbergAbstract:A. Dermal skull roof in ventral view. B. Semitransparent dermal skull roof in dorsal view, showing the small canals transmitting nerve branches to the lateral line grooves (green) and the outline of the underlying cranial cavity. C. Vasculature of the skull roof in dorsal view. Scale bars are 2 mm in length. D, E. Occipital area of the neurocranium in posterior (C) and left posterolateral (D) views. In order to clarify the figure, the Perichondral bone layer under the paranuchal plates (except for Fig 3E, right side) and the parts anterior to the occipital area have been obliterated. White arrows indicate vascular canals at the boundary between dermal and Perichondral bone layers; asterisk indicates radiating centre of nuchal plate. Scale bars are 2 mm in length.
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Nervous system of Romundina stellina [7], specimen MNHN.F.CPW1.
2017Co-Authors: Vincent Dupret, Sophie Sanchez, Daniel Goujet, Per Erik AhlbergAbstract:Filled endocranial cavity and nerve canals and grooves (yellow); Perichondral bone in transparent pink. A. Dorsal view. B. Ventral view. C. Left oblique anterolateral slightly dorsal view (only portion anterior to the oblique crack is presented). D. Right oblique anterolateral slightly dorsal view. Scale bars are 2 mm in length.
Michael W. Caldwell - One of the best experts on this subject based on the ideXlab platform.
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Modified Perichondral ossification and the evolution of paddle-like limbs in ichthyosaurs and plesiosaurs
Journal of Vertebrate Paleontology, 1997Co-Authors: Michael W. CaldwellAbstract:ABSTRACT Evolution of paddle-like limbs in ichthyosaurs and plesiosaurs is correlated with loss of Perichondral bone from the shafts of long bones. Among ichthyosaurs, loss of Perichondral bone is first observed on the shafts of digit bones of Early Triassic taxa. Late Triassic ichthyosaurs show Perichondral bone loss on the postaxial margins of the ulna and fibula. Among plesiosaurs, loss of Perichondral bone is first observed on the postaxial margins of the ulna and fibula of Lower Jurassic taxa. In geologically later species of both groups, Perichondral bone is progressively lost on all margins of the ulna and radius, and fibula and tibia. Late Triassic and Jurassic ichthyosaurs show an absence of Perichondral ossifications on all limb bones distal to the humerus and femur. Delayed ossification of the mesopodium is not observed in ichthyosaurs. Evolutionary changes to the ossification of Perichondral tissues appear to affect the sequence of limb ossification as long bones lose Perichondral bone. Limb b...
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Limb osteology and ossification patterns in Cryptoclidus (Reptilia: Plesiosauroidea) with a review of sauropterygian limbs
Journal of Vertebrate Paleontology, 1997Co-Authors: Michael W. CaldwellAbstract:ABSTRACT Limb osteology and ontogenetic patterns of limb ossification are described for the plesiosaur Cryptoclidus eurymerus (Upper Jurassic: Callovian), and compared to those of other sauropterygians. Major features of limb ossification in Cryptoclidus are identified: 1) delayed mesopodial ossification; 2) alterations to the ossification sequence of the radius/ulna, tibia/fibula, and some metacarpals and metatarsals; 3) the loss of Perichondral bone from the margins of the radius/ulna, tibia/fibula, and some metacarpals and metatarsals; 4) altered bone morphology is correlated with loss of Perichondral bone. Recognition of some of these features in basal sauropterygians, and their application to the study of limb elements in derived sauropterygians such as Cryptoclidus, alters traditional identifications of several bones. The conventional intermedium is re-identified as a centrale. The ‘true’ intermedium is found to be a small bone that is variably free, ossifies to the base of the radius forming a dist...
Dennis R Carter - One of the best experts on this subject based on the ideXlab platform.
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Skeletal Function and Form: Perichondral and Periosteal Ossification
Skeletal Function and Form, 2000Co-Authors: Dennis R Carter, Gary S. BeaupreAbstract:Bone Formation The flat bones of the skull and face are formed by intramembranous ossification within a condensation of cells derived from the neural crest. In the limb bones and most of the postcranial skeleton, however, mesenchymal cell condensations chondrify, creating the endoskeletal cartilage anlagen. These cartilage rudiments form the templates of the future skeleton and subsequently, in the process of growth, undergo a bony transformation. The anlagen of the skeleton in early development are small, avascular rudiments consisting of chondrocytes surrounded by an extracellular matrix (Figure 3.13). The largest and most mature chondrocytes in most rudiments are found in the central region of the diaphysis. The cells in the center are surrounded by more extracellular matrix than those at the rudiment ends, leading to a low cell density. In most rudiments this area becomes the center of growth and ossification. Cartilage growth occurs by mitosis, a net increase in the amount of extracellular matrix, and an increase in cell size. In the end stages of growth in a cartilage region, the cells hypertrophy and die as the extracellular matrix is calcified and then replaced by well-vascularized bone tissue. The cartilage cells within the rudiments therefore undergo a characteristic process of cell proliferation, maturation, hypertrophy, and death, followed by matrix calcification and ossification. Variations in the cartilage growth and ossification rates in different directions within the anlage result in shape changes of developing bones. Five different phases of cartilage growth and differentiation during long bone ossification were described by Streeter (Streeter, 1949) (Figure 4.1).
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skeletal function and form mechanobiology of skeletal development aging and regeneration
2000Co-Authors: Dennis R Carter, Gary S. BeaupreAbstract:Preface 1. Form and function 2. Skeletal tissue histomorphology and mechanics 3. Cartilage differentiation and growth 4. Perichondral and periosteal ossification 5. Endochondral growth and ossification 6. Cancellous bone 7. Skeletal tissue regeneration 8. Articular cartilage development and destruction 9. Mechanobiology in skeletal evolution 10. The physical nature of living things Appendix A. Material characteristics Appendix B. Structural characteristics Appendix C. Failure characteristics Index.
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epigenetic mechanical factors in the evolution of long bone epiphyses
Zoological Journal of the Linnean Society, 1998Co-Authors: Dennis R Carter, Borjana Mikic, Kevin PadianAbstract:Abstract In developing vertebrate long bones in which endochondral ossification occurs, it is preceded or accompanied by Perichondral ossification. The speed and extent of Perichondral apposition relative to endochondral ossification varies in different taxa. Perichondral ossification dominates early long bone development in extinct basal tetrapods and dinosaurs, extant bony fish, amphibians, and birds. In mammals and lizards, Perichondral and endochondral ossification proceed more synchronously. One of the most important epigenetic factors in skeletogenesis is mechanical loading caused by muscle contractions which begin in utero or in ovo . It has been previously shown that the stress distributions created perinatally in the chondroepiphysis during human skeletal development can influence the appearance of secondary ossification centres. Using finite element computer models representing bones near birth or hatching, we demonstrate that in vertebrates in which Perichondral ossification significantly precedes endochondral ossification, the distribution of mechanical stresses in the ossifying cartilage anlagen tends to inhibit the appearance of secondary ossification centres in the ends of long bones. In models representing vertebrates in which endochondral ossification keeps pace with Perichondral apposition, the appearance of secondary centres is promoted. The appearance of secondary centres leads to the formation of bony epiphyses and growth plates, which are most common in mammals and extant lizards. We postulate that genotypic factors influencing the relative speed and extent of Perichondral and endochondral ossification interact with mechanical epigenetic factors early in development to account for many of the morphological differences observed in vertebrate skeletons.
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regular articleepigenetic mechanical factors in the evolution of long bone epiphyses
Zoological Journal of the Linnean Society, 1998Co-Authors: Dennis R Carter, Borjana Mikic, Kevin PadianAbstract:In developing vertebrate long bones in which endochondral ossification occurs, it is preceded or accompanied by Perichondral ossification. The speed and extent of Perichondral apposition relative to endochondral ossification varies in different taxa. Perichondral ossification dominates early long bone development in extinct basal tetrapods and dinosaurs, extant bony fish, amphibians, and birds. In mammals and lizards, Perichondral and endochondral ossification proceed more synchronously. One of the most important epigenetic factors in skeletogenesis is mechanical loading caused by muscle contractions which beginin uteroorin ovo. It has been previously shown that the stress distributions created perinatally in the chondroepiphysis during human skeletal development can influence the appearance of secondary ossification centres. Using finite element computer models representing bones near birth or hatching, we demonstrate that in vertebrates in which Perichondral ossification significantly precedes endochondral ossification, the distribution of mechanical stresses in the ossifying cartilage anlagen tends to inhibit the appearance of secondary ossification centres in the ends of long bones. In models representing vertebrates in which endochondral ossification keeps pace with Perichondral apposition, the appearance of secondary centres is promoted. The appearance of secondary centres leads to the formation of bony epiphyses and growth plates, which are most common in mammals and extant lizards. We postulate that genotypic factors influencing the relative speed and extent of Perichondral and endochondral ossification interact with mechanical epigenetic factors early in development to account for many of the morphological differences observed in vertebrate skeletons.
Jean-yves Sire - One of the best experts on this subject based on the ideXlab platform.
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Development of cartilage and bone tissues of the anterior part of the mandible in cichlid fish : a light and TEM study
The Anatomical record, 1992Co-Authors: Ann Huysseune, Jean-yves SireAbstract:The present paper presents ultrastructural details of chondrogenesis of Meckel's cartilage and of ossification of its associated peri- and parachondral bones in a teleost fish, the cichlid Hemichromis bimaculatus. We have distinguished four stages during chondrogenesis, each of which is characterized by specific cellular and matrix features: blastema, primordium, differentiated cartilage and cartilage surrounded by Perichondral bone. The blastema is characterized by prechondroblasts and the lack of cartilage matrix; the primordium by chondroblasts and the onset of secretion of matrix of fibrillar and granular nature; differentiated cartilage is characterized by chondrocytes and larger amounts of typical hyaline cartilage matrix. Once Perichondral bone is laid down, the chondrocytes show degenerative features but not true hypertrophy. Differentiation of the cartilage cells is attended with cytoplasmic changes indicative of an increasing secretory activity. There is a regional calcification of the cartilage matrix by fusion of calcospherites. Chondrogenesis of the symphyseal area is continuous with that of the rami but starts slightly later. Formation of Perichondral bone at the cartilage surface is attended with the deposition of a transitional zone apparently containing a mixture of the two matrices. The role of the Perichondral cells is discussed and it is proposed that they may contribute to the formation of the two matrices. The transitional zone may then result either from a diffusion process or from the simultaneous deposition of elements of the two matrices. Growth of the cartilage is argued to be largely the result of matrix secretion, except in the symphyseal area where appositional growth probably occurs until the region is completely covered by Perichondral bone. This paper provides a basis for further studies on the developmental interactions between cartilage, bone and teeth during mandibular development in cichlids. © 1992 Wiley-Liss, Inc.
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Bone and cartilage resorption in relation to tooth development in the anterior part of the mandible in cichlid fish: a light and TEM study.
The Anatomical record, 1992Co-Authors: Ann Huysseune, Jean-yves SireAbstract:This paper presents ultrastructural features of the contact region between particular tooth germs and Meckel's cartilage prior to, during, and after initial resorption of the Perichondral bone and of the cartilage in the cichlids Hemichromis bimaculatus and Astatotilapia burtoni. Imminent resorption opposite such teeth is announced by the presence, in this region, of a particular cell type, considered to be a stage in the cytodifferentiation of osteoclasts. Slightly later, an osteoclast with typical ruffled border is seen to open a fenestra in the Perichondral bone which surrounds Meckel's cartilage. Although the action of the osteoclast is directed primarily towards the bone, it may also affect, to a much lesser extent, the underlying uncalcified cartilage. Typically, fibroblast-like cells invade the resorption cavity along with the osteoclast; the tooth germ soon follows. Capillaries are seen to invade the cartilage only at a later stage when a large cavity has been established. It is proposed that the fibroblast-like cells may have a dual function: degradation of cartilage and deposition of new bone. Although these processes are normally limited to the area surrounding tooth germs at specific loci, tooth germs in other positions may sometimes be seen to invade the cartilage. They do so either passively, because of the existence of such a cavity, or as a result of their own resorption-inducing activity. Whatever the mechanism, attachment bone is being deposited within the erosion cavity and on the surface of the exposed Perichondral bone. The stimuli possibly eliciting resorption of Meckel's cartilage are discussed. It is hypothesized that pressure exerted by the growing tooth germ may stimulate the osteoblasts covering the bone surface and, in this way, provoke osteoclastic bone resorption. © 1992 Wiley-Liss, Inc.
Vincent Dupret - One of the best experts on this subject based on the ideXlab platform.
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Endocranial cavity of the braincase of Romundina stellina [7], specimen MNHN.F.CPW1.
2017Co-Authors: Vincent Dupret, Sophie Sanchez, Daniel Goujet, Per Erik AhlbergAbstract:A1-2. Perichondral bone of the neurocranium and the endocranial cavity (A1) with inner ears and right endolymphatic duct (A2) in dorsal view; the Perichondral bone underlying the paranuchal plates has been digitally removed for clarity. A3-4. Dermal bone of the skull roof and Perichondral bone of the endocranial cavity (A3) with the inner ears and right endolymphatic duct (A4) in ventral view. B-C. Endocranial cavity and cranial nerve canals in dorsal (B) and ventral (C) views. The endocranial cavity has been digitally filled in black in order to clarify the lace pattern of the Perichondral bone (otherwise obscured by the visual interaction between the dorsal and ventral sides of the cavity). Scale bars are 2 mm in length.
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The internal cranial anatomy of Romundina stellina Ørvig, 1975 (Vertebrata, Placodermi, Acanthothoraci) and the origin of jawed vertebrates—Anatomical atlas of a primitive gnathostome - Fig 15
2017Co-Authors: Vincent Dupret, Sophie Sanchez, Daniel Goujet, Per Erik AhlbergAbstract:Virtual X-ray slide in the otic (A) and occipital (B) areas of Romundina stellina [7], specimen MNHN.F.CPW1. The lace pattern observed in the internal Perichondral bone structures is not related to the distance to the dermal bone. White arrows indicate vascular canals at the boundary between dermal and Perichondral bone layers.
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Skull roof and external aspect of the braincase of Romundina stellina [7], specimen MNHN.F.CPW1.
2017Co-Authors: Vincent Dupret, Sophie Sanchez, Daniel Goujet, Per Erik AhlbergAbstract:A1-2. Skull roof (orange) and Perichondral bone cover of the braincase (EPB in the text; light pink) in dorsal (A1) and ventral (A2) views. A3-4. Perichondral bone cover of the braincase in dorsal (A3) and ventral views (A4), with emphasis on the different areas of the neurocranium. The Perichondral bone underlying the paranuchal plates has been removed. Notice the oblique crack (that also provoked the collapse of the medial wall of the right orbit), and the incompleteness of the braincase floor. B. Neurocranium in ventral view (the Perichondral bone underlying the paranuchal plates has been removed). C. Skull roof and neurocranium (premedian-ethmoid and orbital areas) in anterior view, slightly dorsal (the lateral semicircular canal is horizontal). D. Skull roof and neurocranium (premedian-ethmoid and orbital areas) in left anterodorsolateral view. E. Skull roof and neurocranium (premedian-ethmoid and orbital areas) in left anterolateral view. F. Skull roof and neurocranium (premedian-ethmoid, orbital and partly otic areas) in right lateral view. Scale bars are 2 mm in length.
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Dermal skull roof and blood vessels of Romundina stellina [7], specimen MNHN.F.CPW1. and occipital area of the braincase.
2017Co-Authors: Vincent Dupret, Sophie Sanchez, Daniel Goujet, Per Erik AhlbergAbstract:A. Dermal skull roof in ventral view. B. Semitransparent dermal skull roof in dorsal view, showing the small canals transmitting nerve branches to the lateral line grooves (green) and the outline of the underlying cranial cavity. C. Vasculature of the skull roof in dorsal view. Scale bars are 2 mm in length. D, E. Occipital area of the neurocranium in posterior (C) and left posterolateral (D) views. In order to clarify the figure, the Perichondral bone layer under the paranuchal plates (except for Fig 3E, right side) and the parts anterior to the occipital area have been obliterated. White arrows indicate vascular canals at the boundary between dermal and Perichondral bone layers; asterisk indicates radiating centre of nuchal plate. Scale bars are 2 mm in length.
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Nervous system of Romundina stellina [7], specimen MNHN.F.CPW1.
2017Co-Authors: Vincent Dupret, Sophie Sanchez, Daniel Goujet, Per Erik AhlbergAbstract:Filled endocranial cavity and nerve canals and grooves (yellow); Perichondral bone in transparent pink. A. Dorsal view. B. Ventral view. C. Left oblique anterolateral slightly dorsal view (only portion anterior to the oblique crack is presented). D. Right oblique anterolateral slightly dorsal view. Scale bars are 2 mm in length.