Imaging of Regional Injuries: The Axial Skeleton — the Skull, Vertebral Column, and Thoracic Cage

The axial skeleton develops from the sclerotome, a mesenchymal cell mass derived from the ventral halves of the somites, segmentally repeated units located on either side of the neural tube. Cells from the medial part of the sclerotome form the axial perichondral tube, which gives rise to vertebral bodies and intervertebral discs; the lateral regions of the sclerotome will form the vertebral arches and ribs. Mesenchymal sclerotome cells condense and differentiate into chondrocytes to form a cartilaginous pre-skeleton that is later replaced by bone tissue. Uncx4.1 is a paired type homeodomain transcription factor expressed in a dynamic pattern in the somite and sclerotome. Here we show that mice homozygous for a targeted mutation of the Uncx4.1 gene die perinatally and exhibit severe malformations of the axial skeleton. Pedicles, transverse processes and proximal ribs, elements derived from the lateral sclerotome, are lacking along the entire length of the vertebral column. The mesenchymal anlagen for these elements are formed initially, but condensation and chondrogenesis do not occur. Hence, Uncx4.1 is required for the maintenance and differentiation of particular elements of the axial skeleton.

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The locomotor system

Anatomy for Dental Students ◽

10.1093/oso/9780199234462.003.0008 ◽

2013 ◽

Author(s):

Martin E. Atkinson

Keyword(s):

Vertebral Column ◽

Cervical Vertebrae ◽

Lumbar Vertebrae ◽

Posterior Wall ◽

Axial Skeleton ◽

Intervertebral Discs ◽

Central Canal ◽

The Body ◽

Thoracic Vertebrae ◽

Locomotor System

The locomotor system comprises the skeleton, composed principally of bone and cartilage, the joints between them, and the muscles which move bones at joints. The skeleton forms a supporting framework for the body and provides the levers to which the muscles are attached to produce movement of parts of the body in relation to each other or movement of the body as a whole in relation to its environment. The skeleton also plays a crucial role in the protection of internal organs. The skeleton is shown in outline in Figure 2.1A. The skull, vertebral column, and ribs together constitute the axial skeleton. This forms, as its name implies, the axis of the body. The skull houses and protects the brain and the eyes and ears; the anatomy of the skull is absolutely fundamental to the understanding of the structure of the head and is covered in detail in Section 4. The vertebral column surrounds and protects the spinal cord which is enclosed in the spinal canal formed by a large central canal in each vertebra. The vertebral column is formed from 33 individual bones although some of these become fused together. The vertebral column and its component bones are shown from the side in Figure 2.1B. There are seven cervical vertebrae in the neck, twelve thoracic vertebrae in the posterior wall of the thorax, five lumbar vertebrae in the small of the back, five fused sacral vertebrae in the pelvis, and four coccygeal vertebrae—the vestigial remnants of a tail. Intervertebral discs separate individual vertebrae from each other and act as a cushion between the adjacent bones; the discs are absent from the fused sacral vertebrae. The cervical vertebrae are small and very mobile, allowing an extensive range of neck movements and hence changes in head position. The first two cervical vertebrae, the atlas and axis, have unusual shapes and specialized joints that allow nodding and shaking movements of the head on the neck. The thoracic vertebrae are relatively immobile. combination of thoracic vertebral column, ribs, and sternum form the thoracic cage that protects the thoracic organs, the heart, and lungs and is intimately involved in ventilation (breathing).

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Chondrification and osteological development of vertebral column in tadpoles of Microhyla ornata

Amphibia-Reptilia ◽

10.1163/156853889x00467 ◽

1989 ◽

Vol 10 (3) ◽

pp. 321-329

Author(s):

D. Dey ◽

S.K. Dutta ◽

P. Mohanty-Hejmadi

Keyword(s):

Vertebral Column ◽

Axial Skeleton ◽

Differential Staining ◽

Stages Of Development ◽

Early Stages ◽

Osteological Development

AbstractChondrification and osteological development of vertebral column in the ornate frog, Microhyla ornata tadpoles has been studied by differential staining. At early stages of development the bones of vertebral column develop as cartilaginous structures. At different stages after chondrification, ossification starts in different components of the axial skeleton. The vertebral column ossifies between Taylor-Kollros stages XV and XXV. Chondrification as well as ossification occur proximodistally.

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An associated partial skeleton of Symbos cavifrons (Artiodactyla: Bovidae) from Montezuma County, Colorado

Journal of Paleontology ◽

10.1017/s0022336000029164 ◽

1987 ◽

Vol 61 (4) ◽

pp. 831-843 ◽

Cited By ~ 3

Author(s):

Jerry N. Mcdonald ◽

Sarah W. Neusius ◽

Vickie L. Clay

Keyword(s):

United States ◽

Vertebral Column ◽

Cervical Vertebrae ◽

Axial Skeleton ◽

The Third ◽

New Information ◽

Four Corners ◽

Loess Deposition ◽

Complete Set ◽

Definition Of

A partial cranium and axial skeleton of an individual Symbos cavifrons were excavated in 1983 from the Mesa Verde Loess on Grass Mesa, Montezuma County, Colorado. Parts of at least 24 bones were recovered, including the first complete set of cervical vertebrae known for Symbos cavifrons. This individual, radiocarbon dated at 15,970 ± 155 yr B.P. (SI-6137), contributes to the definition of the southwestern edge of the range of the species and provides new information about the nature of the vertebral column. Pathologic constriction of the transverse canals is evident in the third and seventh cervical vertebrae. The pattern of bone distribution suggests that carnivores consumed part of this animal. The radiocarbon date also establishes the last major episode of loess deposition in the Four Corners region of the southwestern United States.

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Comparative osteology of the axial skeleton of the genus Pampus (Family: Stromateidae, Perciformes)

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315416000369 ◽

2016 ◽

Vol 97 (2) ◽

pp. 277-287 ◽

Cited By ~ 3

Author(s):

Laith A. Jawad ◽

Liu Jig

Keyword(s):

Vertebral Column ◽

Axial Skeleton ◽

Caudal Fin ◽

Fin Rays ◽

Osteological Characters ◽

Comparative Osteology

Seven osteological characters of the axial skeleton are studied in the eight species of the genus Pampus. The characters include: pattern of interdigitation of the dorsal- and anal-fin pterygiophores with the neural and haemal spines of the vertebrae, structure of the vertebral column, distribution of the dorsal- and ventral- procurrent caudal-fin rays, distribution of the principal caudal-fin rays and the morphology of the caudal-fin skeleton. All these features appear to be useful in the characterization of the eight species of the genus Pampus. Formulae for the structure of the vertebral column, the dorsal- and anal-fin pterygiophores’ interdigitation with the neural and haemal spines of the vertebrae, distribution of the dorsal and ventral procurrent caudal-fin rays, and distribution of the principal caudal-fin rays were developed. Pampus nozawae was recently considered a synonym of P. argenteus. However, according to the characters used in the present study, this species is notably distinct from P. argenteus.

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Of Necks, Trunks and Tails: Axial Skeletal Diversity among Vertebrates

Diversity ◽

10.3390/d13070289 ◽

2021 ◽

Vol 13 (7) ◽

pp. 289

Author(s):

Moisés Mallo

Keyword(s):

Morphological Traits ◽

Vertebral Column ◽

Axial Skeleton ◽

Morphological Features ◽

Individual Species ◽

Vertebrate Species ◽

Genetic Origin ◽

Vertebral Number ◽

The Impact ◽

Skeletal Diversity

The axial skeleton of all vertebrates is composed of individual units known as vertebrae. Each vertebra has individual anatomical attributes, yet they can be classified in five different groups, namely cervical, thoracic, lumbar, sacral and caudal, according to shared characteristics and their association with specific body areas. Variations in vertebral number, size, morphological features and their distribution amongst the different regions of the vertebral column are a major source of the anatomical diversity observed among vertebrates. In this review I will discuss the impact of those variations on the anatomy of different vertebrate species and provide insights into the genetic origin of some remarkable morphological traits that often serve to classify phylogenetic branches or individual species, like the long trunks of snakes or the long necks of giraffes.

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Desarrollo osteológico de la columna vertebral y del complejo caudal de larvas de Lutjanus guttatus (Perciformes: Lutjanidae) en condiciones de cultivo

Revista de Biología Tropical ◽

10.15517/rbt.v63i1.14648 ◽

2015 ◽

Vol 63 (1) ◽

pp. 155

Author(s):

Luz Estela Rodríguez-Ibarra

Keyword(s):

Vertebral Column ◽

Bone Structure ◽

Axial Skeleton ◽

Laboratory Culture ◽

Culture Conditions ◽

Feeding Rates ◽

Alizarin Red ◽

Caudal Region ◽

Abdominal Region ◽

Caudal Complex

The spotted rose snapper (Lutjanus guttatus) is an important commercial species in Mexico with good culture potential. The osteological study at early stages in this species is an important tool to confirm normal bone structure and for the detection of malformations that may occur during early development. This study was carried out in order to evaluate and describe the normal osteological development of the vertebral column and caudal complex of this species grown under controlled conditions. For this, a total of 540 larvae of L. guttatus, between 2.1 and 17.5mm of total length (TL), were cultured during 36 days; culture conditions were 28ºC, 5.74mg/L oxygen and 32.2ups salinity with standard feeding rates. To detect growth changes, a sample of 15 organisms was daily taken from day one until day 36 of post-hatch (DPH). Samples were processed following standard techniques of clearing, and cartilage (alcian blue) and bone staining (alizarin red). Results showed that the vertebral column is composed of nine vertebrae in the abdominal region, and 14 vertebrae including the urostyle in the caudal region. The development of the axial skeleton starts with the neural arches and haemal arches at 3.8mm TL. Caudal elements such as the hypurals and parahypural began to develop at 4.1mm TL. Pre-flexion and flexion of the notochord and the formation of all hypurals were observed between 5.3 and 5.8mm TL. Ossification of the vertebrae in the abdominal region and in some neural arches initiated at 9.5mm TL. In the caudal region, all the neural and haemal arches ossified at 10.2mm TL. All the abdominal vertebrae and their respective neural arches and parapophyses ossified at 11.2mm TL, while the elements of the caudal complex that ossified were the hypurals, parahypurals and modified haemal spines. All caudal fin rays, 12 neural spines and 3 haemal arches were ossified by 15.5mm. The complete ossification process of this specie under laboratory culture conditions was observed when larvae reached 17.3mm TL on 36 DPH. Detailed analysis of the osteological structures will allow a reference description to evaluate and detect malformations that may occur during the larval culture of the spotted rose snapper.

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OCCIPITALISATION OF ATLAS VERTEBRA AND ITS CLINICAL FRAMES OF REFERENCE- AN ANALYSIS

Journal of Ayurvedic Herbal and Integrative Medicine ◽

10.29121/j-ahim.v1.i1.2021.15 ◽

2021 ◽

Vol 1 (1) ◽

pp. 58-61

Author(s):

Neelima P ◽

Ravi Sunder R

Keyword(s):

Vertebral Column ◽

Wide Spectrum ◽

Cranial Nerves ◽

Cervical Vertebra ◽

Chronic Neck Pain ◽

Styloid Process ◽

Axial Skeleton ◽

Foramen Magnum ◽

Posterior Arch ◽

Entire Body

Vertebral column is made of 33 vertebrae named as cervical, thoracic, lumbar, sacral and coccygeal vertebrae. Axial skeleton comprises of skull and vertebral column. 12 pairs of cranial nerves and 31 pairs of spinal nerves exit from the central nervous system which control the entire body. Malformations or fusion of vertebrae could be one of the etiologies of nerve compression syndromes. Vital structures emerge out through intervertebral foramina extending from cervical to coccygeal vertebrae. Occipitalisation of atlas, the first cervical vertebra is one of the emergencies leading to wide spectrum of presentations like chronic neck pain or foramen magnum syndrome or unconscious state due to compression of medulla oblongata. During routine examination of skull bones while teaching, one skull was found to exhibit assimilation of atlas. Photographs were captured and compared with normal skull. Thorough examination revealed incomplete occipitalisation of atlas. The anterior arch was completely fused but the posterior arch was bifid showing a split. The styloid process on right side seemed to be long and very close leading to compression of structures of styloid apparatus in addition. On observation, it was found to be a male skull. Fusion of vertebrae may be a congenital anomaly due to maldevelopment of somites in forming vertebrae. Skeletal element of caudal 4th occipital somite forms the occipital bone and when it is fused with the proximal 1st cervical somite leads to occipitalisation of atlas. Acquired conditions like atlantoaxial subluxation, chiari malformations or cervical vertebral fusion or foramen magnum abnormalities have been associated with assimilation of atlas. The present study reports occipitalisation of atlas which is incomplete with a bifid posterior arch. Prevalence of such anomalies may form the differential diagnosis of chronic headache or myelopathies.

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Pax1 and Pax9 synergistically regulate vertebral column development

Development ◽

10.1242/dev.126.23.5399 ◽

1999 ◽

Vol 126 (23) ◽

pp. 5399-5408 ◽

Cited By ~ 17

Author(s):

H. Peters ◽

B. Wilm ◽

N. Sakai ◽

K. Imai ◽

R. Maas ◽

...

Keyword(s):

Cell Proliferation ◽

Vertebral Column ◽

Cell Lineage ◽

Axial Skeleton ◽

Intervertebral Discs ◽

Potential Interaction ◽

Specific Cell ◽

Gradual Loss ◽

Vertebral Bodies

The paralogous genes Pax1 and Pax9 constitute one group within the vertebrate Pax gene family. They encode closely related transcription factors and are expressed in similar patterns during mouse embryogenesis, suggesting that Pax1 and Pax9 act in similar developmental pathways. We have recently shown that mice homozygous for a defined Pax1 null allele exhibit morphological abnormalities of the axial skeleton, which is not affected in homozygous Pax9 mutants. To investigate a potential interaction of the two genes, we analysed Pax1/Pax9 double mutant mice. These mutants completely lack the medial derivatives of the sclerotomes, the vertebral bodies, intervertebral discs and the proximal parts of the ribs. This phenotype is much more severe than that of Pax1 single homozygous mutants. In contrast, the neural arches, which are derived from the lateral regions of the sclerotomes, are formed. The analysis of Pax9 expression in compound mutants indicates that both spatial expansion and upregulation of Pax9 expression account for its compensatory function during sclerotome development in the absence of Pax1. In Pax1/Pax9 double homozygous mutants, formation and anteroposterior polarity of sclerotomes, as well as induction of a chondrocyte-specific cell lineage, appear normal. However, instead of a segmental arrangement of vertebrae and intervertebral disc anlagen, a loose mesenchyme surrounding the notochord is formed. The gradual loss of Sox9 and Collagen II expression in this mesenchyme indicates that the sclerotomes are prevented from undergoing chondrogenesis. The first detectable defect is a low rate of cell proliferation in the ventromedial regions of the sclerotomes after sclerotome formation but before mesenchymal condensation normally occurs. At later stages, an increased number of cells undergoing apoptosis further reduces the area normally forming vertebrae and intervertebral discs. Our results reveal functional redundancy between Pax1 and Pax9 during vertebral column development and identify an early role of Pax1 and Pax9 in the control of cell proliferation during early sclerotome development. In addition, our data indicate that the development of medial and lateral elements of vertebrae is regulated by distinct genetic pathways.

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hox gene expression predicts tetrapod-like axial regionalization in the skate, Leucoraja erinacea

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2114563118 ◽

2021 ◽

Vol 118 (51) ◽

pp. e2114563118

Author(s):

Katharine E. Criswell ◽

Lucy E. Roberts ◽

Eve T. Koo ◽

Jason J. Head ◽

J. Andrew Gillis

Keyword(s):

Gene Expression ◽

Vertebral Column ◽

Evolutionary History ◽

Cell Lineage ◽

Axial Skeleton ◽

Lineage Tracing ◽

Paraxial Mesoderm ◽

Evolutionary Transition ◽

Geometric Morphometric ◽

Geometric Morphometric Analysis

The axial skeleton of tetrapods is organized into distinct anteroposterior regions of the vertebral column (cervical, trunk, sacral, and caudal), and transitions between these regions are determined by colinear anterior expression boundaries of Hox5/6, -9, -10, and -11 paralogy group genes within embryonic paraxial mesoderm. Fishes, conversely, exhibit little in the way of discrete axial regionalization, and this has led to scenarios of an origin of Hox-mediated axial skeletal complexity with the evolutionary transition to land in tetrapods. Here, combining geometric morphometric analysis of vertebral column morphology with cell lineage tracing of hox gene expression boundaries in developing embryos, we recover evidence of at least five distinct regions in the vertebral skeleton of a cartilaginous fish, the little skate (Leucoraja erinacea). We find that skate embryos exhibit tetrapod-like anteroposterior nesting of hox gene expression in their paraxial mesoderm, and we show that anterior expression boundaries of hox5/6, hox9, hox10, and hox11 paralogy group genes predict regional transitions in the differentiated skate axial skeleton. Our findings suggest that hox-based axial skeletal regionalization did not originate with tetrapods but rather has a much deeper evolutionary history than was previously appreciated.

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