Sept 10

Sept 10 - Skeleton-Neurocranium-Basicranial...

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Skeleton-Neurocranium-Basicranial Region - Parasphenoid -only dermal bone in the basicranial region -a long cross-shaped bone that articulates with the vomer anteriorly and forms the posteroventral base of the skull. -Cranial base is formed by three sets of cartilage bones and one dermal bone -paired exoccipitals-form the sides of the foramen magnum, which is the passageway for the spinal cord -median basioccipital is the most posteroventral neurocranium bone and articulates with the first vertebra -dorsal median supraoccipital – usually bears supraoccipitial crest Skeleton-Branchiocranium -Branchiocranium (visceral cranium or splanchnocranium) consists of a series of arches that form around the pharyngeal region and are associated with the neurocranium -primitive number of arches is believed to be eight -originally formed as gill arch supports -in present day fishes most of the branchiocranium is associated gill supports -some arches have been modified as jaws and jaw supports -one or more of the ancestral arches were lost in the expansion of the mouth cavity -mandibular arch -probably the ancestral second and third arch -forms primary upper and lower jaws in sharks and rays (Class Chondrichthyes) -the mandibular cartilage bears teeth, but in bony fishes it is hidden in the secondary lower jaw Picture 1. Chondrocranium 2. Mandibular arch 3. Palatoquadrate cartilage 4. Mackel’s cartilages
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5. Hyoid arch
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Sept 10 - Skeleton-Neurocranium-Basicranial...

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