. Anatomy, descriptive and applied. Anatomy. THE SKULL AS A WHOLE 141 it and the turbinated bone, and extends from the anterior end of the turbinated to the sphenopalatine foramen of the outer wall of the nasal fossa. Anteriorly it terminates in a depression, the atrium of the nasal meatus {atrium meatiw medii). The middle meatus presents in front the orifice of the infundibulimi, by which the middle meatus communicates with the anterior ethmoidal cells, and through these with the frontal sinuses. The posterior ethmoidal cells also open into this meatus, while at the centre of the outer wall i
. Anatomy, descriptive and applied. Anatomy. THE SKULL AS A WHOLE 141 it and the turbinated bone, and extends from the anterior end of the turbinated to the sphenopalatine foramen of the outer wall of the nasal fossa. Anteriorly it terminates in a depression, the atrium of the nasal meatus {atrium meatiw medii). The middle meatus presents in front the orifice of the infundibulimi, by which the middle meatus communicates with the anterior ethmoidal cells, and through these with the frontal sinuses. The posterior ethmoidal cells also open into this meatus, while at the centre of the outer wall is the orifice of the maxillary antrum which varies somewhat as to its exact position in different skulls. The inferior meatus, the largest of the three, is the space between the turbinated bone and the floor of the nasal fossa. It extends along the entire length of the outer wall of the nose, is broader in front than behind, and presents anteriorly the lower orifice of the canal for the nasal duct. Pituitary fossa Mesoderm of base of skull. Development of the Skull.—Up to a cei-tain stage the development of the skull corresponds with that of the vertebral column; but it is modified later in association with the expansion of the brain vesicles, the formation of the organs of smell, sight, and hearing, and the development of the mouth and pharynx. The notochord extends as far forward in the base of the future skull as the anterior end of the mid-brain, and becomes partly surrounded by mesoderm (Fig. 106). The posterior part of this mesodermal investment corresponds with the future basiocciput, and shows a subdivision into four segments, which are separated by the roots of the hypoglossal nerve. The mesoderm then extends over the brain vesicles, and thus the entire brain is enclosed by a mesodermal investment, which is termed the membranous primordial cra- nium. From the inner layer of this the bones of the skull and the membranes of the brain are de- veloped; from the outer lay
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1913
