Five bones of the skull, the frontal, ethmoid, sphenoid, and two maxillae, contain paranasal sinuses which are paired cavities lined with mucous membranes and connected to the nasal cavity. These cavities lighten the bones of the skull and serve to provide resonance when we speak or sing.
Locate the paranasal sinuses in the bones of the disarticulated skull You will not be able to see the frontal sinuses. Label the sinuses on Figure 9.7.
Ethmoidal air cells (sinuses) Frontal sinus Maxillary sinus Sphenoidal sinus (X2)
Base of Skull sella turcica: anterior clinoid process hypophyseal fossa posteriorclinoid process jugular foramen hypoglossal canal
foramen lacerum foramen magnum
Floor of cranium
The human skull is not completely composed of bone at birth, but still contains a significant amount of fibrous membrane. This dense connective tissue forms "soft spots" called fontanels in the skull of the baby. The largest of these spots is the anterior fontanel. Note that the frontal bone begins in the fetus as two bones, but ossification (replacement of cartilage by osseous tissue) causes the two halves to fuse to form the frontal bone. The posterior fontanel is the smaller fontanel located at the lambdoidal suture. The sagittal suture connects the posterior and anterior fontanels. There are two smaller fontanels on each side of the skulls, making a total of six fontanels.
Carefully examine the fontanels on the laboratory fetal skull DO NOT PUSH ON THE FONTANELS! THEY ARE NO LONGER SOFT! Label the fontanels on Figure 9.8.
Figure 9.8 Fetal Skull
Figure 9.8 Fetal Skull
Anterior fontanel (X2) Coronal suture Lambdoidal suture Posterior fontanel Sagittal suture
List the bones of the cranium in alphabetical order.
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