Anatomy & Physiology

Anatomy & Physiology Study Guide

The Skull The skull is composed of eight cranial bones and 14 facial bones. The bones of the skull protect the brain and guard the entrances to the digestive and respiratory systems. The eight cranial bones form the cranium, which houses the brain. The cranial bones are the occipital bone, frontal bone, sphenoid, ethmoid, and the paired parietal and temporal bones. The cranial bones enclose the cranial cavity, a fluid-filled chamber that cushions and supports the brain. The inner surface of the cranium facilitates the attachment of the structures that stabilize the position of the brain. These parts include blood vessels, nerves, and membranes. Facial bones protect and support the structural entrances to the gastrointestinal and respiratory tracts. The superficial facial bones (the paired maxillae, lacrimal, nasal, zygomatic bones, and the mandible) provide areas for the attachment of many small muscles. These muscles of facial expressions, and some muscles of food manipulation of the oral cavity, are attached to the superficial facial bones. The deeper facial bones (the paired palatine bones, inferior nasal conchae, and the single median vomer) help separate the oral and nasal cavities. Several bones of the skull contain air-filled chambers called sinuses. Joints, also called articulations, form where two bones interconnect. The connections between the skull bones of adults are immovable joints called sutures . Many different centers of ossification are utilized to form the skull. As development proceeds, the centers fuse, producing a smaller number of composite bones. The largest fibrous areas between the cranial bones are known as fontanelles . Fontanelles are non-ossified areas between cranial bones that allow for brain growth. The anterior fontanelle is often referred to as the “soft spot” on newborns.

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