Head & Neck Anatomy | Bones of the Skull | INBDE

Summary

In this video, Ryan provides an in-depth look at the bones of the skull, exploring their structure, functions, and development. He explains the division between the cranium and facial bones, the role of sutures and fontanelles in skull growth, and the impact of craniosynostosis. The video covers the function of sinuses, the mandible’s adaptation over time, and weak areas of the skull, such as the terion and LeFort fracture lines. Ryan also gives a helpful mnemonic for the bones making up the orbit and discusses other anatomical features like the ethmoid and sphenoid bones, nasal septum, and meatuses. A comprehensive guide for students in head and neck anatomy.

Takeaways

• 😀 The skull is a bony structure that protects the brain and supports the face, divided into the cranium (brain protection) and the face (facial support).
• 😀 Sutures in the skull are fibrous joints that allow brain growth during childhood and fuse in adulthood once growth is complete.
• 😀 The cranium is divided into the roof and base, with the roof protecting the brain from above and the base supporting it from below.
• 😀 The face consists of 14 bones that support soft tissues, housing the orbits, nasal cavity, oral cavity, and sinuses.
• 😀 Fontanelles are gaps between skull bones in infants that fuse as the skull matures, with two main fontanelles at the frontal and occipital regions.
• 😀 Craniosynostosis refers to the premature closure of sutures, causing abnormal skull shape such as scaphocephaly, brachycephaly, or plagiocephaly.
• 😀 Sinuses are air-filled spaces that reduce skull weight and contribute to voice resonance, temperature regulation, and immune defense.
• 😀 The mandible's structure changes over time, with its angle becoming more obtuse in childhood and more acute in adulthood as teeth develop.
• 😀 The terion is a weak area of the skull where several bones meet, and trauma here can result in dangerous epidural hematomas.
• 😀 The bones forming the orbit (eye socket) include the frontal, maxillary, palatine, lacrimal, ethmoid, sphenoid, and zygomatic bones, and a helpful mnemonic for this is 'FM Please'.

Q & A

What is the primary function of the skull?

The skull forms a protective cavity for the brain and supports the face.

How do sutures contribute to skull development?

Sutures are fibrous joints unique to the skull that allow for brain growth during childhood and adolescence, and later fuse in adulthood once brain growth is complete.

What is the difference between the cranium and the face of the skull?

The cranium, or neurocranium, protects the brain, while the face (or visceral cranium) supports the face and houses features like the orbits, nasal cavity, and oral cavity.

What are fontanelles and when do they fuse?

Fontanelles are incompletely fused joints in infants that appear as wide membranous gaps between skull bones. They typically fuse by 18 months, with the exception of the frontal suture, which closes much earlier, around 3 to 9 months after birth.

What is craniosynostosis, and what are its manifestations?

Craniosynostosis involves the premature closure of the fontanelles and sutures, leading to abnormal skull growth. Types include scaphocephaly (elongated skull), brachycephaly (vertically elongated skull), and plagiocephaly (asymmetrical skull).

What are the primary functions of the sinuses?

The primary function of the sinuses is to reduce the weight of the skull. Secondary functions include affecting voice resonance, insulating sensitive structures, regulating intranasal pressure, and providing immunological defense.

How does the mandible change during development?

At birth, the mandible has no teeth, and the alveolar process has not formed, making the angle of the mandible obtuse. As the mandible develops and teeth appear, the angle becomes less obtuse, reaching about 120–130 degrees in adults. In edentulous individuals, the mandible undergoes resorption, and the angle can revert to a more obtuse shape.

What are the principle lines of force in the skull?

The principle lines of force are strong areas in the skull that develop in response to local mechanical stress, especially masticatory forces. These areas are reinforced to withstand stress, while weak points, known as fracture lines (or LeFort fracture lines), are more susceptible to fractures.

What is the terion and why is it significant?

The terion is a weak area in the skull where the frontal, parietal, sphenoid, and temporal bones meet. It is a critical point because the middle meningeal artery runs beneath it, and trauma to this area can result in an epidural hematoma, which can be a dangerous condition.

Which bones make up the orbit, and is there a mnemonic to remember them?

The bones that make up the orbit are the frontal, maxillary, palatine, lacrimal, ethmoid, sphenoid, and zygomatic bones. A helpful mnemonic to remember these is 'FM Please' – standing for Frontal, Maxillary, Palatine, Lacrimal, Ethmoid, Sphenoid, and Zygomatic.