Anatomy Lecture: Cranial Bones

Overview

• Objective: Identify all eight cranial bones.
• Total cranial bones to know: 8 out of 206 bones in the body.

Cranial Bones Overview

1. Frontal Bone

   • Location: Forehead area, top of eye sockets.
   • Contains sinuses.
   • Features:
     • Coronal Suture: Connects frontal bone to parietal bone; resembles a crown.
     • Supraorbital Foramen: Located above the eyes allowing passage for blood vessels and nerves.

2. Parietal Bones

   • Location: Sides and roof of the skull.
   • Features:
     • Sagittal Suture: Connects two parietal bones along the midline.

3. Temporal Bones

   • Location: Sides of the skull, near temples.
   • Features:
     • Squamous Suture: Connects temporal bone to parietal bone.
     • Zygomatic Process: Projection that touches the zygomatic bone.
     • Mandibular Fossa: Depression for jaw articulation.
     • Auditory Meatus: Ear canal; both external and internal.
     • Mastoid Process: Large projection for muscle attachment.
     • Styloid Process: Pointy projection for muscle attachment.

4. Occipital Bone

   • Location: Back of the skull.
   • Features:
     • Lambdoid Suture: Connects occipital bone to parietal bones.
     • Foramen Magnum: Large hole for brainstem and spinal cord connection.
     • External Occipital Protuberance (EOP): Bump for muscle attachment.
     • Occipital Condyles: Articulate with the first vertebra for nodding motion.

5. Sphenoid Bone

   • Location: Central bone of the skull.
   • Features:
     • Sella Turcica: Holds the pituitary gland.
     • Touches all other cranial bones and serves as a keystone.

6. Ethmoid Bone

   • Location: Central skull, near nasal cavity.
   • Features:
     • Crista Galli: Anchors brain.
     • Cribriform Plate: Contains small holes for olfactory nerves.
     • Perpendicular Plate: Forms part of the nasal septum.
     • Nasal Conchae: Help warm and filter air.

Key Concepts

• Soft Spots in Infants: Due to unfused cranial bones; bones form via intramembranous ossification.
• Cranial Sutures: Critical in the identification and connection of cranial bones.
• Bone Features: These include processes, sutures, foramina, and other structures important for attachment, articulation, and passage of nerves and vessels.

Review Questions

1. Which cranial bone touches every other cranial bone?
   • Answer: Sphenoid Bone.
2. What keeps the brain from moving in the cranial cavity?
   • Answer: A membrane anchors it to the crista galli on the ethmoid bone.
3. Why are infants born with soft spots on their skull?
   • Answer: Due to the lack of sutures; cranial bones form via intramembranous ossification.

These notes cover the crucial elements from the lecture, focusing on the eight cranial bones, their features, and important related concepts.