CRANIAL BONES

Cranial Bones:

• 📌The cranial bones form the cranium, which protects the brain and supports the structures of the face.

• 📌There are 8 cranial bones.

• 📌They are tightly joined together (mostly by immovable joints called sutures).

Cranial Bones and Their Anatomy:

📌Frontal Bone:

• • Forehead region

• • Forms the anterior cranium and the roof of the orbits (eye sockets)

• • Contains the frontal sinuses

📌Parietal Bones (2):

• • Located on the sides and roof of the cranium

• • Join at the sagittal suture

• • Articulate with frontal, temporal, and occipital bones

📌Temporal Bones (2):

• • Sides and base of the cranium

• 🔺Key features:

  • • External auditory meatus (ear canal)

  • • Mastoid process

  • • Styloid process

  • • Zygomatic process (part of the cheekbone)

📌Occipital Bone:

• • Forms the back and base of the skull

• 🔺Key features:

  • • Foramen magnum (where spinal cord exits the skull)

  • • Occipital condyles (articulate with the first cervical vertebra)

📌Sphenoid Bone:

• • Butterfly-shaped bone at the base of the skull

• • Forms part of the floor of the cranium and sides of the orbits

• 🔺Key feature:

  • • Sella turcica (houses the pituitary gland)

📌Ethmoid Bone:

• • Located between the eyes

• • Forms part of the nasal cavity and the medial wall of the orbits

The Eight Cranial Bones Form the Protective:

• 📌Skull

• 📌Neurocranium enclosing and shielding the brain.

• These bones are:

  • 📌The frontal bone (forms the forehead)

  • 📌Two parietal bones (form the roof and sides)

  • 📌Two temporal bones (form the sides and lower cranial base)

  • 📌The occipital bone (forms the back and base)

  • 📌The sphenoid bone (forms part of the cranial floor)

  • 📌The ethmoid bone (forms part of the nasal cavity and medial orbit wall)

Blood Supply:

• 📌The cranial bones are primarily supplied by branches of:

  • 🔺The external carotid artery

  • 🔺To a lesser extent, internal carotid artery and vertebral arteries

Venous Drainage:

• 🔺Cortical veins

• 🔺Sagittal sinuses

• 🔺Anastomotic vein

• 🔺Internal cerebral vein

• 🔺Great cerebral vein

Nerve Intervention:

• 🔺The cranium, or skull, receives nerve innervation from twelve pairs of cranial nerves originating from the brain.

• 🔺These nerves are responsible for various sensory and motor functions in the head and neck.

Clinical Significance:

🔺Brain Protection:

• The cranium's bony structure acts as a protective shell for the brain, safeguarding it from injury.

🔺Neurovascular Structures:

• 📌The cranial base contains foramina (openings) that allow the passage of major blood vessels and nerves, such as the carotid artery and cranial nerves, ensuring their safe passage and protection.

🔺Structural Support:

• The cranium provides a rigid framework for the head, supporting the facial bones and muscles.

🔺Attachment Points:

• The cranium serves as an anchor for various muscles involved in head movement, chewing, and facial expressions.

🔺Facial Structures:

• 📌The cranial bones contribute to the formation of the facial skeleton, shaping the eye sockets, nose, and other facial features.

🔺Clinical Relevance:

• 📌Understanding the cranium's anatomy and function is crucial for diagnosing and treating various conditions, including head injuries, skull fractures, and tumors.

🔺Traumatic Brain Injuries:

• A significant impact to the head can lead to a traumatic brain injury (concussion) if the brain strikes the inside of the skull.

🔺Infections:

• Infections within the cranial cavity, such as meningitis, can be serious and potentially life-threatening, highlighting the importance of protecting the brain.