Bio1 skull orbit

• Outer: Periosteum (dense connective tissue)
•  
• Inner: Endosteum (fine connective tissue)

• Outer shell
• Hard & rigid = Compact or ‘Lamellar’ bone

• Inner core
• Softer & lighter = Cancellous or ‘Spongy’ bone
• Contains Marrow & Air pockets

Purpose: Greatest strength at minimum weight

Living (dense connective) tissue: Cells, collagen fibres & ground substance

• Specializations:
•      
• Bone-forming cells: Osteo-blasts (-cytes)
•      
• Bone-remodelling cells: Osteo-clasts
•      
• Extracellular matrix components mineralized:
• - Calcium & Phosphate
• - 66-75% by weight = calcium (-hydroxy apatite) crystals
• - Confers hardness & rigidity

Osteo-blasts:

• - Related to fibroblasts
• - Matrix production, calcium deposition    
• - RER + Golgi Apparatus
•   (Osteocyte)

Osteoclasts:

• - Related to macrophages
• - Digestion bone debris (wear-&-tear), calcium retrieval
• - Lysosomes

•     
• N=22: 6 unpaired, 8 paired

•    
• -Shape: flat or irregular
•      
• - Articulations (joints) via ‘sutures’
• Except Mandible (ball-&-socket)
•      
• - Form or contain holes (fissures,
• foramina)
• Transmission of cranial nerves &
• blood vessels     

-Several possess air sinuses

-‘Intra-membranous’ Development

• Cranium (Vault), N=8:
• -Unpaired:               -Paired:
• frontal*                    parietal
• occipital                   temporal
• sphenoid*
• ethmoid*

• These 3*
• also contribute to the Orbital Cavity

• Facial, N=14:
• - Paired:              -Unpaired:
• maxilla*               mandible
• zygomatic*           vomer
• lacrimal*
• palatine*
• nasal
• inferior conchae

• These 4* also contribute to the Orbital Cavity

Temporal (5 parts):

Squamous (flat), Petrous (hard) portions

Zygomatic, Mastoid & Styloid processes


Sphenoid (5 parts):

Greater* & Lesser* Wings, Body*

• Anterior & Posterior Clinoid
• processes

Ethmoid (3 parts):

Cribiform, Perpendicular & Orbital* plates

• These 4* also contribute to the Orbital
• Cavity