HEWB 134 Skull Lecture 2025 PDF

The Human Skull Head & Neck Structure & Function HEWB 134 Meghan M. Newcomer, PhD [email protected]  Outline ▪ Bones of skull Unpaired Paired ▪ Calvaria ▪ Cranial Base ▪ Cranial Fossae ▪ Skull Classifications Intramembranous...

The Human Skull Head & Neck Structure & Function HEWB 134 Meghan M. Newcomer, PhD [email protected]  Outline ▪ Bones of skull Unpaired Paired ▪ Calvaria ▪ Cranial Base ▪ Cranial Fossae ▪ Skull Classifications Intramembranous & Endochondral ossification Neurocranium & Viscerocranium ▪ Fontanelles ▪ Sutures ▪ Foramina Learning Objectives 1) Recognize all bones of the human skull. 2) Understand the functional role that the skull plays in support of structures of the head, face, and brain. 3) Understand the differences between intermembranous and endochondral forms of ossification in relationship to the human skull. 4) Understand the relationship between the bones of the skull, the articulations, and sutures. 5) List the foramina of the skull and structures that pass through them. Skull: Axial Skeleton ▪ Skeleton divided into two divisions: 1) Appendicular skeleton – bones of the upper & lower limbs 2) Axial skeleton – skull, hyoid, ribs, sternum, vertebrae, sacrum Bones of the Skull ▪ 28 bones of the skull: Unpaired Paired Frontal Parietal Occipital Temporal Sphenoid Zygomatic Vomer Palatine Ethmoid Maxilla Mandible Lacrimal Inferior concha Nasal Ear ossicles (Malleus, Incus, Stapes) Unpaired Bones Unpaired Bones: Frontal ▪ Frontal Bone Supraorbital margin ▪ Supraorbital notch/foramen Superciliary arch Glabella Nasion Unpaired Bones: Frontal Anterior Inferior Lateral Unpaired Bones: Occipital ▪ Occipital Bone Foramen magnum Occipital condyles External occipital protuberance Superior nuchal line Inferior nuchal line Unpaired Bones: Occipital ▪ Occipital Bone Basilar part Clivus Hypoglossal canal Unpaired Bones: Sphenoid ▪ Sphenoid Bone Greater wing Lesser wing Sella turcica Hypophyseal fossa Unpaired Bones: Sphenoid ▪ Sphenoid bone: Foramina Optic canal Superior orbital fissure Foramen rotundum Foramen ovale Foramen spinosum Unpaired Bones: Vomer ▪ Vomer Bone Vomer Unpaired Bones: Ethmoid ▪ Ethmoid Bone Anterior view Cribriform plate Crista galli Unpaired Bones: Ethmoid ▪ Ethmoid Bone Perpendicular plate Superior concha Middle concha Anterior view Nasal cavity: medial wall Posterior view Nasal cavity: lateral wall Unpaired Bones: Mandible ▪ Mandible Condylar process ▪ Head (condyle) ▪ Neck Coronoid process Mandibular notch Neck Ramus Angle Body Body Unpaired Bones: Mandible ▪ Mandible Alveolar processes ▪ Alveoli Mental protuberance Mental foramen Mandibular foramen Lingula Paired Bones Paired Bones: Parietal ▪ Parietal Bones Paired Bones: Zygomatic ▪ Zygomatic Bones Temporal process Zygomatic arch = Zygomatic process of temporal bone + Temporal process of zygomatic bone Paired Bones: Temporal ▪ Temporal Bones Squamous part Paired Bones: Temporal ▪ Temporal Bones Petrous part Internal acoustic meatus Paired Bones: Temporal ▪ Temporal Bones Anterior Styloid process Mastoid process Stylomastoid foramen Carotid canal Mandibular (glenoid) fossa Posterior Paired Bones: Temporal ▪ Temporal Bones Zygomatic process External acoustic meatus Paired Bones: Maxillae ▪ Maxillae Paired Bones: Maxillae ▪ Maxillae Palatine process ▪ Incisive foramen Alveolar processes Paired Bones: Nasal & Lacrimal ▪ Nasal Bones ▪ Lacrimal Bones Paired Bones: Inferior Concha ▪ Inferior conchae Paired Bones: Palatine ▪ Palatine Perpendicular plate Horizontal plate Pyramidal process Greater palatine foramen Lesser palatine foramen Horizontal plate of palatine bone Anterior Calvaria ▪ Calvaria (“skull cap”): Frontal Parietal Occipital  Calvaria ▪ Most bones of calvaria consist of internal & external tables of compact bone, separated by diploë (cancellous bone containing red bone marrow) ; diploic veins found within diploë Cranial Base ▪ Cranial Base – forms floor of cranial cavity Cranial Fossae ▪ Cranial Fossae – large stair-stepped depressions forming bowl-shaped floor of cranial cavity occupied by the brain Anterior Cranial Fossa Anterior cranial fossa: formed by frontal bone, ethmoid bone, lesser wing of sphenoid bone; houses frontal lobes Middle Cranial Fossa Middle cranial fossa: formed by greater wing of sphenoid bone, temporal bone; houses temporal lobes  Sella Turcica ▪ Sella turcica = “Turkish saddle”; body of sphenoid Formed by: 1) Tuberculum sellae 2) Hypophysial fossa 3) Dorsum sellae Houses pituitary gland Posterior Cranial Fossa Posterior cranial fossa: formed by temporal & occipital bones; houses brainstem, cerebellum, occipital lobe Skull Classification A. Developmental B. Functional 1) Intramembranous ossification 1) Neurocranium 2) Endochondral ossification 2) Viscerocranium Skull Classification: Developmental ▪ Skeletal system develops from mesenchyme (derived from mesoderm & neural crest cells): 1) Flat bones of the skull undergo intramembranous ossification → mesenchyme cells directly transformed to osteoblasts 2) Base of the skull (& some other bones) undergoes endochondral ossification → mesenchyme condenses to form hyaline cartilage model; ossification centers appear in models, bone ossifies Neural crest – blue Mesoderm – purple Neural crest – purple Mesoderm – blue Skull Classification: Functional ▪ Skull functionally subdivided into: 1) Neurocranium – bony case for brain & its membranous coverings (cranial meninges) 2) Viscerocranium – facial bones; support the orbits, nasal, and oral cavities (“viscera” of the face) Neurocranium ▪ Neurocranium = bony case for the brain Unpaired: Frontal, Ethmoid, Sphenoid, Occipital Parietal Paired: Temporal & Parietal Frontal Occipital Sphenoid Temporal Ethmoid Neurocranium ▪ Neurocranium is divided into 2 portions: 1) Membranous part – consists of flat bones surrounding brain Mesenchyme (neural crest & mesoderm) undergoes Intramembranous ossification Frontal, Parietal, Temporal (squamous portion), Occipital (intraparietal part) 2) Cartilaginous part (Chondrocranium) – forms the bones of the base of the skull Mesenchyme (neural crest & mesoderm) undergoes Endochondral ossification Ethmoid, Sphenoid, Temporal (petrous & mastoid parts), most of Occipital Viscerocranium ▪ Viscerocranium = facial skeleton Unpaired: Mandible & Vomer Paired: Maxillae, Zygomatic, Nasal, Inferior Nasal Conchae, Lacrimal, Palatine, *Ethmoid *Ethmoid is part of both Neurocranium & Viscerocranium Viscerocranium ▪ Viscerocranium – mesenchyme of viscerocranium derived from neural crest cells; undergoes: Intramembranous ossification ▪ Maxilla, Zygomatic, Palatine, Lacrimal, Nasal, Vomer, Mandible (all but condyle) Endochondral ossification ▪ Inferior concha, Condyle of mandible, Styloid process of temporal bone *Ear ossicles develop from endochondral ossification  Skull Ossification 1. Frontal Intramembranous 2. Parietal Neurocranium 3. Occipital (intraparietal part) 4. Temporal (squamous part) 1. Temporal (petrous & mastoid parts) 2. Sphenoid Endochondral 3. Occipital (most) 4. Ethmoid 1. Nasal Intramembranous 2. Maxilla 3. Lacrimal Viscerocranium 4. Vomer 5. Zygomatic 6. Palatine 7. Mandible (most) 1. Temporal (styloid process) Endochondral 2. Inferior concha 3. Mandible (head) Fontanelles ▪ Fontanelles – seen in neonatal skull; large fibrous areas where several sutures meet; intramembranous bone deposition as skull/brain grows Anterior – largest; closes ~ age 2 Posterior – closes ~2 months Sphenoid – closes ~ 6 months Mastoid – closes ~ age 2 Fontanelles Anterior Fontanelle Anterior Fontanelle Anterior Fontanelle Posterior Fontanelle Mastoid Fontanelle Sphenoid Fontanelle Sutures ▪ Sutures – fibrous joints of cranial bones Coronal – between frontal & parietal bones Sagittal – between parietal bones Lambdoid – between parietal & occipital bones Squamosal – between temporal & parietal bones  Sutures ▪ Areas where two or more sutures meet: Nasion – between frontal & nasal bones Bregma – where sagittal suture meets coronal suture Pterion – where greater wing of sphenoid, frontal, parietal, & squamous part of temporal bone meet Lambda – where lambdoid suture meets sagittal suture Sutures ▪ Other sutures:  Aging the Skull by the Sutures ▪ The frontal (metopic) suture typically closes by the eighth year of life, while the others slowly close into adulthood Cranial Nerves ▪ Cranial nerves are “cranial” because they emerge from the cranial cavity via foramina or fissures in the cranium  CN I CN II CN III, IV, V1, VI CN V2 CN V3 Middle meningeal a. Covered by cartilage; ICA crosses superiorly CN VII, VIII CN IX, X, XI; internal jugular v. CN XII Spinal cord, Vertebral aa., CN XI (enters skull) Cranial Foramina & Contents [email protected]