Skull and Cranial Cavity Flashcards
Protects the brain, allowing it to expand and develop.
-Creates the Cranial Cavity (pit the brain sits in) and the Skull Cap (Calvaria - the dome)
-Upper 2/3 of orbit and up (except for nasal bone)
-Frontal Bone
-2 Parietal
-2 Temporal
-Occipital Bone
Neurocranium
Facial Skeleton
-Lower 1/3 of orbit and down, plus Nasal bones.
-2 Nasal Bones
-Horizontal plate of the Palatine Bone
-2 Lacrimal Bones (right behind nasal bones)
-Ethmoid Bone (perpendicular plate)
-2 Zygomatic Bones (cheekbones)
-Maxilla
-Inf nasal conchae
-Vomer
-Mandible
Viscerocranium
Bones are separated by Fibrous sutures that make fibrous joints.
-Start out with very loose and expansive sutures as the brain enlarges in size.
As we grow older, sutures become ossified. When they are completely ossified, say they are synostosis (suture has been replaced with a bony line).
Sutures
In infancy, frontal bone is actually 2 bones separated by this. Closes and starts ossifying early in life (3-9 months of age)
Metopic Suture
-Soft spots not covered by bone, just covered by meninges (dura mater)
-Unossified gaps between bones
-Generally close within the first year of extrauterine life
-Complete ossification (Synostosis) occurs during the 5th decade of life.
Fontanelles
Diamond Shaped.
Between the frontal and parietal bones.
Anterior Fontanelle
Triangular Shaped. Between the parietal and the occipital bones.
Posterior Fontanelle
Fontanelle between the Parietal bone and greater wing of the Sphenoid.
-Begins to close during the first year of life
Anterolateral Fontanelle
Fontanelle between the temporal bone and occipital bone.
-Begins to close during the first year of life
Posterolateral Fontanelle
Children are more likely to develop ear infections (Otitis Media) than adults due to this being more horizontal (Adults point forward, down, and medially)
Eustachian tube
Bones that lie within the sutures, mainly within Lambdoid Suture.
-Genetic aberration or due to disease (Osteogenesis Imperfecta, Rickets, Vit D deficiency, Cleidocradnial Dysostosis, Down Syndrome)
Wormian Bones
Superficial Layer, compact and dense bone
Outer Table
Intermediate layer. Cancellous (spongy) bone containing red marrow and venous pathways.
Diploe
Deep layer, compact and dense bone that is brittle and breaks easily
Inner Table
-Frontal Diploic Vein
-Anterior Temporal Diploic Vein
-Posterior Temporal Diploic Vein
-Occipital Diploic Vein
Drain the scalp, bones of the neurocranium, and terminate in dural venous sinuses to be returned into peripheral circulation
Diploe
Draining blood out of the scalp, pierces outer table of the bone, and lies in the intermediate layer (Diploe) layer. Joined by the Diploic vein.
Scalp Vein
Where scalp vein and Diploic Vein come together.
-Receives venous drainage from the scalp veins and Diploic Veins.
Pierces the skull and drains into the Superior Sagittal Sinus. Blood goes back into circulation to be recycled.
Valveless - allow for retrograde flow (infection risk)
Emissary vein
-Roof: Frontal Bone with 2 orbital plates
-Medial Wall: Lacrimal Bone, Orbital Plate of the Ethmoid Bone, Perpendicular Plate of the Palatine bone (very tiny) and the Crista Galli
-Lateral Wall: Zygomatic Bone
-Floor: Maxilla
Apex: Greater wing of Sphenoid; contains Optic Canal (for CN II) and Ophthalmic Artery.
Orbit
Optic Nerve and Ophthalmic Artery pierce the skull via this
Optic Canal
Contains the infraorbital vein (drains orbit) and also running with it is Inferior Orbital Nerve (supplies general sensation to the face)
Inferior Orbital Fissure
Groove coming out of the Inferior Orbital Fissure that conducts the Infraorbital Nerve (Gen sen to face/viscerocranium)
Infraorbital Groove
Contains the Nasolacrimal Duct (terminates in Inf. Nasal Concha)
Nasolacrimal Canal
Thinnest area of the skull; start at top of ear and measure out in front about 1.25 in.
-Coming together of squamous portion of temporal bone with greater wing of sphenoid and parietal bone
-Location of Anterior Branch of Middle Meningeal Artery (Supplies blood flow to Meninges)
-Fx here = Epidural Hematoma
Pterion
Positioned between the Dura Mater and the Inner table of the bones of the periosteum (epidural space).
Injuries can cause hematoma - compresses brain and pushes it over to one side
Middle Meningeal Artery
-Forms the orbital plates
-Forms the forehead
-Contains the Frontal Lobes and Cerebral Cortex
-Shallow depression in the front is where the frontal lobe sits (Anterior Fossa)
Frontal Bone
-Posterior portion of the skull and cranial cavity
-Deep well to contain the cerebellum and the brainstem
-Foramen Magnum: Large opening in the center. Allows the brainstem to transition to the spinal cord
Occipital Bone
-Singular bone with 2 greater wings and 2 lesser wings with 2 Anterior Clinoid Processes
-Body contains Hypophyseal fossa (pituitary gland sits here)
-Dorsum Sellae contains Posterior Clinoid Processes
-Tuberculum Sellae
-Lateral and Medial Pterygoid Plates (with Hamulus of Medial)
Sphenoid Bone
-Hypophyseal Fossa
-Posterior Clinoid Processes
-Dorsum Sellae
-Tuberculum Sellae
Sella Turcica
Squamous: Flat portion
Zygomatic: Helps form cheek
External Auditory (Acoustic) Meatus: Hole
Mastoid Process: behind ear
Styloid Process: needle-like structure
Petrous Portion: Rock cliff
Temporal Bone
Basilar part
Occipital condyles (where the skull articulates with the 1st cervical vertebrae)
Foramen magnum
External Occipital Protuberance
Superior Nuchal Line
Inferior Nuchal Line
Clivus
Internal Occipital Protuberance
Occipital Bone
Space medial to mandible.
-In between lateral pterygoid plate
-above greater wing of the sphenoid
-below it is skin
-Depression underneath mandible
Infratemporal Fossa
-Runs diagonally, very hard bone
-Contains the inner ear (Cochlea - hearing, Vestibule - static positioning, and 3 Semicircular Canals - balance and equilibrium)
-Run in different planes so we can keep our balance and equilibrium. Contain receptors within each.
Internal Acoustic Meatus:
-Runs with Vestibulocochlear Nerve (CN VIII). Balance, equilibrium, and hearing.
-Facial Nerve also runs through internal acoustic meatus
Petrous Portion of Temporal Bone
Anterior: very shallow, frontal lobe/cerebral cortex
Middle: deeper than anterior, contains temporal lobes of the cerebral cortex
Posterior: Deepest. Contains cerebellum and brainstem.
Cranial Fossae
Occipital bone
Parietal bone
Petrous portion of the temporal bone
Posterior Cranial Fossa
Greater wing & Body of the sphenoid bone
Petrous and squamous part of the temporal bone
Middle Cranial Fossa
2 Lesser wings of the sphenoid bone (with anterior clinoid processes)
Frontal Bone & 2 Orbital plates
2 Cribriform plates of the ethmoid bone
Crista galli of the ethmoid bone
Anterior Cranial Fossa
Forms the lower jaw.
Articulates with the Temporal Bone at the TMJ (Temporomandibular Joint)
-Can get arthritis in this joint, pain, etc.
Mandible
Composed of a mandibular condyle and the mandibular fossa (in the temporal bone).
-can open/close jaw and lateral movement (grind), protraction/retraction.
TMJ
-Elevation (closes): Temporalis, masseter, and medial pterygoid
-Depression (opens): Digastric, geniohyoid, mylohyoid, and Lateral Pterygoid Muscle
Movement of the Mandible
The Mandibular Foramen transmits this nerve.
-Branch of Trigeminal n.
-Runs into jaw, penetrates mandibular foramen, continues down into lower jaw and gives sensation to lower teeth. Emerges on either side of the chin via the mental foramen and then it becomes the mental nerve.
Inferior Alveolar Nerve
Supplies general sensation to the lower teeth, lower lip, and chin; lies right behind the Lingual Nerve
Mental Nerve
SCALP:
-Skin
-Connective Tissue (bleeding occurs if cut happens here)
-Aponeurosis (thin muscle that connects frontalis m. with occipitalis m.)
-Loose Connective Tissue: Allows you to wiggle skin around on your scalp (infection risk!!!! no resistance to keep it from spreading)
-Pericranium (periosteum): Connective tissue (stiff) surrounding the bone
Layers of the Scalp
Also called the Galea Aponeurotica
-3rd Layer of the Scalp
-Attachment of the Frontalis m. and the Occipitalis m.
Scalp Aponeurosis
