Osteology Flashcards
How do the bones of the calvaria, of the neurocranium, develop?
Intramembranous Ossification
How do the bones of the base of the skull, of the neurocranium, develop?
Endochondral Ossification
From what does the viscerocranium develop?
From Pharyngeal arches
What is the cartilaginous structure, from the 1st pharyngeal arch, that developes into the template for the developing mandible?
Meckel’s Cartilage
What is significant about the superior and inferior temporal lines of the squamus portion of the temporal bone?
They mark the attachment of the temporalis fascia and temporalis muscle respectively. These lines also demarcate the superior limit of the temporal fossa.
What is the nasion?
The intersection of the frontal bone with the two nasal bones. Located b/t the eyes.
What is the significance of the frontal crest?
The frontal crest is a vertical feature of the internal midline of the frontal bone that serves as an attachment for the anterior end of the faulx cerebri, a reflection of the dura mater, the outermost layer of the meninges, which separates the eft and right cerebral hemispheres.
What is the importance of the sagittal sulcus and its contents?
The sagittal sulcus is an internal, midline feature that houses the superior sagittal (dural venous) sinus. The superior sagittal sinus, found b/t the periosteal and meningeal layers of the dura, carries blood along the superior margin of the falx cerebri.
What are the fossae of the orbital portion of the frontal bone that house the lacrimal glands during life?
Lacrimal fossae
What is found within the ethmoid notch of the orbital portion of the frontal bone?
Cribriform plate of the ethmoid bone
In what portion of the frontal bone are the frontal sinuses found?
Orbital portion
Where is the foramen caecum found and what is its significance?
Forament caecum is found inferior to the frontal crest at the midpoint of the frontoethmoidal articulation (just abouve the cribriform plate). It transmits an emissary vein from the frontal (paranasal) sinus to the superior sagittal (venous dural) sinus.
What is transmitted through the supraorbital foramen?
The supraorbital neurovascular bundle. The supraorbital nerve is a branch of the frontal nerve of the opthalmic division of the trigeminal nerve (V1). The supraorbital nerve provides sensory innervation to the skin of the forehead.
The parietal bones articulate at the midline along what suture?
Sagittal suture
What is the point of intersection of the coronal and sagittal sutures called? Significance?
Bregma. Marks the site of the anterior (bregmatic) fontanelle in the neonate.
What is point of intersection of the lambdoidal and sagittal sutures called? Significance?
Lambda. Marks the site of the posterior fontanelle in the neonate.
A skull fracture in the viscinity of pterion may impact what middle meningeal vessels found in the grooves for the middle meningeal vessels of the parietal bone. What is a possible consequence?
The pterion is the intersection of the parietal, frontal, temporal and sphenoid bones and is known as the weakest portion of the skull. A fracture here could damage the anterior division of the middle meningeal vessels causing an epidural hematoma where blood builds up b/t the dura mater and the skull.
The middle meningeal artery is a branch of what artery? Be specific. What foramen allows middle meningeal vessels to enter the skull?
Middle meningeal artery is the 3rd branch of the first portion of the maxillary artery (one of the two terminal branches of the external carotid), the retromandibular portion.
The middle meningeal artery is intimately associated with what nerve, which wraps around the artery, making both easily identifiable in a cadaver?
The auriculotemporal nerve is a branch of the mandibular nerve, V3. It arises as two roots that wrap around the middle meningeal vessels before joining to form a single auriculotemporal nerve.
What is found within the arachnoid fovea that are concentrated along the sagittal sulcus? Importance?
Arachnoid granulations that are responsible for resorption and filtration of the cerebrospinal fluid, CSF, which fills the subarachnoid space during life.
What foramina, located posteriorly, adjacent to the sagittal sinus in the parietal bone, transmit emissary veins b/t the scalp and the superior sagittal sinus?
Parietal foramina
The Superior Nuchal lines, bilateral ridges extending to the right and left from the external occipital protuberance, mark the origin of what two muscles and insertion of what two muscles?
Origin: Occipitalis & Trapezius
Insertion: SCM & splenius capitis
The nuchal ligament attaches to what bony element of the occipital bone?
The median nuchal line
What is the significance of the nuchal ligament?
The nuchal ligament is a band of fibroelastic tissue that limits forward flexion of the head and provides surface area for the attachment of deep muscle of the posterior neck that are critical for both maintaining head position against gravity and moving the head quickly in response to visual and acoustic stimuli.
The inferior nuchal lines act as insertion sites for what two small sub-occipital muscles?
rectus capitis posterior major AND minor
What is the significance of the internal occipital protuberance which lies at the center of the cruciform eminence?
The internal occipital protuberance marks the drainage point of the superior sagittal sinus/sagittal sulcus as it drains into the confluence of sinuses. The cruciform eminence marks the separation of the cerebral fossae superiorly and the cerebellar fossae inferiorly.
What sinus corresponds to the internal occipital crest and what dural septum attaches here?
The falx cerebri, a dural septum which separates the right and left hemispheres of the brain, and the occipital sinus.
What is the main route of venous drainage from the confluence of sinuses?
The Transverse sinuses, generally the right is larger and communicates directly with the sagittal sulcus. The transverse sinuses travel laterally in the transverse sulci, draining into the sigmoid sinuses and eventually connect to the internal jugular vein after exiting the skull through the jugular foramena.
Confluence of sinuses marks the intersection of superior sagittal, trasverse, occipital and one other sinus. What is the fourth sinus that does not correspond to any sulcus in the endocranial bone. Why?
The straight (rectus) venous sinus does not lie in a sulcus b/c it lies at the intersection of the falx cerebri and tentorium cerebelli.
What structure on the basilar part of the occipital bone, about 1 cm anterior to forament magnum, marks the attachment site of the fibrous pharyngeal raphe?
Pharyngeal tubercle
The inferior petrosal sulci, which are found along the anterolateral margins of foramen magnum internally, house what sinuses?
Inferior petrosal sinuses
The superior aspect of the base of the occipital bone unites with the posterior aspect of the dorsum sella of the sphenoid bone to form a slope descending from sella turcica to foramen magnum called what?
Clivus
In life, what rest on the clivus? 3 things
- Basilar (venous dural) plexus
- Basilar artery
- Brainstem
What convex, oval facets articulate bilaterally with the atlas, the first cervical vertebra? What depressions, posterior to the aforementioned oval facets, accommodate the superior articular facets of the atlas when the head is extended?
Occipital condyles.
Condylar Fossae.