Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Bones of the skull
Cranium






The cranium/skull is the skeleton of the head
In the anatomical position, the cranium is oriented so that the inferior margin
of the orbit and the external acoustic meatus lie in the same horizontal plane
– known as the orbitomeatal plane
Formed from two parts - neurocranium and viscerocranium
Some bones of the cranium contain air spaces (large sinuses) to decrease
weight; known as pneumatised bones (frontal, temporal, sphenoid, ethmoid)

Neurocranium





Formed from eight bones
o Four singular centred on midline – frontal, ethmoid, sphenoid, occipital
o Two sets occurring as bilateral pairs – temporal and parietal
Dome-like roof is the calvaria, the floor is the cranial base (basicranium)
Most calvarial bones joined by fibrous interlocking sutures
o During childhood, some of the bones (sphenoid and occipital) are
joined by hyaline cartilage (synchondoses)

Viscerocranium




Comprises 13 bones that form the skeleton of the face
o One singular bones centred on midline – vomer
o Six sets occurring as bilateral pairs – maxillae, inferior nasal conchae,
zygomatic, palatine, nasal, lacrimal
Mandible is a singular bone considered separate to the viscerocranium

Image taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
...


Taken from Slideshare
...
slideshare
...
com, Skull, Sinuses and Facial Bones, available at
https://uk
...
com/pin/511158626432667613/

Superior aspect of cranium









Superior vertical aspect is generally oval in form, broadening posterolaterally
at the parietal eminences
Coronal suture separates the frontal and parietal bones
Sagittal suture separates the two parietal bones
Lambdoid suture separates the parietal and temporal bones from occipital
Bregma is the intersection of the coronal and sagittal sutures
Lambda is the intersection of the sagittal and lambdoid sutures
The vertex is the most superior point of the calvaria, and is located near the
midpoint of the sagittal suture
Parietal foramen is a small, inconsistent aperture in parietal bone near the
sagittal suture

Taken from Principles of Human Anatomy and Physiology, Chapter 7: Anatomy of Bones and
Joints, available at http://hap1nuo1group3
...
co
...
html

External surface of cranial base








Basicranium is the inferior part of the neurocranium and viscerocranium,
minus the mandible
External surface features
o Alveolar arch of maxillae
o Palatine processes of maxillae
o Palatine, sphenoid, vomer, temporal and occipital bones
Hard palate (bony) is formed by the palatine processes of the maxillae
anteriorly and the palatine bones posteriorly
o Free posterior border of the hard palate projects posteriorly in the
medial plane as the posterior nasal spine
o The incisive foramen are located in the midline of the hard palate
inbetween the two maxillae bones – incisive canals open into here
 Right and left nasopalatine nerves pass from the nose through
incisive canals and foramina
o Posterolaterally are the greater and lesser palatine foramina, located
in the palatine bones
Superior to posterior ridge of hard palate are chonae, separated by the
vomer (flat, unpaired, trapezoid-shaped bone, major part of nasal septum)
The sphenoid is an irregularly shaped bone wedged between the frontal,
temporal and occipital bones
o Consists of a body and three processes – greater wings, lesser wings,
and pterygoid processes
o Greater and lesser wings spread laterally from lateral aspects of body
o Pterygoid processes consist of lateral and medial pterygoid plates











 Extend inferiorly at junction of the body and the greater wings
o Groove for the cartilaginous part of pharyngotympanic (auditory) tube
lies medial to spine of the sphenoid, inferior to where the great wing of
sphenoid meets the petrous (rock-like) section of the temporal bone
Depressions in the squamous part of the temporal bone (mandibular fossae)
accommodate the mandibular condyles when the mouth is closed
Posterior part of the cranial base is formed from the occipital bone
(articulates with sphenoid anteriorly)
The parts of the occipital bone are arranged around the foramen magnum
o Lateral aspect of occipital bone are the occipital condyles – cranium
articulates with the vertebral column
Structures passing through the foramen magnum
o Spinal cord (becomes continuous with medulla oblongata)
o Meninges
o Vertebral arteries
o Anterior and posterior spinal arteries
o Spinal accessory nerve (CN XI)
Jugular foramen is located between the occipital bone and petrous part of
the temporal bone – internal jugular vein and CN IX-XI pass
Carotid canal anterior to the jugular foramen, in temporal bone – internal
carotid artery passes
Stylomastoid foramen lies posterior to styloid process – facial nerve (CN VII)
and stylomastoid artery go via here

Taken from Slideshare
...
com/slide/8629130/

Internal surface of cranial base


Three large depressions located at different levels, which form cranial cavity
o Anterior cranial fossa (highest level)
o Middle cranial fossa
o Posterior cranial fossa (lowest level)

Anterior cranial fossa




Inferior and anterior parts of frontal lobes occupy the anterior cranial fossa
Shallowest of the three fossae
Formed by the following bones
o Frontal bone anteriorly (greater part of the fossa)
 Supports frontal lobes – can see brain markings (sinous
impressions)
 Frontal crest is a median bony extension of the frontal bone –
foramen cecum located at its base (vessels pass in foetus but
no function in adults)
o Ethmoid bone medially
 Crista galli is thick, median ridge of bone posterior to the
foramen cecum
 Cribiform plate of the ethmoid located laterally to the crista
galli; contains numerous tiny foramina to transmit the olfactory
nerve (CN I) from olfactory areas to the olfactory bulb of the
brain, which lies on this plate
o Body and lesser wings of sphenoid posteriorly

Middle cranial fossa








Butterfly shaped
Central part composed of the sella turcica located on the body of the
sphenoid, and lateral parts on each side composed of greater wings of
sphenoid and temporal bones
Separated from the anterior fossa by the spenoidal limbus centrally and
sphenoidal crests laterally
Sphenoid crests form mostly from posterior borders of lesser wings of sphenoid
o Sphenoid crests end medially in two sharp bony projections – anterior
clinoid processes
Limbus of sphenoid forms the anterior boundary of the prechiamatic sulcus

Taken from Studyblue
...
studyblue
...
Moore et al
...
Seventh Edition

---