Anatomy Wk 3 Flashcards
What two sets of bones is the skull formed by
The neurocranium - encloses and protects the fragile brain tissue and its divided into calvaria (skullcap), and a floor or cranial base (basicranium)
The facial bones
All but one of the bones of the skull are joined together by sutures, which are interlocking, immovable joints.
Only the mandible (jawbone) is attached to the rest of the skull by a freely movable joint.
What is the neurocranium
The boxlike cranium is composed of eight large flat bones. Except for two sets of paired bones (the parietal and temporal), they are all single bones (frontal, ethmoid, sphenoid and occipital)
Most calvarial bones are united by fibrous interlocking sutures; however, during childhood, some bones (sphenoid and occipital) are united by hyaline cartilage (synchondroses)
What are the fortanelles (soft spots)
membranous connective tissue between the bones of the skull, particularly between the large flat bones, allow:
The head to deform during its passage through the birth canal (molding of the cranium)
The average closure time of fontanelles
are 6 - 24 months
What is the anterior view of the cranium
the forehead superiorly and inferiorly the orbits
What is the lateral view
frontal, parietal, occipital, sphenoid and
temporal bones
What is the posterior view
occipital, parietal and temporal
What is the superior view
The frontal bone, parietal bones and occipital bone are seen in superior view of the skull
In an anterior to posterior direction:
- The unpaired frontal bone articulates with the paired parietal bones at the coronal suture
• The two parietal bones articulate with each other in the midline at the sagittal suture
• The parietal bones articulate with the unpaired occipital bone at the lambdoid suture
What is the function of the lambda and the bregma
stereotactic identification of parts of the brain as in neurosurgery or in research, it is important to know where in the brain a surgical intervention will take place
What is the inferior view
the base of the skull is often divided into:
• An anterior part, which includes the teeth and hard palate
• A middle part, which extends from behind the hard palate to the anterior margin of the foramen magnum
• A posterior part, which extends from the anterior edge of the foramen magnum to the superior nuchal lines
What is the cranial cavity (roof)
The calvaria is the dome-shaped roof that protects the superior aspect of the brain. It consists mainly of the frontal bone anteriorly, the paired parietal bones in the middle and the occipital bone posteriorly
Sutures visibile internally include:
The coronal suture, between the frontal and parietal bones
The sagittal suture, between the paired
parietal bones
The lambdoid suture, between the parietal and occipital bones
What are the cranial cavity markings
Frontal crest - a midline ridge of bone extending from the surface of the frontal bone which is a point of attachment for falx celebri
Groove for the superior sagittal sinus - which marks the position of the superior sagittal sinus (an intradural venous structure)
Granular foveolae - which mark the location of arachnoid granulations (structures involved in the reabsorption of cerebrospinal fluid)
On the lateral aspects smaller grooves created by various meningeal vessels
What is frontal bone
Frontal bone - forms the forehead, the bony projections under the eyebrows and superior part of each eye’s orbit
What does the frontal bone also form
superior part of the rim of each orbit
Superior to the rim of the orbit on each side are raised superciliary arches
Between these arches is a small depression (the glabella)
In supra orbital notch (foramen) passes - supra orbital nerve and vessels
What are the parietal bones
the paired bones form the most of the superior and lateral walls of the cranium.
The sagittal suture is formed at the midline where the two parietal bones meet and the
coronal suture is formed where the paired parietal bones meet the frontal bone
What are the temporal bones
lie inferior to the parietal bones and join them at the squamous sutures
What are the bone markings on the temporal bones
The external acoustic meatus is a canal that leads to the eardrum and the middle ear
The styloid process, a sharp , needlelike projection. Many neck muscles use the styloid process as an attachment point
The zygomatic process, is a thin bridge of bone that joins with the zygomatic bone anteriorly
The mastoid process, which is full of air cavities (the mastoid sinuses), is a rough projection. It provides an attachment site for some muscles of the neck
What is the jugular foramen
at the junction of the occipital and temporal bones allowes passage of the jugular vein, the largest vein of the head, which drains blood from the brain
Just anterior to it in the cranial cavity is the internal acoustic meatus which transmits cranial nerves VII and VIII (the facial and vestibulocochlear nerves)
What is anterior to the jugular foramen
on the skull’s inferior aspect is the carotid canal, through which the internal carotid artery runs, supplying blood to most of the brain
What is the occipital bone
Is the most posterior bone of the cranium. It forms the base and back wall of the skull.
The occipital bone joins the parietal bones anteriorly at the lambdoid suture.
In the base of the occipital bone is a large opening, the foramen magnum.
Lateral to the foramen magnum on each side are occipital condyles, which rest on the first vertebra of the spinal column
What is the sphenoid bone
The butterfly shaped sphenoid bone spans the width of the skull and forms part of the floor of the cranial cavity
In the midline of the sphenoid is a small depression, the sella turcica (*lat.) or Turk’s saddle, which forms a snug enclosure for the pituitary gland
The foramen ovale, a large oval opening in line with the posterior end of sella turcica, allows fibers of cranial nerve V (the trigeminal nerve) to pass to the chewing muscles of the mandible
What are the two most important openings of the sphenoid bone
The optic canal, which allows the optic nerve to pass to the eye
The superior orbital fissure, through which cranial nerves controlling eye movements (III, IV, and VI) pass
What is the ethmoid bone
Is very irregularly shaped and lies anterior to the sphenoid. It forms the roof of the nasal cavity and part of the medial walls of the orbits
Projecting from its superior surface is the crista galli. The outermost covering of the brain attaches to this projection
On each side of the crista galli there are many small holes. These holey areas, the cribriform plates, allow nerve fibers carrying impulses from the olfactory (smell) receptors of the nose to reach the brain
What are the cranial sutures
Begins anteriorly with the frontal bone, which in upper regions articulates with the parietal bone at the coronal suture
The parietal bone then articulates with the
occipital bone at the lambdoid suture
In lower parts the frontal bone articulates with the greater wing of the sphenoid bone, which then articulates with the parietal bone at the sphenoparietal suture and with the anterior edge of the temporal bone at the sphenosquamous suture
Articulation between the temporal bone and the
occipital bone - occipitomastoid suture
What is Pterion
In the anterior part of the temporal fossa, superior to the midpoint of the zygomatic arch, is the pterion
It is usually indicated by a roughly H shaped formation of sutures that unite the frontal, parietal, sphenoid (greater wing) and temporal bones
The anterior branch of the middle
meningeal artery runs beneath the pterion
The skull at this point is thin, therefore it is
vulnerable to injury
What are sutures bones
Along the lambdoid suture small islands of bone (sutural bones or wormian bones) may be observed
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