Anatomy Wk 3

Question 1

What two sets of bones is the skull formed by

Answer 1

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.

Question 2

What is the neurocranium

Answer 2

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)

Question 3

What are the fortanelles (soft spots)

Answer 3

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

Question 4

What is the anterior view of the cranium

Answer 4

the forehead superiorly and inferiorly the orbits

Question 5

What is the lateral view

Answer 5

frontal, parietal, occipital, sphenoid and
temporal bones

Question 6

What is the posterior view

Answer 6

occipital, parietal and temporal

Question 7

What is the superior view

Answer 7

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

Question 8

What is the function of the lambda and the bregma

Answer 8

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

Question 9

What is the inferior view

Answer 9

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

Question 10

What is the cranial cavity (roof)

Answer 10

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

Question 11

What are the cranial cavity markings

Answer 11

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

Question 12

What is frontal bone

Answer 12

Frontal bone - forms the forehead, the bony projections under the eyebrows and superior part of each eye’s orbit

Question 13

What does the frontal bone also form

Answer 13

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

Question 14

What are the parietal bones

Answer 14

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

Question 15

What are the temporal bones

Answer 15

lie inferior to the parietal bones and join them at the squamous sutures

Question 16

What are the bone markings on the temporal bones

Answer 16

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

Question 17

What is the jugular foramen

Answer 17

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)

Question 18

What is anterior to the jugular foramen

Answer 18

on the skull’s inferior aspect is the carotid canal, through which the internal carotid artery runs, supplying blood to most of the brain

Question 19

What is the occipital bone

Answer 19

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

Question 20

What is the sphenoid bone

Answer 20

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

Question 21

What are the two most important openings of the sphenoid bone

Answer 21

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

Question 22

What is the ethmoid bone

Answer 22

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

Question 23

What are the cranial sutures

Answer 23

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

Question 24

What is Pterion

Answer 24

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

Question 25

What are sutures bones

Answer 25

Along the lambdoid suture small islands of bone (sutural bones or wormian bones) may be observed

Question 26

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