Head & Skull

Cranium

-anatomical position for head

2 parts

• neurocranium

• viscerocranium

Orbitomeatal plane

defined by inferior margin of orbit & superior margin of
the external acoustic meatus (EAM)

Calvaria

the roof of the neurocranium

Neurocranium “the brain case”

formed by 8 bones:

4 singles- frontal, occipital, sphenoid, ethmoid

2 paired- 2 temporals and 2 parietals

Occipital bone

• Landmarks-

• Internal surface-

Landmarks
▪ Foramen magnum
▪ Occipital condyles – bilateral convexities that
articulate with C1
▪ Superior and inferior nuchal lines
▪ External occipital protuberance
Internal surface:
▪ Internal occipital protuberance
▪ deep grooves for transverse sinuses

Temporal Bone

• lateral view

• medial view

Lateral view
▪ External acoustic meatus
▪ Styloid process

▪ Mastoid process
▪ Zygomatic process
▪ Squamous part

Medial view
▪ Petrous part - (L. stone-like)
▪ Internal acoustic meatus (CN VII & CN VIII)
▪ Styloid process - a sharp spine, about 2 - 2.5 cm. in length

Sphenoid bone

A very complex, irregular bone
Forms : Part of orbit
- part of Ant. Cranial Fossa
- part of Middle Cranial Fossa
- part of the Temple, just anterior to the temporal bone
Contains:
- Ant. poles of frontal lobes
- Sella Turcica
- Multiple Neural foramina
- Pterygoid plates : muscle attachments

Sphenoid bone superior view

• sella turcica “turkish saddle”

• sella turcica contains the hypophysial fossa in which lies the pituitary gland (hypophysis)

• Sphenoid also contains:

  • optic canal, foramen rotundum, foramen ovale

Sphenoid bone

• Trans-sphenoidal surgical approach

• Utilized for intracranial surgery, such as pituitary tumor

• Instruments are inserted into part of the brain by passing through an incision made under the upper lip or at the bottom of the nose between the nostrils and then through the sphenoid bone

• Notably less invasive than open procedure

Cranial sutures

• sagittal

• bregma

• lambda

• Sagittal suture formed by joining of two parietal bones

• Bregma junction of coronal and sagittal sutures

• Lambda λ junction of sagittal and lambdoid sutures

Viscerocranium

• Facial skeleton

  • upper and lower jaw

  • nose and nasal cavity

  • most of the orbits

Viscerocranium is composed of 15 irregular bones

• 3 singular bones lying in midline: Mandible, ethmoid, vomer

• 6 bones as bilateral pairs: Maxillae, zygomatic, palatine, nasal,
  Lacrimal , inferior nasal conchae

Viscerocranium

• orbits (eye sockets)******

  • orbital rim formed by _,_, &_

  • remaining bones of orbit: _,_,_,&_

  • Orbit houses and protects…

• Orbital rim formed by maxilla, zygomatic, and frontal bones

• Remaining bones of orbit: Sphenoid, Lacrimal, Ethmoid, Palatine

• Orbit houses and protects eyeball, extraocular muscles, related nerves & vessels, lacrimal gland, orbital fascia and fat

Cranium landmarks/features (“know these landmarks for the skull!”)

• Temporal fossa

• External occipital protuberance (EOP)

• **Pterion**- 4 bones meet**- anterior branch of the middle meningeal artery passes beneath pterion

• Zygomatic arch

• Mastoid process

• External acoustic meatus

Mandible (“you should know these landmarks”)

▪ -Body
▪ -Ramus - the “vertical portion”
▪ -angle - intersection of Ramus & body
▪ -mental protuberance - prominent anterior region
▪ -condylar process - blunt, posterior knuckle-shaped
projection that forms convexity of the TMJ
▪ -coronoid process - more sharply angled projection- anterior to condylar process. Inferior attachment of temporalis

Skull (median section)

• internal features

• Cribiform plate (ethmoid bone)

• Internal acoustic meatus

• Basilar aspect of occipital bone

• Foramen magnum

• Sella turcica

• Jugular foramen

Foramina of Cranial Base

• inferior view

• Mandibular fossa

• Zygomatic process

• Basilar part of Occiput

• Foramen Magnum

• Mastoid Process

• Stylomastoid foramen (CN VII)

• Carotid canal

• External acoustic meatus

Foramina of Cranial base (will ask questions on superior )

• Optic canal

  • CN II Optic nerve

• Superior orbital fissure

  • CN V1 (5- the 1st part) Ophthalmic nerve

  • CN III Oculomotor nerve

  • CN IV Trochlear nerve

  • CN VI Abducent nerve

• Foramen rotundum

  • CN V2 Maxillary nerve

• Foramen Ovale

  • CN V3 Mandibular nerve

internal carotid artery

ICA enters inferior aspect of temporal bone. The artery takes a near 90 degree turn and travels anteromedially – emerges internally at foramen lacerum and turns superiorly to join Circle of Willis

Dura Mater

• Dura mater adheres to internal aspect of calvaria (periosteal layer)

• The deeper layer (meningeal layer), folds back from the periosteal layer to form infoldings that create the dural sinuses and as well as the following:

  • Falx cerebri

  • Tentorium cerebelli

  • Falx cerebelli

Falx cerebri

• Large dural infolding between cerebral hemispheres

• Runs anterior to posterior

• Attaches anteriorly: frontal crest of frontal bone & crista galli of ethmoid

• Posterior attachment: internal occipital protuberance

Tentorium cerebelli

• is “tent-like” (L. tentorium, tent)

  • Dural infolding that separates the Occipital lobes of the cerebral hemispheres from cerebellum

• Compartments formed by tentorium are known as:

  • Supratentorial

  • Infratentorial

• The Falx cerebelli is a dural infolding that partially separates the cerebellar hemispheres

Pia mater

• deepest meningeal layer

• Very thin, highly vascularized

• Pia adheres to brain surface and follows contours into sulci of cerebral cortex

• Also covers spinal cord and its fissures

“NO QUESTIONS ON DURAL VENOUS SINUSES ON FINAL”

Epidural hemorrhage

• occurs in the potential space between the dura and the cranium

• Laceration of the middle meningeal artery and its accompanying dural sinuses is the most common etiology.

Subdural hematoma

• Bleeding within the dural-arachnoid junction creates a “pathological space”

• Shift of midline structures and is visible with imaging

  • Usually results from head trauma
    - 50% mortality rate

will not ask function of the lobes of cerebrum, may reference them in a question referring to an injury

• will not ask about sulci

• will not need to know cerebrum medial stem

• will not ask about ventricles

• WILL ASK ABOUT THREE PARTS OF BRAINSTEM

Need to know three parts of brain stem***

• Brainstem

• Midbrain (Mesencephalon) is the most superior aspect of

brainstem

• Pons (L. bridge ) lies between midbrain and medulla oblongata

  • Pons lies in anterior aspect of posterior cranial fossa

• Medulla oblongata is the most inferior division of the brainstem

  • Medulla continuous with spinal cord

3 parts of brain stem:

1. Brainstem

• Midbrain (Mesencephalon) is the most superior aspect of

brainstem

3 parts of brain stem

2. Pons

• Pons (L. bridge ) lies between midbrain and medulla oblongata

  • Pons lies in anterior aspect of posterior cranial fossa

3 parts of brain stem

3. Medulla oblongata

is the most inferior division of the brainstem
- Medulla continuous with spinal cord