1. Part 1: Bones of the Cranium
Parts of the Skull
Part 1: Bones of the Cranium

2. Objectives
Be able to locate and identify the bones and the major features of the bones that comprise the skull
Be able to describe the distinguishing features between males and females in the features of the skull

3. Anterior View of the Skull

4. Orbit of the Eye

5. Lateral View of the Skull

6. inferior View of the Skull

7. The Human Skull
Consists of 22 bones that are firmly interlocked along sutures, except for the lower jaw
Eight of these bones make up the cranium
Fourteen of these bones make up the facial skeleton
The mandible or lower jawbone is movable and attached to the cranium by ligaments
Some facial and cranial bones together form the orbit of the eye

8. The Cranium Encloses and protects the brain
Its surface provides attachments for muscles that allow chewing and head movements
Some cranial bones contain air-filled cavities called paranasal sinuses

9. The Sinuses
These cavities are lined with mucous membranes and are connected by passageways to the nasal cavity
They reduce the weight of the skull
Serve as resonant sound chambers by increasing the intensity of the voice

10. Paranasal Sinuses

11. Bones of the Cranium Frontal bone Parietal bone (2) Occipital bone
Temporal bone (2)
Sphenoid bone
Ethmoid bone

12. Frontal bone Forms the anterior portion of the skull above the eyes
Makes up the forehead, the roof of the nasal cavity and the roofs of the orbits (sockets) of the eyes
On the upper margin of each orbit, the frontal bone is marked by a supraorbital foramen (or supraorbital notch)
Through here blood vessels and nerve pass to the tissues of the forehead
Within the frontal bone, are the two frontal sinuses
The frontal bone is a single bone in adults but develops in two parts and is not completely fused until 5-6 years of age

13. Parietal bone
Locate on each side of the skull just behind the frontal bone
Shaped like a curve plate and has four borders
Together, the parietal bones form the bulging sides and roof of the cranium
They are fused at the midline along the coronal suture

14. Occipital bone Joins the parietal bones along the lambdoid suture
Forms the back of the skull and the base of the cranium
A large opening on its lower surface is the foramen magnum
This is where the inferior part of the brain stem connects with the spinal cord
Rounded processes called occipital condyles, located on each side of the foramen magnum, articulate with the first vertebra (atlas) of the vertebral column

15. Temporal bone Located on each side of the skull
It joins the parietal bone along a squamous suture
Forms part of the side and base of the cranium
Located near the inferior margin is an opening, the external acoustic meatus, which leads inward to parts of the ear
The temporal bones house the internal ear structures
They also have depressions called the mandibular fossae (glenoid fossae) that articulate with condyles of the mandible

16. Projections of the Temporal bone
Below each external acoustic meatus are two projections:
A rounded mastoid process and a long, pointed styloid process
The mastoid process provides an attachment for certain muscles of the neck
The styloid process anchors muscles associated with the tongue and pharynx
The zygomatic process projects anteriorly from the temporal bone
It joins the temporal process of the zygomatic bone and helps form the prominence of the cheek known as the zygomatic arch

17. Openings near the Temporal bone
The carotid canal, which transmits the internal carotid artery is located near the mastoid process
Between the temporal and occipital bones is an opening called the jugular foramen, which accommodates the internal jugular vein

18. Sphenoid bone
Is wedged between several other bones in the anterior portion of the cranium
Consists of a central part and two wing-like structures that extend laterally toward each side of the skull
Helps to form the base of the cranium, the sides of the skull, and the floors and sides of the orbits
A portion of the sphenoid bone indents to form the saddle-shaped sella turcica (Turk’s saddle)
The pituitary gland lies here
There are also two sphenoidal sinuses within

19. Ethmoid bone Is located in front of the sphenoid bone
Consists of two masses, one on each side of the nasal cavity that are joined horizontally by thin cribriform plates
These plates form part of the roof of the nasal cavity and nerves associated with the sense of smell pass through tiny openings called olfactory foramina
Portions of this bone also form sections of the cranial floor, orbital walls, and nasal cavity walls
It contains ethmoidal sinuses, who warm and filter the air that enters the respiratory system

20. Other Structures Connected to the Ethmoid bone
A perpendicular plate projects downward in the midline from the cribriform plates to form most of the nasal septum
Delicate, scroll-shaped plates called the superior nasal concha and the middle nasal concha project inward toward the perpendicular plate
Projecting upward into the cranial cavity between the cribriform plates is a triangular process called the crista galli (cock’s comb)

21. The Ethmoid Bone