1. Axial Skeleton: Cranial Bones
Nestor T. Hilvano, M.D., M.P.H.
(Illustrations Copyright by Frederic H. Martini, Pearson Publication Inc., and The McGraw-Hill Companies Inc.)

2. Learning Objectives You should be able to:
Identify the bones of axial skeleton and their functions.
Identify the cranial bones including its parts and surface markings.
Describe the differences among the skull of infants and children compared to adults.
Define craniostenosis and discuss the consequences associated with this anomaly.

3. Overview of Skeletal System
Number of bones
206 in adult skeleton
start at 270 at birth
Regions of the skeleton
I- Axial skeleton
= 80 bones
1) Skull and associated bones
2) Thoracic cage
3) Vertebral column
II- Appendicular skeleton
= 126 bones
1) Pectoral (shoulder) girdle and Upper limbs
2) Pelvic (hip) girdle and Lower limbs

4. Skull: Cranial Bones
8 Cranial bones – frontal (1), parietal (2), occipital (1), temporal (2), sphenoid (1), and ethmoid (1)
7 associated bones – auditory ossicles (6) and hyoid bone (1)

5. Sutures
Calvaria (skullcap) is formed by frontal, parietal, and occipital bones
Sutures:
___ between the frontal bone and parietal bone.
___ between the parietal bone and occipital bone.
___ between the two parietal bones.
___ between the parietal bone and temporal bone.
a. sagittal suture b. squamous suture
c. lambdoid suture d. coronal suture

6. Frontal Bone
Forms the anterior part of the ___________ and roof of the _________
Contains frontal sinus
Landmarks: frontal squama, supraorbital margin, lacrimal fossa
Supraorbital foramen

7. Parietal Bone Form part of the ____ and ____ surfaces of cranium
Bordered by 4 sutures
Landmarks: Temporal lines for attachment of _________ muscle

8. Temporal Bone ________ wall and part of ______ of cranial cavity
Consists of:
a. Squamous part
- zygomatic process
- mandibular fossa
b. Mastoid process
c. Styloid process
d. Petrous (bone) part
- houses middle and inner ear cavities
- internal acoustic (auditory) meatus
- jugular foramen

9. Right Temporal Bone

10. Openings in Temporal Bone
Carotid canal
passage for __________
artery
Jugular foramen
Passage for __________

11. Occipital Bone ______________ of skull Foramen magnum
Skull rests on atlas (C1) at occipital condyles
Hypoglossal canal transmits ___________ nerve
External occipital protuberance
Nuchal lines mark neck muscles

12. Sphenoid Bone Part of the floor of the cranium Lesser wing
Greater wing
Body of sphenoid
Medial and lateral pterygoid processes
- attachment sites for
muscles that move the
mandible and soft palate
___________ sinus

13. Sphenoid Bone Body of the sphenoid Lesser wing Greater wing
sella turcica (hypophyseal fossa) contains ____.
Lesser wing
optic foramen
Greater wing
foramen rotundum and ovale for brs. trigeminal nerve
foramen spinosum for meningeal artery

14. Ethmoid Bone Medial orbital wall Lateral walls and roof nasal cavity
Cribriform plate and crista galli
Ethmoid air cells form ethmoid sinus
Perpendicular plate forms _______ septum
Superior and middle Conchae on lateral wall

15. Ethmoid Bone Perpendicular plate Superior and middle of nasal septum
concha

16. Skull of infants and children
Spaces between unfused bones = fontanelles (fontanels)
What purpose does a fontanel serve? ______.
Anterior fontanel closes at 2 yrs. old.
2 frontal bones fuse by age six (metopic suture)
Skull reaches adult size by 8 or 9
Craniostenosis – premature closure of cranial sutures

17. Craniostenosis
Long and narrow head is formed by early closure of sagittal suture
Broad (tower) skull results from premature closure of coronal suture

18. Bones Associated With Skull
Ossicles
malleus, incus, and stapes
Hyoid bone
suspended from styloid process of skull by muscle and ligament
Supports larynx and attachment site for muscles of pharynx, larynx, and tongue
Body, greater and lesser cornua (horns)
Only bone in the body that does not articulate with another bone
* What are the smallest bones? _____

19. Homework Describe the cranial sutures and fontanelles.
Identify the cranial bones associated with the following regions or landmarks.
__ temporal lines a) occipital
__ sella turcica, lesser/greater wings b) frontal
__ roof of orbits, bone of forehead c) parietal
__ crista galli & cribriform plate d) temporal
__ mastoid process, petrous bones e) ethmoid
__ base of skull, foramen magnum f) sphenoid
What is craniostenosis?
The internal acoustic meatus is located in which bone?
What is the content of the hypophyseal fossa of the sella turcica?