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.)

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.

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

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)

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

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

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

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

Right Temporal Bone

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

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

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

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

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

Ethmoid Bone Perpendicular plate Superior and middle of nasal septum concha

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

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

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? _____

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?