1111V TOPIC 4 LECTURE 1

Introduction to the skeleton and the skull

How many bones are in the skeleton and what is its body weight percentage makeup?

206 bones, around 20% of body weight

What are the two divisions of the skeleton and explain their respective parts

Axial (skull, thoracic cage and vertebral column) and the appendicular (upper and lower limbs, pelvic girdle, pectoral girdle)

What kind of bones form the skull and how many are there in total?

The skull is formed by 22 bones, which include both the cranial and facial bones.

How are bones connected?

through sutures, which are serrated (almost ridged looking) interlocking joints 

What kind of bones are most skull bones, explain any extra information.

Most skull bones are flat, except for the mandible which is very irregular

Cranium

Upper part of the skull, includes all cranial bones (ethmoid, frontal, occipital, parietal, sphenoid, temporal)

What are the two parts of the cranium?

Vault (superior, lateral and posterior skull and the forehead) and the base (inferior aspect of the skull) 

What is the main role of the cranium? 

Houses and protects the brain and organs of hearing and balance 

What are the three parts of the cranial base

anterior fossa, middle fossa, posterior fossa

What do facial bones do

1) framework of the face 2) cavities for sensory organs (sight, smell, etc.) 3) provide openings for air and food passage 4) secure the teeth 5) anchor facial muscles to create expressions 

Describe pairings of the cranial bones and how of them there are (including the paired) 

8 parts total, paired: temporal, parietal; unpaired: ethmoid, sphenoid, occipital frontal

What advantage does the structure give the skull

curvature strengthens the skull but it still is able to be thin but protective

What are the fossa and what is their job

anterior, middle posterior fossa are shelving units that support the weight of the brain

Frontal bone

1) forms the roof of the orbits and the anterior cranial fossa

2) articulates with paired parietal bones posteriorly 

3) has holes superior to orbit (supraorbital foramen) 

4) supraorbital margin 

5) flat part above nasal bone (glabella) which includes left and right sinuses 

Parietal bones

1) paired

2) bulk of cranial vault

Occipital bone 

1) single nome 

2) posterior aspect of the skull and fossa (base of the skull) 

3) attaches anteriorly to the 2 parietals and 2 temporal and attaches to sphenoid

4) passage for vertebral column (foramen magnum)

5) occipital condyles: boney projections, sit on top of the first cervical vertebra, move head

6)  external occipital protuberance: projection at the back of the skull

Temporal bones

1) below parietal bone

2) squamous, tympanic

3) petrous

Squamous part

1) zygomatic process (attaches the zygomata) 

2) flat

3) receives condyle of mandible (so you can move jaw) 

Tympanic part

surrounds external acoustic meatus (hear things)

Petrous part

1) cranial base, ear cavities

2) mastoid process: attachment site for neck muscles)

3) styloid process: (skinny projection) attachment area for muscles of the tongue/some neck muscles

Sphenoid bone

1) complex (wings, processes) and central (articulation)

2) base of middle cranial fossa

Sphenoid projections (names only) 

1) greater and lesser wings 

2) pterygoid processes 

3) optic foramina 

4) superior orbital fissure 

5) central body 

Greater and lesser wings 

Greater (bigger) and lesser (smaller) contribute to orbits and MCF and ACF 

pterygoid processes

attachment site for chewing muscles in the sphenoid

Optic canal / foramina 

openings for optic nerves 

Superior orbital fissures

passageways for nerves (eye movement)

Central body

contains the sphenoid sinuses