KIN 1Y03 Lecture 25: Axial Skeleton (Skull + Hyoid)

how many bones in body

206 (more in children but they fused together)

divisions of bones

axial (skull, hyoid, vertebrae, ribs, sternum, auditory ossicles)

• 80 bones

appendicular (on limbs, pevic, pectoral girdles)

• 126 bones

girdles

attachment sites between axial and appendicular skeletons

ridges vs projections vs openings vs depression

ridges: point of attachment for muscles on bones, providing bony feature that stick out → allowing muscles and tendons to attach (eg. spine of scapula)

projections: (AKA processes)provide attachment point for muscles/ligaments that are trying to cross joints (eg. tubercles)

openings: “holes“ (eg. formina, canals)

depression: shallow depressions (eg. fossa, grooves, notches)

condyle vs facet of bones

condyle: smooth, rounded articular surfaces (where joints will form)

facet: small flatten part of bone

2 major portions of the skull bones

cranial bones (8)

• 2 parietal

• 2 temporal

• 1 frontal

• 1 occipital

• 1 sphenoid

• 1 ethmoid

facial bone (14)

• 2 maxilla

• 2 zygomatic

• 2 palatine

• 2 lacrimal

• 2 nasal

• 2 inferior nasal conchae

• 1 vomer

• 1 mandible

cranial bones how many and what

(8 bones total) PTFOSE

• 2 parietal

• 2 temporal

• 1 frontal

• 1 occipital

• 1 sphenoid

• 1 ethmoid

facial bones how many and what

(14 bones total) MZPLNIVM (mom! zoe palatine loves nasty, innocent, viggo mortensen)

• 2 maxilla

• 2 zygomatic

• 2 palatine

• 2 lacrimal

• 2 nasal

• 2 inferior nasal conchae

• 1 vomer

• 1 mandible

parietal bone

2 bones (R/L) that make up sides and roots of cranial cavity

temporal bone

2 bones (R/L) that make up lateral cranial cavity + floor of cranial cavity

• 3 projections

  • zygomatic process: bone projection that makes up regions of the cheek (cheekbone)

  • mastoid process: attachment point for neck muscles

  • styloid process: attachment bone for muscles of tongue + neck

• 1 fossa

  • mandibular fossa: depression forms part of the temporomandibular joint (TMJ)

• 2 foramen

  • carotid foramen: where arteries enter into the cranial cavity

  • jugular foramen: where veins that are draining blood from skull/brain are leaving

what are the projections in the temporal bone

• 3 projections

  • zygomatic process: bone projection that makes up regions of the cheek (cheekbone)

  • mastoid process: attachment point for neck muscles

  • styloid process: attachment bone for muscles of tongue + neck

what are the fossa’s and foramens in the temporal bone

• 1 fossa

  • mandibular fossa: depression forms part of the temporomandibular joint (TMJ)

• 2 foramen

  • carotid foramen: where arteries enter into the cranial cavity

  • jugular foramen: where veins that are draining blood from skull/brain are leaving

zygomatic arch and external auditory canal

Zygomatic arch: connection between zygomatic bone & temporal bone ⇒ forms cheekbone 

External auditory canal: (AKA external auditory meatus/external acoustic meatus) 

⤷ hole leading into temporal bone, w reach middle/inner ear structure 

frontal bone

1 bone that makes up forehead, root of orbit (hole of the eye), anterior part of the cranial floor — allows it to be kept in the upper portion of the skull

• og = made of 2 front bones, but fused together @ age 6

occipital bone

1 bone in the posterior-inferior side that is mostly the base of the skull

occipital condyle

in occipital bone

will articular w C1 vertebrae that allows for movement of skull relative to C1 vertebrae in DIR of nodding YES/tilt ear to shoulders

external occipital protuberance

in occipital bone

bump on back of skull that joins 2 ligaments that hold upright

sphenoid bone

“bat/butterfly“ shaped structure that articulates w all other cranial bones

• makes up portion of lateral, cranial floor + portion of orbital (eye)

ethmoid bone

1 bone thats located at the roof of the nasal cavity between the eyes, separating the nose from the brain and forming part of the eye sockets

• has cribiform

facial bones

(14 bones total)

• 2 maxilla

• 2 zygomatic

• 2 palatine

• 2 lacrimal

• 2 nasal

• 2 inferior nasal conchae

• 1 vomer

• 1 mandible

maxilla bone

2 bones (AKA maxillary bones) that form upper jaw, floor of orbits, nasal cavity, and most of hard plate

alveolar process of maxilla

create spaces so teeth can fit into upper and lower jaw

• part of the maxillary bone

zygomatic bone

2 bones that form the prominent part of the cheek and the outer side of the eye socket

palatine process

part of maxilla, that makes up large portion of roof of mouth and will fuse tog during embryo

• bad fusion = cleft lip/palate

what happens if the palatine process isn’t properly fused

Bad fusion

⤷ cleft lip: not fused on soft portion of skin 

⤷ cleft palate: when maxillary bones are not fusing together 

→ results in space between oral and nasal cavity (life threating bc can’t eat properly and food goes into nasal 

palatine bone

2 bones that are “L-shaped“, forming a horizontal plate @ back of roof of mouth

lacrimal bone

2 bones — smallest bone in face, has canals w lacrimal sac, found in eye orbit (makes tears)

nasal bone

2 bones that form upper portion of bridge of nose + anterior roof of nasal cavity

• has 3 main components:

  • perpendicular plate of ethmoid bone: making up superior and posterior portion of nasal septum

  • middle nasal concha of ethmoid bone: has superior nasal concha → both ridges on ethmoid bone

• inferior nasal conchae of ethmoid bone: ridges that help create turbulent flow of air → help trap air particles before they enter respiratory system

  • » move odorants towards olfactory epithelium regions

vomer bone

1 bone that’s thin, small, and separates the L/R nasal cavities

• forms inferior and posterior regions of nasal septum

mandible

1 bone — the strongest and largest bone thats not actually “attached to other bones”

• only articulates w temporal bone @ mandibular fossa

• only moveable bone in skull (other than auditory ossicles and hyoid)

foramen magnum

large, round, hole, where spinal cord will connect to brainstem

hyoid bone

unpaired (“floating bone:”) — single bone that doesn’t articulate w any other bone

• found just below chin, “floating“ under mandible

has attachment point for tongue muscles (superior side) + neck muscles that elevate larynx (inferior side) during speech/swallowing