ANAT200 axial skeleton

kms

functions of the axial skeleton

SPHAM!!!

1. Supportive & PROTECTIVE framework for internal organs

   (e.g., brain, spinal cord, heart, lungs…)

2. Skull Houses special sensory organs

   (e.g., ear - hearing, tongue - taste, eyeball - sight,

   nose - smell)

3. Vertebral column & ribs provide extensive Attachment

   for muscles moving the head, neck, trunk, & limbs

4. Thoracic cage performs Movements during respiration (it helps you breathe)

how many bones are in the axial skeleton?

80

true or false: most bones in the axial skeleton are paired up, but not all

true

true or false: the skull is not divided into parts

false.

what are the two skull divisions?

cranial and facial

how many bones are in the cranial part of the skull?

8

how many bones are in the facial part of the skull?

14

frontal bone

• one bone

• the forehead of the skull + part of superior part of skull

• makes roofs of the orbits

parietal bones

• two bones

• makes up most of the superior part of the crania

occipital bone

• one bone

• kinda triangle shape (due to the lambdoid sutures)

• makes up most of the inferior + posterior part of the skull

• houses foramen magnum

temporal bones

• two bones

• squamous (soft) + petrous (hard/rock-like) parts

• petrous part houses internal auditory (acoustic) meatus + all your ear stuff goes so it’s protected!)

mandible

FOUR PARTS:

1. body

2. ramus

3. coronoid process

4. mandibular condyle

• connected to the temporal bone (aka the skull) by the TMJ (temporomandibular joint)

body of mandible

• actually two bones fuses in the midline (is just considered one bone tho)

• houses bottom row of teeth

ramus of mandible

• where a lot of muscle attachments (for chewing) are

• unites with the body of the mandible at an angle known as the mandibular angle. creates a wider + stronger leverage system for the muscles that attach to it, enabling effective forces for mastication (chewing)

coronoid process of mandible

• serves as a key attachment point for the temporalis and masseter muscles, which are essential for chewing (mastication) and mandibular stabilization.

mandibular condyle of mandible

• articulates with mandibular fossa

• a crucial component of the TMJ, facilitating jaw movement for functions like talking and eating by allowing the jaw to open, close, and move forward and backward. 

maxilla

• two bones

• houses top row of teeth

• what the eyeball rests on (forms bottom of orbits)

• forms part of your palette (roof of mouth)

zygomatic bones

• two bones

• your cheek bones!

• forms lateral (outside) side of orbit

sphenoid bone

• one bone

• butterfly-shaped

• separates neurocranium from the face; touches almost everything

• forms back/posterior wall of eyeball

• houses sella turcica

ethmoid bone

• one bone

• includes the superior and middle nasal conchae

• houses the cribform plate

cribform plate

• a bone in the ethmoid bone

• allows the olfactory (smell) nerves to pass to the brain, enabling your sense of smell!

superior and middle nasal conchae

• bony, curled structures within the nasal cavity, both part of the ethmoid bone, that filter, humidify, and warm inhaled air. they sit right behind frontal bone; forms medial side of orbit and back of nasal cavity

• fills with blood which helps warm up the air you breathe!

• superior conchae is the smallest and serve to protect the olfactory bulb,

• middle conchae, the largest of the pair, regulate airflow and are crucial for the sense of smell.  

lacrimal bones

• two bones

• forms the medial (inner side) of orbits

• associated with a divot (it accumulates tears and goes into nasal cavity (which causes the sniffling when crying!)

nasal bones

• two bones

• forms the bridge + upper third of your nose

coronal suture

• joint that connects frontal + parietal

• forms the nice “tiara” of your skull hence its name

lambdoid suture

• joint that connects parietal bones + occipital bone

• forms a triangle at the back (which is why your occipital bone is like a triangle!)

squamous suture

• joints that connects the temporal + parietal bones

• named after this scale-like part of the temporal bone because its edges fit together in a manner that looks like overlapping scales

mastoid process (air cells)

• very specialized

• has a big attachment, and lots of air for HEARING

external auditory (acoustic) meatus

• hole in the side of your skull + the tubular passageway from the auricle (outer ear) to the tympanic membrane (eardrum)

• collects and channels sound waves toward the middle ear

Internal acoustic/auditory meatus

• canal in the petrous part of temporal bone that goes from your inner ear —> posterior cranial fossa

styloid process (muscles)

• major point of muscle attachment for tongue and larynx

mandibular fossa

• mandibular = related to the jaw

• fossa = depression

• a joint with mandible

zygomatic arch

• temporal + zygomatic bones connected together

• passage for muscles

• allows for space (for chewing muscles to go in there + mandible)

• also part of your cheekbone

• provides structural support and protects the eye

saggital suture

• connects the two parietal bones

• called this because is it right down the midline of your skull!

superior orbital fissure

the big one; all vasculature and nerves that go into the cavity travels through this fissure (an opening but not a hole; palantine closes it off a little making it technically not a hole)

optic canal

• canal goes to eyeball

• hole that goes through the bone into the eyeball

• transmits the optic nerve and the ophthalmic artery (so you can see!)

inferior nasal conchae

• two of them

• bone that is so big its it own bone

• increases the surface area within the nose, which serves to filter, warm, and humidify inhaled air (same as the other conchae!)

• unique from the other conchae cause the inferior meatus beneath it receives tears from the nasolacrimal duct, providing a drainage pathway for them

palatine bones

• two of em

• your palette. forms roof of mouth and goes all the up to the back of the orbit

vomer

• goes from palette and separates nasal cavity

sella turcica

• name comes from “turkish saddle”

• houses the pituitary gland (your hormone boss)

• Anterior, middle, & posterior cranial fossae

anterior, middle, & posterior cranial fossae

where the lobes of the brain rest/sit within the cranial cavity (with meninges)

occipital condyle

joint that articulates with vertebral column

foramen magnum

• literally means “large hole”

• hole for your spinal cord to go in so it can reach + connect to the brain

cartoid canal

• hole where the artery that carries blood into the crania goes

• lots of vascularture in the skull for brain

jugular foramen

• hole where the vein that carries blood out the crania goes

• lots of vascularture in the skull for brain

why have skull cavities?

• crania is heavy and needs some space to make it lighter

• houses sensory organs (brain, tongue, eyes, nose)

the four skull cavities

1. cranial cavity (for brain)

2. orbit (for your eyes)

3. nasal cavity (drainage of air sinuses in nose)

4. oral cavity (for tongue)

paranasal sinuses

• hollow, air-filled cavities within the bones of the face and skull, surrounding the nasal cavity

• mucus lining (that is lined up w the respiratory epithelium) that makes a ton of mucus, which helps humidify & warm the inhaled air

• lightens the weight of your skull + facial bones

• provides resonance to the voice (enhances intensity of phonation) (we all have different shapes of sinuses which makes all our voices different!)

• all of them are paired

what are the four paranasal sinuses?

1. Frontal sinus

2. Ethmoid air cells

3. Sphenoidal sinus

4. Maxillary sinus

infant skull + growth

• has dense regular CT (fontanelles) areas where sutures will eventually form, meaning the different bones of the skull are not yet conencted!)

• Allows for distortion of the skull during childbirth (can see

  rhythmic pulsation of blood vessels)

• Many ossification (bone formation) centres (intramembranous ossification) in the formation of the skull

• At birth some have not fused (2 frontal bone elements, 4 occipital and a number of sphenoidal & temporal)

• Brain growth is about 90-95% complete by age 5 (their head is adult size but their body is not which is why their heads are so big!)

• once the bones are sutured and jointed, the bones cannot move or grow

• when you are a kid they are not even touching to allows them to move on top of each other which makes it easier to birth out the vagina, and allows for growth

auditory ossicles

• malleus (hammer), incus (anvil) and stapes (stirrup)

• within the temporal bone: middle ear

• forms synovial joints – transfer vibrations

• the only bones that are fully ossified at birth

hyroid bone

• Does not have any bony articulations/joints: VERY mobile

• Serves as points of attachment for muscles, ligaments + membranes

• Muscles move tongue, mandible, & larynx (helps you swallow and speak)

vertical column

• made of 26 bones

  • 7 cervical vertebrae

  • 12 thoracic vertebrae

  • 5 lumbar vertebrae

  • 5 fused sacral vertebrae = 1 sacrum

  • 3-5 fused coccygeal vertebrae = 1 coccyx

primary curvatures

• develops before birth

• continues to accommodate thoracic & pelvic organs as adults

• thorax + sacrum = kyphosis = breathing and sitting doesn’t change a lot therefore PRIMARY

• hypherkydosis = hunchback

secondary curvatures

• develop after birth

• cervical (balance of head) & lumbar (weight of trunk when bipedal

• cervical + lumbar = lordosis needs more time to develop therefore SECONDARY

vertebral anatomy

1. body

2. Vertebral arch (pedicle + lamina)

3. vertebral foramen

4. Transverse process (lateral)

5. spinous process (posterior)

6. Superior & inferior articular processes (also called zygapophysial processes)

body of vertebrae

• anterior side carries most of the weight (its central mass follows the body)

vertebral arch of vertebrae

• pedicle (foot of arch)

• lamina (roof of arch)

• forms lateral + posterior vertebral foramen

vertebral foramen of vertebrae

• where the spinal cord goes through the vertebrae

transverse process (lateral) of vertebrae

• provides attachment points for muscles and ligaments out the sides of the vertebrae

spinous process (posterior) of vertebrae

• provides attachment points for muscles and ligaments out the back of the vertebrae

superior & inferior articular processes (also called zygapophysial processes) of vertebrae

• articulates with the other vertebrae above and below it

vertrbral bodies are…

interconnected by ligaments and separated by intervertebral discs

joints of the vertebral column

1. Intervertebral joint: intervertebral disc (mainly fibrocartilage) attached between two adjacent vertebrae (known as the secondary cartilaginous joint in adults)

2. Zygapophysial joint: joint between two adjacent articular processes (synovial joint – movement vertebral column)

   • Superior & inferior articular processes: orientation depends on the location

fibrocartilage (fiber) and hyaline-like (watery) cartilage

• two diff types of cartilage is important cause hyaline-like cartilage has more water content so it allows for more movement (healthy disc has water content at the midline)

vertebral canal

• created all the vertebrae formamen holes stacked on top of each other

• houses the spinal cord + meninges

intervertebral foramen

• inter = between

• all the nerves come out into here

cervical vertebrae

• Smallest body but largest vertebral foramen (the superior of the spinal cord is GIANT), short spinous process that’s bifurcated (forked)

• Allows controlled movement of head

• has transverse foramen (allows passage of vertebral artery going uo to supply the brain)

• C1 (atlas) does NOT have a body

• C2 (axis) stole the body of C1 and is the ONLY one to have a dens (odontoid process)

• C7 has a long prominent spinous process (can be palpated) — nice and straight; larger and flatter (cause its transitional vert)

joints + movements of cervical spine

• Atlanto-axial joint: synovial joint between C1 & C2 (allows rotation of the head — allows you to shake your head no!)

• Atlanto-occipital joint: synovial joint between occipital condyles & C1 (allows flexion and extension of the head — allows you to nod your head yes!)

• Cervical (zygapophysial) joints: synovial joints sloped from anterior to posterior (allows lateral flexion of the head & neck — allows you to tilt your head!)

thoracic vertebrae + joints

• Heart shaped body, smaller vertebral foramen then cervical, support weight of head & upper limbs

• articulates with ribs (needs two jointsvvv)

• Costovertebral joint: two synovial joints between thoracic vertebra & associated rib (coastal facets) – allows the rib to move during respiration by changing thoracic volume

• Thoracic (zygapophysial) joints: vertical synovial joints, very little rotation & lateral flexion of the trunk

what makes up the thoracic cage?

Sternum (manubrium, body, xiphoid process), ribs & costal cartilage

(hyaline cartilage), thoracic vertebrae (12)

ribs of the thoracic cage

• Costal cartilages (hyaline cartilage)

  • Ribs 1-7: true ribs to a costal cartilage — directly attaches to sternum; a TRUE attachment

  • Ribs 8-10: false ribs to costal margin — costal cartilage attaches to the cartilage of the rib above them (rib 7) rather than directly to the sternum; FALSE attachment

  • Ribs 11-12: floating ribs – no costal cartilage — do NOT attach to sternum at all; FLOATING

ribs

• 12 of them

• T AND T = transverse + tubercule connect

  • they MOVE so when you breathe they go up n down

• the way they’re angled — a little costal groove inside that has a little artery and vein nerve in it

lumbar vertebrae

• five of them

• has the biggest vertebral bodies as they support the weight of the body

• largest processes for strong muscles, small vertebral foramen

• Lumbar (zygapophysial) joints: curved synovial joints (flexion & extension, lateral flexion, rotation of the trunk)

• the MOST movement is here

• MOST weight is focused on these vetebrae

• the area where most vertebral injuries happen

herniation

• hernia = something travelling somewhere it’s NOT supposed to travel

• example: herniation in an intervertebral disc vvvvvvvv

• exccess water pushed towards back (we lean forward lots so it can cause this)

  • between nerve so it squishes / pinches the nerve which prevents feeling which can lead to numbness tingling, or weakness

sacrum and coccyx NOT DONE

• one each