lecture 8, the axial skeleton

lateral

to the side (left or right)

anterior (ventral)

to the front

ex. ventral bone

posterior (dorsal)

to the back

ex. dorsal bone

superior

to the top

ex. superior vena cava

inferior

to the bottom

ex. inferior vena cava

articulate

attach to

ex. muscle articulates with bone via the tendon

proximal

near to

closest to body

distal

far from

distance

medial

to the middle

ex. duplicated chromosome move to middle

the skeleton

• the skeletal system is divided into two components

  1. axial

  2. appendicular skeleton

1. axial skeleton

   • this is the skeletal system that can be found down the midline of the body

   • composed of 80 bones including

     a. the skull

     b. the hyoid bone

     c. the vertebral column

     d. thoracic cage: composed of the sternum and the ribs

• cartilage is in between the bones

axial skeleton: the skull

i. cranium

• encages the brain

• 8 bones that function to protect the brain

• 1 frontal bone

• 2 parietal bones

• 2 temporal bones

• 1 occipital bone (if damage could loose vision and worse)

• 1 sphenoid bone (connected in middle as it shows on both sides, unpaired)

• 1 ethmoid bone: superior and middle nasal conchae

in babies there is more flex in the cranium so they can actually be birthed

axial skeleton the skull: facial bones

• 14 bones in total

• 2 nasal bones

• 2 maxillae: form upper jaw

• 2 zygomatic bones: form the eye socket and the cheekbone

• 2 lacrimal bones: form the sides of the nose and the remaining portion of the eye socket

• 2 palatine bones: in the pallet (anterior portion of the superior of mouth)

• 2 inferior nasal conchae

• 1 vomer: found behind the pallet

• 1. mandible: forms the lower jaw

the axial skeleton the skull: auditory ossicles

• found in the middle ear

• the smallest bones found in the body consists of

• 2 malleus

• 2 incus

• 2 stapes

axial skeleton: the hyoid bone

• this bone forms no articulations with bone

• functions to attach muscles of the tongue, neck, and pharynx

axial skeleton: the vertebral column

• also called the spinal column (protection for the nervous tissue within)

• each vertebra of the spinal column consists of

  • body: thick and located on the anterior end

  • lamina

  • pedicle

  • vertebral arch

  • vertebral foramen: line up for each individual vertebra forming a canal through which the spinal cord passes

  • spinous process (only 1, landmark)

    • serve as attachment sites for muscles and ligaments

  • two transverse processes

    • serve as attachment sites for muscles and ligaments

  • superior and inferior articular processes: contain smooth surfaces formed from hyaline cartilage → called facets

    • serve as attachment sites for vertebra above and vertebra below

the axial skeleton: the vertebral column five regions

1. cervical → neck

2. thoracic → lungs

3. lumbar → biggest of the vertebrate

4. sacral → 3-5 bones (didn’t start that way, fuse)

5. coccyx → tail bone

the vertebral column: cervical region

• there are 7 vertebrae found within the cervical region: C₁-C₇

  • these are the smallest and the lightest weight vertebrae (delicate)

• C₁ is the atlas

  • has no body (very delicate)

  • has no spinous process (allows for head to move “yes”)

  • the absence of these joints allow you to move your head up and down in a yes motion

  • articulates superiorly with occipital condyle

the vertebral column: cervical region C₂, C₃-C₇

• C₂ is the axis

  • contains all of the typical vertebral components (body/spinous process)

  • not as specialized as the atlas

  • contains knoblike process called the dens (odontoid process) that projects superiorly from the body of the vertebrae

    • acts as a pivot atlas rotation allowing you to move your head in a ‘no’ motion

  • fits into C₁ like a puzzle piece

• C₃-C₇

  • distinguishing feature found on all of these vertebrae is the transverse foramina (hole on side)

    • opening found in transverse process where the vertebral arteries pass in order to service the brain

  • very large

the vertebral column: thoracic region

• the thoracic region contains 12 vertebrae labelled T₁-T₁₂

  • these articulate posteriorly with the ribs

  • the thoracic vertebrae increases in size from first to last

  • the distinguishing feature it the articular facet (made from cartilage)

    • used for rib articulation

    • protects against erosion

the vertebral column: lumbar region

• this region has 5 vertebrae: L₁-L₅

  • these vertebrae function to support the body’s weight

  • commonly referred to as the “small of the back”

  • contain a large, very thick body

  • processes are heavy and rectangular

  • takes a lot to break

the vertebral column: the sacrum

• the sacrum consists of five fused vertebrae

  • articulate with the ilium, a part of the appendicular skeleton, specifically the pelvis

  • also articulates with the 5th lumbar vertebra superiorly (sits on top of sacrum)

  • contain intervertebral foramina

    • exit sites of spinal nerves

    • sensory information that needs to come back

the vertebral column: the coccyx

• the coccyx consists of 3-4, but usually 4 fused vertebrae

  • known as tailbone

  • generally useless

  • soft tissue there that easily bruises

spinal curvature

• normal curvature of the vertebral column

  • the cervical and the lumbar sections are curved concave posteriorly

  • the thoracic and the sacral sections are curved convex posteriorly

• abnormal curvature of the vertebral column

  1. scoliosis

  2. kyphosis

  3. lordosis

scoliosis

• the spinal column cure laterally

• as though you continually carried a heavy bag on the same shoulder

kyphosis

• hunchback

• caused by an exaggerated thoracic curve which can be caused by osteoporosis

lordosis

• swayback

• caused by an exaggerated lumbar curve which can be caused be pregnancy or pot bellies

the axial skeleton: the thoracic cage, sternum

• the sternum

  • the breast bone

    • the manubrium is superior

    • the body is portion (biggest)

    • the xiphoid is inferior

the axial skeleton: the thoracic cage, ribs

• there are 12 pair of ribs

• they articulate posteriorly with thoracic vertebrae

• there are true ribs and false ribs

  • true ribs: attach directly to the sternum via costal cartilage (hyaline cartilage) → there are 7 pair of true ribs

  • false ribs: attach either indirectly to the sternum or not at all

    • pairs 8-10 attach indirectly to the sternum via costal cartilage

    • pairs 11 and 12 are not attached and are embedded in muscle → called floating ribs