Axial Skeleton Test

Cranial bones

8 bones that enclose the cranial cavity (fluid filled chamber that cushions and supports brain)

• Inner surface acts as attachment point for blood vessels, nerves and membrane’s stabilizing brain position

• Outer surface acts as attatchment for for muscles that move eyes, jaws and head

• Calvaria (skullcap) is the roof of the skull formed by occipital, parietal and frontal bones

• Occipital bone (1)

  • External occipital crest: Attachment for ligament that helps stabilize neck vertebrae

• Parietal bones (2)

• Frontal bone (1)

• Temporal bones (2)

• Sphenoid bone (1)

  • Bat shaped

• Ethmoid bone (1)

Facial bones

14 bones that protect digestive and respiratory tracts and provide attachment points for muscular control of facial expressions and assistance in manipulation of food

• Maxillary bones (2)

  • Support upper teeth

  • Form inferior orbital rim, upper jaw, lateral margins of external nares and part of hard palate

• Palatine bones (2)

• Nasal bones (2)

  • Bridge of nose

• Inferior nasal conchae (2)

• Zygomatic bones (2)

  • Cheekbone

• Lacrimal bones (2)

  • Medial wall of orbit

  • Tears

• Vomer (1)

  • Inferior portion of nasal septum

• Mandible (1)

  • Lower jaw

  • Only movable bone

External auditory meatus

• Tube like opening for ear canal

• Begins on lateral surface of temporal bone and ends at tympanic membrane

Mastoid process

• Rounded projection posterior to external acoustic meatus

• Part of inferior temporal bone

• Attachment for muscles that rotate/ extend head

Suture

Immovable joint between skull bones of adults

• Dense fibrous connective tissue

Squamous suture

Attaches temporal to parietal bones

Coronal suture

Attaches frontal to parietal bones

Sagittal suture

Attaches parietal bones

Lambdoid suture

Attaches occipital to parietal bones

• Sutural bones may be present along this

Palatine bone

Posterior portion of hard plate and contributes to floor of each orbit

Occipital condyle

• Rounded processes on each side of foramen magnum

• Articulates with atlas

  • Connects skull with vertebrae

Foramen magnum

• Large medial opening connecting cranial cavity to vertebral canal

  • Surrounds connection b/w brain and spinal cord

• In occipital bone

Zygomatic arch

• Bony bridge on side of head created by zygomatic and temporal bones

• Facial structure, connect facial bones to cranium and attach to chewing muscles

Nasal conchae bones

• Scroll like projections on each lateral wall of nasal cavity

• Superior and middle part of ethmoid, inferior own bone

• Create turbulence in air entering nasal cavity

• Increase epithelial surface to warm and humidify inhaled air

Ethmoid bone

Forms anteromedial floor of cranium, roof of nasal cavity, part of nasal septum and medial orbital wall

• Cribeform plate: Form roof of nasal cavity and anteromedial cranial floor; nasal foramina permit passage of olfactory nerves

• Crista gali; bony ridge projection for attachment of membranes covering brain; superior to cribriform plate; “cocks comb”

• Perpendicular plate: Form upper part of nasal septum

Sella turcica

• Part of sphenoid bone

  • Saddle shaped depression

• Houses pituitary gland

Sinuses

• Chamber within bone, normally filled with air

  • Lighten skull

  • Lined w/ mucous membrane → filter air before reach lungs and moisten

• Nasal

• Paranasal

  • Ethmoid

  • Sphenoid

  • Frontal

  • Maxillary

Hyoid bone

• Associated bone; not attached to another bone

• Supports larynx

  • Attachment site for larynx, pharynx and tongue

Functions of axial skeleton

• Supports and protects the brain, spinal cord, and organs in the trunk's body cavities.


• Provides attachment sites for muscles that:

  • Adjust position of head, neck, and trunk.


    • Vertebral column helps maintain upright position

  • Perform respiratory movements.


  • Stabilize the appendicular skeleton (supports limbs).

    • Vertebral column transfer body weight to lower limbs

Cervical vertebrae

• 7

• Location: Neck

• Small body, large foramen

• Long, bifid spinous process

• Has transverse foramina

  • Protects vertebral arteries/ veins serving brain

• Include atlas and axis

• Vertebra prominens (C7)

  • Long, prominent spinous process felt at base of neck making it good landmark

• Function: Support skull, stabilize relative positions of brain and spinal cord and allow controlled head movement

Thoracic vertebrae

• 12

• Location: Chest

• Medium heart shaped body

• Long, slender spinous process

• Costal facets for rib articulation

• Functions: Support head, neck, upper limbs and chest and articulates w/ ribs to allow change in volume of thoracic cage

Lumbar vertebrae

• 5

• Location: Inferior back

• Big oval body W/ small triangular foramen

• Blunt, broad spinous process

• Short transverse process

• Support most weight

Sacrum

• 5, fuse after puberty (complete ~25-30) 2/ transverse lines marking former boundaries

• Functions: Protect reproductive, digestive and urinary organs and attach axial skeleton to appendicular

• Base: Broad, superior surface; ala/ wing extends from each base side; Sacral foramina: Intervertebral foramina of fused disc; Apex: narrow inferior portion; superior articular process w/ last lumbar vertebrae

Coccyx

• 3-5 fused vertebrae (begin at age 26)

• Attachment for pelvic floor muscles

• Tailbone

Atlas

• C1

• No spinous process or body

• Large round formaen

• Articulates w/ occipital condyles

• Allows nodding yes

Axis

• C2

• Has dens/ odontoid process on superior surface to bind to atlas by transverse ligament

• Allow shaking head no

Primary/kyphotic curves

Develop before birth; curve posteriorly

• Thoracic: Accommodates thoracic organs

• Sacral: Accommodates abdominopelvic organs

Secondary/lordotic curves

Develop after birth; curve anteriorly

• Cervical curve: Develops as infant lifts head, balances head on neck.

• Lumbar curve: Develops with ability to stand, balances trunk weight over lower limbs

Scoliosis

“S-shaped” curve

Structure of basic vertebrae

• Vertebral Body: Transfers weight along column (gets bigger as go down).


• Vertebral Arch: Forms posterior and lateral margins of vertebral foramen.

  • 
 Laminae: Form roof of vertebral foramen.


  • Pedicles: Form sides of vertebral arch.


  • Spinous process: Projects posteriorly from laminae fusion (e.g., granny hunch).


  • Transverse processes: Project laterally from pedicles/laminae junction (muscle attachment, rib articulation).


• Articular Processes: Extend superiorly/inferiorly to articulate with adjacent vertebrae.

  • 
Articular facet: Smooth surface for joints.


    • Superior articular processes: Articulate with inferior processes of superior vertebra.


    • Inferior articular processes: Articulate with superior processes of inferior vertebra.

• Vertebral Foramen: Opening framed by body and arch.


• Vertebral Canal: Formed by successive vertebral foramina, encloses spinal cord.


• Intervertebral Discs: Fibrocartilage pads separating vertebral bodies providing shock absorption and support

• Intervertebral Foramina: Spaces between successive pedicles, allow nerve/blood vessel passage.

Vertebrosternal ribs

• “True” ribs

• Connected to sternum w/ individual costal cartilage

• Ribs 1-7

Vertebrochondral ribs

• Connect to sternum by shared costal cartilage

• Ribs 8-10

• Part of “false” ribs

Vertebral ribs

• No connection to sternum

• Ribs 11-12

• Floating ribs

• Part of false ribs

Parts of sternum

• Manubrium

  • Trapezoid shaped

  • Superior portion

  • Articulates w/ clavicles and 1st rib pair

• Body

  • Inferior to manubrium

  • Articulates w/ rib pairs 2-7

• Xiphoid process

  • Inferior to sternum body

How should CPR be administered to minimize injury

• Do not press on the xiphoid process, as it could break, puncturing the lung

  • Use 2 finger rule: Place palm 2 fingers above xiphoid process tip (where lowest ribs meet at bottom of breastbone)\

• Ribs like bucket handle: Push down → ribs move in; pull up → ribs move out: sternum moves accordigly

  • Affects width and depth of thoracic cage, increasing/ decreasing w/ volume

Structure of nasal septum

• Perpendicular plate of ethmoid bone (superior)

• Vomer (inferior)

Herniated/ slipped disc

• Occurs when fibrocartilage of intervertebral discs stressed or cracked

• Inner, pulp like center protrudes out, causing pressure on spinal cord or nerve

Intervertebral foramen

• Spaces formed b/w successive pedicles

• Allows nerve/ blood vessel passage

Fontanelles

• Large fibrous areas between cranial bones.


• Ease head passage through birth canal and allow cranial growth for brain development.


• Replaced by sutures over time.


  • All replaced before age 5 (when brain growth slows).


• Anterior Fontanelle ("soft spot"):


  • Large, diamond shape intersection of frontal, sagittal, and coronal sutures.


  • Largest, persists until ~age 2.


  • Shallow (dehydration), bulging (increased pressure), pulses with heartbeat (covers major blood vessel)

• Posterior/occipital fontanelle small, triangular intersection where occipital and parietal bones meet

  • Close w/ 1st few months

• Sphenoid and mastoid fontanelles (2 each)

Projection functions

• Tendon and ligament attachment

• At joints where adjacent bones articulate

Depression/ grooves/ tunnels functions

Sites for blood vessels or nerves to lie alongside or project into bone

Process

Any projection/ bumb

Tubercle

Small, rounded projection

• Wannabe trochanter

• For muscle attatchment

Tuberosity

Small, rough projection that takes up a broad area

Trochlea

Smooth, grooved articular process shaped like a pulley

Condyle

Smooth, rounded articular process

Trochanter

Large, rough projection

• Proximal femur only

• Muscle attatchment

Facet

Small, flat articular surface

Crest

Prominent ridge

Line

Low ridge, more delicate than a crest

Spine

Pointed/ narrow process

Ramus

extension of bone that makes angle with rest of structure

Canal/ meatus

Large passageway through bone

Foramen

Small, rounded passageway for blood vessels or nerves to pass through bone

Fissure

Elongated cleft or gap

Sulcus

Deep, narrow groove

Fossa

Shallow depression/ recess in bone surface