Axial Skeleton (Ch 7) Flashcards
What are the parts of the axial skeleton?
skull hyoid bone vertebral column thoracic cage -80 named bones
What are the functions of the axial skeleton?
- supports head, neck, and trunk
2. protects brain, spinal cord, and thoracic organs
Foramen
a hole in a bone
–> typically for nerves/blood vessels
Fossa
a depression in a bone
Process
projection from a bone, narrow or wide, protrudes from surrounding bone
Meatus
hole/tube-like structure
Canal
a groove/tube-like structure, passageway for nerves/blood vessels
The Skull
- 28 bones (complex!)
- mostly flat bones formed via intramembranous ossification
- bones united by sutures
- subdivides into cranial and facial divisions
What are sutures?
interlocking, immoveable joints
What are the functions of the cranial bones?
- protect brain
2. provide attachment for some head/neck muscles
What are the functions of the facial bones?
- form framework of face
- openings for passage of food/air
- hold the teeth
- anchor muscles of the teeth
What are the subdivisions of the cranium?
- Vault: superior, lateral, and posterior bones of the skull (including the forehead)
- Base: inferior part of the crainum
What are the bones of the cranium?
- Frontal
- Occipital
- Sphenoid
- Ethmoid
- Parietals (2)
- Temporals (2)
Coronal Suture
between the frontal and two parietal bones
Squamous Sutures
between temporal and parietal bones (lateral)
Lambdoid Suture
between parietal bones and occipital bone
Saggital Suture
runs along midline of skull, between parietal bones
Frontal Bone
- makes up forehead
1. Superciliary Arches: deep to eyebrows at superior edge of orbit
2. Labella: superior to bridge of nose, smooth medial part
Parietal Bones
- posterior to frontal bone, make up most of superior part of skull
- touch saggital/lambdoid sutures
Occipital Bone
- bone at back of head, posterior to cranium/cranial base
- foramen magnum
- occipital condyles
foramen magnum
large opening of occipital bone the allows spinal cord to pass and connect with the brain
occipital condyles
where the skull articulates with the vertebral column
Temporal Bones
- paired temporal bones house opening to ear, base of cheekbone
- 3 main regions: petrous, tympanic, squamous
- -> petrous best seen internally (contains middle/inner ear cavities)
- External Acoustic Meatus
- mastoid/styloid processes: sites of muscle attachment
- TMJ
External Acoustic Meatus
opening in tympanic region leading to middle/inner ear
Temporomandibular Joint
the condylar process of the lower jaw fits into a depression in the temporal bone (mandibular fossa) –> creates jaw joint
Middle Ear Cavity
3 ossicles in middle ear
- Malleus (lateral) “hammer”
- Incus “anvil”
- Stapes (medial) “stirrup”
- -> sound waves cause vibrations that are transmitted to the inner ear
Sphenoid Bone
large/wing-shaped bone
- landmark: sella turcica
- only cranial bone that articulates with every other cranial bone
Sella Turcica
in sphenoid bone
-bony depression that holds pituitary gland (“master gland”)
Ethmoid Bone
- just anterior to the sphenoid –> forms roof of nasal cavity
- takes up most of area between nasal cavity and orbits
- forms some boundaries of nasal cavity = separates nasal cavity from brain
- peaks up into frontal bone
- includes: cribriform plate and crista galli
cribriform plate
in ethmoid bone
- helps form roof of nasal cavities; foramina allow passage of olfactory nerves into brain = smell
- superior
crista galli
in ethmoid bone
- attaches to cribriform plate; separates nasal cavity from brain
- site of attachment for dura mater (brain membrane)
- inferior
Nasal Cavity
- lateral walls made up of nasal bones
- nasal conchae (superior, middle, inferior)
- frontal process of maxillae
- perpendicular plate of the palatines
- floor made up of hard palates –> formed by palatine process of maxillae and horizontal plate of palatine
What are the bones of the facial skeleton?
- 14 bones
1. Mandible
2. Vomer
3. Two Nasals
4. Two Lacrimals
5. Two Maxillae
6. Two Zygomatic
7. Two Palatine
8. Two Inferior Nasal Conchae
Maxilla
-makes up part of nasal cavity, oral cavity, and orbit
-forms upper jaw
-articulates with ALL facial bones (except mandible)
Includes:
-alveolar, frontal, zygomatic processes
-infraorbital foramen
What is the alveolar process?
part of maxilla- contains teeth
What are the frontal processes?
part of maxilla- extend upward to reach frontal bone
What are the zygomatic processes?
part of maxilla- articulate with zygomatic bone
What is the infraorbital foramen?
part of maxilla- provides passage for infraorbital artery, vein, and nerve (below orbit)
The Orbit (what bones are the walls formed by?)
- supports the eyes and muscles that move them
- include fat and tear producing glands
- walls formed by frontal, sphenoid, zygomatic, maxillary, palatine, lacrimal, and ethmoid bones
Palate
-hard palate = ventral maxillary bones (anteriorly) and the palatine bones (posteriorly)
Inferior Nasal Septum
-vomer forms inferior portion of nasal septum
Cleft Palate
failure of the two sides of palate to join during development
- opening between mouth and nasal cavity makes nursing hard
- surgery –> good outcomes
Mandible
-largest/strongest bone in face
-body contains lower teeth
-tooth sockets on superior border
Two parts: ramus (superior/inferior) and body (anterior/posterior)
Includes:
- mandibular symphysis
- mental protuberance
- mental foramen
- condylar process
- coronoid process
mandibular symphysis
in mandible- where two halves of body join to form the chin (mental protuberance)
mental protuberance
on mandible- chin
mental foramen
in mandible- opening below teeth for vessels/nerves
condylar process
in mandible- articulate with temporal bone to form the TMJ (on both sides of jaw)
coronoid process
in mandible- serves as attachment site for temporalis (chewing) muscle
Fetal/Infant Skull
- skull bones not yet fully joined –> allows head to deform as it passes through the birth canal/allows brain growth
- fontanelles: sturdy membranous covering between cranial joints
- bones fuse over time
- cranium is proportionally huge relative to face in infancy
Craniosynostosis
fetal sutures fuse too early, surgically correctable
The Hyoid
- “free floating” bone in neck inferior to mandible
- only bone in skeleton that doesn’t articulate with another bone
- acts as base for tongue, site for muscle attachments for muscles that move larynx/tongue muscles
Thoracic Cage parts
includes: thoracic vertebrae, ribs, sternum, and costal cartilages
What are the functions of the thoracic cage?
- protect heart, lungs, and other organs
- supports pectoral girdle
- provides attachment points for upper limb and trunk muscles
- intercostal spaces hold muscles that aid in breathing
Sternum
3 bones: manubrium, body, xiphoid process
-articulates with clavicles and ribs/costal cartilage
Includes:
-jugular notch
-sternal angle
Rib Cage
Function: protects internal organs, aids in respiration
- 12 pairs of ribs
- all ribs attached posteriorly to thoracic vertebrae
1. true ribs: attach to sternum by costal cartilage
2. false ribs: no direct attachment to sternum
3. floating ribs: do not attach anteriorly (just to vertebrae)
Rib Structure
- main part = shaft (body)
- articulates with vertebrae at head and tubercle
- “neck” = thinner region between head and tubercle
- “head” = two demifacets (one attaches to body of “its” vertebra and one attaches to the superior vertebra)
- tubercle articulates with a facet on the transverse process of vertebrae
The Vertebral Column
- 26 vertebrae (7-12-5-5-4)
- 7 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral (fuse into 1)
- 4 coccyx (fuse into 1)
Functions of the vertebral column
- protect spinal cord
- support body axis
- attachment points for ribs/muscles of neck/back
- anchor pectoral and pelvic girdles
“Typical” Vertebra
- vertebral arch (includes pedicles/lamina)
- spinous process
- transverse process
- articular processes/facets
vertebral arch
- around vertebral foramen
- protects spinal cord passing through vertebral foramen and spinal nerves traveling through INTERvertebral foramen
- -> includes: pedicles (between transverse process/body) and lamina (between spinous/transverse process)
spinous process
attachment site for muscles, most posterior
transverse process
attachment sites for muscles (on lateral sides)
articular processes/facets
where vertebrae articulate (joints)
Vertebral Column/Spinal Cord
- spinal cord passes through and is protected by the spinal canal
- spinal nerves exit between body of the vertebra and neural arch in intervertebral disc (between each vertebra)
Laminectomy
removal of one or more lamina in vertebrae
-take pressure off spinal cord = pain relief for pt with herniated disc
Cervial Vertebrae
- 7 (C1-C7)
- transverse foramen on transverse process (major head artery goes through here)
- articular facts face superior/inferior
- bifid (split) spinous process
- -> atlas/axis are unusual
Atlas
- C1
- no body or spinous process
- articulates with occipital condyles –> allows flexion/extension of head (nodding yes)
Axis
- C2
- dens articulates with Atlas –> allows rotational movement on anterior midline (shaking head no)
Thoracic Vertebrae
- 12 (T1-T12)
- COSTAL FACETS for ribs, on body/transverse processes
- articular facets face anterior/posterior
- spinous processes are long/project inferiorly
Lumbar Vertebrae
- 5 (L1-L5)
- in lower back
- large bodies, support LOTS of weight
- articular facets face medial/lateral
- short/flat spinous processes, project almost anteriorly
Sacrum
- 5 fused vertebrae
- forms posterior wall of pelvis
- Ala: “wings” on lateral sacrum articulate with hip bones to form SI joints
Coccyx
- 4 fused vertebrae
- “tailbone”
Curves of the spine
- increase flexibility and maintain center of gravity over body axis
- curvature for each region (ex. sacral curvature)
Scoliosis
lateral curvature of spine
- abnormal
- usually treated with braces/surgery when young
Kyphosis
*excessive curvature of thoracic spine
-typically result of spinal fractures caused by osteoporosis
(“Dowager’s Hump”)
Lordosis
- excessive curvature of lumbar spine
- usually temporary and resulting from shift in larger front load (ex. pregnancy/beer belly)
cranial stenosis
early fusion of skull plates
Where does the action of nodding happen?
between skull and axis
Where does the action of shaking head “no” happen?
between atlas and axis
What vertebrae has 3 holes?
cervical
What vertebra has no body?
atlas
What vertebra has a dens?
axis
What vertebrae have one hole only?
thoracic and lumbar
What vertebrae have costal facets?
thoracic
What sinus is only completely drained when laying down?
maxillary sinus
