Chapter 7 A Axial SKeleton Flashcards
Skeletal System
is an organized and orderly arrangement of osseous tissue
- 206 in typical adult skeleton
- start at 270 at birth but decreases with fusion
2 primary regions of the skeleton:
- axial skeleton
- appendicular skeleton
Axial Skeleton
skull, vertebral column, ribs, sternum and sacrum
appendicular skelton
upper and lower limbs and pectoral and pelvic girdles
axial skelton
forms longitudinal axis of body (80 bones)
bones of the axial skelton
- skull
8 cranial,14 facial bones, 6 auditory ossicles & hyoid bone
- vertebral column
24 vertebrae, sacrum, and coccyx
- thoracic cage
24 ribs and sternum
Functions of axial skelton bones
-supports/protects organs and provides extensive surface area for muscle attachment
- adjustment of head, neck, and trunk
- respiration
- stabilization of the appendicular skeleton
Skull
protects the brain and provides entrance to respiratory and digestive system
- bones joined together by sutures
- immovable joints of the skull*
Skull has 22 bones
- 8 cranial bones
- 14 facial bones
8 cranial bones
that form the cranium
- encloses fluid-filled cranial cavity
- cushions and supports brain*
- bones contact the meninges on inside and muscles outside
14 facial bones
protect and support entrances to respiratory/digestive systems
- protect entrances to respiratory/digestive tracts
- attachment of facial and jaw muscles
Sinuses
are cavities that decrease the weight skull
-lined with mucus membranes
- filters the air entering the respiratory system
- add resonance to voice
4 major skull sutures
coronal suture
joins frontal & parietal
sagittal suture
joins parietal
squamous suture
joins parietal & temporal
lambdoid suture
joins occipital & parietals
Frontal Bone Forms
- forehead, part of the cranium and roof of the orbits
- contains frontal sinus
Marks of the frontal bone
-frontal squama (forehead)
-supraorbital margin
protects eye
-supraorbital foramen
for blood vessels of eyebrows, eyelids, and frontal sinuses
Parietal Bone Forms:
- superior and lateral surfaces of the cranium
- bordered by 4 sutures
- coronal, sagittal, lambdoid and squamous
Marks of parietal bone
- superior and inferior temporal lines
- attachment of temporalis muscle
Temporal bone
forms lateral walls of cranium and zygomatic arches, articulates with mandible and protects inner ear
Parts of the temporal Bone
squamous part
- zygomatic process
- mandibular fossa
tympanic part
- external auditory meatus
mastoid part
- mastoid process
Petrous part
houses middle and inner ear cavities
-receptors for hearing and sense of balance
- cochlea
- vestibular complex
Internal Auditory meatus
opening for the vestibulocochlear nerve
Temporal Bone Specializations
- *Carotid canal**
- passageway for internal carotid artery
- *Jugular foramen**
- passageway for drainage of blood to internal jugular vein
- *Auditory ossicles:**
- malleus, incus, and stapes in tympanic cavity
- transfers sound from tympanic membrane to inner ear
Occipital Bone
forms rear and inferior surface of the cranium
Marks of the occupital Bone
-occipital condyles
- articulation point of atlas
- external occipital protuberance
- attaches nuchal ligament
binds skull to neck
Foramen magnum
is the major opening of occipital bone
- allows spinal cord to exit cranium
Sphenoid
forms part of cranial floor; joins cranial and facial bones
- strengthens sides of the skull and contains sphenoidal sinuses
Parts of sphenoid
-body
- sella turcica
- houses pituitary gland - superior orbital fissures
lesser wing
- optic canal
- allows passage of optic nerve from eye to brain
-greater wing
Ethmoid
forms part of the cranial floor & lateral/roof walls nasal cavity
Ethmoid Bone plates
-cribriform plate
- olfactory foramina
- passageway for olfactory nerves
crista galli
- serves as a membrane stabilization point for brain
-perpendicular plate
forms part of nasal septum
2 lateral masses of ethmoid
-ethmoidal labyrinth
- ethmoidal air cells form ethmoid sinuses
- nasal chonchae (superior and middle)
- cleanse, humidify, and warm inhaled air
- house olfactory cells
Damage to the ethmoid (upward blow to the nose) can cause
loss of smell, brain damage and even death
facial bones
have no contact with the brain or meninges
-give shape and individuality to the face
9 crucial bones (14 total)
- *-2 maxillae
- 2 zygomatic bones
- 2 nasal bones
- 2 inferior nasal chonchae
- 1 mandible**
Maxiallary Bones
forms upper jaw, inferior wall of orbit, external nares, and anterior 2/3’s of hard palate
- largest facial bones
- contain maxillary sinuses
- largest sinuses
parts of maxillary bones
-alveolar processes are bony points between teeth
sockets formed hold teeth
-incisive foramen
incomplete closure results in cleft palate
Zygomatic Bones
form the angles of the cheekbones and part of lateral orbital wall
Specialization of Zygomatic Bones
-zygomatic arch
processes of zygomatic bone and temporal bone
Nasal Bones
form bridge of nose
- supports cartilages of nose
- attaches external nares
Nasal bones are often fractured by
blow to nsoe
Inferior Nasal Chonchae
are not part of ethmoid
-separate bone
Inferior nasal chonchae increase the epithelial surface area and create air turbulence in the nasal cavity
warm, humidify, and cleanse inhaled air
Mandible
forms the lower jaw and is the only movable bone of the skull
-holds the lower teeth
Parts of the Mandible
- *-ramus
- body
- angle of mandible**
- masseter attachment
Body
is horizontal part of mandible; gives mandible it’s strength
–alveolar processes
support the lower teeth
-mental protuberance
attaches face muscles
Ramus
ascends from the mandiblular angle
-condylar process
articulates with temporal bone at temporomandibular joint
-coronoid process:
insertion point for temporalis muscle (closes the jaws)
-mandibular notch:
separates condylar and coronoid processes
Auditory Ossicles
malleus, incus, and stapes
Hyoid Bone
supports/attaches muscles of the larynx, pharynx, and tongue
-body
- attaches muscles of larynx, tongue, and pharynx
-greater horns (greater cornua)
supports larynx; attaches muscles of tongue
-lesser horns (lesser cornua)
supports hyloid and larynx
Infant Skull
Grows rapidly and is lare compared to the boyd; fusion is not complete at birth
2 frontal bones and 4 occipital bones
Fontanelles
are spaces between unfused bones in infant skulls
-allow shifting of bones during birth and growth of brain
Changes after birth
- 2 frontal bones fuse by age six
- metopic suture
- skull reaches adult size by 8 or 9
Vertebral Column
protects the spinal cord and supports the head and body
-transfers weight to lower appendicular skeleton
Vertebrae form an s-shaped column with 4 curvature regions
- cervical (C) - 7
- thoracic (T) - 12
- lumbar (L) - 5
- sacrum and coccygeal
Primary Curves (accomadation)
- thoracic and sacral
- present during fetal development; accomodate internal organs
Secondary Curves (compenstaion)
lumbar and cervical
- appear after birth; shift body weight for upright posture
Cervical curvatures develop from a baby lifting its head while walking upright
develops lumbar curvature
Abnormal spinal curvature results from
disease, posture, paralysis or congenital defect
3 abnormal curvatures
scoliosis
lacks proper development of one vertebrae
kyphosis
osteoporosis
lordosis
weak abdominal muscles
Parts of vertebrae
vertebral body
- transfers weight along spine
vertebral arch
- pedicles (arch walls)
- laminae (roof of arch)
articular processes
- spinous process
- transverse process
-lateral projections of vertebral arch
Intervertebral Foramen
are notches between adjacent vertebrae
-passageway for nerves
Intervertebral Discs
bind vertebrae together and absorb shock
-pads of fibrocartilage
Disc structure
gelatinous nucleus pulposus surrounded by anulus fibrosus
Cervical Vertebrae
-small body
- supports only weight of the head
-large vertebral foramen
- largest part of spinal cord
-notched (bifid) spinous process
- except for C1 (atlas)
Transverse processes are used to costal processes
creates transverse foramina
- protects vertebral blood vessels
Atlas
(C1) supports skull and is a ring surrounding a large vertebral foramen
- no vertebral body]
- concave superior articular facet
nod your head in “yes” movement
Axis
(C2) attaches and supports the atlas
- dens is held in place inside the vertebral foramen of the atlas by ligaments
- allows rotation of head “no
Vertebra prominens(c7)
- transitions to thoracic vertebrae and has a long spinous process with a broad tubercle
- has large transverse processes for additional muscle attachment
Ligamentum nuchae
(elastic ligament) extends from C7 to skull
-helps to raise head from downward position
Thoracic Vertebrae (T1-T12)
- have heart-shaped bodies
- larger than cervical but smaller than lumbar
- long, slender spinous processes
- angled downward
- smaller vertebral foramen than in C1–C7
Dorsolateral surfaces
have costal facets
articulate with heads of ribs
Transverse costal facets
are located on thick transverse processes for rib articulation
Rib attachment
- T1–T10 articulate with 2 pairs of ribs
- superior and inferior costal facets
- T11–T12 articulate with 1 pair of ribs
- T11–T12 transition to lumbar vertebrae and do not contact transverse processes
- called “floating ribs”
Lumbar Vertebrae (L1-L5)
- largest vertebrae with oval-shaped bodies
- thicker than T1–T12 bodies
- triangular vertebral foramen
Superior articular
processes face medially
-resist twisting movements
Spinous process
is short and heavy
attachment of lower back muscles
Sacrum
is curved and protects reproductive, urinary, and digestive organs
-
consists of 5 fused sacral vertebrae
- fuse between puberty and ages 25–30 leaving transverse lines
Parts of Sacrum
-base is the broad superior surface
- ala are wings at side of the base used to attach muscles
-apex is the narrow inferior portion that articulates with the coccyx
- sacral hiatus is the opening at the inferior end of the sacral canal
median sacral crest are fused spinous processes with 4 pairs of sacral foramina
auricular surface is the thick, flattened area that articulates with pelvic girdle (sacroiliac joint)
coccyx
consists of 3 to 5 fused coccygeal vertebrae
- attaches ligaments and muscles of pelvic floor
coccygeal cornua
formed by laminae of 1st coccygeal
- attachment point of sacrum
can be fractured by fall or during childbirth
coccyx
Thoracic Cage
is skeleton of the chest and is the attachment site for pectoral girdle
-consists of thoracic vertebrae, ribs, and sternum (breastbone
Functions of the thoracic Cage
protect organs of the thoracic cavity
- heart, lungs, and thymus
respiration
- rhythmically expanded by respiratory muscles to draw air into the lungs
- allows for muscular movement of the pectoral girdle and upper limbs
Sternum
is a flat bone located in the midline of the thoracic wall
Parts of the sternum
manubrium
- triangular portion of sternum that articulates with collarbones and cartilage of 1st rib pair
body
- articulates with ribs 2-7
xiphoid process
- attached to the sternal body and to the diaphragm and rectus abdominis muscles
- the smallest part of the sternum; easily broken
Ribs
are 12 pairs of long, curved, flat bones extending from the thoracic vertebrae
-flexible, mobile, and can absorb shock
- head articulates with body of vertebrae
- tubercle articulates with transverse process
Ribs are dived into two types
true and false ribs
True Ribs (1-7)
are connected to the sternum by costal cartilages
False Ribs
do not attach directly to the sternum
- vertebrochondral ribs (8–10)
- fuse together and merged with cartilage before reaching the sternum
- floating ribs (11–12)
- connect only to the vertebrae
