Chapter 7 A Axial SKeleton Flashcards
1
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Skeletal System
A
is an organized and orderly arrangement of osseous tissue
- 206 in typical adult skeleton
- start at 270 at birth but decreases with fusion
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2 primary regions of the skeleton:
A
- axial skeleton
- appendicular skeleton
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Axial Skeleton
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skull, vertebral column, ribs, sternum and sacrum
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appendicular skelton
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upper and lower limbs and pectoral and pelvic girdles
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axial skelton
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forms longitudinal axis of body (80 bones)
6
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bones of the axial skelton
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- skull
8 cranial,14 facial bones, 6 auditory ossicles & hyoid bone
- vertebral column
24 vertebrae, sacrum, and coccyx
- thoracic cage
24 ribs and sternum
7
Q
Functions of axial skelton bones
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-supports/protects organs and provides extensive surface area for muscle attachment
- adjustment of head, neck, and trunk
- respiration
- stabilization of the appendicular skeleton
8
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Skull
A
protects the brain and provides entrance to respiratory and digestive system
- bones joined together by sutures
- immovable joints of the skull*
9
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Skull has 22 bones
A
- 8 cranial bones
- 14 facial bones
10
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8 cranial bones
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that form the cranium
- encloses fluid-filled cranial cavity
- cushions and supports brain*
- bones contact the meninges on inside and muscles outside
11
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14 facial bones
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protect and support entrances to respiratory/digestive systems
- protect entrances to respiratory/digestive tracts
- attachment of facial and jaw muscles
12
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Sinuses
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are cavities that decrease the weight skull
-lined with mucus membranes
- filters the air entering the respiratory system
- add resonance to voice
13
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4 major skull sutures
A
coronal suture
joins frontal & parietal
sagittal suture
joins parietal
squamous suture
joins parietal & temporal
lambdoid suture
joins occipital & parietals
14
Q
Frontal Bone Forms
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- forehead, part of the cranium and roof of the orbits
- contains frontal sinus
15
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Marks of the frontal bone
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-frontal squama (forehead)
-supraorbital margin
protects eye
-supraorbital foramen
for blood vessels of eyebrows, eyelids, and frontal sinuses
16
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Parietal Bone Forms:
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- superior and lateral surfaces of the cranium
- bordered by 4 sutures
- coronal, sagittal, lambdoid and squamous
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Marks of parietal bone
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- superior and inferior temporal lines
- attachment of temporalis muscle
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Temporal bone
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forms lateral walls of cranium and zygomatic arches, articulates with mandible and protects inner ear
19
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Parts of the temporal Bone
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squamous part
- zygomatic process
- mandibular fossa
tympanic part
- external auditory meatus
mastoid part
- mastoid process
20
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Petrous part
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houses middle and inner ear cavities
-receptors for hearing and sense of balance
- cochlea
- vestibular complex
21
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Internal Auditory meatus
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opening for the vestibulocochlear nerve
22
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Temporal Bone Specializations
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- *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
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Occipital Bone
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forms rear and inferior surface of the cranium
24
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Marks of the occupital Bone
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-occipital condyles
- articulation point of atlas
- external occipital protuberance
- attaches nuchal ligament
binds skull to neck
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Foramen magnum
is the major opening of occipital bone
* allows spinal cord to exit cranium
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Sphenoid
forms part of cranial floor; joins cranial and facial bones
* strengthens sides of the skull and contains sphenoidal sinuses
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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**
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Ethmoid
forms part of the cranial floor & lateral/roof walls nasal cavity
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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
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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
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Damage to the ethmoid (upward blow to the nose) can cause
loss of smell, brain damage and even death
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facial bones
have no contact with the brain or meninges
-give shape and individuality to the face
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9 crucial bones (14 total)
* *-2 maxillae
- 2 zygomatic bones
- 2 nasal bones
- 2 inferior nasal chonchae
- 1 mandible**
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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
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parts of maxillary bones
**-alveolar processes** are bony points between teeth
sockets formed hold teeth
**-incisive foramen**
incomplete closure results in cleft palate
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Zygomatic Bones
form the angles of the cheekbones and part of lateral orbital wall
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Specialization of Zygomatic Bones
**-zygomatic arch**
processes of zygomatic bone and temporal bone
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Nasal Bones
form bridge of nose
- supports cartilages of nose
- attaches external nares
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Nasal bones are often fractured by
blow to nsoe
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Inferior Nasal Chonchae
are not part of ethmoid
-separate bone
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Inferior nasal chonchae increase the epithelial surface area and create air turbulence in the nasal cavity
warm, humidify, and cleanse inhaled air
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Mandible
forms the lower jaw and is the only movable bone of the skull
-holds the lower teeth
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Parts of the Mandible
* *-ramus
- body
- angle of mandible**
* masseter attachment
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Body
is horizontal part of mandible; gives mandible it’s strength
**--alveolar processes**
support the lower teeth
**-mental protuberance**
attaches face muscles
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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
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Auditory Ossicles
malleus, incus, and stapes
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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
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Infant Skull
Grows rapidly and is lare compared to the boyd; fusion is not complete at birth
2 frontal bones and 4 occipital bones
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Fontanelles
are spaces between unfused bones in infant skulls
-allow shifting of bones during birth and growth of brain
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Changes after birth
- 2 frontal bones fuse by age six
* metopic suture
- skull reaches adult size by 8 or 9
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Vertebral Column
protects the spinal cord and supports the head and body
*-transfers weight to lower appendicular skeleton*
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Vertebrae form an s-shaped column with 4 curvature regions
- cervical (C) - 7
- thoracic (T) - 12
- lumbar (L) - 5
- sacrum and coccygeal
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Primary Curves (accomadation)
- thoracic and sacral
* present during fetal development; accomodate internal organs
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Secondary Curves (compenstaion)
lumbar and cervical
* appear after birth; shift body weight for upright posture
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Cervical curvatures develop from a baby lifting its head while walking upright
develops lumbar curvature
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Abnormal spinal curvature results from
disease, posture, paralysis or congenital defect
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3 abnormal curvatures
**scoliosis**
lacks proper development of one vertebrae
**kyphosis**
osteoporosis
**lordosis**
weak abdominal muscles
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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
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Intervertebral Foramen
are notches between adjacent vertebrae
-passageway for nerves
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Intervertebral Discs
bind vertebrae together and absorb shock
-pads of *fibrocartilage*
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Disc structure
gelatinous nucleus pulposus surrounded by anulus fibrosus
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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)**
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Transverse processes are used to costal processes
creates transverse foramina
* protects vertebral blood vessels
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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
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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
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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
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Ligamentum nuchae
(elastic ligament) extends from C7 to skull
-helps to raise head from downward position
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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
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Dorsolateral surfaces
have costal facets
articulate with heads of ribs
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Transverse costal facets
are located on thick transverse processes for rib articulation
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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”
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Lumbar Vertebrae (L1-L5)
- largest vertebrae with oval-shaped bodies
* thicker than T1–T12 bodies
- triangular vertebral foramen
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Superior articular
processes face medially
*-resist twisting movements*
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Spinous process
is short and heavy
attachment of lower back muscles
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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
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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)
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coccyx
consists of 3 to 5 fused coccygeal vertebrae
* attaches ligaments and muscles of pelvic floor
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coccygeal cornua
formed by laminae of 1st coccygeal
* attachment point of sacrum
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can be fractured by fall or during childbirth
coccyx
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Thoracic Cage
is skeleton of the chest and is the attachment site for pectoral girdle
-consists of thoracic vertebrae, ribs, and sternum (breastbone
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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
82
Sternum
is a flat bone located in the midline of the thoracic wall
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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
84
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
85
Ribs are dived into two types
true and false ribs
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True Ribs (1-7)
are connected to the sternum by costal cartilages
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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
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