Download The Axial Skeleton The Axial Skeleton

The Axial Skeleton
Figure 7–1a
The Axial Skeleton
Figure 7–1b
1
Functions of the Axial Skeleton
• Supports and protects organs in body
cavities
• Attaches to muscles of:
– head, neck, and trunk
– respiration
– appendicular skeleton
The Skull
Figure 7–2
2
Sinuses
• Cavities which decrease the weight of the
skull:
– lined with mucus membranes
– protect the entrances of the respiratory
system
The 4 Major Sutures
1.
2.
3.
4.
Lambdoid suture
Coronal suture
Sagittal suture
Squamous suture
3
The Cranial Bones
•
•
•
•
•
•
Occipital bone
Frontal bone
Sphenoid
Ethmoid
Parietal bones
Temporal bones
The Occipital Bone
•External occipital protuberance
•Occipital condyles:
–articulate with neck
•Inferior and superior nuchal lines:
–to attach ligaments
•Foramen magnum:
–connects cranial and spinal cavities
•Jugular foramen:
–for jugular vein
Figure 7–5a
4
The Parietal Bones
Figure 7–5b
The Frontal Bone
Figure 7–6
5
The Temporal Bones
•Mastoid process:
–for muscle attachment
•Styloid process:
–to attach tendons and ligaments of the hyoid,
tongue and pharynx
•Carotid canal:
–for internal carotid artery
•Foramen lacerum:
–for carotid and small arteries
–External acoustic canal:
–ends at tympanic membrane
•Stylomastoid foramen:
–for facial nerve
•Internal acoustic canal:
–for blood vessels and nerves of the
inner ear
Figure 7–7
The Sphenoid
•Sella turcica:
–saddle-shaped enclosure
–on the superior surface of the body
–Lesser wings:
–anterior to the sella turcica
•Greater wings:
–form part of the cranial floor
–sphenoidal spine
–posterior wall of the orbit
•Optic canals:
–for optic nerves
•Foramen rotundum:
–for blood vessels and nerves of the face
•Foramen ovale:
–for blood vessels and nerves of the face
•Foramen spinosum:
–for blood vessels and nerves of the jaws
Figure 7–8
6
The Ethmoid
The cribriform plate
contains the crista galli
Figure 7–9
The Maxillary Bones
• The largest facial bones
Figure 7–10a
7
The Palatine Bones
Figure 7–10b,c
The Small Bones of the Face
Figure 7–11
8
The Mandible
Figure 7–12a,b
The Hyoid Bone
Figure 7–12c
9
The Orbital Complex
–frontal bone (roof)
–maxillary bone (floor)
–maxillary, lacrimal and ethmoid bones (orbital rim and medial wall)
–sphenoid and palatine bones
Figure 7–13
The Nasal Complex
•
•
•
Frontal bone, sphenoid, and ethmoid:
– superior wall of nasal cavities
Maxillary, lacrimal, ethmoid, and inferior nasal conchae:
– lateral walls of nasal cavities
Maxillary and nasal bones:
– bridge of nose
Figure 7–14
10
Fontanels
• Are areas of fibrous connective tissue (soft
spots)
• Cover unfused sutures in the infant skull
• Allow the skull to flex during birth
Regions and Curves of the
Vertebral Column
• 26 bones:
– 24 vertebrae, the
sacrum, and coccyx
• The spine or vertebral
column:
– protects the spinal
cord
– supports the head and
body
Figure 7–16
11
Vertebrae of the
Vertebral Column
• The neck:
– 7 cervical vertebrae
• The upper back:
– 12 thoracic vertebrae
– each articulate with one or more pairs of ribs
• The lower back:
– 5 lumbar vertebrae
Curves
• Thoracic and sacral curves:
– are called primary curves (present during fetal
development)
– or accommodation curves (accommodate internal
organs)
• Lumbar and cervical curves:
– are called secondary curves (appear after birth)
– or compensation curves (shift body weight for upright
posture)
12
Structure of a Vertebra
•The vertebral body (centrum):
–transfers weight along the spine
•The vertebral arch:
–posterior margin of vertebral foramen
•The articular processes:
–lateral projections between laminae and pedicles
Figure 7–17a,b
The Vertebral Arch
•Pedicles:
–walls of the
vertebral arch
•Laminae:
–roof of the
vertebral arch
•Spinous process:
–projection
where vertebral
laminae fuse
•Transverse process:
–projection
where laminae
join pedicles
Figure 7–17c
13
The Vertebral Canal
•Superior articular process
•Inferior articular process
•Intervertebral foraminae:
–gaps between pedicles of
adjacent vertebrae
–for nerve connections to
spinal cord
•Vertebral canal:
–formed by vertebral
foraminae
–encloses the spinal cord
Figure 7–17d,e
Vertebral Regions
Figure 7–16
14
The Cervical Vertebrae
–small body (support only head)
–large vertebral foramen (largest part of spinal cord)
•C1 (atlas) has no spinous process
•All others have short spinous processes
•Tip of each spinous process is notched (bifid)
Figure7–18a, b
The Cervical Vertebrae
•Atlas (C1):
•Axis (C2):
–articulates with occiptal condyles of skull
–supports the atlas
–has no body or spinous process
–has heavy spinous process
–has a large, round foramen
–to attach muscles of head and neck
•dens
Figure7–18c, d
15
Characteristics of Cervical
Vertebrae
• Vertebra prominens (C7):
– transitions to thoracic vertebrae
– has a long spinous process with a broad
tubercle
– has large transverse processes
• Ligamentum nuchae (elastic ligament)
extends from C7 to skull
The Thoracic Vertebrae
•Thoracic vertebrae (T1–T12):
–have heart-shaped bodies
–larger bodies than in C1–C7
–smaller vertebral foramen than
in C1–C7
–long, slender spinous
processes
–which articulate with heads of
ribs
Figure 7–19b, c
16
The Lumbar Vertebrae
–largest vertebrae
–oval-shaped bodies
–triangular vertebral foramen
Figure 7–20b, c
Comparing Vertebrae
Table 7–2
17
The Sacrum and Coccyx
consists of 5 fused sacral vertebrae
•Sacral canal:
–replaces the vertebral canal
is curved, more in males than in females
•Attaches:
–the axial skeleton to pelvic girdle of appendicular skeleton
–broad muscles that move the thigh
Figure 7–21
Characteristics of the Coccyx
• The coccyx:
– attaches ligaments and a constricting muscle
of the anus
• Mature coccyx:
– consists of 3 to 5 fused coccygeal vertebrae
18
The Rib Cage
• Formed of ribs and sternum
Figure 7–22a
Articulations of Ribs and
Vertebrae
Figure 7–22b
19
The Ribs
•Ribs
–are 12 pairs of long, curved, flat bones
–extending from the thoracic vertebrae
•Ribs are divided into 2 types:
–true ribs
–false ribs
Figure 7–23
Structures of the Ribs
•
•
•
•
The head (capitulum):
– at the vertebral end of the rib
– has superior and inferior
articular facets
The neck:
– the short area between the
head and the tubercle
The tubercle (tuberculum):
– a small dorsal elevation
– has an auricular facet that
contacts the facet of its
thoracic vertebra (at T1–T10
only)
The tubercular body (shaft):
– attaches muscles of the
pectoral girdle and trunk
– attaches to the intercostal
muscles which move the ribs
20
3 Parts of the Sternum
1. The manubrium
–
–
–
articulates with collarbones (clavicles)
articulates with cartilages of 1st rib pair
has a jugular notch between clavicular articulations
2. The sternal body
–
–
–
is tongue-shaped
attaches to the manubrium
attaches to costal cartilages of ribs 2–7
3. The xiphoid process
attaches to diaphragm and rectus abdominis
muscles
KEY CONCEPT
• The axial skeleton:
– protects the brain, spinal cord, and visceral
organs of the chest
• Vertebrae:
– conduct body weight to the lower limbs
• Lower vertebrae are larger and stronger:
– because they bear more weight
21