Axial Skeleton - Mt. SAC 35/pdf... · 2012-01-25 · Axial skeleton • Central supporting axis of...
Transcript of Axial Skeleton - Mt. SAC 35/pdf... · 2012-01-25 · Axial skeleton • Central supporting axis of...
Axial SkeletonAxial SkeletonAxial Skeleton
Dr. Carmen E. RexachAnatomy 35
Mt San Antonio College
Axial skeleton
• Central supporting axis of body• Components:
25Thoracic cage26Vertebral column22Skull# of bonesStructure
SkullVertebraeThoracic Cage
Axial Skeleton
Skull• Most bones joined by sutures• Cranial bones and facial bones• Prominent cavities• Foramina
Cranium• Encloses cranial cavity• 8 Cranial bones• Meninges• 2 parts
– Calvaria = skull cap– Base = floor
• Cranial fossae = 3 basins– Anterior– Middle– posterior
Cranial Bones• 1 frontal bone• 2 parietal bones• 2 temporal bones• 1 occipital bone• 1 sphenoid bone• 1 ethmoid bone
Calvarium = skull cap
Right lateral view
Interior view of right half of skull
Superior View (into cranial fossa)
Cranial Fossae
inferior view
posterior view• Wormian (sutural)
bones
Cavities of the Skull
Paranasal Sinuses
Sphenoid Bone
Ethmoid Bone
Shaken baby syndrome
Facial bones
• Do not directly contact brain or meninges
• Functions– Support teeth– Shape and individuality to face– Form part of orbital and nasal cavities– Attachment site for muscles used for
facial expression and for mastication
Facial bones• 2 maxillae• 2 palatine bones• 2 zygomatic bones• 2 lacrimal bones• 2 nasal bones• 2 inferior nasal conchae• 1 vomer• 1 mandible
anterior view
The Orbit (7 bones)
The Mandible
The Nasal Cavity
The Hyoid Bone
• does not attach to any other bone
• attaches to the larynx and stylohyoidmuscles
Auditory ossicles
Vertebral column• Physical support for skull and trunk• Protects spinal cord• Absorbs stress from movement• Attachment for postural muscles, limbs,
and thoracic cage• Composition
– 33 vertebrae– Intervertebral discs
Vertebral Column
7 cervical
12 thoracic
5 lumbar
4-5 sacral
3-5 coxygeal
Spinal Curves
primary - present at birth = “C”
secondary - form after birth as postural muscles strengthen = “S”
General vertebral structure
Articulated vertebrae
Cervical vertebrae: Atlas and Axis
Cervical Vertebra
• bifid spines in C3-6– No bifurcation in C7– “vertebra prominens”
• transverse foramina– C1-6 = passageway for
vertebral arteries– C7 = passageway for
vertebral veins
• General Characteristics:– Pointed spinous process with sharp downward angle– Heart shaped body, more massive than cervicals– Costal facets for attachment of ribs
Thoracic Vertebrae
Lumbar Vertebrae
• Thick, stout body• Blunt, square
process• Orientation of the
articular processes– Superior = medial– Inferior = lateral
Sacrum
• Five separate bones begin to fuse ≈ 16yo– Transverse ridges (8)
• Anterior– Promontory (4)– Sacral foramina (11)– Alae (6)
• Posterior– Median sacral crest (11)– Lateral sacral crest (10)– Posterior sacral foramina (5)– Sacral tuberosity (4)
• Sacral canal (2)• Sacral hiatus (8)• Auricular surface (12)• Superior articular process (1)
anterior
posterior
Coccyx
• 4-5 fuse by age 20-30• Co1 = cornua
– Attachment of coccyx to sacrum by ligaments
• transverse processes
Thoracic Cage• Components
– Thoracic vertebrae– Sternum
• Manubrium• Body• Xiphoid
– Ribs• 7 true• 3 false• 2 floating
Thoracic cage• Functions
– Encloses lungs & heart– Attachment for pectoral girdle and
upper limbs– Protect spleen, liver, and help protect
kidneys
Thoracic cage
• 12 pairs (1-7 true, 8-12 false)• Proximal end attached to vertebral column• Costal cartilage
– Connects ribs 1-7 to sternum at distal ends– Connects ribs 8-10 to rib 7– Not present on ribs 11 & 12 (floating ribs)
Ribs
Rib 1
Ribs 2-10
Ribs 11 & 12