Download The Axial Skeleton

Zoology 141
Chapter 7
Dr. Bob Moeng
The Axial Skeleton
Four Principal Types of Bones
• Long
– Primarily compact bone with spongy bone at ends
– Slight curve to distribute force
– Important for leverage
– Examples: femur, fibula, tibia, phalanges, ulna, radius, humerus
• Short
– Spongy bone with thin layer of compact bone
– Examples: carpals, tarsals
• Flat
– Thin plates of compact bone over spongy bone
– Examples: cranium, sternum, ribs, scapula
• Irregular
– Varying amounts of spongy and compact bone
– Examples: vertebrae, some facial bones
Other Types of Bones
• Sutural (Wormian)
– Found between sutures of some cranial bones
– Presence and size variable
• Sesamoid
– Develop in tendons
– Examples
• Knee cap & other locations including thumb and big toe
Bone Surface Structures
• Structures are important for articulation, muscle attachment and penetration by blood
vessels and nerves
• Depressions or openings
– fissure, foramen, fossa, sulcus, meatus, sinus
• Processes - for articulations
– condyle, facet, head
• Processes - for connective tissue attachment
– epicondyle, linea, spinous process, trochanter, tubercle, tuberosity
Axial vs. Appendicular Skeleton
• Axial
– Bones along the longitudinal axis of body
– 80 of 206 bones
– Skull, hyoid, vertebrae, sternum, ribs, ossicles
• Appendicular
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Zoology 141
Chapter 7
Dr. Bob Moeng
– Pelvic and pectoral girdles
– Appendages
Bones of the Cranial Cavity
• Frontal
• Ethmoid
• Sphenoid
• Temporal
• Parietal
• Occipital
Cranial Fossae
• Anterior fossa
– Frontal lobes of cerebrum
• Middle fossa
– Temporal lobes of cerebrum
• Posterior fossa
– Cerebellum, brain stem
• Other cavity structures
– Sella turcica (sphenoid) - holds pituitary
– Crista galli (ethmoid) - attaches meningeal membrane
Bones of the Orbit
• Frontal
• Zygomatic
• Maxillary
• Ethmoid
• Sphenoid
• Lacrimal
• Palatine
Bones of the Nasal Cavity
• Nasal
• Frontal
• Ethmoid (including superior and middle nasal conchae, perpendicular plate)
• Inferior Nasal Concha
• Maxillary
• Palatine
• Vomer
• Paranasal sinuses - enclosed in ethmoid, frontal, sphenoid & maxilla
Mandible
• Condylar process articulates with mandibular (glenoid) fossa of temporal bone
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Zoology 141
Chapter 7
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Dr. Bob Moeng
Coronoid process and ramus important for muscle attachment
Mandibular and mental foramina - nerve supply
Structure of Vertebrae
• Centrum (body)
• Vertebral arch consisting of pedicles and laminae with vertebral foramen
• Vertebral notches creating intervertebral foramen
• Processes
– Transverse (2)
– Spinous (1)
– Superior & inferior articular (4)
Vertebral Column
• Cervical (7) including atlas & axis (dens) vertebra prominens on C7
• Thoracic (12) rib attachment
– vertebrosternal (7), vertebrochondral (3), floating (2)
– Head and tubercle bracing of rib
– Costal groove for blood vessels and nerves
• Lumbar (5)
• Sacrum (5 fused to 1)
– Sacral hiatus - site of epidurals
• Coccyx (4 fused to 1)
Intervertebral Discs
• Structure
– Annulus fibrosus - fibrocartilagenous disc
– Nucleus pulposus - elastic core
• Function
– Flexibility
– Shock absorption
• Herniated disc
• Normal curves
– Thoracic and sacral primary curves
– Cervical and lumbar secondary curves
• Abnormal curves
– Scoliosis - lateral curvature, usually in thoracic region
– Kyphosis - exaggerated thoracic curve
– Lordosis - excessive lumbar curve
Vertebral Curves
• Normal curves
– Thoracic and sacral primary curves
– Cervical and lumbar secondary curves
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Zoology 141
Chapter 7
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Abnormal curves
– Scoliosis - lateral curvature, usually in thoracic region
– Kyphosis - exaggerated thoracic curve
– Lordosis - excessive lumbar curve
Skeletal System Maturation
• Fontanels
– Ossify by early childhood
• Xiphoid process
– Ossify by about age 40
• Sacrum
– Fuse by late teens - early 20’s
• Coccyx
– Fuse by about age 30
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Dr. Bob Moeng