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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 7-1 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 7-2 Zoology 141 Chapter 7 • • 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 7-3 Zoology 141 Chapter 7 • 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 7-4 Dr. Bob Moeng