Chapter 5 Axial Skeleton 3 parts skull vertebral

Chapter 5 Axial Skeleton 3 parts: skull, vertebral column, bony thorax

Skull: cranium and facial – all but one joined by sutures • Cranium: 8 large flat bones – 2 paired – rest single – Frontal – Parietal (pair) • Meet at sagittal suture • Coronal suture – btw parietal and frontal

– Temporal (pair) – meet parietal at squamous suture • External acoustic meatus – canal to eardrum • Styloid process – inferior to acoustic meatus – neck muscle attachment • Zygomatic process – joins cheek bone • Mastoid process – posterior and inferior to acoustic meatus • Jugular foramen – allow passage of jugular vein

– Occipital – joins parietal at lamboid suture • Foramen magnum – large opening for spinal cord • Occipital condyles – sit on 1 st vertebra – Sphenoid bone – butterfly shaped – floor of cranial cavity • Sella turcia – depression that holds pituitary • Foramen ovale – opening for cranial nerve to mandible • Optic canal and superior orbital fissure – allow nerves for eye

– Ethmoid bone – anterior to sphenoid • Roof of nasal cavity and medial walls of orbits • Crista galli – outer brain covering attaches • Cribriform plates – allow nerves through

• Facial: 14 bones – 6 paired – 2 single – Maxillae (maxillary bones) • Upper jaw – keystone of face • Alveolar margin – holds teeth • Palatine processes – anterior portion of hard palate • Paranasal sinuses – openings – drain into nasal passage

– Palatine bones • Posterior to palatine processes • Posterior part of hard palate • Failure to fuse = cleft palate – Zygomatic bones – cheekbones – Lacrimal bones • Fingernail size • Medial wall of orbit • Grooved for tear passage

– Nasal bones - bridge of nose – Vomer – single – nasal septum – Inferior Nasal Conchae • Project from lateral walls of nasal cavity – Mandible – single • Lower jaw • Only free movable joint of skull – meets temporal bones • Body – horizontal part • Rami (ramus) – upright bars

• Hyoid bone – Suspended in midneck region • 2 cm above larynx – Held by ligaments – touches no other bones – Body and 2 pairs of horns (greater and lesser) – Movable base for tongue • Fetal skull – Fontanels – soft spots • allow compression during birth

Vertebral column (spine) • Before birth – 33 vertebrae • 9 fuse to form sacrum and coccyx • 24 single vertebrae – 7 cervical – neck – 12 thoracic – back – 5 lumbar – lower back • Vertebrae separated by intervertebral discs – Cushion and absorb shock

• Primary curvature – In thoracic and sacral – present from birth • Secondary curvature – Cervical – appears when baby begins to raise head – Lumbar – appears when baby begins to walk

• Vertebrae – Parts • Body (centrum) – weight bearing – faces anterior • Vertebral arch – joining of lamina and pedicle • Vertebral foramen – canal for spinal cord • Transverse processes – projection off arch • Spinal processes – projection off posterior • Superior and inferior articular processes – Lateral to vertebral foramen – Joints w/ other vertebrae

• Cervical – C 1 – C 7 – 1 st – atlas – no body • Depressions in transverse processes to receive occipital condyles • Allow nodding – 2 nd – axis – acts as a pivot • Dens – pivot point – All have transverse foramen for cranial nerves

• Thoracic – T 12 – Costal facets – receive ribs – Have long spinous processes • Lumbar – L 1 – L 5 – Short, chunky spinous processes • Sacrum – 5 fused vertebrae – Alae – wings – articulate w/ hips – Median sacral crest – fused spinous processes – Sacral foramen – openings – Sacral canal – for spinal cord – ends @ sacral hiatus • Coccyx – 3 -5 fused vertebrae – tailbone

Bony Thorax – thoracic cavity • Sternum – breastbone – Fusion of manubrium, body, and xiphoid process – 7 ribs attach – Jugular notch – upper border of manubrium – Sternal angle – where manubrium and body meet – Xiphisternal joint – where body and xiphoid process meet – Sternal puncture – w/draw hematopoietic tissue

• Ribs – 12 – True ribs – 1 st 7 – attach to sternum – False ribs – next 5 • 3 – attach to ribs by costal cartilage • 2 – floating – don’t attach to anything – Intercostal space – btw ribs – filled w/ muscle