The Axial Skeleton Forms the longitudinal axis of the body Divided into three parts Skull Vertebral column Bony thorax

The Axial Skeleton Figure 5.6a

The Skull Two sets of bones Bones are joined by sutures Cranium Facial bones Bones are joined by sutures Only the mandible is attached by a freely movable joint

SKELETAL DIVISIONS Skull A. Cranium (8 bones) 1. frontal – forms forehead, projections under eyebrows, and superior part of eye socket 2. parietal (2) – superior and lateral walls, joined together at sagittal suture, joined with frontal bone at coronal suture

3. temporal (2) – inferior to parietal- squamous sutures a. external acoustic (auditory) meatus (ear canal) b. styloid process – attachment for neck muscles c. zygomatic arch (process) d. mastoid process – contains mastoid sinuses and provides for neck muscle attachment (mastoiditis) e. jugular foramen – jugular vein (“brain drain”) f. carotid canal – internal carotid artery (anterior to jugular foramen)

a. foramen magnum – opening for spinal cord 4. occipital – floor and back of skull, joins parietals at lambdoid suture a. foramen magnum – opening for spinal cord b. occipital condyles – articulates with first vertebrae (atlas) 5. sphenoid – forms part of cranial floor, eye orbits, and lateral part of skull a. sella turcica – holds pituitary gland b. sphenoid sinuses – air cavities within the sphenoid bone c. optic canal-optic nerve to pass to eye d. superior orbital fissure- cranial nerves controlling eye pass through

6. ethmoid – forms nasal cavity roof and medial walls of orbits a. crista galli – attachment for outermost covering of the brain b. cribriform plates – holes allowing impulses from smell receptors to reach the brain

B. Facial bones (14 – only mandible & vomer single) 1. mandible – lower jaw a. alveolar margins (for lower teeth) 2. maxillae (2) – upper jaw, “keystone” face bones a. palatine processes – anterior part of hard palate b. alveolar margins (for upper teeth) 3. palatine (2) – posterior part of hard palate 4. zygomatic (2) – cheekbones; lateral walls of orbits

5. lacrimal (2) – medial walls of. orbits, contains passageway for 5. lacrimal (2) – medial walls of orbits, contains passageway for tears - lacrimal fossa (groove) 6. nasal (2) – bridge of nose 7. vomer – nasal septum 8. Nasal conchae (2) – curved projections form lateral walls of nasal cavity

C. Hyoid Bone (non-articulating) 1. movable base for tongue 2. attachment for neck muscles that raise & lower larynx during swallowing & speaking

Fetal Skull - fontanels

II. Vertebral Column (spine – 26 irregular bones) A. common features of vertebrae: 1. body/centrum 2. vertebral arch – laminae and pedicles 3. vertebral foramen – opening for spinal cord 4. transverse processes (2) – lateral projections 5. spinous process – projection (“spine”) from vertebral arch 6. superior and inferior articular process – joints with adjacent vertebrae 7. intervertebral disks – fibrocartilage (herniated/slipped disks)

B. sections 1. cervical (C1-C7) – smallest and lightest a. atlas – articulates with occipital condyles to allow “yes” motion b. axis – pivot point allowing rotation between C1 and C2 to allow “no” motion c. foramina – openings for vertebral arteries and nerves

2. thoracic (T1-T12) a. spinous process – long and hook-like b. contain two costal facets – side for ribs

3. lumbar (L1-L5) a. most massive b. spinous process – hatchet-shaped

4. sacrum – fusion of 5 vertebrae a. alae (wings) – articulate with hipbones to form sacroiliac joints b. forms posterior pelvic wall * vertebral column continues in sacrum as sacral canal 5. coccyx (3-5 bones) – tailbone

B. curvatures 1. primary – thoracic (convex) & sacral (convex), present at birth 2. secondary – cervical (concave) appears when baby begins to raise head & lumbar (concave) when begins to walk

D. Abnormalities (text pg. 154) 1. scoliosis – abnormal side-to-side curvature 2. kyphosis – “hunchback,” abnormal thoracic curvature 3. lordosis – “swayback,” exaggerated lumbar curvature

Bony Thorax A. sternum 1. consists of 3 bones: a. manubrium b. body c. xiphoid process 2. sternal puncture – procedure where needle is inserted into the marrow of the sternum to withdraw hematopoietic tissue (bone marrow)

B. ribs (12 pairs) - attachments made by costal cartilage - spaces between filled with intercostal muscle 1. true ribs – first 7 pairs, attached to sternum 2. false ribs – next 5 pairs, either indirectly attached to sternum or not attached at all a. floating ribs – last 2 pair of false ribs, have no attachment to sternum