II Axial Skeleton (E-F)

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

The Vertebral Column (spine) Vertebrae separated by intervertebral discs The spine has a normal curvature Each vertebrae is given a name according to its location Figure 5.14

Improper Vertebral Curvatures

E. Vertebral Column (spine) 1. Cervical (C1 – C7) C1 – atlas – articulates with occipital condyles of skull; allows you to nod “yes” C2 – axis – pivots skull; allows you to indicate “no” Smallest vertebrae Spinous process is short and branched (forked) Transverse processes contain foramina for arteries going to the brain

E. Vertebral Column (spine) 2. Thoracic (T1 – T12) Articulate with ribs Larger than cervical Spinous process is long and hooks sharply downward 3. Lumbar (L1 – L5) Largest and sturdiest with massive block like bodies Spinous process is short and hatchet-shaped

E. Vertebral Column (spine) 4. Sacrum Formed from five fused vertebrae 5. Coccyx Formed from three to five fused vertebrae Forms the human “tailbone”

Structure of a Typical Vertebrae Figure 5.16

Cervical Vertebrae (C1-C7) Figure 5.17a–b

Thoracic(T1-T12) and Lumbar Vertebrae(L1-L5) Figure 5.17c–d

Coccyx and Sacrum

F. Function of Thoracic Cage (Bony Thorax) 1. Protects vital organs such as heart, lungs, and liver 2. Plays a role in breathing 3. Supports the pectoral girdle and arms

The Thoracic Cage (Bony Thorax) Made-up of three parts Sternum Ribs Thoracic vertebrae Figure 5.19a

G. Thoracic Cage (Bony Thorax) 1. Sternum - 3 fused bones which articulate with first 7 pair of ribs Manubrium- articulates with the clavicle (collarbone) Body Xiphoid process 2. Ribs – 12 pair True ribs (1-7) – 7 pair; attach directly to sternum False ribs (8-12) – 5 pair; attach indirectly to sternum or not attached at all Floating ribs (11,12) – 2 pair; lack sternal attachment 3. Thoracic Vertebrae – 12