The Skeletal System

The Thorax Forms a cage to protect major organs 3 Parts: Sternum Ribs Thoracic Vertebrae Figure 5.19a

Sternum 3 Parts: Ossification begins at age 6-10 Manubrium (large, triangular) Body Xiphoid Process Ossification begins at age 6-10 Completed fusions occurs at age 25 Manubrium Body Xiphoid Process Figure 5.19a

Ribs 12 pair in each sex Ribs 1-7 are “TRUE” ribs: connected to the sternum and separated by cartilaginous extensions (costal cartilage) Ribs 8-12 are “FALSE” ribs: do not attach directly to the sternum Ribs 8, 9, 10 fuse with the cartilage of rib 7 Ribs 11 and 12 are “floating” ribs – do not attach to the sternum at all

Thoracic Cage Figure 6-20(b)

The Vertebral Column Vertebrae separated by intervertebral discs Each vertebrae is given a name according to its location

Vertebral Column 7 cervical 12 thoracic 5 Lumbar 1 sacrum 1 coccyx

The Vertebral Column Concave – curved inward Convex – curved outward Cervical Vertebrae Lumbar Vertebrae Convex – curved outward Thoracic Vertebrae Sacrum

Structure of a Typical Vertebrae Figure 5.16

Vertebral Column/Thoracic Cage Typical Vertebrae of the Cervical, Thoracic, and Lumbar Regions Figure 6-17(a)

Vertebral Column/Thoracic Cage Typical Vertebrae of the Cervical, Thoracic, and Lumbar Regions Figure 6-17(b)

Vertebral Column/Thoracic Cage Typical Vertebrae of the Cervical, Thoracic, and Lumbar Regions Figure 6-17(c)

The Vertebral Column Atlas (C1) Axis (C2) First cervical vertebrae Holds up the head Articulates with the skull Axis (C2) Articulates with C1 through the DENS (odontoid process) Creates a pivot joint between C1 and C2 Nodding/shaking head “no”

Vertebral Column The Atlas and Axis Figure 6-18