They are bound to each other and skull by ligamentous connections. If upper cervical vertebrae are in malposition they may distort posterior pharyngeal wall - hypernasality. They have 3 costal facets to articulate with the ribs. Powerful back muscles attach. Considered to be weight-bearing vertebrae.
Spinous processes run horizontally.
Articulates above with 5th lumbar vertebra. Iliac bones join to form pelvic girdle. They form a slightly movable joint. They attach to the sacrum via a small intervertebral disc. Floor of cage is diaphragm.