Costochondral joint
The costochondral joints are the articulations between the ribs and costal cartilage. They are hyaline cartilagenous joints. Each rib has a depression shaped like a cup that the costal cartilage articulates with. There is normally no movement at these joints. Joints between costal cartilages of ribs 6-9 are plane synovial joints. Articulation between costal cartilage of rib 9 and rib 10 is fibrous.

Costochondral Articulations.—The lateral end of each costal cartilage is received into a depression in the sternal end of the rib
In vertebrate anatomy, ribs are the long curved bones which form the rib cage. In most vertebrates, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the chest cavity. They serve to protect the lungs, heart, and other internal organs of the thorax...

, and the two are held together by the periosteum
Periosteum is a membrane that lines the outer surface of all bones, except at the joints of long bones. Endosteum lines the inner surface of all bones....

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