The human rib cage contains 37 bones. That total includes 24 ribs (12 on each side), 12 thoracic vertebrae that form the back wall of the cage, and one sternum (breastbone) in the front. Together, these 37 bones and 98 joints form a flexible, protective structure around your heart, lungs, and other vital organs.
The 24 Ribs and Their Three Types
Your 24 ribs come in pairs, one on each side, and are classified into three groups based on how they connect to the sternum at the front of your chest.
- True ribs (pairs 1 through 7): These 14 ribs attach directly to the sternum through strips of flexible cartilage. They provide the most rigid protection for your chest organs.
- False ribs (pairs 8, 9, and 10): These six ribs don’t reach the sternum on their own. Instead, their cartilage connects to the cartilage of rib 7, creating an indirect link to the breastbone.
- Floating ribs (pairs 11 and 12): These four ribs are the shortest. They attach to your spine in the back but have no connection to the sternum at all, which is why they’re called “floating.” They sit at the very bottom of the rib cage.
The Sternum: Three Parts, One Bone
The sternum is the flat, vertical bone running down the center of your chest. It’s made up of three distinct sections: the manubrium (the wide, handle-shaped top), the body (the long, narrow middle), and the xiphoid process (a small, pointed piece at the bottom that starts mostly as cartilage).
These three sections don’t start out fused. In children, the sternum exists as separate pieces that gradually harden and join together over the course of childhood and adolescence. The lower segments fuse first, typically around age 8 to 10, while the bottom tip of the sternum finishes fusing around age 16 or 17. This is why the total bone count of the rib cage can technically be higher in a child than in an adult.
The 12 Thoracic Vertebrae
The back wall of the rib cage is formed by 12 thoracic vertebrae, labeled T1 through T12. Each vertebra has small facets, or smooth contact points, where the ribs attach. Most ribs actually connect to two neighboring vertebrae, bridging the gap between them. The exceptions are the first rib, which connects only to T1, and the lowest two floating ribs, which each connect to a single vertebra with just one contact point.
These vertebrae do double duty. They’re part of the spinal column that protects your spinal cord, and they also serve as anchor points that give the rib cage its structural backbone.
How the Rib Cage Moves When You Breathe
Despite being made of bone, the rib cage is surprisingly flexible. When you inhale, your diaphragm contracts and pulls downward while the small muscles between your ribs contract and pull the ribs upward and outward. This expands the chest cavity, drops the pressure inside, and draws air into your lungs. When you exhale, those muscles relax and the rib cage springs back to its resting size.
The cartilage connecting your ribs to the sternum is essential for this movement. Without it, your chest wall would be too rigid to expand with each breath.
Not Everyone Has Exactly 24 Ribs
About 2% of people have an extra rib, called a cervical rib, that grows from the lowest neck vertebra (C7) rather than from the thoracic spine. Among people with cervical ribs, roughly 40% have them on both sides and 60% have one on just one side. Most cervical ribs cause no symptoms and are discovered incidentally on imaging.
Another variation is the bifid rib, where the front end of a rib splits into two branches. Bifid ribs show up in roughly 0.15% to 3.4% of the general population, though rates as high as 8.4% have been documented in certain geographically isolated populations. They account for about 20% of all congenital rib anomalies. Most bifid ribs are completely asymptomatic, though in rare cases the split can narrow the space between ribs enough to compress nearby nerves, causing chest pain or breathing difficulties.
Quick Count Summary
- Ribs: 24 (12 pairs)
- Thoracic vertebrae: 12
- Sternum: 1
- Total: 37 bones