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Rib

life science Maturity 9-11 Next article →

Ribs are long, curved bones that form the rib cage. This structure is a vital part of the axial skeleton. In most tetrapods, these bones surround the thoracic cavity. This cavity houses the heart and the lungs. By enclosing this space, the ribs protect these essential organs. In certain animals, such as snakes, the ribs provide support and protection for the entire body.

Ribs labeled
Ribs labeled

Human ribs are classified as flat bones. Most humans possess 24 ribs, organized into 12 pairs. These ribs attach at the back to the thoracic vertebrae. They are numbered from 1 to 12 based on the specific vertebrae they connect to. For example, the first rib attaches to the first thoracic vertebra, known as T1. Interestingly, about 1 in 500 people have an extra rib. This is called a cervical rib, and it can appear on the right side, the left side, or both.

Each rib has several specific parts that allow it to function. The head of the rib sits next to a vertebra. The neck is a flattened section about 3 cm long that extends from the head. Below the neck is the body, also called the shaft. There is also a tubercle, which is a prominent part of the rib. The ribs connect to the vertebrae through two specific points. The first is the costovertebral joint at the head. The second is the costotransverse joint, located between the tubercle and the transverse process of the vertebra.

Inside the body, the ribs work closely with the thoracic diaphragm to manage breathing. The diaphragm is a muscle that separates the rib cage from the lower abdomen. When the diaphragm contracts, it expands the thoracic cavity. This action reduces intra-thoracic pressure, which draws air into the lungs. This process can happen in two ways. If the lower ribs are stabilized, the diaphragm pulls the central tendon down to expand the cavity downward. If the central tendon is stabilized, the diaphragm elevates the ribs to expand the cavity upward.

Humans categorize their ribs into three distinct types. The first seven pairs are called "true ribs." These are attached directly to the sternum via costal cartilage. The next five pairs are known as "false ribs." Three of these share a common cartilaginous connection to the sternum. The final two pairs, the eleventh and twelfth ribs, are called "floating ribs." These are attached only to the vertebrae and do not connect to the sternum at all.

Eptesicus fuscus ribcage
Eptesicus fuscus ribcage

Ribs begin their development very early in the embryo. During the fourth week of development, small protrusions called costal processes form on the vertebral bodies. By the fifth week, these processes grow longer to become the ribs. In the sixth week, the costovertebral joints begin to develop. Initially, the ribs are made of cartilage. They eventually turn into bone through a process called endochondral ossification. Primary ossification centers appear near the angle of each rib. During adolescence, secondary ossification centers form in the tubercles and heads.

Different species show incredible variety in their rib structures. Dogs typically have 26 ribs. Turtles have only eight pairs, which develop into their bony carapace and plastron. Birds have ribs on the thoracic region with a unique projection called an uncinate process. This process serves as an attachment point for shoulder muscles. In fish, there can be two sets of ribs: dorsal ribs and ventral ribs. However, tetrapods like mammals, birds, and reptiles only possess a single set of ribs.

Dog anatomy lateral skeleton view (full)
Dog anatomy lateral skeleton view (full)

Beyond biology, ribs are also a common part of human cuisine. They are often used as food because they are a part of the meat chop. A collection of five or more ribs is often called a rack, such as a rack of lamb. Beef ribs can be served as individual short ribs or as a plate. Pork ribs, including spare ribs, are also very popular in many different types of cooking.

Ribs labeled
Ribs labeled
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File:Ribs labeled.png
Ribs labeled.png
File:Dog anatomy lateral skeleton view (full).jpg
Dog anatomy lateral skeleton view (full).jpg
File:Eptesicus fuscus ribcage.jpg
Eptesicus fuscus ribcage.jpg
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