Question

Which of the following is incorrect about ribs? (a) Each rib is a thin and cat bone connected dorsally to the vertebral column and ventrally to the sternum. (b) Ribs has two articulation surfaces on its dorsal end which are called bicephalic. (c) Ventrally ribs are connected to sternum by elastic cartilage. (d) First 7 pairs are called true ribs. The 8,9 and \(10^{\star}\) pair is known as false (vertebracondral) ribs and the 2 pairs (11" and \(12^{\text {th }}\) ) are known as floating ribs.

Short answer

The incorrect statement about the ribs is (d). The 8, 9 and 10 pair should be referred to as 'vertebrocostal' ribs, not 'vertebracondral' ribs.

Step-by-step solution

Analyze each statement individually

Let's start by understanding each statement and what it asserts about the anatomy of ribs. (a) Each rib is a thin, flat bone that connects dorsally to the vertebral column and ventrally to the sternum. Truely, ribs are flat bones that do connect to the vertebral column dorsally (towards the back) and to the sternum ventrally (towards the front). (b) Ribs have two articulation surfaces on their dorsal end, which are called bicephalic. Correctly, ribs do have dual articulation surfaces on their dorsal end, which are indeed called bicephalic. (c) Ribs are connected to the sternum ventrally by elastic cartilage. This statement, associating that the ribs are connected to the sternum through 'elastic cartilage', is true. (d) The first 7 pairs are known as true ribs, the next three pairs (8, 9 and 10) are termed false ribs, and the last two pairs (11 and 12) are called floating ribs. This last statement is partially incorrect. The 8, 9, and 10 pairs of ribs are indeed known as false ribs, but they are referred to as 'vertebrocostal' ribs, not 'vertebracondral'.

Identify the incorrect statement

Statement (d) is identified as the incorrect statement because it mislabels the false ribs. They should correctly be referred to as vertebrocostal ribs.

Key concepts

Vertebral Column Connection

Understanding the relationship between the ribs and the vertebral column is crucial in grasping rib anatomy. The ribs are long, curved bones that form the rib cage, which plays a significant role in protecting vital thoracic organs. At the dorsal end, each rib is connected to the vertebral column. There are 12 pairs of ribs, each articulating with the thoracic vertebrae at two points—the head and the tubercle of the rib. This articulation is important as it allows for a degree of movement which is essential for the breathing process. The connection of the ribs with the vertebral column is a synovial joint, meaning it's a movable connection that is lubricated by a fluid enabling smooth motion.

It is also noteworthy to mention that the articulation surfaces on the dorsal end of the ribs, known as costal facets, interface with the thoracic vertebrae. These points are what allow the ribs to move along with the spine during breathing and other bodily movements. Incorrectly referring to these as 'bicephalic,' which suggests a two-headed feature, can lead to confusion. The term 'bicephalic' is not commonly used in this context in the anatomical description of ribs.

Articulation of Ribs

Moving onto the specifics of rib articulation, we find two primary types based on their attachment to the sternum. The true ribs, or the first seven pairs, have a direct articulation with the sternum through their costal cartilages. This direct attachment is crucial for the stability and protection of the chest cavity.

In contrast, the false ribs (the 8th, 9th, and 10th pairs) articulate with the sternum indirectly. They are connected to the cartilage of the rib above rather than bonding directly to the sternum. This type of connection is termed 'vertebrocostal,' and it allows some flexibility in the costal margin. Students might easily mislabel false ribs as attached by 'elastic cartilage' which is an oversimplification; while cartilage does have elastic properties, the actual term is hyaline cartilage, which provides both the necessary rigidity and flexibility for rib movement. This precise understanding of how the ribs articulate, both directly and indirectly, with the sternum is vital in studying chest mechanics and functions such as respiration.

True, False, and Floating Ribs

The categorization of ribs into true, false, and floating ribs is determined by their connection to the sternum—a key area of confusion for many students. As we've established, the first seven pairs are regarded as 'true ribs' because of their direct cartilaginous link to the sternum. This secure connection contributes significantly to thoracic structure and respiration.

The false ribs include the 8th, 9th, and 10th pairs. They are referred to as 'vertebrocostal' because their cartilage connects to the cartilage of the rib above them, eventually joining the sternum. Lastly, we have the 'floating ribs', comprising the 11th and 12th pairs. These ribs are not attached to the sternum at all. Instead, their anterior ends are free, which is why they are termed 'floating'. These ribs provide a degree of protection despite their lack of sternal attachment but are more susceptible to injury due to their relatively freer movement.