Typical and atypical ribs are two types of ribs in the rib cage that contribute to maintaining the proper upper body structure in humans. The ribs are a set of twelve paired bones. They form the protective cage of the thorax. Ribs protect the internal thoracic organs, which include the thymus gland, the breasts, the heart, and the lungs. Ribs can be classified into two types based on their structure: typical and atypical ribs.
The key difference between typical and atypical ribs is their structure. Typical ribs have a generalized structure, while atypical ribs have variations in their structure that are not common to all other ribs in the rib cage.
CONTENTS
1. Overview and Key Difference
2. What are Typical Ribs
3. What are Atypical Ribs
4. Similarities – Typical and Atypical Ribs
5. Typical vs Atypical Ribs in Tabular Form
6. Summary – Typical vs Atypical Ribs
7. FAQ – Typical and Atypical Ribs
What are Typical Ribs?
Typical ribs are ribs that possess a generalized structure. They consist of a head, neck, and body. The head of these ribs has a wedge shape. Atypical rib also has two articular facets separated by a wedge of bone. One of these facets articulates with the numerically corresponding vertebra, and the other facet articulates with the vertebra located above. The neck simply connects the head with the body. It has no bony prominences.
The body of the rib is flat and curved. Moreover, the internal surface of the body has a groove for the neurovascular supply of the thorax. This protects the blood vessels and nerves from damage. Furthermore, except ribs 1, 2, 10, 11, and 12, the rest of the ribs are typical ribs. There are seven pairs of typical ribs and a total of 14 in number.
Figure 01: Typical and Atypical Ribs
What are Atypical Ribs?
Atypical ribs are those that do not have a generalized structure. Ribs 1, 2, 10, 11, and 12 are described as ‘atypical’. They have features that are not common to all other ribs in the rib cage. Rib 1 is shorter and wider than other ribs in the rib cage. It also has one facet on its head for articulation with its corresponding vertebra.
Rib 2 is thinner and longer than rib 1, but it has two articular facets on the head, just like other normal ribs. Rib 10 only has one facet for articulation with its numerically corresponding vertebra. Moreover, ribs 11 and 12 have no neck, and they have one facet for articulation with their corresponding vertebra. Furthermore, there are 5 pairs of atypical ribs and a total of 10 in number.
Similarities Between Typical and Atypical Ribs
- Typical and atypical ribs are two types of ribs in the rib cage.
- Both types contribute to maintaining the proper upper body structure in humans.
- They help to protect the thoracic organs like the heart and lungs.
- Both types help protect nerves and blood vessels and also facilitate muscle attachment and breathing.
- They are important structural units in the human skeleton.
Difference Between Typical and Atypical Ribs
Definition
- Typical ribs are ribs in the rib cage that have a generalized structure.
- Atypical ribs are ribs in the rib cage that have features that are not common to all other ribs in the rib cage.
Structural Features
- Typical ribs have a head with two facets that articulate with numerically corresponding vertebra and the vertebra above; a neck simply connects the head with the body and has no bony prominences, and a flat, curved body has a groove for neurovascular supply.
- Atypical rib 1 is shorter and wider and has one facet articulate with corresponding vertebra, rib 2 is thinner and longer than rib 1 but has two articular facets as normal rib, rib 10 has one facet for articulation with its numerically corresponding vertebra, ribs 11 and 12 with no neck and consist of one facet for articulation with their corresponding vertebra.
Function
- Typical ribs are important in protecting thoracic organs and providing neurovascular supply to the thorax.
- Atypical ribs are important in protecting thoracic organs as typical ribs, also make way for the subclavian vessels and facilitate the origination of serratus anterior muscle.
Number
- There are 7 pairs of typical ribs and a total of 14 in number.
- There are 5 pairs of atypical ribs and a total of 10 in number.
Examples
- Ribs 3, 4, 5, 6, 7, 8, and 9 are typical ribs.
- Ribs 1, 2, 10, 11 and 12 are atypical ribs.
The following table summarizes the difference between typical and atypical ribs.
Summary – Typical vs Atypical Ribs
Ribs are curved and flat bones. They make up the majority of the thoracic cage. Moreover, there are two classifications of ribs: atypical and typical. Ribs three to nine are considered typical ribs that have a generalized structure. Their major features include having a head, neck, tubercle, body (shaft), and costal grooves. The first, second, tenth, eleventh, and twelfth ribs are known as atypical, and they have features that are not common to all other ribs. This is the basic difference between typical and atypical ribs.
FAQ: Typical and Atypical Ribs
1. How many ribs in a cage?
- The rib cage consists of 24 ribs or 2 sets of 12. The ribs are attached to a long, flat bone in the center of the chest or thorax called the sternum. The ribs are connected to the sternum with a strong, flexible cartilage.
2. What are the organs in the rib cage?
- There are many organs inside the rib cage. These vital organs are the lungs, bronchi, trachea, and pleura from the respiratory system, the heart, major vessels, and pericardium from the cardiovascular system.
3. What are the features of the typical ribs?
- The typical ribs mainly consist of a head, neck, and body. The head is wedge-shaped. The head has two articular facets separated by a wedge of bone. One facet articulates with the numerically corresponding vertebra; the other facet articulates with the vertebra above. The neck contains no bony prominences and simply connects the head with the body. Moreover, the body or shaft is flat and curved. It also has an internal surface for the neurovascular supply of the thorax.
4. How many pairs of floating ribs are there?
- There are 2 pairs of floating ribs. Floating ribs, vertebral ribs, or free ribs refer to ribs 11 and 12. These last two pairs of ribs have no anterior articulation with the sternum or the other ribs and costal cartilage. Ribs 11 and 12 are also considered atypical ribs.
5. What is the main function of the ribs?
- The ribs help to protect the contents of the thoracic cavity, such as organs, nerves, and blood vessels. They also serve as an attachment point for many muscles and are active during respiration.
Reference:
1. Janis Savlovskis, Kristaps Raits. “Ribs. the Classification of Human Ribs.” Ribs, Classification of Ribs & Costal Topography.
2. Safarini, Omar A. “Anatomy, Thorax, Ribs.” StatPearls., U.S. National Library of Medicine.
Image Courtesy:
1. “721 Rib Cage” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia
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