How Do Ribs Protect Organs and Support Breathing?
The ribs are the thoracic cavity's bony framework. The ribs are the main structural component of the thoracic cage, protecting the thoracic organs, although their primary purpose is to aid in breathing. Each rib articulates posteriorly with two thoracic vertebrae via the costovertebral joint, which has twelve pairs. The first rib only articulates with the first thoracic vertebra, which is an exception to this.
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Classification of Ribs
According to the attachment of ribs to the sternum, the ribs are mainly classified into 3 groups: true, false, and floating ribs.
The true ribs are ribs 1–7, which have costal cartilages that directly articulate with the sternum. They are connected to the sternum via the sternocostal joints. The first rib is an exception; it is a synarthrosis, and the costoclavicular joint permits the first rib to articulate with the clavicle in an unusual fashion.
The false ribs (8,9,10) are ribs that indirectly articulate with the sternum through the costochondral joint, which connects their costal cartilages to the seventh costal cartilage.
The floating ribs do not articulate with the sternum (11,12).
Ribcage Anatomy
In vertebrate anatomy, the rib cage is a basketlike skeletal structure made up of the ribs and their corresponding attachments to the sternum (breastbone) and the vertebral column that forms the chest, or thorax. The lungs and heart are protected by the rib cage, which provides bone protection for these vital organs. In addition to the sternum, the rib cage comprises the 12 thoracic vertebrae and 24 ribs. The curve of the rib cage opens up with each subsequent rib, starting with the first or highest. The rib cage is semirigid but expansile, meaning it can expand. During breathing and other activities, the little joints between the ribs and the vertebrae allow the ribs to move slightly across the vertebrae.
True ribs are the first seven ribs in the rib cage that are linked to the sternum by malleable cartilages called costal cartilages. The first three of the remaining five fake ribs have their costal cartilages attached to the cartilage above them. The cartilages of the last two, the floating ribs, culminate in a muscle in the abdominal wall. The lowest five ribs are arranged in such a way that they allow the lower half of the rib cage to expand and the diaphragm, which has an extensive origin from the rib cage and the spinal column, to move freely. The range of motion is limited due to ligamentous attachments between the ribs and vertebrae.
Structure of Ribs
Ribs are classified according to their location and relationship to the sternum. All ribs are linked to the thoracic vertebrae posteriorly and are numbered from one to twelve. True ribs are those that articulate directly with the sternum, while false ribs are those that do not. The floating ribs (eleven and twelve) are false ribs since they are not linked to the sternum at all.
Typically, the anatomical components of the ribs bone are as follows:
Head with two articular facets
Tubercle
Neck
Shaft
Costal groove
The majority of ribs in the human body are typical ribs, as they have all of these characteristics.
Atypical ribs are those that lack all of these characteristics:
The first rib (wide and short, has two costal grooves, and one articular facet).
Rib number two (thin, long, and has a tuberosity on its superior surface for the attachment of the serratus anterior muscle).
The tenth rib (only one articular facet).
The eleventh and twelfth ribs (one articular facet with no neck).
The Function of Rib Cage
In humans, a rib cage is a unit of the respiratory system. It protects the lungs by enclosing the thoracic cavity. During inhalation, the muscular diaphragm in the thoracic cavity contracts and flattens, while the intercostal muscles contract and raise the rib cage up and out.
The vertical, anteroposterior, and transverse axes all contribute to thoracic cavity expansion. The diaphragm contracts and the abdominal muscles relax, extending the vertical plane to accommodate the downward pressure supplied to the abdominal viscera by the diaphragm contracting. The diaphragm itself can move down, rather than the domes flattening, to achieve a greater extension. The anteroposterior plane is the second and is enlarged by a movement known as the 'pump handle.' Because of the downward slanting shape of the top ribs, this is possible. The upper ribs can also push the sternum up and out when the external intercostal muscles contract and lift the ribs.
This movement expands the thoracic cavity's anteroposterior diameter, making breathing easier. The lower ribs (some suggest the 7th to 10th ribs in particular) expand the third, transverse plane, with the diaphragm's central tendon acting as a fixed point. The ribs are able to evert and produce the bucket handle movement when the diaphragm contracts, which is aided by gliding at the costovertebral joints. The transverse diameter of the lungs is therefore increased, allowing the lungs to fill. During inhaling, the circumference of a normal adult human rib cage grows by 3 to 5 cm.
Facts About Ribs in Human Body
Some of the facts about ribs in human body are mentioned below:
Ribs are thin, flat bones that curl over the chest.
The ribcage of the human body is conical in shape and this conical structure helps to maintain the shape of the upper body.
Your skeleton relies on it for support.
Floating ribs are the shortest of your ribcage's ribs.
The ribs are separated by gaps. Intercostal spaces are the term for these gaps. Thin muscle sheets can be found in these places. While breathing, these muscles contract and relax.
Because a sharp piece of rib might enter your heart or lung and cause major problems, a rib injury can be fatal.
Every breath you take causes your ribcage to expand by 3 to 5 cm.
The sternum, or breastbone, is where the cartilage sections of the ribs connect. The sternum is a three-bone plate that is flat.
The sternum is detached from the floating ribs.
A flail chest occurs when several ribs are shattered and removed from the cage.
The ribs in the centre are the most likely to break.
FAQs on Ribs: Anatomy, Structure, and Their Functions
1. What are ribs and what is a rib cage?
Ribs are long, curved bones that form the main structure of the thoracic cage, commonly known as the rib cage. The rib cage is a bony and cartilaginous enclosure in the chest that includes 12 pairs of ribs, the sternum (breastbone), and the thoracic vertebrae. It serves to protect vital organs like the heart and lungs.
2. How many pairs of ribs are in the human body?
The human skeleton typically contains 12 pairs of ribs, making a total of 24 ribs. These are attached to the thoracic vertebrae at the back. While rare variations exist, 12 pairs is the standard number as per the NCERT syllabus.
3. What are the three main types of ribs found in humans?
Human ribs are classified into three types based on their attachment to the sternum:
- True Ribs: The first 7 pairs (ribs 1-7), which connect directly to the sternum via their own costal cartilage.
- False Ribs: The next 3 pairs (ribs 8-10), which are attached to the sternum indirectly by connecting to the cartilage of the 7th rib.
- Floating Ribs: The last 2 pairs (ribs 11-12), which do not connect to the sternum at all and are only attached to the vertebrae.
4. What is the functional difference between true, false, and floating ribs?
The functional difference lies in the degree of mobility and protection they offer. True ribs provide the most rigid and stable protection for the heart and lungs due to their direct sternal connection. False ribs offer protection while allowing more flexibility for diaphragm movement. Floating ribs are the most mobile, allowing for significant expansion of the diaphragm during deep breathing and primarily protecting posterior organs like the kidneys.
5. How do the ribs and sternum form the thoracic cage?
The thoracic cage is formed by the 12 thoracic vertebrae posteriorly (at the back), the sternum anteriorly (at the front), and the 12 pairs of ribs laterally (on the sides). Each rib articulates with its corresponding thoracic vertebra. The first ten pairs of ribs curve around the chest and connect to the sternum, either directly or indirectly, via costal cartilage, creating a strong yet flexible protective barrier.
6. What is the primary role of the rib cage in the human body?
The primary role of the rib cage is to perform two critical functions:
- Protection: It forms a protective shield around the vital thoracic organs, including the heart, lungs, trachea, and oesophagus, safeguarding them from external trauma.
- Respiration: It plays a crucial mechanical role in breathing. The elevation and depression of the rib cage changes the volume of the thoracic cavity, causing air to move in and out of the lungs.
7. How do the ribs facilitate the process of breathing?
During inhalation, the external intercostal muscles contract, lifting the ribs upwards and outwards. This movement increases the volume of the thoracic cavity, which decreases internal pressure and causes air to rush into the lungs. During normal exhalation, these muscles relax, the ribs move downwards and inwards due to elastic recoil, decreasing the thoracic volume and forcing air out. This mechanism is often called the 'pump handle' and 'bucket handle' movement.
8. Is there a difference in the number of ribs between males and females?
No, this is a common anatomical misconception. Both males and females typically have the same number of ribs: 12 pairs, for a total of 24. The structure of the skeletal system, including the rib cage, is consistent across sexes, with variations being individual rather than gender-based.
9. Why are the last two pairs of ribs called 'floating ribs'?
Rib pairs 11 and 12 are called floating ribs because their front ends do not connect to the sternum or to the cartilage of other ribs. Their only point of connection is to the thoracic vertebrae at the back. This lack of an anterior connection gives them their 'floating' appearance and name, and it allows for greater movement of the diaphragm.
10. What are the key anatomical features of a typical rib bone?
A typical rib bone has several key features. It has a head with two facets for articulating with the vertebral bodies, a neck, and a tubercle that articulates with the transverse process of the vertebra. The main part of the rib is the shaft or body, which is curved and has a costal groove on its inner surface to protect the intercostal nerve and blood vessels.
