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What are Ribs?

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:

  1. Head with two articular facets

  2. Tubercle

  3. Neck

  4. Shaft

  5. 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.

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FAQs on Ribs

1. What is rib cage?

Ans: In most vertebrates, the rib cage is an arrangement of ribs linked to the spinal column and sternum in the thorax that encloses and protects critical organs like the heart, lungs, and major vessels. The thoracic cage, which includes the rib cage and sternum, is a semi-rigid bony and cartilaginous structure that surrounds the thoracic cavity and supports the shoulder girdle to create the core section of the human skeleton. 

2. How many ribs does a human have and what is the top rib called?

Ans: The average person is born with 12 ribs on each side of the body, for a total of 24. Some people have more than 24 ribs when they are born. Supernumerary ribs refer to these extra ribs. Rib 1 is the most superior rib, and it articulates with the T1 thoracic vertebrae. The next rib down is rib 2, which links to the T2 thoracic vertebra, and so on.

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