Ribs

Meaning Of Rib Bones

Rib bones refer to the 12 sets of arched, level bones that constitute the thoracic enclosure or rib cage, the bony framework that forms the thoracic pit and safeguards various organs. Despite being comparatively thin and light, these bones are highly resilient.

Location of the Ribs

Ribs are situated in the chest and link to the sternum or breastbone at the front and the thoracic spine in the back. The ribs are palpable and visible both at the front and back of the upper body. They are a component of the axial skeleton.

The ribs are labeled from 1 to 12 from top to bottom to correspond with the numbering of their respective thoracic vertebrae.

Quick Information

Roles

Given that the ribs create the ribcage, their leading function involves enabling it to operate in order.

• The ribs encompass the chest cavity and safeguard the heart and lungs, the two vital organs in this area.
• They aid respiration by making movements both to the front and back, and upward and downward to accommodate the lungs during inhalation and exhalation. The diaphragm and intercostal muscles oversee these movements.
• They also offer origin points or attachment for several vital muscles in the chest and thoracic wall.
• Rib bones take part in erythropoiesis (the process of generating red blood cells). They constitute one of the locations where erythropoiesis happens throughout adult life.

Structure

Varieties of Ribs

The 24 ribs are categorized in two distinct ways. There are three kinds of ribs determined by their connection to the sternum:

1. True ribs are the initial 7 pairs that attach to the thoracic vertebra in the spine and then directly articulate with the sternum through their costal cartilage.
2. False ribs are the subsequent 3 pairs (8th, 9th, and 10th ribs). Their costal cartilages join with that of the 7th rib to connect indirectly to the sternum.
3. Floating ribs are the final 2 pairs (11th and 12th ribs) without any articulation with the sternum.

The second method of categorizing ribs is based on their structure and anatomical variations. According to this, they can be of two types — typical and atypical.

Typical Ribs

The 3rd to 9th pairs of ribs are classified as typical ribs as they all possess a standard structure with the following features and landmarks:

Head: It is the wedge-shaped (medioposterior) end of a rib bone where two articular surfaces are divided by a bony ridge. The larger one of the two surfaces articulates with the superior costal facet of the corresponding thoracic vertebra, while the smaller one with the inferior costal facet of the vertebra above.

For instance, the larger articular surface of the third rib attaches with the T3 (second thoracic vertebra) and the smaller surface with the T2.

Neck: This segment connects the head to the rib shaft. There are no bony markings in this area.

Tubercle: The rough bony protrusion where the neck and shaft meet. The sole articular surface in this region is for the transverse process of the corresponding vertebra.

Shaft: The lengthy, thin curved part of the rib following the tubercle. The curve towards the front of the body is most pronounced at the costal angle. This angle marks the point of attachment for several deep back muscles.

At the end of the shaft is a cup-shaped surface where the rib connects with costal cartilage.

Costal Groove: The groove or depression along the inferior border. It allows passage to the neurovascular bundle which includes the intercostal blood vessels and nerves.

Atypical Ribs

These are the ribs possessing unique characteristics not found in other ribs.

1st Rib: This short and thick rib has only one articular surface for the T1 vertebra. It has a head, neck, and body but does not curve as sharply as the typical ribs and lacks a costal groove. The superior surface is marked with two grooves, with a small ridge in between allowing passage to the subclavian blood vessels. It is also the first point of origin of the serratus anterior muscle.

2nd Rib: Although smaller than a typical rib, it is longer and thinner than the 1st rib, with two articular facets on the head for T1 and T2. Its main distinguishing feature is the rough tuberosity on its upper surface which acts as one of the points of origin of the serratus anterior muscle.

10th Rib: It has only a single articular surface for its corresponding vertebra (T10).

11th and 12th Ribs: Like the 10th rib, they also have a single facet for their corresponding vertebra. Additionally, these two ribs are very short, with no neck or tubercle.

Articulations

1. Costovertebral joints: Link the head of the rib to the corresponding thoracic vertebrae, and the one above it
2. Costochondral joint: Connects the costal groove of a rib to its corresponding costal cartilage
3. Costotransverse joint: Connects the tubercle to the transverse process of the corresponding vertebra
4. Sternocostal joint: Connects the true ribs to the sternum or breastbone
5. Costoclavicular joint: An anatomical variant where the 1st rib connects with the clavicle

Muscle Attachments

Several crucial muscles attach to the ribs, govern or influence their movement. Following are the names of some of the most significant muscles around the ribs:

• Intercostals (external, internal, innermost)
• Subcostales
• Transversus thoracis
• Serratus posterior
• Serratus anterior
• Levatores costarum
• Pectoralis major
• Pectoralis minor
• Latissimus dorsi
• Rectus abdominis

FAQs

Q.1. Do men and women have the same number of ribs?

Ans. There is no difference in the number of ribs in men and women. All humans have 12 pairs of ribs.

Q.2. What is the difference between true and false ribs?

Ans. The primary difference between true and false ribs is that the former attaches to the sternum directly, while the latter attaches to the sternum indirectly (through the 7th costal cartilage).

Q.3. Can your ribs regenerate?

Ans. Research indicates that ribs and costal cartilage can regenerate as long as the connective tissues surrounding them are intact. The ribs are surrounded by the vascular connective tissue perichondrium, while the periosteum surrounds the cartilages.

Q.4. What is a cervical rib?

Ans. A cervical rib is a rare anatomical variation present at birth in 0.5-1% of people with an extra rib above the 1st rib. It might grow on one or both sides, either as a bony outgrowth or as a fully formed rib. Cervical ribs are more common among women than men.

It often does not cause any problems in the individual. Still, in some cases, the bony growth might press on the nerves and blood vessels in the area, causing neck pain and weakness, numbness, or dislocation of the arm (thoracic outlet syndrome).

References

1. 1. The Ribs: TeachMeAnatomy.info
   2. Ribs: KenHub.com
   3. Anatomy, Thorax, Ribs: NCBI.nlm.nih.gov
   4. Typical Ribs: RadioPaedia.org
   5. Structure of the Ribcage and Ribs: GetBodySmart.com
   6. 3D Skeletal System: Bones of the Thoracic Cage: VisibleBody.com