The ribs space curved, level bones which type the majority of the thoracic cage. They are very light, however highly resilient; contributing to their function in protecting the inner thoracic organs.

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There space twelve bag of ribs, every one of which articulate with the vertebral column. However, only seven have actually a straight articulation through the sternum. As such, ribs deserve to be allocated to one of three unique types; true (vertebrosternal) ribs, false (vertebrochondral) ribs and floating (vertebral, free) ribs. Ribs one to 7 are thought about true ribs and also attach straight to the sternum via their own costal cartilage.

Ribs eight to ten room the false ribs and also are connected to the sternum indirect via the cartilage of the rib above them. The final two pairs of ribs room floating ribs and the cartilage of this ribs tends to end within the ab musculature. This three types can then be classified together either typical or atypical.

Key facts around ribs
ClassificationBased on articulations - true ribs (1 come 7), false ribs (8 come 12) (inc. Floating ribs (11 and also 12)Based ~ above structure - typical (3 come 9) and atypical (1, 2, 10, 11, and 12) ribs
StructureTypical (3 come 9) and atypical (1, 2, 10, 11, and 12) ribs
Structure of common ribsHead (contains two articular facets), neck, tubercle (has one articular and non articular part), and also body (curves at the costal angle, the interior surface has the costal groove and also it joins v the costal cartilage)
Structure of patent ribsFirst - widest, shortest, it has the sharpest curve and only one articular surface, contains two grooves because that the subclavian vesselsSecond - it has actually two facets and a roughened tuberosity on its posterior surfaceTenth, eleventh, twelfth - they have actually only one facet and also neither a neck or tubercles
LigamentsCostotransverse ligament (lateral and superior)
MusclesExternal intercostals (elevate ribs), internal intercostals (depress ribs), innermost intercostals (depress ribs during forced expiration), subcostales (depress ribs), transversus thoracis (depress ribs), serratus posterior (elevates ribs), levatores costarum (elevate ribs)
ClinicalChest drain insertion (superior border that rib), fractures, flail chest

In this post we shall take into consideration the osteology and also articulations of the ribs, also ligamentous and muscular attachments, finishing through some clinical notes.


Contents
Typical ribsAtypical ribsMuscles attachmentsClinical notes
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Typical ribs

Ribs 3 to nine room the ‘typical’ ribs and the major landmarks space the head, neck, tubercle and body.

Head


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The head of every rib is wedge shaped and also has 2 articular facets, which room separated by a wedge the bone, known as the crest that the head. The bigger of the two facets is because that articulation with the exceptional costal facet of its equivalent vertebral body, while the smaller sized of the two articulates through the inferior costal page on the body of the superior vertebra.

Neck

The neck the the rib is normally unremarkable in terms of bony landmarks and is merely a flat piece the bone that connects the head that the rib with the body.

Tubercle

The tubercle is a bony prominence located at the junction between the neck and also body which jobs posteriorly. It consists of 2 parts, a smooth articular part which articulates with the transverse process of the connected vertebra and also a roughened non articular part which develops the attachments of the costotransverse ligament.

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Body

The body, or shaft, that the rib is thin, flat and also curved. The curve i do not care most prominent at the costal angle, i m sorry is once the rib turns anterolaterally. The costal angle also marks the attachments for some of the deep earlier muscles come the ribs. The interior surface is concave and also contains the costal groove which uses some protection and a course for the neurovascular bundle come follow. The human body ends through a cup because that the costal cartilage, which allows the rib to articulate v the sternum.

Atypical ribs

The first, second and tenth come twelfth ribs are well-known as atypical and also as such will be taken into consideration individually.


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First rib

The an initial rib is the widest, shortest and also has the sharpest curve of all the ribs. The head just articulates through the body of the T1 vertebra and also therefore only one articulatory surface is present. Together in the common ribs, the tubercle has a facet for articulation with the transverse process of vertebrae. The remarkable surface is distinct in that it is marked by 2 grooves that allow passage of the subclavian vessels. This grooves are separated by the scalene tubercle – to which the anterior scalene muscle attaches.

Second rib

The second rib is thinner and significantly much longer than the first. There are two facets present on the head to enable articulation with the T1 (superior) and T2 (corresponding) vertebrae. Its main unusual feature is a roughened tuberosity top top its premium surface, i m sorry forms part of the beginning for serratus anterior

Tenth, eleventh, twelfth ribs

The tenth to twelfth ribs have actually only one side on their heads, and also as such only articulate with a solitary vertebra. Ribs eleven and also twelve in details are short and have no necks or tubercles.

Ligaments


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The main ligamentous attachments to the ribs is the costotransverse ligament, this is a fairly facility ligament i beg your pardon is consisted of of 3 parts. The first part is known as ‘The’ costotransverse ligament and it fills the gap in between the rib and also the equivalent transverse process.

The next group of fibres are recognized as the lateral costotransverse ligament, i beg your pardon lies posteriorly and also attaches the transverse procedure of the vertebra come the rib, simply distal come the tubercle. The final part is the superior costotransverse ligament i beg your pardon is a two-layered ligament through the fibres orientated at ideal angles. This overcome from the superior margin of the neck that the rib to the transverse process of the above vertebra.

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Ribs check out study unit
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There space eleven pairs of outside intercostal muscles and these are the many superficial in the area. They extend indigenous the lateral border the the costal grooves to the superior margins the the ribs below. The fibres the this muscle pass anteroinferiorly in an slope manner and extend approximately the thoracic wall from the tubercles come the costal cartilages the the ribs. This muscles assist to elevate the ribs in inspiration.

Internal intercostal muscles

The eleven bag of interior intercostal muscles are uncovered posterior to the external intercostals. These pass from the worse edge that the costal groove to the superior margins the the ribs below. This muscle fibres expand in a posteroinferior direction and again happen in an tilt manner. These muscles room only current from the parasternal area to the edge of the ribs. Their activity is come depress the ribs in forced expiration.

Innermost intercostal muscles 

The fibres of this muscles prolong in the exact same direction that the inner intercostal muscles. They prolong from the medial sheet of the costal groove to the medial surface that the rib below and are mainly present within the lateral thoracic wall. However these muscles are notable in the the neurovascular bundles pass v the opening between the internal and also innermost intercostal muscle layers. This muscles aid with depression that the ribs in forced expiration.

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Subcostales

The subcostales muscles are located within the same plane as the innermost intercostals. Lock are distinct in the they may span one or many ribs and become much more numerous in ~ the inferior areas of the posterior thoracic wall. They expand from the inner surface that one rib come the inner surface of one of two people the next rib or also the one below that. This muscle assists the inner intercostal muscles.

Transversus thoracis

These muscles are discovered deep in ~ the anterior thoracic wall. The transversus thoracic muscle originate indigenous the posterior surface ar of the xiphoid process and the lower component of the body that the sternum. The fibres happen superolaterally come insert into the internal surface the costal cartilages of ribs two to six. This muscle assists in depression of the ribs.

Serratus posterior

This muscle is current posteriorly within the thoracic wall. It is split into superior and inferior fibres. The inferior fibres originate native the spinous procedures of the T11 to L2 vertebrae and attach to the lower borders of ribs eight to twelve close to the angle. The part of the muscle is assumed to depress the ribs. The superior fibres originate from the spinous procedures of the C7 come T3 vertebrae and also attach come the superior boundaries of ribs two to four. This component of the muscle is assumed to elevate the ribs

Levatores costarum

Levatores costarum originates from the transverse processes that vertebrae C7 come T11 and attaches to the external surface between the tubercle and the angle the the rib below. Its activity is to aid in elevation the the ribs.

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Clinical notes

Chest drainpipe insertion

This is a frequently performed procedure and is necessary in situations of pneumothorax, pleural effusion, empyema and postoperatively complying with thoracic surgery. The is an especially important to location the tube in line through the superior border that the rib. This is because the neurovascular bundle (intercostal nerve, vein and also artery) passes along the costal groove, i beg your pardon is situated on the worse border that a rib. This placing minimises the risk of damage to bordering structures.

Rib fractures

Fractures of the ribs have tendency to existing with ache on respiration, coughing, laughing and most other chest movements. They space most generally caused by blows or crushing injuries. The weakest component of a rib is just anterior to its angle and also as together this is the most usual site the injury – yet it is crucial to remember that a straight blow can lead come a fracture at any point.

Middle ribs room the most most likely to fracture and are dangerous since the broken end deserve to puncture plenty of organs, such as the lungs. Fractures the the upper ribs are rare as result of their fairly protected position, yet if it occurs there deserve to be damages to the brachial plexus. Furthermore lower rib fractures can an outcome in tearing that the diaphragm.

The main worries tend to arise when multiple ribs space fractured, for example after a significant trauma. In this case, if sufficient ribs are damaged a flail segment, or flail chest, can happen – this is when the separated team of ribs moves in opposing direction to chest wall expansion throughout inspiration, restricting breathing. If the segment is big enough assisted ventilation may be required until the ribs have healed.


Sources

References:

Richard L. Drake, A. Wayne Vogl and Adam W.M. Mitchell: Gray"s Anatomy for Students, 2nd edition, chapter 3 Thorax, skeleton framework, pg. 141-146.Werner Platzer: color Atlas of person Anatomy Volume 1, sixth edition, Trunk, Ribs, pg. 64-66.Ibrahim, AF and Darwish: The costotransverse ligaments in human: a thorough anatomical study. Clinical Anatomy. HH. (2005) 18 (5), pg 340-345.

Author and also layout:

Catarina Chaves

Illustrators:

Typical rib (superior view) - Begoña RodriguezOverview of ribs - Begoña RodriguezSuperior costotransverse ligament - lateral-left see - Begoña RodriguezExternal intercostal muscles - ventral view - Yousun KohSubcostal muscle - ventral see - Yousun KohTransversus thoracis muscle - ventral view - Yousun KohSerratus posterior remarkable muscle - dorsal see - Yousun KohLevatores costarum muscles - dorsal see - Irina Münstermann

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