The thorax consists of the ribs, the sternum, and thoracic vertebrae.
There are 12 pairs of ribs (costae) in the human body, which are divided into several types:
True ribs I-VII (costae verae). Each is connected to the sternum by a separate cartilage.
False ribs VIII-X (costae spuriae), the cartilages of these ribs fuse with each other and with the cartilages of the upper ribs. Consequently, a costal arch (arcus costalis) is formed.
False ribs VIII-X (costae spuriae) 
Floating ribs XI-XII (costae fluctuantes), the anterior edges of these ribs are not attached to the sternum, and simply lie in the muscle thickness.
Sometimes the last two ribs are also referred to as false ribs, and the term “floating” is used as a subdivision. Hoever, this is not of high importance.
Let us look at the typical rib structure (some ribs have their own features, which will be described later).
A rib has two parts — a bony part and a cotal cartilage (cartilago costalis);
two surfaces — an internal (facies interna) and external surface (facies externa);
and two borders — the superior border (margo superior) and the inferior border (margo inferior).
The bony part consists of the head (caput costae), the neck (collum costae) and the body (corpus costae).
On the head is the articular surface of the rib head (facies articularis capitis costae), which is used for articulation with the costal facets on the bodies of the respective vertebrae.
The heads of all ribs except I, X, XI, and XII have a crest of the rib head (crista capitis costae) that is wedged between the demi-facets of the overlying and underlying vertebrae. Because these ribs are connected to the larger facet on the vertebrae separately, they do not have a crest.
The neck of the ten upper ribs also has a ridge (crista colli costae), which serves as an attachment point for the costotransverse ligament.
The main formation on the rib body is the tubercle (tuberculum costae).
It is present on the ten upper ribs and contains an articular facet (facies articularis tuberculi costae) for articulation with the costal facet of the transverse process of the corresponding thoracic vertebra.
The articular facet (facies articularis tuberculi costae)
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The costal surface curves slightly in front of the tubercle to form the angle of the rib (angulus costae).
On the internal surface of the ten upper ribs, at their INFERIOR border, there is a costal groove (sulcus costae) in which the intercostal artery, vein, and nerve pass.
Let us examine some characteristics of the first rib (costa prima).
In contrast to the others, it has other orientations because it has a more horizontal position. These are two facets — the superior facet (facies superior) and the inferior facet (facies inferior), and two borders — the medial border (margo medialis) and the lateral border (margo lateralis).
Moreover, the angle of the first rib matches its tubercle.
On the superior facet, the scalene tubercle (tuberculum musculi scaleni anterioris) can be distinguished.
Behind this tubercle lies the groove for the subclavian artery (sulcus arteriae subclaviae) and in front lies the groove for the subclavian vein (sulcus venae subclaviae).
It is also to be repeated that the first rib has no crest on the head.
Let us consider the specificity of the second rib (costa secunda).
On the external surface of this rib lies the tuberosity for the serratus anterior (tuberositas musculi serrati anterioris).
Ribs & Rib cage
- ribs
- costae
- true ribs
- costae verae
- false ribs
- costae spuriae
- costal arch
- arcus costalis
- floating ribs
- costae fluctuantes
- costal cartilage
- cartilago costalis
- internal surface
- facies interna
- external surface
- facies externa
- superior border
- margo superior
- inferior border
- margo inferior
- head of rib
- caput costae
- neck of rib
- collum costae
- body of rib
- corpus costae
- articular facet of head of rib
- facies articularis capitis costae
- crest of head of rib
- crista capitis costae
- crest of neck of rib
- crista colli costae
- rib tubercle
- tuberculum costae
- articular facet of rib tubercle
- facies articularis tuberculi costae
- costal angle
- angulus costae
- costal groove
- sulcus costae
- first rib
- costa prima
- superior facet
- facies superior
- inferior facet
- facies inferior
- medial border
- margo medialis
- lateral border
- margo lateralis
- scalene tubercle
- tuberculum musculi scaleni anterioris
- groove for subclavian artery
- sulcus arteriae subclaviae
- groove for subclavian vein
- sulcus venae subclaviae
- second rib
- costa secunda
- tuberosity for serratus anterior
- tuberositas musculi serrati anterioris
