11.10
La cage thoracique : les côtes
Les côtes sont des os courbés et aplatis formant la paroi de la cavité thoracique avec les muscles thoraciques. Il y a 12 paires de côtes thoraciques.…
La cage thoracique comprend le sternum, douze paires de côtes et leurs cartilages costaux.
Les sept premières paires, les côtes vraies ou vertébrosternales, s’attachent directement au sternum par leurs extensions cartilagineuses antérieures ou les cartilages costaux.
Les cinq paires restantes, les fausses côtes ou les côtes vertébrochondrales, rejoignent les cartilages costaux au-dessus d’elles ou flottent librement avec leurs cartilages costaux encastrés dans la paroi thoracique.
Une côte typique a une tête, un cou et un corps. Un tubercule naissant du cou court se joint à la facette costale transversale de la vertèbre de même numéro.
Dans chaque côte, la facette articulaire de la tête rejoint les facettes costales de deux vertèbres thoraciques, le même numéroté et celui au-dessus.
Le corps a un sillon costal interne pour le passage des vaisseaux sanguins et des nerfs. Sa surface externe s’attache aux muscles de la ceinture pelvienne et du tronc.
Les muscles intercostaux entre les côtes se contractent et se détendent pendant la respiration, modifiant la largeur et la profondeur de la cage thoracique. Cela aide à augmenter le volume de la cavité thoracique lors de l’inspiration et à le diminuer lors de l’expiration.
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Q1: What are the main components of a typical rib?
A typical rib has three main parts: the head, neck, and body. The head articulates with costal facets of thoracic vertebrae, while a small bump called the tubercle on the neck joins the transverse process of the same-numbered vertebra. The body, or shaft, contains a costal groove along its inferior margin for blood vessels and nerves to pass through.
Q2: How do true ribs differ from false ribs?
True ribs, ribs 1-7, attach directly to the sternum through their costal cartilages. False ribs, ribs 8-12, attach indirectly to the sternum. Ribs 8-10 connect to the cartilage of the 7th rib, while ribs 11-12, called floating ribs, do not attach to the sternum at all and terminate within the abdominal wall musculature.
Q3: Where do ribs articulate with the vertebral column?
All 12 pairs of ribs articulate posteriorly with thoracic vertebrae T1-T12. The articular facet in each rib's head joins the costal facets of two vertebrae: the same-numbered vertebra and the one above it. The tubercle on the rib's neck articulates with the transverse process of the same-numbered vertebra.
Q4: What is the costal groove and what structures pass through it?
The costal groove is a shallow groove located along the inferior margin of each rib. Blood vessels and nerves pass through this groove, allowing them to travel safely along the rib without obstruction. This anatomical feature protects vital neurovascular structures during respiration and movement.
Q5: How do intercostal muscles affect the thoracic cage during breathing?
Intercostal muscles between the ribs contract and relax during respiration, changing the width and depth of the thoracic cage. When these muscles contract during inhalation, they increase the volume of the thoracic cavity. During exhalation, they relax, decreasing the cavity's volume and facilitating air expulsion.
Q6: What is the angle of the rib and why is it anatomically significant?
The angle of the rib is the point on the rib where it has its highest degree of curvature, located just posterior to the tubercle. The angles of all ribs form the posterior extent of the thoracic cage, providing structural support and defining the cage's posterior boundary.
Q7: How many ribs comprise the thoracic cage and what are they called?
The thoracic cage comprises 12 pairs of ribs along with the sternum and costal cartilages. These ribs are classified as true ribs (1-7), false ribs (8-10), and floating ribs (11-12). Together with thoracic muscles, they form the thoracic cavity wall and are part of the overview of the axial skeleton.