11.10
La Caja Torácica: Costillas
Las costillas son huesos curvados y aplanados que forman la pared de la cavidad torácica junto con los músculos torácicos. Hay 12 pares de costillas t…
La caja torácica está formada por el esternón, doce pares de costillas y sus cartílagos costales.
Los primeros siete pares, las costillas verdaderas o vertebroesternales, se unen directamente al esternón a través de sus extensiones cartilaginosas anteriores o los cartílagos costales.
Los cinco pares restantes, las costillas falsas o vertebrococondrales, se unen a los cartílagos costales por encima de ellas o flotan libremente con sus cartílagos costales incrustados en la pared torácica.
Una costilla típica tiene cabeza, cuello y cuerpo. Un tubérculo que surge del cuello corto se une con la faceta costal transversal de la vértebra del mismo número.
En cada costilla, la faceta articular de la cabeza se une a las facetas costales de dos vértebras torácicas, la misma numerada y la que está por encima de ella.
El cuerpo tiene un surco costal interno para que pasen los vasos sanguíneos y los nervios. Su superficie externa se une a los músculos de la cintura pélvica y el tronco.
Los músculos intercostales entre las costillas se contraen y relajan durante la respiración, cambiando el ancho y la profundidad de la caja torácica. Esto ayuda a aumentar el volumen de la cavidad torácica al inhalar y a disminuirlo al exhalar.
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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.