Skip to main content
Biology LibreTexts

8.6: Thoracic Cage

  • Page ID
    53634
  • \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \) \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\)\(\newcommand{\AA}{\unicode[.8,0]{x212B}}\)

    Thoracic Cage

    The thoracic cage, also called the rib cage, surrounds and protects the heart and lungs in the thoracic cavity. It consists of the ribs, the sternum, and the thoracic vertebrae, to which the ribs articulate.

    There are twelve pairs of ribs. The number is the same in both males and females. Each pair articulates with a different thoracic vertebra on the posterior side of the body. The most superior rib is designated rib 1 and it articulates with the T1 thoracic vertebrae. The rib below that is rib 2, and it connects to the T2 thoracic vertebra, and so on. Ten of the twelve ribs connect to strips of hyaline cartilage on the anterior side of the body. The cartilage strips are called costal cartilage (“costal” is the anatomical adjective that refers to the rib) and connect on their other end to the sternum.

    Rib pairs 1-7 are considered true ribs because they attach to the sternum via their own separate costal cartilages. Rib pairs 8-12 are considered false ribs because they only attach to the sternum by attaching their combined costal cartilages with the costal cartilage of the 7th rib. Lastly, rib pairs 11-12 are considered floating ribs because they do not have any costal cartilages attaching them in any way to the sternum.

    Diagram of the thoracic cage showing the true ribs, false ribs, and floating ribs

    Above: The right side of the rib cage and the with the sternum. The true ribs are shown in red, the false ribs are shown in green and blue, and the floating ribs are blue. The sternum is the neck-tie shaped bone at the center of the chest shown in white. The white extensions of the ribs are costal cartilage connecting the ribs to the sternum.

    On an individual rib, one end has various processes, facets, and bumps. This is the end that articulates with the vertebra. The other end is blunt and smooth. This is the end that connects to costal cartilage (unless it is a floating rib).

    Diagram of a rib

    Above: The structure and markings of a rib.

    Diagram of rib markings

    Above: Markings of a rib (medial view).

    The articular facets on the head and costal tubercles of the rib articulate posteromedially with costal facets on the thoracic vertebrae. The anterior aspects of the ribs (located medially) attach to costal cartilages which allow for elasticity of the thorax while linking the ribs to the costal notches on the sternum.

    sternum regions, markings, and attachment to the costal cartilage

    Rotating sternum

    Above: The sternum. (A) The sternum with costal cartilage shown in blue, anterior view. (B) Anterior view of the sternum. (C) Lateral view of the left side of the sternum. (D) Posterior view of the sternum.

    The sternum has three parts: the manubrium, the body, and the xiphoid process. The manubrium, at the superior end of the sternum and wider than the rest of the bone, provides articulation points for the clavicles and for the costal cartilage extending from rib 1. The central, thin body provides articulation points for costal cartilage from ribs 2 through 7. The xiphoid process which hangs down at the inferior end of the process (“xiphoid” is from the Greek for sword), starts out as cartilage, and does not typically ossify into bone until an individual is about 40 years old.

    Attributions


    This page titled 8.6: Thoracic Cage is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Rosanna Hartline.

    • Was this article helpful?