Rib cage

The thorax (compages thoracis) is a bone-cartilaginous formation consisting of 12 thoracic vertebrae, 12 pairs of ribs and sternum, connected by joints, synchondroses, ligaments. The thorax is the skeleton of the walls of the thoracic cavity in which the heart and large vessels, lungs, esophagus and other organs are located.

The thorax is flattened in anteroposterior direction, looks like an irregular cone. She has 4 walls (anterior, posterior, lateral and medial) and 2 holes (upper and lower). The front wall is formed by the sternum, costal cartilages, the posterior wall by the thoracic vertebrae and the posterior ends of the ribs, and the lateral ones by the ribs. The ribs are separated from each other by intercostal spaces (spatia intercostalia). The upper aperture of the thorax (apertura thoracis superior) is limited to the thoracic vertebrae, the inner edges of the first ribs and the upper edge of the sternum arm. Anteroposterior size of the upper aperture is 5-6 cm, transverse - 10-12 cm. The lower aperture of the thorax (apertura thoracis inferior) behind is limited by the body of the XII thoracic vertebra, in front - the xiphoid process of the sternum, and on the sides - by the lower ribs.

The median anteroposterior size of the lower aperture is 13-15 cm, the largest transverse dimension is 25-28 cm. The anterolateral edge of the lower aperture formed by the compounds of the VII-X ribs is called the archus costalis. The right and left costal arches from the front limit the pectoral angle (angulus infrasternalis) open to the bottom. The vertex of the sternum is occupied by the xiphoid process of the sternum.

The shape of the chest depends on many factors, especially on the type of physique. In people of brachymorph type of constitution, the thorax is conical in shape. Its upper part is considerably narrower, the subhorbid corner is blunt. The ribs are slightly inclined forward, the difference between the transverse and anteroposterior dimensions is small. With a dolichomorph type of constitution, the thorax has a flattened shape. Anteroposterior its size considerably inferior to the transverse, the ribs are strongly inclined anteriorly and downward, the podruzdin angle is acute. For people of the mesomorphic type of constitution, a cylindrical thorax is characteristic. In form, it occupies an intermediate position between conical and flattened. In women, the thorax is usually more rounded, shorter than that of men. In newborns, the anterior to posterior size of the thorax predominates over the transverse dimension. In old age, the chest becomes flattened, it becomes longer. This is due to the age-related decrease in muscle tone and the lowering of the anterior ends of the ribs. Some diseases and professions affect the shape of the chest. With rickets, the anteroposterior size of the thorax increases, the sternum extends substantially forward ("chicken breast"). The musicians playing on the tube, the thorax is wide and convex anterior.

Movement of the chest

The movements of the chest are associated with breathing, i.e. With the processes of inhalation and exhalation. When inhaling, the front ends of the ribs together with the sternum rise. This leads to an increase in anteroposterior and transverse dimensions of the chest, widening of the intercostal spaces and a corresponding increase in the volume of the thoracic cavity. When exhaling, the front ends of the ribs and sternum descend, the size of the chest decreases, the intercostal spaces narrow. This leads to a decrease in the volume of the chest cavity.

The lowering of the ribs occurs not only due to the work of the corresponding muscles, but also due to the severity of the thorax and the elasticity of the costal cartilage.

[1], [2], [3]