Human Anatomy, Part 1 - K. A. Dyubenko, A. K. Kolomiytsev, Yu. B. Chaykovsky 2002

Special Part
Arthrology, artrologia [the study of bone joints] - Classification of joints and their general characteristics
The thoracic cage as a whole

The Thorax [cavea thoracis] (Fig. 85), or the skeletal rib cage (sceleton thoracis), is formed by twelve pairs of Ribs, twelve thoracic vertebrae, the Sternum, and an articular-ligamentous apparatus. It encloses the thoracic cavity (cavitas thoracis) to house Internal Organs.

The rib cage protects the organs contained within its cavity from trauma, participates in external Respiration, and serves as a site for hematopoiesis (Bone Marrow). It is flattened anteroposteriorly and widened transversely. The thorax features a superior and an inferior aperture: apertura thoracis superior and apertura thoracis inferior.

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Fig. 85. Anterior view of the thorax

The inferior aperture is bounded posteriorly by the body of the XII thoracic vertebra, laterally and anteriorly by the XI and XII ribs, the costal margins, and the xiphoid process; the superior aperture is bounded posteriorly by the body of the I thoracic vertebra, laterally by the I rib, and anteriorly by the manubrium of the sternum. Passing through the superior thoracic aperture are the Esophagus, Trachea, major Blood Vessels, and nerves. The inferior aperture is sealed by the Diaphragm; traversing it are the esophagus, aorta, INFERIOR VENA CAVA, Thoracic duct, autonomic nerve trunks, as well as other Vessels and nerves. The right and left costal margins form the infrasternal angle (angulus infrasternalis), the dimensions of which determine the shape of the rib cage. On the external surface of the thorax, between the spinous processes of the vertebrae and the angles of the ribs, lie grooves that house deep Muscles. On the internal surface of the thorax, between the vertebral bodies and the angles of the ribs, run the pulmonary grooves (sulci pulmonales). The spaces between adjacent ribs are called intercostal spaces (spatia intercostalia) and are filled with intercostal muscles and membranes.

The shape of the thorax varies individually depending on the constitutional type, sex, and age of the person. Two extreme thoracic shapes are distinguished: a flat and long type with low-lying ribs and an acute infrasternal angle, typically found in tall individuals; and a wide and short type with a markedly widened inferior aperture and a large infrasternal angle, characteristic of short individuals with a voluminous Abdominal cavity. Respiratory diseases can alter the shape of the chest; for instance, in pulmonary emphysema, the thorax assumes a barrel-like shape.

The Anatomy of the newborn's thorax exhibits specific features: its lower section predominates over the upper, and the sagittal diameter exceeds the transverse. The anterior ends of the ribs and the HEAD lie on the same plane. With age, the shape of the chest changes due to the downward Displacement of the ribs and The Development of costal breathing. In cases of congenital developmental anomalies, the thorax may acquire a funnel-shaped or keel-shaped deformity, known as "Pigeon chest" (O. V. Dolnytskyi, 1985).¹ Congenital chest deformations resulting from anomalies in the Development of Muscles, THE Vertebral Column, ribs, sternum, and scapulae also occur. In old age, the inclination of the ribs increases, while Muscle tone decline leads to a reduction in the infrasternal angle and in both transverse and sagittal dimensions, concurrently elongating the thorax. In women, the chest is flatter, shorter, and narrower in its lower part, with a predominance of costal breathing. Men breathe primarily by means of the diaphragm, exhibiting a predominantly abdominal breathing pattern.

X-ray anatomy of the thorax. An anteroposterior chest radiograph visualizes the dorsal segments of the ribs, whereas their lateral portions project onto one another. The costal cartilages are radiolucent. Examination of the costal heads and necks requires an anteroposterior projection. To study the sternum, an eccentric posteroanterior radiograph is used, which projects the sternum adjacent to the shadow of the vertebral column. Such an image clearly delineates the sternoclavicular joint, the manubrium, the body, and the xiphoid process of the sternum.

¹ Dolnytskyi Oleh Volodymyrovych, Professor at NMU, a prominent Ukrainian surgeon, orthopedic traumatologist, microsurgeon, and State Prize Laureate of Ukraine.