MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Y.I. Fedoniuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

SECTION 2. THE MUSCULOSKELETAL SYSTEM (THE MECHANICS OF MOVEMENT)

THE SKELETON OF THE TRUNK

2. THE THORAX

2.4. THE THORAX AS A WHOLE

The Thorax encloses the thoracic cavity, which houses Internal Organs such as The Heart, Lungs, Trachea, Esophagus, Blood Vessels, and nerves. The shape of the thorax depends on sex, age, body build, and physical development.

It can be broad and short or long and narrow; however, unlike in animals, the anteroposterior diameter of the human thorax is always smaller than the transverse diameter.

The superior thoracic aperture is bounded by the body of the first thoracic vertebra (TI), the first pair of Ribs, and the upper margin of the manubrium of the Sternum. The inferior aperture is bounded by the body of the twelfth thoracic vertebra (TXII), the costal margins, and the xiphoid process, and is closed by the Diaphragm. In women, the thorax is shorter than in men.

The right and left costal margins form the infrasternal angle, which opens inferiorly. Intercostal spaces are located between the ribs.

Previous diseases can alter the shape of the thorax. For instance, Rickets can result in a so-called Pigeon chest (pectus carinatum), where the sternum protrudes anteriorly like the keel of a bird. Similarly, conditions that impair respiratory function may lead to a barrel-shaped chest.

Thoracic movements during breathing are uneven because the lower ribs are longer and more curved, whereas the upper ribs are shorter and less curved. In the upper Regions of the thorax, so-called costal breathing occurs, whereby the chest expands in the sagittal direction during inspiration. Simultaneously, the lower regions expand in the transverse direction (abdominal breathing). The first rib has very limited mobility, which is why the apexes of the lungs are insufficiently ventilated. Under certain conditions, this predisposes the lung apices to pathological processes, such as tuberculosis.

The following conventional vertical lines are mapped on the external surface of the thorax: anterior median line, parasternal line, midclavicular (mamillary) line, anterior, middle, and posterior axillary lines, scapular line, paravertebral line, and posterior median line.