Breathing

By Dr. Stefano Casali

The chest wall

The coasts

The first nine ribs are articulated with the corresponding vertebral body and also with the upper vertebral body, while the last three ribs articulate only with the corresponding vertebral body. Before the ribs articulate with the handlebar of the sternum and its junction (I and II), or with the sternum (III-VIII), while the IX and X articulate with the upper cartilages, and the XI and XII are free. Under the pressure of the intercostal muscles, the articulation of the first five ribs generates an upward and forward movement, while the articulation of the VI-X ribs generates a forward and outward / downward movement.

The Diaphragm

The diaphragm muscles are divided into sternal, costal, which are inserted on the last six ribs, and vertebral, inserted on the arcuate ligaments and on the vertebral processes.

The Diaphragm seen from below

There are frequent defects of the sternal muscles (foramen and hernia of Morgagni), of the muscles of the ligaments or of the posterior ribs (Bochdalek's hernia), and there are frequent communications between peritoneum and diaphragm, more frequent on the right, which are the basis of pleural effusions in course of subdiaphragmatic pathology (Meigs syndrome, peritoneal dialysis etc.).

The diaphragm is innervated by the phrenic nerves, which run in the mediastinum. The sensory innervation of the diaphragm is poor. Moreover, the sensory fibers of the phrenic are located at the level of the shoulder, so that the diaphragmatic pain can be referred to the shoulder, and the neurites of the relative metamers can give diaphragmatic paralysis.

The intercostal muscles

The external intercostal muscles run down and forward, the inner intercostals down and back. A thin muscular layer is located immediately below the parietal pleura. The vessels and intercostal nerves run below and within the lower edge of the coast (important for pleural puncture).

The thoracic wall and the pleural cavity

The pleural cavity extends above the clavicle, at the level of the neck of the first rib. The dome of the pleura makes contact with the subclavian vessels anteriorly, the scalene muscles superiorly, the brachial plexus laterally and the sympathetic ganglion superiorly and posteriorly (Horner's syndrome in the Pancoast tumor). The costofrenico breast is represented, during the calm breath, by the reflection of the two parietal and visceral sheets and the lung occupies it only in the deep breath. The lower line of the phrenic cost runs horizontally and upwards. The pleural cavity extends from the thoracic wall to the hilum, accompanying the lobar divisions.

The airways

• High airways include: nasal cavities, pharynx, larynx
• The lower airways include: the trachea, which originates from the cricoid cartilage, is 10 11 cm long and bifurcates at the 5th vertebra; the main bronchi and their branches

The trachea and the bronchi

The trachea consists of a cartilaginous wall (15-20 rings linked anteriorly by a

connective ligament and posteriorly from a muscular wall) and it is lined with ciliated columnar glandular epithelium. The structure of the main bronchi is similar to that of the trachea. The bronchial divisions are 24, and it is estimated that the normal lung contains a number of 20, 000-30, 000 terminal bronchioles, tributaries of as many acini in which each terminal bronchiole divides into eight respiratory bronchioles.

Lobule and pulmonary berry:

Towards the edge of each auriferous pathway the terminal bronchiole is reached. The lobule represents the structural unit of the lung and consists of three or five terminal bronchioles. Each lobule consists of 10-15 elementary units, the pulmonary acini. The acinus, or respiratory unit, is defined as the part of the lung fed by a terminal bronchiol. The berries vary in size and shape; in the adult the berry can reach up to 1 cm in diameter. Within the berry, three to eight generations of respiratory bronchioles can be seen

and the structure of the bronchioles, but with pulmonary alveoli that open directly into their lumens. After them are the alveolar ducts and the alveolar sacs before reaching the pulmonary alveoli. None of these units is isolated; in fact, a passage of collateral air between the berry and the berry occurs, and between the lobule and lobule, through the pores of Kohn in the alveolar wall and through accessory communications between the distal bronchioles and the adjacent pulmonary alveoli.

Second part "