Internal Intercostals Of A Male As, Lateral View

Description

Seen in lateral profile, the thoracic cage is opened to emphasize the internal intercostal muscle layer (intercostales interni) occupying the intercostal spaces between adjacent costae, deep to the external intercostals and superficial to the innermost intercostals. Fibers course inferoposteriorly from the inferior border of the rib above to the superior border of the rib below, becoming most conspicuous anterolaterally where the muscular slips approach the costal cartilages. Posteriorly, the thoracic vertebrae and costovertebral articulations form the fixed medial boundary of the rib arc, while the iliac crest and sacral region appear inferiorly as orienting skeletal landmarks. For teaching respiratory mechanics, the internal intercostals are easiest to understand in this side-on relationship to rib curvature and the vertebral column. Their interosseous portion contributes to forced expiration by depressing the ribs, a distinction that matters when you contrast them with the external intercostals during inspiration and with the interchondral internal intercostals near the sternum. This layer is also encountered in tube thoracostomy and thoracotomy planning because it sits superficial to the endothoracic fascia and parietal pleura, and it is traversed near the neurovascular plane that runs along the inferior margin of each rib. Use this artwork for gross anatomy lab manuals, respiratory physiology lectures, and surgical skills curricula covering safe intercostal access, including why instruments are advanced over the superior border of a rib to reduce risk to the intercostal nerve and vessels. It also fits well in publisher plates explaining intercostal muscle layers in relation to rib fractures and intercostal neuralgia. Anatomical accuracy verified by SciePro's Medical Advisory Board.