Atelectasis as a collapse of lung tissue, atelectasis is not synonymous with a pneumothorax, which is a more specific condition that features atelectasis. Acute atelectasis may occur as a post-operative complication or as a result of surfactant deficiency. In premature neonates, this leads to infant respiratory distress syndrome. The term uses combining forms of "atel-" + "ectasis", from , "incomplete" + ἔκτασις, "extension". May have no signs and symptoms or they may include: It is a common misconception that atelectasis causes fever. A study of 100 post-op patients followed with serial chest X-rays and temperature measurements showed that the incidence of
Ultimopharyngeal body Ultimopharyngeal body The ultimopharyngeal body or ultimobranchial body or ultimobranchial gland is a small organ found in the neck region of many animals. In humans, the ultimobranchial body is an embryological structure that gives rise to the calcitonin-producing cells—also called parafollicular cells or C cells—of the thyroid gland. In humans, this body is a derivative of the ventral recess of the fourth pharyngeal pouch (technically fifth, but that one is rudimentary and merges with the fourth). The cells that give rise to the parafollicular cells are actually derivatives of the endoderm. These cells migrate and associate with the ultimopharyngeal body