Trachea into left and right main bronchi. The trachea begins level with the sixth cervical vertebra and the carina is found at the level of the fifth thoracic vertebra (T5), opposite the sternal angle and can be positioned up to two vertebrae lower or higher, depending on breathing. The trachea is surrounded by rings of hyaline cartilage; these rings are incomplete and C-shaped. The cricoid cartilage is attached to the first tracheal ring at top of the trachea and acts as the bottom of the larynx. There are fifteen to twenty rings in total, separated by narrow intervals. These reinforce the
What Is Intelligence? What Is Intelligence? What Is Intelligence?: Beyond the Flynn Effect is a book by psychologist James R. Flynn which outlines his model for an explanation of the eponymous Flynn effect. The book summarizes much of the work of Flynn in this area, as well as that of his colleague William Dickens of the Brookings Institution. The book begins with a description of what has generally become known as "the Flynn effect": the steady rise from one generation to the next in average scores on IQ tests over time. Flynn notes that this effect apparently contradicts some fundamental beliefs about IQ