Cartilage. Light micrograph of metaplastic cartilage of the larynx. The larynx is situated at the top of the trachea (windpipe) and contains the voice box. Metaplasia is the normal transformation of tissue from one type to another. In this case cartilage is transforming into bone, a process known as ossification. Elastic cartilage cells are seen centre to lower left, boney tissue borders the image at left, top and right. The cartilage of the larynx begins this process during middle-age. By the age of 65 some laryngeal cartilages are completely converted to bone.