The cartilage rings are C-shaped because the back of the trachea presses against the esophagus. The cartilage opens at the esophagus and is replaced by connective tissue and muscle. This gives the esophagus space to allow food to be swallowed easily. The rings of the trachea are stacked one on top of the other, with a small space between them.
In 2014, a survey of the Australian working population revealed that the most common carcinogenic exposures in the workplace were solar ultraviolet radiation, diesel engine exhaust, environmental tobacco (second-hand) smoke, benzene, lead and silica.
Some common types of carcinoma include: 1  Basal cell carcinoma: The most common type of skin cancer. 2  Squamous cell carcinoma: The second most common type of skin cancer. 3  Renal cell carcinoma (RCC): The most common type of kidney cancer.  Ductal carcinoma in situ (DCIS): The most common type of breast cancer.