Trachea synthetic windpipes; however, a successful method for this method of transplant does not currently exist and development of such a method remains theoretically daunting. The word "trachea" is used to define a very different organ in invertebrates than in vertebrates. Insects have an open respiratory system made up of spiracles, tracheae, and tracheoles to transport metabolic gases to and from tissues. An adult's trachea has an inner diameter of about and a length of about 10 to 11 centimetres (4 in.). It begins at the bottom of the larynx, and ends at the carina, the point where the trachea branches
Composition of the human body Not all elements which are found in the human body in trace quantities play a role in life. Some of these elements are thought to be simple bystander contaminants without function (examples: caesium, titanium), while many others are thought to be active toxics, depending on amount (cadmium, mercury, radioactives). The possible utility and toxicity of a few elements at levels normally found in the body (aluminium) is debated. Functions have been proposed for trace amounts of cadmium and lead, although these are almost certainly toxic in amounts very much larger than normally found in the body. There is evidence that