This report was written by a Ga-Matoran scientist on the city of Metru-Nui, and is among the most advanced of the time period. It should be accepted completely and invariably as the truth.
The Matoran design is a complex piece of work, and truly a tribute to the Great Beings work. Each Matoran is unique, be it physically or mentally. Most species in our Universe have shown similiar biological functions and traits, with a few differentiations regarding the location of organ systems within the body. Almost all species have a structure of metallic protodermis composing some eighty five to ninety percent of the body, with from twelve to eight percent being purely organic, and the remainder of whatever occurs being techno-organic. In the case of the Matoran, this is eighty-six - nine - five.
Skin & External Armoring[]
The visible compontents of the Matoran is the skin and external armoring. Close to ninety percent of the Matorans body is plated in metallic protodermis. The remainder is mostly a techno-organic hybrid that acts as the skin, and it stretches underneath most of these metallic areas for a short while as well. The skin appears to be capable of secreting sweat and, when cut, blood. Others species, such as the Prime species the Barraki Pridak hailed from, have lower amounts of external armoring and large areas of the skin being purely organic protodermis. And some, such as that of Barraki Carapar, have almost no skin, and can only bleed by penetrating their thick armor platings.
Head & Face[]
Of interest is the head of the Matoran - nearly the entire surface is metallic protodermis. Only on the inside of the mouth, and the brain cavity, is organic material. The techno-organic protodermis mentioned earlier also contributes, but it is not part of the skin - there is none on the head, save for a few strips going up along the back of the neck to the bottom.
A few species, such as Vortixx and Steltians, have much greater amounts of organic material on their head, even possessing what are called lips. Some, like the mysterious and seclusive Skakdi of Zacax, have heads entirely covered in skin, save for around their mouths. Vortixx are almost unique among all species by having long, thin stands of organic protodermis of 1/250th of a Bio in thickness that emerge from certain points on their head known as hair. This hair is ritually tied into two knots along both sides of the head for those who fail the rite of passage on the island, four for those who have passed, and six for the especially honored or vicious. Males are forced to remove it.
In the center of the head is a component known as the nose that connects with the respiratory system (as below) and to sensors that connect to the brain, allowing the sense of smell, the weakest of the five senses possessed by Matoran.
Kanohi Masks[]
Most species, even with the most outlandish features, can wear Kanohi Masks by placing them on their face. The masks, if properly made, 'fuse' to the face, granting meager protection and sometimes powers. However, not all beings can use mask powers. In order to use them, a certain mental discipline must be held (intelligence plays some role, but even the brilliant Vortixx are incapable of properly activating them). This cannot be explained by science yet, but one day we'll figure it out.
Of the species capable of using Masks, none are more well known then Matoran. Matoran are, in fact, completley reliant on their masks in order to survive - when their facial structure is exposed, their body forces them to become catatonic rather than dying, which is what seems to have happened to those who did not for unknown reasons. Toa are not as subjected to this, perhaps due to their innate Toa Power, but they are incredibly weak without a mask and can barely tap into elemental powers. Turaga are also somewhat more hardy in the face of exposed features, but can only last for a short time.
Brain & Nervous System[]
The brain of nearly every species is nestled within their head, protected along all sides by heavy plating. Due to the complex design of a Matorans head, it is almost impossible for them to damage their brain through repeated trauma unless the strike breaks the initial armoring. By then, though, the mask has likely been damaged, and much worse things are to occur. Or the heads gone.
The Matorans brain is highly complicated, formed of solely organic protodermis in a very unique variety. Not much is known about it so far.
The nervous system stretches out from the brain and goes throughout the body. Almost any harm cause to the organic protodermis of a Matoran will result in pain, and techno-organic parts seem to be particularly susceptible.
Heart & Circulatory System[]
The heart of the Matoran. The heart is a somewhat simple organ, serving the simple but important purpose of pumping the small amounts of liquid known as blood throughout the body, carrying oxygen (presumably) to the muscles and transferring vital nutrients from the digestive tract.
The heart is composed purely of techno-organic protodermis, in all species save the purely organic ones like Zyglak. As stated above, it is a pump. But it carries one other purpose - it is connected to the Heartlight, a complicated mechanism that is still not fully understood. The heartlight glows when a Matoran is still alive, but dims as they are dying and finally turns completely dull when they die. It appears as a small, glowing light in the center of their chest.
The Heartlight appears closer to a piece of technology, far beyond the scope of Matoran creation. Unlike other biological components, it appears to be connected to the Matorans unseen life force. The author of this report sees this entire concept as a sham - the heartlight is merely a monitor of life to denote a worker as retaining his function. Nevertheless, the heartlight is viewed by many without scientific background as being what contains a beings 'soul', and its destruction is just as fatal as the destruction of any other important organs.
Lungs & Respiratory System[]
The lungs are located within the chest of a Matoran, and act in connection with a tract known as the trachea that leads up to the end of the mouth. The lungs are connected to the circulatory system, which transfers the oxygen that is filtered through them. Not much is known about how this works.
The current theory is that somehow oxygen from the air is taken in and passed through, and put to some use, while other stuff is pushed out. However, we're only now beginning to figure out how. Many so-called 'scientists' retain that the vital essence of the air is pushed through the blood. This is to be ignored as false science with no proof to back it up.
What is known is that the lungs of Matoran and other species are not designed to go for extended periods holding their breath, save for those such as Ga-Matoran. Thus, the Great Kakkau was desgined for Toa. Some species who are amphibious show no worry about this at all - the obsevations of them filtering oxygen through their unique systems has led to the theory above, about oxygen being taken out and used. The size of a species seems to show no link to breath capacity.
Stomach & Digestive System[]
The digestive tract of the Matoran is simple. A second tube, the esophagus, goes along the trachea. It passed through the stomach and is dissolved by incredibly strong acids. A few other organs seem to filter everything before separating the essential nutrients out and passing them through the circulatory system
Excretory System[]
And, of course, there is the excretory system. After a few final filtrations to remove poisons, everything that is of waste is forced out in liquid form and expelled through a shaft leading out of the body. There is a sack in the center capable of storage.
Most Matoran have the capcity to stroe the waste of a few weeks at any given time before being forced to expel it. It is commonly relieved once each day. It is not something most choose not to talk about.
Theory of Generative Nutrients[]
There are numerous glands in the body of no known purpose that go alongside the circulatory system. They are listed here because of their theorized purpose. Matoran dissected after electrical death have ocassionally shown a stimulation to these glands resulting in vital nutrients being produced. Tests have shown that particular fluxuations of electrical energy may be able to activate them, and provide what is necessary for a Matoran to survive without consuming any food.
Until more advanced technologies are present, it will be impossible to determine whether this is true or not. If it was, it could mean the removal of Rahi farms and the like from Metru-Nui, allowing more important things to be focused on.
Skeletal System & Muscle System[]
The skeletal system is the composition of most of the Matoran body. Composed solely of metallic protodermis, it is bonded with the armoring on the outside of the Matorans body and makes the framework of the entire form. It stretches over areas to provide extra support and holds almost all of the organs individually to keep them safe against stress and trauma.
The muscle system makes up all remaining organic components. It is connected with the circulatory and nervous systems. Information from the brain to the nerves to the muscles command them to move, and it is believed that oxygen is transferred to them to provide fuel.
Immune System[]
Finally, we reach the immune system. Scatter across the body, it is a very poorly understood system. A few things are known, though - it helps to remove poisons and diseases from the body.
Toa have the strongest known immune systems, perhaps due to the Toa Power that they are capable of releasing from within. As the abilities of Toa to use elemental abilities and Toa power falls outside the realms of science - for now - that is our best explanation.
Organic Decay[]
There have been reports to show organic decay in Matoran, Toa, and the like. The most common cause of organic decay is the Zyglak spread disease, which can within a few hours cause any being compoed of organic protodermis to die. It is also believed to affect them to some degree throughout their life, occasionally causing fits of pain and agony and leading to a shorter life (as mentioned below).
There is another, more benign cause - devices known as Toa Canisters, scattered across the Matoran Universe with unknown reason. When a being is stored within, the Canister shuts down all life processes and puts the inhabitant in stasis, completely protected from aging and anything else that could harm them.
The Canisters, however, must remain hooked to the strange locations they are found in, or they begin using the inhabitants only energy. Over a couple thousand years, as was found with one Matoran who had accidentally been placed within, ejected, and then lost, the organic components of a being begin to decay, leaving them to die a terrible death - and we pray to Mata-Nui that said Matoran felt nothing.
Toa, however, do no meet the same death, as another example (tied to the first) showed. Instead, after a similar time frame, they awake with their mucles decayed and their organs mostly shut down. Infact, their limbs and the like begin to fall off, leaving them awakened with disconnected pieces. However, there are enough internal, organic components remaining that they can put themselves back together, and the Toa Power within them begins to rapidly regenerate their body.
Note, however, that the actual loss of limbs in combat does not seem to be something that can be restored at this time. Many tests with the Kiril to regenerate the metal components together and Toa Power have been made, but there has yet to be any luck.
Rahi[]
Rahi, unlike Matoran and the like, show a much higher amount of organic material in their make. The reasons for this are unknown, but it proves beneficial in the production of organic components.
Namely, the head of a Rah is almost entirely organic, and much more developed for sensory abilities. The spaces between armoring and skin are much fewer, with some areas having plates under the skin - however, the skin is also much thicker in the places where it does appear. Some possess scales and even fur, much like the hair on Vortixx.
Rahi generally are about 65-30-5 for metallic, organic, and techno-organic as far as percentages go.
Other Systems[]
There are other organ systems that have been found within purely organic beings such as Zyglak. This report shall not further detail them; it merely mentions them to detail that not everything remains the same. The one most of note is the reproductive system, which compensates for their shorter life spans of only ten thousand years.