The oral cavity is one of the many systems that is perfectly designed while a fetus develops in a mother’s womb

The first event that takes place inside the mother’s womb is the union of sperm and egg to form into a single cell which later takes the shape of an embryo by rapid division and development. This embryological development occurs in three stages.

In the first of these stages (2-5 weeks), the fertilized egg (zygote) proliferates by dividing and planting itself to the womb wall (implantation). During the advance of the zygote towards the womb, some biochemical signals are sent in order to make the mother sense this situation. Via these signals, the mother’s body is prepared to supply the necessary nutrients to this cellular mass. When these biochemical signals reach the ovaries, various hormones are secreted and the ovulation that occurs during monthly periods is ceased.

During the second stage (5-6 weeks), major activities are started inside the cellular mass, which is now in the form of an embryo. The developmental process of organ and system generation from cells begins.

And during the third stage (from the 8^th week until birth), the embryo has become a fetus, and its facial and bodily structures have begun to be immaculately shaped (Figure-1).

How do organs develop?

Tissues and organs of the embryo, which morphologically starts to look like a human, develop from three layers, which are called the ectoderm, mesoderm, and endoderm. While the baby continues to come to life inside the mother’s womb, the cranial and facial regions, along with oral cavity, start to form via the development of cells in the area called the neural crest. This development is the result of perfectly corresponding functions in between the epithelium and outer mesenchyme, which results in the facial skeleton and formation of teeth.

Jaw and facial development occur during the 4-12 weeks in the womb. By the end of the 10^th week, the face can be seen with an ultrasonographic examination.

The nose forms at this point. Mid and lateral nose projections develop. A forehead projection called the “frontonasal protrusion” forms in between the two sided mid nose projections. These projections initially develop towards the lower direction because of the volume of the tongue. Later, after the palate has begun to form, and with the growth of the lower jaw and the downward extension of the tongue, like an open-close bridge, the lower and upper jaw join at the midline by rising upward. This union takes place from front to back, like closing a zipper, stage by stage.

This way, the oral cavity and the surrounding structures (tongue, teeth, etc.) that will enable speech and taste are knit, loop by loop, inside the mother’s womb. (Figure 1-2)

Due to the complexity of this process, if there happens to be any failure in the merging, some anomalies can form, such as split lips or palates. These splits are anomalies present at birth. Such lip or palate splits may arise during this phase of the pregnancy because of various negative factors: they can stem from inter-family marriages, diseases that the mother experiences during the first three months of the pregnancy (especially measles or toxoplasmosis), exposure to radiation, alcohol consumption during pregnancy, or various drugs the mother uses. These anomalies need to be corrected by plastic surgeons, upper respiratory tract specialists, and orthodontists.

Despite these anomalies, most of the time, babies are born with their oral cavities in perfect working order – which is extraordinary given the complexity of the process.

Reference

Oral R. J, Goldman H.M. Thoma’s oral Pathology.The CV Mosby Comp. St. Louis.

Figure-1: Ultrasonographic image of the facial region of a fetus in the mothers womb.

Figure-2: Upper jaw bone

I have been positioned in the center of your face so masterfully and delicately that even my slightest displacement would cause your face to become disfigured immediately. You would lose your good looks if I were wounded or spoiled. It seems to me that after creating your whole face and body, God placed me very accurately so that I can be in perfect harmony with them, and even with your soul. We noses appear in countless shapes-slender, long, narrow, wide, flat, Roman (convex), sharp and stubby noses. In the past, some wise men used to comment on people’s personality by looking at the posture and shape of their faces and bodies. The different shapes of noses would give them ideas about the intelligence and the will power of each person. It is true that there is a relationship between my shape and your personality. However, it would be wrong for someone to claim to know all about you just by looking at my shape, since your other organs affect one another too; some can neutralize the effects of others. Moreover, discipline and education can change many of the characteristics of a person. So, do not judge people just by looking at their nose.

Anyway, since these are subjective matters, they are not our focus now. What I would like to tell you about is the objective truth about the delicate art and meaning in my creation. My Creator has designed me as a projecting organ on the head-and not only on your face, but also all vertebrate animals, especially mammals. I am the organ that is used most by animals to hunt for food, to feed, and to look for their young or their mate. I am placed at the front of your body, and like a detector I sensitively recognize smells. When animals find something new, they first poke me into it to understand what it is. That is why the idiom “to poke your nose into something” is used commonly among humans, meaning to interfere with something that does not concern one. Most animals use the sense of smell more than humans do. Since they do not possess the intelligence and consciousness of humans, they acquire some of the necessary knowledge to survive through their sense of smell. However, humans are given intelligence and consciousness, and so they are not supposed to “poke their nose” into everything. Of course, that does not mean that I am useless. On the contrary, I have many functions and a complex and meaningful structure.

In the middle of your face is my external component, which is shaped like a pyramid. Because it is made of cartilage, this part is quite flexible. My tip is beaked and there are plates on my two sides. The cartilage in my tip is connected to a bone in my upper part between your eye sockets. This bone, called the nasal bone, is a part of the main bone of the forehead. A cartilaginous bridge that is lined in the middle divides my nasal cavity into two nostrils which lead to the outside. The hard palate at my base also makes up the roof of your mouth. The soft palate that is behind this extends to the nasal portion of the throat (nasopharynx). During the act of swallowing, it rises and closes off the upper pharynx to prevent food and saliva from escaping from your throat and being forced up into my back. If, when eating, you feel tickling in your throat and cough, this palate cannot close off, and the food can lodge in me and come out of my nostrils. Another benefit of this system can be seen in patients and those who are about to have surgery, when their pharynx is closed off. In such situations, patients are provided with food, liquids and air via a tube which runs through me.

The journey of the air you breathe, which you have to do in order to survive, starts with me and continues as far as your lungs. The air that enters through my nostrils is not always clean and of good enough quality to enter your lungs. If low-quality air reaches your lungs, you will get cold, infected, and sick. To protect you from that, our All-knowing God created everything carefully, taking measures to ensure your well being. He has placed air-filtering hairs at the front part of my cavity, and He has covered the inner surface of my rear with a mucous membrane (mucosa) that has a fluid form. The structure of my cavity is quite complex. Along with my two lateral walls, there are three horizontal bone shelves called the concha (or the turbinate), comprising the inferior, the middle and the superior turbinates. These narrow, shell-like structures increase the surface area of my cavity and thus help to warm and humidify the air easily before it reaches the lungs. That is, the air you inhale does not pass to your lungs until it is conditioned and filtered by me. This process is initiated by the hair in my front part, which prevents the entry of dust particles. Then, the air passes through the curled aperture formed by the concha. The concha is covered by a sticky mucous membrane which produces a secretion. This slippery secretion, along with the cilia, traps smaller foreign particles such as the dust of coal, soot, bacteria or pollen. In addition to that, since the pressure inside me is lower than the pressure outside, I can easily warm and humidify the air that passes through me.

The sides and the surface of my superior concha are lined with a very special epithelium which has a role in the sense of smell. The smell receptors, which are the cilia cells, and other supporting cells constitute the olfactory epithelium for smell. Everything that releases molecules into the air has a smell of its own. Perception of a smell occurs in the brain as a result of a very complex chain of reactions. Indeed, I have no idea about how this process happens but people talk about several theories. Since the vibration and the structure of every molecule which reaches me through the air currents differ from every other, each molecule causes different chemical reactions and electrical impulses. The molecules that come through the air dissolve in the moisture which lies on my epithelium and they chemically stimulate the cells for smell. If my mucosa dries out and loses all its moisture in dry air, it becomes more difficult for the molecules to dissolve and for you to breathe. My sense of smell also weakens or gets lost in the event of a lack of the element of zinc, which normally exists in small amounts in your body.

There is a reason why the color, taste and smell of garlic are different than that of a rose or jasmine flower: it is because each creature is created out of different compounds, as if in a laboratory of its own. Therefore, the molecules that spread into the air from those different compounds and the impact they cause will naturally be different. Indeed, what is interesting here is the wonderful system which perceives each of the molecules of so many different compositions as a different smell, categorizes it, and stores its information in memory. Whenever I experience a new smell, by its composition and vibrations, I instantly figure out its difference from other smells. Then, I help to store it in the brain’s memory related to the smell so that I can recognize that smell if I come across it again. All of those functions in their complexity remain an enigma which is still being studied by physiologists of smell. Another wonderful attribute of my smell-receptor cells is the fact that they sense the smell very strongly at first and after a while, they are not as strongly stimulated as before, resulting in a temporary paralysis of those cells. Thus, a situation called “habituation” occurs, and this is an indication of God’s mercy. If God had not created this “fading” of constantly existing smells, the sewage, garbage, tannery or butchery workers would not be able to do their work.

The mucosa that lines my cavity can easily become swollen with blood and tissue liquids. During viral or bacterial infection, or an allergy like hay fever, my cavity might become blocked completely, which makes it hard for you to breathe. Infection of your upper respiratory tract causes me to run and get blocked. You know how stagnant water gets smelly and swampy, whereas running water does not hold dirt. Similarly, when I get blocked, bacteria reproduce very fast and get transmitted to other respiratory organs. That is why, when you catch cold, you must do your best to prevent my getting blocked. Hot, aromatic or spiced teas might help you, but the best thing is to pour a weak solution of saline (salt water) into your nostrils, which will clear the congestion. As for nasal drops, do not use them unless you have to, since they will cause addiction and other side effects.

Your skull also contains four major pairs of air-filled cavities (sinuses) at my sides behind your cheeks and above me behind the forehead. In the event of infection of your sinuses, inflammation of your tonsils, or the growth of polyps, my discharge becomes constant and turns into flu or chronic rhinitis. Besides that, if I bleed it may be an important first symptom of many illnesses. Many conditions, including high blood pressure and several illnesses with fever cause bleeding inside me. Indeed, bleeding from me in patients with high blood pressure can be seen as a warning and protection against serious conditions. If, because of high blood pressure, my blood vessel did not split, bleed and decrease the pressure, a vessel in your brain would split, which would result in a much worse scenario.

Peter, from now on, do not ever forget to give thanks to God when you smell a flower or anything else with a beautiful scent. Inhale the air deeply with the pleasant impression the scent leaves on your soul. Our Lord God Almighty, who has given you the air as a blessing, bestowed you with me as a filter to clean the harmful particles from that air. If He had not done so, your lungs would fill with soot and dust and they would fail eventually. You would not be able to sense the taste of food because the experience of flavor cannot be achieved by the taste buds alone. It is me that helps them to do that. For instance, a person whose olfactory epithelium has been ruined cannot tell whether it is an apple or a radish that he or she is eating. If you cannot sense the odor of the foods you eat, you will not be able to get their flavor, either.

Dear Peter, I think I have described myself to you sufficiently. I even support your spectacles for you! I have given you brief information without too much detail about my microscopic intricacies. While even one hair inside me cannot be placed by itself, do you think it is possible for me to have formed myself when I am equipped with thousands of intricate elements, each with a reason? Which sculptor, do you think, can make the nose of a sculpture, without a hammer and chisel in his hands and without a model and will in his mind? Other than the belief in God, there is no way of explaining my creation, which is a thousand times more splendid than the making of the nose of a sculpture. So, whenever you wash your face and look into the mirror, examine me carefully again and remember our God Almighty who created us out of nothing.

Irfan Yilmaz is a professor of biology at Dokuz Eylul University, Izmir, Turkey.

I am placed inside your chest cavity as two air sacks-or bellows-surrounded by your muscles. I took my first breath right after birth and I still keep working non-stop. Even while you are sleeping, I fulfill my function with the automatic command I receive from the respiratory center at the back of your brain. My close friend Heart started working even before me while you were in the womb. I was resting then; actually I hadn’t even formed fully. As all your needs like food and oxygen were met in the body of your mother-whose heart you occasionally break-I didn’t have to make extra effort to get air, being filled and emptied. Even if I had attempted to do so, I would have had no chance of succeeding; since you were contained in the amniotic fluid, an attempt to breathe could have caused you to drown.

The first breath I take after birth is critical and rather difficult, since the windpipe is still much narrower than normal. On the other hand, the number of my alveoli where oxygen exchange with the capillaries is realized is so high in relation to body size that it balances the situation. When I make my first move and fill with air, I put pressure on the arteries and veins. Then the vessel directly connecting my artery to my mother’s aorta is dismissed, the curtain between the valves is closed and the blood circulations are separated. If this curtain is not properly closed and a gap remains in between, the oxygen-rich blood and the used-up blood mix and result in the disease known as cyanosis-or “blue baby” syndrome. As these two kinds of blood mix, the tissues are not supplied with sufficient oxygen and the white parts of the skin and eyes assume a bluish appearance.

Turning blue-purple due to lack of oxygen in the tissues is the same for smokers. Cigarettes-my archenemy-contain hundreds of toxic substances, such as carbon monoxide, which combine with the hemoglobin in blood and prevent oxygen transfer. Therefore, the lips of smokers turn slightly purple. You need to be careful with the air you inhale. The windpipe which brings air into me is covered with a ciliated epithelial tissue which catches the dust brought along and sweeps it outside. While you are asleep, the vibrating cilia of this sweeper work throughout the night and in the morning you get rid of the outcome of their propulsion by clearing your throat. However, every draw of a smoker kills 800–1,000 of our ciliated epithelial cells. After some time, they become unable to sweep the toxins (carbon, sulfur, lead, etc) inhaled with the air. I can’t stand it anymore! The increased air pollution is already putting enough strain on us… this habit is just too much for a lung to handle! It is just… an open invitation for cancer! Sorry, Peter, I didn’t mean to be rude. I appreciate that you don’t smoke, but I wish those who do would realize how splendid a mechanism they are destroying.

Now let me tell you about what a work of art I am. As you also know, art in a structure becomes more meaningful with functionality. As is the case with my other friends with which I work in your body, I am perfectly made to fulfill my duty. In other words, never mind forming an organ like me as a consequence of molecules and cells accidentally coming together, even a single protein molecule in my structure does not come to existence through unconscious causes.

With every breath you take, the pressure of the oxygen within the air inhaled rises, so it passes through my membranes by diffusion and into the adjacent capillaries; there it combines with hemoglobin molecules. At the same time, the carbon dioxide passes through the same membranes into me, and I dispose of it. Both of these are easier said than done! You breathe 13–14 times a minute and the whole thing is repeated over and over. As I keep expanding and contracting during breathing, which you are unaware of most of the time, first of all I need to be very flexible. Together with this flexibility, my most important quality is having the largest possible surface area within the smallest volume. My surface area of around 100m2 (as large as a tennis court) is made to fit into your chest cavity in the form of thin membranes so that my large surface allows gas diffusion. These membranes need to be kept wet; a special fluid is secreted as a precaution and respiration is realized smoothly. Without this fluid, my membranes would just stick together, unable to carry out their duty.

You can compare the course of the air inhaled to that of a car passing from a highway onto increasingly smaller roads and in the end reaching a dead end in the small sacks named alveoli. The air coming in through the mouth and nose unites at the expressway named the trachea, or the windpipe, which is 15cm long and 2–3cm in diameter. Incidentally, I have a couple of things to tell you about the way you breathe. As a matter of fact, inhaling is the duty of the nose. I’m sure it also has a lot to say as well, but let me just mention a simple fact about it. Now, you should inhale through your nose, so that the air you take in gets warm, wet, and is cleaned from dust. If you try to breathe this way, you do not trouble me much, and reduce the risk of catching a cold or an infection of upper respiratory system. Inhaling through the mouth helps dust and germs get into me and you might contract various illnesses from bronchitis to pneumonia. Now you know why kids who have adenoids who sleep with their mouth open get ill so easily. Sorry, I couldn’t help speaking on behalf on the nose.

Well, what were we talking about before that? Oh yes! The ways through which the inhaled air passes. As the name suggests, the windpipe which makes the air reach me is a cylindrical tube surrounded by 16–20 cartilaginous rings. As it is placed beside the esophagus, one side of the rings is made of soft cartilaginous tissue instead of hard, so that they don’t hinder swallowing. The muscular tissue near these rings helps them widen and narrow during respiration or coughing. I sometimes warn you by making you cough. Maybe it seems to be a disturbance, but if I don’t push out air by coughing through the contracted windpipe, contaminants can clog me up and cause you to suffocate. Therefore, the burst of air-what you call a cough-is a great blessing to you.

The sound system at the tip of the windpipe is another wonder. The used air I send out vibrates the cords in that voice-box and produces such melodies, gives voice to such speech! The air divides into the two lungs. My two sides are not symmetrical; the one on the right is divided into three, and the one on the left into two. I think this was meant to make room for the neighbor on the left, the heart. In addition, if there’s any cancer growth in me, the diseased part can be taken out by an operation and I can keep on functioning. God knows the wisdom behind this form. After that, these main bronchi separate into 8–10 thinner branches, like highways connecting to narrower roads. This branching resembles a tree turned upside down. At the tips of these thin branches are the respiratory bronchioles resembling clusters of grapes. The small spheres which make up the cluster are the end of the road and are the most vital parts. These spheres named alveoli are made of very thin membrane and they are surrounded by a net of capillaries (picture 5). These are the functional spots where gas exchange is realized.

I hang in the thorax with veins and arteries all around. There are two layers of protective membrane over me. One of them is stuck on me, whereas the other is stuck on the ribs which form the chest cavity. There is a fine and slippery fluid in between these two layers and it neutralizes the friction every time I inflate and deflate. If it hadn’t been placed there, I would wear out and be damaged. As I inflate during inhalation, the chest cavity should expand simultaneously to make space for me. If it weren’t given a flexible form, I would fail to breathe and you would eventually die. Fortunately, the protective set of ribs and their connection with the spine are flexible enough to make me work comfortably. In addition, the dome-shaped muscular partition (diaphragm) separating the thorax from the abdomen contracts and pushes down the organs in the abdomen. Thanks to the simultaneously programmed movement of both the ribs and the diaphragm I inflate with air and expand.

Being in constant contact with the outer environment makes me susceptible to various diseases. Coughing is among the foremost signals I give in the case of disease, and sometimes-excuse me-I produce a mixture of blood and phlegm. Also, I may have difficulty in breathing and warn you with chest pain. You should be alert to my signals. If bacteria and viruses infect me, they might reproduce inside my air sacs, and cause stiffening and suppuration.

I am particularly sensitive to allergic disorders. When the straight muscles on the walls of my bronchi contact an alien substance, pollens for instance, the consequent histamine secretion makes my muscles contract. In addition, allergic diseases, which can affect blood vessels, affect me a lot since I happen to be one of the major organs contributing to blood circulation. As a result of the contraction of my bronchial muscles and difficulty in disposing of the mucus I secrete to defend myself, I have trouble with breathing-you call it asthma.

In addition to this, we can mention diseases like emphysema, acute or chronic bronchitis as problems I frequently face. Even your anger has a great impact on me. Breathing becomes more difficult immediately.

Peter, I’m sorry, it is not possible to summarize a work of art like me within a few pages, but I need to stop now… but please, keep away from polluted areas and cigarette smoke! Send me as much fresh air as you can. And even though you mostly take me for granted, like my other teammates, please reflect upon what a blessing I am.

Irfan Yilmaz is a professor of biology at Dokuz Eylül University, Izmir, Turkey.