My name is Urkle Olus Oxygen. I'm going to tell you about a hair raising adventure I had about 157 years ago. Me and my best friend CO2, were in the Structural Bases of Life Research Centre working on a Cray supercomputer, trying to figure out why those huge monstrous humans need us to live. The computer had been working for weeks and it still didn't have the answer. Then CO2 had one of the scariest ideas I have ever heard in my entire life. He suggested to boldly do what no Oxygen or CO2 molecule had done before, to make a record and map the path and make a report on why the human race needs us to live. I suggested that his idea could be tested on someone else, but he insisted that his brain wave was one that only we could execute because of our experience. I know that I personally have travelled through 1,204,621,057 humans but it was always accidental. I would be travelling on my way when all of a sudden the Nitrogen, Oxygen, Argon, Water Vapour, Carbon Dioxide, Neon, Helium, Krypton, Hydrogen, Xenon, and Ozone gasses (all are commonly known as AIR) started to move towards this black hole. Of course we all started screaming and then we closed our eyes till we came out of the black hole again. But this time CO2 and I would keep our eyes open and write down the horrendous experience we had. But this experience I was about to have, took some school work. I had to learn how to write, spell, and to go into depth on the anatomy of the human body. After 16 years in school I graduated with first class honers and my title was a "hyper supergenitic counter clockwise Oxygen atom."
Since I am telling you about what happened to me, I think I should go into depth about myself. If you are not a moron, you would know that my atomic number is 8 and my weight is 15.9994 and I make up about 20% of , I forgot the name.........OH!! Earth's atmosphere. My boiling point or the temperature in which I turn into gas is -182.962. Pretty chilly hey. If you are a person who likes science you could tell me that liquid oxygen is magnetic and can be held between the poles of a strong magnet. Cool!! Anyway, I got a little side tracked.
A few days before I was to go on the mission, I took out life insurance, just in case what I was about to see gave me a vasospasm, or what we call it, a heart-attack. I also went to a psychiatrist because I was so nervous that when I tried to stand up my knees would knock together. The trauma I was experiencing was incredible, so incredible that it even amazed the leading doctors at that time. There was no cure, the doctors said that I was "self destructing" my "sub atomic nucleic structure" and if I didn't get myself under control, I would collapse because of exhaustion. I took dozens of sleeping pills to get to sleep. In the morning, I had to drink at least three cans of Jolt (twice the caffeine) to keep me awake. Around lunch time, I would get out the Molson Canadian Ice (fungus pea) just to keep myself settled down. You could say I was "a living hell."
Then the day came. It came with such swiftness that it just about knocked me over, but it came. It was the day that I was to do what no sane oxygen atom had done before, to keep my eyes open and record what happens to me when I first go into that "black hole", sorry the nose. You see I got a got a lot smarter since I went to school. Just befor I go on my trip, I want to talk about the things that I will write down. I will be writing down notes as I see things happen. I will be writing in the present tense, not the past. I will be doing that because that is what will be happening. As you may know, this is the first time in my life that I will be doing this so I might get scared but please stay with me. When I see things I will expand on what I see because that is why I went to school. So here we go!!
As I enter the nose I see that the air enters in two streams, because the nostrils (the two openings in the nose) are divided by the septum ,which is a thin wall of cartilage (tough tissue) and bones. I see the nostrils contain hairs which aid in filtering dirt out of the air. This guy had a lot of dirt on the sides of his nostrils so I knew he didn't pick his nose. From the nostrils I enter the nasal passage, which lies above the mouth. It was getting a little bit dark so I decided to turn my flashlight on. I saw above the nasal passage three shelflike bones called turbinates which were covered with mucus membranes which moisten the air. While looking at those structures, I observed that these bones help warm the inhaled air also. Looking closely at the mucus membrane, I see they are covered with microscopic, hairlike projections called cilia. They were waving back and forth constantly, moving dust, bacteria, and fluids from the nose to the throat for swallowing. Shifting my gaze to the highest part of the nasal cavity, I could see the olfactory nerve receptors lying in a small piece of mucus membrane about as big as a dime. These receptors give the human his sense of smell by generating nerve impulses in response to chemicals in the air. One thing that really struck me is that the main thing the nasal passage does is to warm the air and add moisture to it before it goes any farther.
From the nasal cavity, I go into the pharynx, which is a cone-shaped tube that connects the nose and mouth with the voice box and oesophagus. It looks about 5 inches long and has muscular walls lined with mucus membrane. As I'm going down, I see a flap of cartilage called the epiglottis which is open. I guess I will be going through it. Now I begin to see the Larynx, or the "Adam's apple," sometimes called the voice box because it contains the vocal cords. While I keep observing, I notice that the larynx is shaped like a box, and it has a supporting structure made up of nine sections of cartilage. The thyroidcartilage, in front, and the cricoid cartilage, in the back, which look to me as the most important structures. The thyroid cartilage consists of two wing-shaped plates that meet to form the projection called the "Adam's apple." These plates make up the side walls of the larynx. The ring-shaped cricoid cartilage forms the back wall of the larynx. Now I begin to see the vocal cords, two bands of elastic tissue that lie along the sides of the glottis wall. These muscles can stretch the cords, change their shape or bring them close together. When the cords are close together, air rushing between them produce sound. The shape and stretch in the cords determines the pitch (highness or lowness) of the voice. The shape of the throat, nose, and mouth determines the quality of a person's voice.
Now I begin to enter the t-t-trachea. It looks to me like a tube reinforced with cartilaginous rings to prevent collapse. I look closely and notice that the trachea is lined with cilia. Cilia look like hair. They are always in constant motion moving back and forth, and carry dust or dirt taken in with the air upward toward the mouth. The dust is mixed with mucus and the mucus even traps more particles in the air. I can hear the swishing of the cilia as they move back and forth. As I am going down they were getting pretty thick and I was weaving in and out of them. As I was doing that I could see hundreds of dirt particles stuck to the mucus that the upper hairs had missed. The farther down I go, the smaller the dirt particles get! At the lower end, the trachea divides into two branches called bronchi. One extends to each lung. These too have cilia and mucus in them. One thing I am noticing is that there are more special cells called alveolar macrophages which are engulfing the particles and carrying them to the mucus or destroying them. Now the bronchi tube I am in begins to divide into countless small bronchial tubes and these are dividing into even smaller tubes called bronchioles. While this is going on I am going to go over the mechanics of breathing. Inspiration, or the intake of air, occurs when the chest cavity is increased in size and therefore decreased in pressure. The enlargement of the chest cavity involves the following movements: (1) The rib muscles contract and pull the ribs upward and outwards and can be aided with the shoulder muscles. (2) The muscles of the resting, dome-shaped diaphragm contract. This action straightens and lowers the diaphragm and increases the size of the chest cavity below. (3) The abdominal muscles relax and allow compression of the abdominal organs by the diaphragm. The enlargement of the chest cavity results in decreasing of the air pressure within. In an equalizing movement, air passes through the trachea and inflates the lungs. Expiration, or the expelling of air from the lungs, results when the chest cavity is reduced in size. The action involves the following four movements: (1) The rib muscles relax and allow the ribs to spring back. (2) The diaphragm relaxes and rises to assume its dome-shaped position. (3) The compressed abdominal organs push up against the diaphragm. This action is increased during forced exhalation by contraction of the abdominal muscles. (4) The elastic lung tissues, stretched while the lugs are full, shrink and force air out. Now back inside the lungs. The bronchiole I am in ends in a sac called alveoli which is composed of lung tissue. The walls of the alveoli are very thin, only one cell thick but they are very elastic. While I am floating around in the alveoli, I make an inspection. I notice that I can see many minute blood vessels outside the alveoli walls called capillaries. Now I am beginning to see that I am moving toward the wall of the alveoli. As I am moving, I can see spaces between the cells so I can squeeze through; and I do.
I thought that the respitory system was exciting, but the circulatory system is even better!! Now I am in a fluid called blood. Its main purpose is that it is a transporting medium for all substances in the body. For example it assists in the transportation of digested food, cell wastes, water, oxygen, heat, and secretions. Blood is a fluid tissue. It is a peculiar tissue in that the cells are scattered among the nonliving substances composing the fluid portion. The average human has about 12 pints of blood, which compose about nine per cent of the body weight. The fluid portion of the blood is the plasma, and the blood cells are called the solid components, or the corpuscles.
Blood plasma looks straw-coloured and nine-tenths of it is water. The proteins in plasma give it the sticky quality. One of them, fibrinogen, is essential in the clotting of the blood. When fibrinogen is removed from plasma, two other proteins remain. One is serum albumin, which is necessary to normal blood and tissue relationship during absorption. The other is serum globulin, which gives rise to antibodies causing immunity to various diseases. Inorganic minerals, dissolved in water give plasma a salt content of about 1%, while sea water is approximately 3%. These compounds include carbonates, chlorides, and phosphates of the elements calcium, sodium, magnesium, and potassium. They are absolutely essential to the blood and to the normal functioning of the body tissues. Without calcium compounds, blood will not clot in a wound. Digested foods are present in plasma in the form of glucose, fatty acids and glycerin, and amino acids. Nitrogenous wastes, resulting from protein metabolism in tissues, and urea are also in plasma.
Now I am going to explain the solid components of the blood which I can see all around me. First I will start with the red blood cells which are shaped liked disks with both sides concave. The red cells are so small that ten million of them can be spread in one square inch. They are so numerous that, placed side by side, they would cover an area of 3,500 square yards. It is estimated that the blood of a normal person contains 25 trillion (25 000 000 000 000) red blood cells, or enough to go around the earth four times at the equator if they were laid side by side. The red blood cells are produced in the marrow of the bones. During development, they have nuclei, as do other cells. Normally, by the time they are ready to be released into the blood stream they have lost their nuclei. The average life of a red cell is about 20-120 days. Worn-out cells are filtered out of the blood in the spleen and liver. At the same time, certain compounds are released into the blood stream and used in the manufacture of new red blood cells. I'm not sure what role they do in the body but I am sure that I will find out.
The white blood cells which I can see are larger than the red blood cells and differ from them in three ways: (1) White blood cells have nuclei. (2) White corpuscles do not contain haemoglobin. (3) Some white cells move much like the ameba. The white blood cells are less numerous than the red cells, the ratio being about one white cell to every 600 red cells. White corpuscles are formed in the red bone marrow and in the lymph glands. Normally there are about 8,000 in one cubic millimetre of blood as against four and one-half to five million red cells.
The white blood cells that can move about are able to ooze through the capillary walls into the tissue spaces. Here they engulf solid materials, including bacteria. They are a important defence of the body against infection. Whenever an infection develops in the tissues, the white cell count may go from 8,000 to more than 25,000 per cubic millimetre. White cells collect in the area of an infection and destroy bacteria. the remains of dead bacteria, white corpuscles, and tissue fluid is pus.
Another solid component of blood is the blood platelets. As I look around me they look like they are irregularly shaped, colourless bodies, much smaller than the red cells. Platelets are not capable of moving on their own but float along in the blood stream. They have an important function in the formation of a blood clot.
Now enough of my babbling. At this moment I am moving toward a red blood cell. On the red blood cell is a substance called haemoglobin. Haemoglobin is a conjugated protein, containing four atoms of iron, which forms bonds easily and permits carbon dioxide and oxygen (that's me!) to transport. I see a molecule of CO2 leave the red cell and I am moving toward it like it is a magnet. I stick to the haemoglobin which is on the red blood cell. I can't even move and I am scared. I think I am going to die. I notice that all the red cells are red and not as pale as they used to be. I also see that I am moving, I am out of the capillary, have passed through the venules and am in the left pulmonary veins. As I am travelling, I hear a loud thumping sound, and it is getting louder. I look in my note book and find that I am nearing the heart. Now I am getting closer and the sound is getting very loud. I feel a suction all around me. As I come out of the left pulmonary veins, I enter a big space in the heart called the left atrium. This is where the blood enters from the lungs. Then I pass through the bicuspid valve into an even larger opening than the atrium and this is called the left ventricle. The left ventricle is where most of the muscle is on the heart and it pumps the blood to the entire body. As it compresses, the red blood cell I am attached to passes out through the aortic semilunar valve into the aorta.
As I am in the aorta, I am going to talk about the heart. The heart, as you know, is an organ that pumps blood to the body. An adult heart is about 5 inches long and weighs about 9 ounces. The heart is completely enclosed by a thin sac called the pericardium. The inside of the pericardium has a smooth lining that discharges a slippery liquid. The heart beats smoothly and with little friction against the moistened lining. A muscular wall called the septum divides the heart lengthwise. The heart has four chambers two of which I have described. An adult's heart beats about 70 times a minute. The walls of the heart are made of a special kind of muscle. The heart muscle contracts and relaxes regularly and automatically. A beat is one complete contraction and relaxation of the heart muscle. One part of the heart's muscle system, the sinoatrial node, has the job of starting each heartbeat, setting the pace, and causing the contraction of the heart muscle. It has been called the "pacemaker" of the heart. I could go on and on about this vital organ but I will stop there.
Right now I am in the aorta which is one of many arteries in the body, but it is the biggest. As blood comes out of the left ventricle it expands and adds to the pressure of the blood and helps force it to the body. I refer to this as systolic pressure. The recoil of the artery wall maintains part of the pressure while the ventricles are at rest. This is the lowest pressure in the arteries, or diastolic pressure. If the aorta were cut blood would spurt out in a stream six feet or more. While I am going through the aorta I pass the openings of the left and right coronary arteries. They are the ones that supply blood to the heart. Now I am in the aortic arch and it starts to branch off into separate arteries. The blood cell I am on I guess decides to take me down the thoracic aorta which is going down through the chest. Then I go down to the abdominal aorta which splits in to two different arteries. And of all things we get caught in a whirlpool and I decide to take the time to socialize.
I see another molecule and stop him and ask him his name. He tells me that his name is Brutus Thorac the 3rd. I ask him how he got to the place and this is his story.
Brutus was in a hamburger and was part of a long chain of sugars called carbohydrates? As you may know it is part of a long chain of sugars called starch, which is made up of single hexose molecules and Brutus's chemical formula is C6H12O6. Anyway he is a molecule and was in a hamburger and then that big black hole picked him up and put him in the hole. In the hole called the mouth were teeth that the bread he was in was crushed into little bits. Let me describe the mouth. The mouth has structures in it called teeth. There are 32 teeth in the mouth. The first two teeth are the incisors which cut the food. Next is the canine tooth which rip the food. They are sharpm and pointed. The next are the premolars that crush the food into little bits. The molars which have a large surface area and are grinding and crushing teeth too. There is a tooth called a wisdom tooth but it gets usually pulled out. Haa!! The chief function of the mouth is to prepare the food for digestion. The top of the mouth is called the hard palate and is a bony structure covered with several membranes. The soft palate lies just back of the hard palate. It is formed by folded membranes which extend from the rear portion of the hard palate and fasten along the sides of the tongue. The tongue lies in the floor of the mouth and extends into the throat. This muscular organ performs several different functions. 1. It acts as an organ of taste. Scattered over the surface are tiny projections called papillae. These papillae contain taste buds. They have nerve endings that are stimulated. The result is that the humans can taste sweet, bitter, salty, and sour. 2. The tongue aids in chewing by keeping the food between the teeth. 3. During swallowing, food is worked to the back of the tongue. When the tongue is jerked downward, food lodges in the pharynx and the food goes down. 4. The tongue rolling in the mouth keeps the inner surface of the teeth clean. 5. The tongue is essential in speech. Also in the mouth are the three pairs of salivary glands that secrete saliva. The names of the three glands are the parotid, sublingual, and the submaxillary glands. The parotid gland is on top of the mouth. The saliva helps in the digestion of food and cleaning of the teeth, being alkaline, it neutralizes acids in the mouth. Saliva also lubercates the food, kill bacteria, and stops the sensation of thirst. An important enzyme in saliva is called amylase which breaks down starch into smaller parts called maltose. Saliva contains more than 95% water and contains mineral salts, lubercating mucus, and the enzyme ptyalin. Ptyalin converts starch (Brutus) into maltose, a disaccharide.
Now I will get back to Brutus. While he was getting chewed up by the molars the saliva was breaking him down too. He saw his chain break off ahead of him and he got scared. When the chain finished breaking off all around him, he was only connected to a fraction of what once the chain was. He was then a double sugar. And, mean while, he and his buddies were getting sloshed around by that wicked tongue and that sticky saliva was everywhere. With all this happening, he was being slowly moved to the back of the mouth. In the act of swallowing, which is when the food goes from the mouth to the stomach, he passed through the pharynx (it is where I passed through too) to the oesophagus. This is a tube which is about a foot in length and connects the mouth to the stomach. He went down the tube with the aid of layers of muscle in the wall of the oesophagus. One layer is circular, and squeezes inward. The other layer is longitudinal, and contracts in a wave which travels downward, pushing the food ahead of it. Just before he entered the organ called the stomach he passed the cardiac notch.
Now he entered the stomach which is a somewhat J-shaped. It lies in the upper left region of the abdominal cavity just below the diaphragm. The stomach wall contain three layers of smooth muscle, each arranged differently. One layer is longitudinal, one is circular, and one is angled, or oblique. Contraction of the smooth muscle fibers of the various layers in different directions causes the twisting, squeezing, and churning movement of the stomach. The lining of the stomach is thick, wrinkled membrane. Numerous gastric glands are embedded in the stomach lining. Each gland is a tiny tube with an opening into the stomach. The walls of each gland are lined with cells which secrete gastric fluid containing an enzyme and hydrochloric acid. This secretion passes directly into the stomach. The principal enzyme in gastric fluid is pepsin. This enzyme acts on protein, splitting the complex molecules into simpler groups of amino acids, known as peptones and proteoses. The hydrochloric acid, in addition to providing the proper medium for the action of pepsin, dissolves insoluble minerals and kills many bacteria which enter the stomach with food. It also regulates the action of the pylorus, which opens at the completion of the stomach digestion and allows food to pass to the small intestine.
The food which passes from the stomach to the small intestine contains: 1. fats, unchanged 2. sugars, unchanged 3. some starches which were not acted upon by the ptyalin of saliva 4. coagulated milk casein 5. some proteins unchanged by the pepsin of the gastric fluid 6. peptones and proteoses formed from pepsin acting on protein. Poor Brutus remained in the stomach for three hours. While he was there he was churned back and forth in a circular path. This action separates the food particles and mixes them thoroughly with stomach secretions. At the completion of stomach digestion, the valve at the intestinal end, the pyloric valve, opens and closes several times sending Brutus through on the second squirt. Now he was in the duodenum, the upper ten inches of the small intestine. The duodenum carves upward, then backward and to the right, beneath the liver. Here is where secretions of the liver and pancreas enter. Beyond the duodenum is a second much longer region, the jejunum. This portion, about seven and one-half feet in length, is less coiled than the other regions. The lower part of the small intestine is the ileum and it is about 15 feet long, coils through the abdominal cavity before joining the large intestine.
As Brutus entered the duodenum, secretions from the liver entered. The liver is the largest gland in the body and it weighs about 3 and a half pounds. It is a dark chocolate colour and lies in the upper right region of the abdominal cavity. Bile is produced by the liver and is a brownish-green fluid. It passes from the liver in a series of bile ducts which form a Y. As bile is secreted in the liver, it passes down one branch of the Y, then travels up the other branch to the gull bladder. Here the bile is stored and concentrated as part of the water is removed. The base of the Y is the common bile duct. This tube carries bile from the gull bladder to the upper end of the small intestine, or duodenum. If the common bile duct becomes clogged by a gallstone, or a plug of mucus, bile enters the blood stream and causes a yellowing of the eyes and skin, known as jaundice. The liver performs several vital functions. In receiving glucose from the blood and changing it to glycogen, it serves as a storehouse in holding reserve carbohydrates as glycogen. In acting on amino acids and forming urea, it is an organ of excretion. All these changes involve food after digestion. As a digestive gland, the liver secretes bile which acts on food in the small intestine. In the formation of bile, the liver plays a part in using what might otherwise be discarded as waste. Part of the bile is formed from worn-out haemoglobin that the blood system can no longer use. Bile has several important functions: l. It is partially a waste substance containing material from dead red blood corpuscles filtered from the blood stream by the liver. 2. It increases the digestive action of lipase, an enzyme produced in the pancreas, by breaking globules of fat into small droplets, in the process called emulsification. 3. It helps to neutralize the hydrochloric acid from the stomach so that digestion can take place in the intestine. Actually, bile is not a digestive secretion. In emulsifying fats, it splits large fat particles into smaller ones, producing a milky liquid called an emulsion. In this form, pancreatic fluid can act on fats more readily.
The pancreas is a many-lobed, long, whitish gland, quite similar in general appearance to a salivary gland. It lies behind the stomach and the upper end of the small intestine, against the back wall of the abdominal cavity. It performs two entirely different functions. The production of insulin and the digestive secretion, pancreatic fluid, passes into the small intestine through the pancreatic duct, which leads to a common opening with the bile duct in the wall of the duodenum. Pancreatic fluid acts upon all three classes of organic nutrients. This digestive fluid contains the following three enzymes: l. trypsin; 2. amylase; 3. lipase. Trypsin continues the breakdown of proteins which began in the stomach, by changing peptones and proteoses to still simpler amino acid groups called paptids. In addition, it may act upon proteins which were not simplified during stomach digestion. Peptide are not the final product of protein digestion. Only one additional step is necessary to form the amino acids which are used by the body tissues. Amylase duplicates the action of the ptyalin in saliva by changing starch into maltose. This is how the potatoes you did not chew enough are changed to sugar. Lipase splits fat into fatty acids and glycerin. This is the only digestive action on fats which reduces them to the form in which they are absorbed. The intestinal glands secrete intestinal fluid. The mucous lining of the small intestine contains many tiny embedded glands that are called intestinal glands. They secrete intestinal fluid, a highly alkaline substance containing four principal enzymes: 1. erepsin; 2. maltase; 3. lactase; and 4. sucrase. Erepsin completes protein digestion by changing peptids, formed by the pancreatic fluid, to amino acids. Maltase splits the double sugar, maltose, into the simple sugar, glucose,(so Brutus is now a single sugar called glucose) the final product of carbohydrate digestion. Lactase has a similar action on lactose, or milk sugar, in changing it to glucose. Sucrase acts on sucrose and changes it to the simple sugars glucose and fructose. Thus, with the combined action of bile, pancreatic fluid, and intestinal fluid in the small intestine, all three classes of foods are completely digested. As simple sugars, fatty acids and glycerin, and amino acids, they leave the digestive system and enter the blood and lymph.
The duodenum is also where secretions from the pancreas enter, this process is described above.
For Brutus to be absorbed into the blood stream, another process must occur. This process occurs in the villi. A magnified portion of the small intestine shows that its irregular lining gives rise to great numbers of fingerlike projections called villi. These projections are so numerous that they give a velvety appearance to the intestinal lining. Within the villi are branching lymph vessels, called lacteals, and blood vessels. The villi bring blood and lymph close to the digested food and increase the absorption surface area of the intestine enormously. Absorption is increased further by a constant swaying motion of the villi through the intestinal content.
Glycerin and fatty acids enter the villi and are carried away by the lymph. They eventually reach the general circulation and travel to the tissues. Glucose (Brutus) and amino acids, however, enter the blood vessels of the villi. Brutus, however, does not get carried by a red blood cell but floats around in the plasma. From the villi they are carried directly to the liver through the portal vein. This is called portal circulation and it includes an extensive system of veins which lead from the spleen, stomach, pancreas, small intestine, and colon. The large veins of the portal circulation unite to form the portal vein, which enters the liver. In the liver some of the wastes and poisons of the blood are taken out. Additionally, some substances produced by the liver help the body fight disease and enable blood to clot. The liver also manufactures various blood proteins, including albumin, globulins, and fibrinogen. The liver also secretes cholesterol, a fatty substance. The body uses cholesterol to build cell membranes and to manufacture certain hormones, including the sex hormones. Hormones are chemicals that influence various body functions. Liver cells use cholesterol to manufacture bile salts.
From the liver, Brutus, entered the inferior vena cava which is to the right of the heart. Then he was pushed and sucked into the right atrium and passed through the tricuspid valve. From the valve he entered the right ventricle, passed through the semilunar valves of the pulmonary artery and entered the pulmonary artery. The pulmonary artery branched off in two directions and Brutus took the left pulmonary artery. This artery took him to the left lung which has two lobes. Here the blood looses CO2 and get O2 then Brutus went back to the heart through the left pulmonary veins. He then entered the left atrium and passed through the bicuspid valve into the left ventricle. From here he went through the semilunar valves of the aorta and then was in the aorta. He went by the aortic arch and into the thoracic aorta, then down to the abdominal aorta where he met me!!
I told him that was some story and that his journey was even worse than mine. He asked me why I was here and I told him that I was recording everything that happened to me, I was kind of an experiment. He said that was cool and we said our good byes and then we went our separate ways.
Now I am out of the whirlpool and going into the left branch of the abdominal aorta called the common iliac artery. This artery goes down the left leg of the individual I am inside of. The common iliac branches off and I go into the external iliac artery. It branches off so I go into the femoral artery. From there I then go into the post peroneal artery which is just below the left knee. I know I am sounding complicated but please stay with me. From the post peroneal artery I go into the lateral plantar artery which is near the heal of the foot. I keep branching off into smaller and smaller arteries until they aren't arteries anymore. They are than called arterioles which are small blood vessels that carry blood away from the heart. The arterioles then branch into capillaries which my red blood cell can barely fit through. Only one blood cell can go through at a time and they go one after the other.
As I am in the capillary the walls are thin and one-celled. The spaces between the cells are big enough so I can pass through but not my red blood cell. Since there is more carbon dioxide where I am than oxygen the carbon dioxide takes my place by the process of diffusion. I then pass through a membrane and if you don't know what a membrane is I will tell you. A membrane is a layer of tissue through which the cells are enclosed in and through which they can obtain their food. The membrane is made up mainly of protein. The membrane also hold the protein in the blood from getting in. Now I am in between the cell and in a fluid called tissue fluid. The tissue fluid is connected to the lymphatic system but this system is another story. While I am here I will tell you facts about cells. The cell is the basic unit of life. The body of a human being has more than 10 million million (10,000,000,000,000) cells. Also there are all different kinds of cells. If you want to know, I am near a group of muscle cells. I will talk more about the cell in a minute.
Now I am floating around in the tissue fluid and I am getting nearer to one of the cells. As I get closer I see spaces in the cell wall or membrane. The membrane encloses the entire cell, the nucleus, and all the organelles. The membrane also hold the cell together. Most membranes consist of a double layer of fatty substance called phospholipid. Proteins occur at various points and extend to different depths within the double layer of phospholipids. Only needed materials can enter the cell and its parts because of the structure and chemical composition of the membranes.
Now I have squeezed through the cell wall and I am floating around in a substance called cytoplasm. The cytoplasm is all the cell except the nucleus. Proteins are made in the cytoplasm, and many of the cell's life activities take place there. Also in the cytoplasm the sugars are broken down into pyruvic acid, and a small amount of ATP is produced. Many tiny structures called organelles are located in the cytoplasm. Each has a particular job to do. These organelles are called mitochondria, lysosomes, the endoplasmic reticulum, centrioles, and golgi bodies. Mitochondria are the power producers of the cell. A cell may contain hundreds of mitochondria. These sausage-shaped structures produce almost all the energy the cell needs to live and to do its work. Most of your energy comes from the mitochondria, the power producers of a cell. The mitochondria are like a power plant which burns fuel to produce the electricity that runs machines. The food humans eat is the fuel that is "burned" inside the mitochondria. A product of this burning is a compound called adenosine triphosphate (ATP). ATP is the "electricity" that runs the cell.
Forside
