Introduction

Have you ever wondered what is inside of you? What happens after you finish eating your food? Have you wished to travel inside yourself to see the processes your organs go through, just to keep you working? Although we can't physically go inside of your body, there are numerous pictures that can show us what the organs look like. Through research, Doctors can tell us what happens at every little stop in our bodies. There are over 30 organs in our body! That is a lot to visit in one day, so I picked, what I thought to be the 8 most important organs. Of course they are all important because they all have a special function to keep us living.

So take a journey with me, inside of the human body, where no kid has been before! Take a trip though the bodies digestive system, where we'll make a stop for the brain, lungs and heart too! Are you ready? Then let's go!

The Brain

The average brain weighs 3 pounds. The brain can be divided into two halves called the cerebral hemispheres. Each hemisphere is divided into four lobes by various sulci and gyri. The sulci are the groves and the gyri are the bumps that can be seen on the surface of the brain. Most people have the same pattern of sulci and gyri on the cerebral cortex, but no two brains are the same!

The first of four lobes is call the Frontal Lobe. It is located in the front and is colored blue in the picture above. Some of the things this part of the brain is in charge if include reasoning, planning, parts of speech and movement (motor cortex), emotions, and problem-solving.

The second lobe is called the Parietal Lobe. It is located behind the frontal lobe and is colored red in the picture above. This part of the brain controls the perception of stimuli related to touch, pressure, temperature and pain.

The third lobe is called Temporal Lobe. It is located below the frontal lobe and the parietal lobe and is colored green in the picture above. This part of the brain controls the perception and recognition of auditory stimuli (hearing) and memory (hippocampus).

The last lobe is called the Occipital Lobe. It is behind the parietal and temporal lobe and is colored yellow in the picture above. This part of the brain controls the many aspects of vision.

The Mouth

The mouth is the entrance to both the digestive and the respiratory systems. The inside of the mouth is lined with mucous membranes. When healthy, the lining of the mouth (oral mucosa) is reddish pink; the gums are paler pink and fit snugly around the teeth.

The roof of the mouth (palate) is divided into two parts. The front part has ridges and is hard (hard palate); the back part is relatively smooth and soft (soft palate). The moist mucous membranes lining the mouth continue outside, forming the pink and shiny portion of the lips, which meets the skin of the face at the vermilion border.

At the back of the mouth hangs a narrow muscular structure called the uvula, which can be seen when a person says "Ahh." The uvula hangs from the back of the soft palate, which separates the back of the nose from the back of the mouth. Normally, the uvula hangs vertically.

On the floor of the mouth lies the tongue, which is used to taste and mix food. The tongue is not normally smooth; it is covered with tiny projections (papillae) that contain taste buds, which sense the taste of food. The sense of taste is relatively simple, distinguishing only sweet, sour, salty, and bitter. Sweet and salty taste receptors are located at and near the tip; sour, on the sides; and bitter, on the most posterior (back) part of the tongue. Smell is sensed by olfactory receptors high in the nose. The sense of smell is much more complex than that of taste, distinguishing many subtle variations. The senses of taste and smell work together to enable people to recognize and appreciate flavors.

Saliva serves several purposes. Saliva aids in chewing and eating by gathering food into lumps so that food can slide out of the mouth and down the esophagus, and by dissolving foods so that they can more easily be tasted. Saliva also coats food particles with digestive enzymes and begins digestion. After food is eaten, the flow of saliva washes away bacteria that can cause tooth decay (cavities) and other disorders. Saliva helps keep the lining of the mouth healthy and prevents loss of minerals from teeth. It not only neutralizes acids produced by bacteria but also contains many substances such as antibodies and enzymes that kill bacteria, yeasts, and viruses.

The Esophagus

The esophagus connects the pharynx (throat) with the stomach. It lies between the trachea (windpipe) and the spine. It passes down the neck and joins the cardiac (upper) end of the stomach. In an adult, the esophagus is about 25 centimeters (10 inches) long. When a person swallows, the muscular walls of the esophagus contract to push food down into the stomach. Glands in the lining of the esophagus produce mucus, which keeps the passageway moist and facilitates swallowing.

The Lungs

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Your lungs are in your chest, and they are so large that they take up most of the space in there. You have two lungs, but they aren't the same size the way your eyes or nostrils are. Instead, the lung on the left side of your body is a bit smaller than the lung on the right. This extra space on the left leaves room for your heart.

Your lungs are protected by your rib cage, which is made up of 12 sets of ribs. These ribs are connected to your spine in your back and go around your lungs to keep them safe. Beneath the lungs is the diaphragm, a dome-shaped muscle that works with your lungs to allow you to inhale (breathe in) and exhale (breathe out) air.

You can't see your lungs, but it's easy to feel them in action: Put your hands on your chest and breathe in very deeply. You will feel your chest getting slightly bigger. Now breathe out the air, and feel your chest return to its regular size. You've just felt the power of your lungs!

From the outside, lungs are pink and a bit squishy, like a sponge. But the inside contains the real lowdown on the lungs! At the bottom of the trachea, or windpipe, there are two large tubes. These tubes are called the main stem bronchi, and one heads left into the left lung, while the other heads right into the right lung.

Each main stem bronchus — the name for just one of the bronchi — then branches off into tubes, or bronchi, that get smaller and even smaller still, like branches on a big tree. The tiniest tubes are called bronchioles, and there are about 30,000 of them in each lung. Each bronchiole is about the same thickness as a hair.

At the end of each bronchiole is a special area that leads into clumps of teeny tiny air sacs called alveoli. There are about 600 million alveoli in your lungs and if you stretched them out, they would cover an entire tennis court. Now that's a load of alveoli! Each alveolus — what we call just one of the alveoli — has a mesh-like covering of very small blood vessels called capillaries. These capillaries are so tiny that the cells in your blood need to line up single file just to march through them.

The Heart

The heart is made up of four different blood-filled areas, and each of these areas is called a chamber. There are two chambers on each side of the heart. One chamber is on the top and one chamber is on the bottom. The two chambers on top are called the atria. If you're talking only about one, call it an atrium. The atria are the chambers that fill with the blood returning to the heart from the body and lungs. The heart has a left atrium and a right atrium.

The two chambers on the bottom are called the ventricles. The heart has a left ventricle and a right ventricle. Their job is to squirt out the blood to the body and lungs. Running down the middle of the heart is a thick wall of muscle called the septum. The septum's job is to separate the left side and the right side of the heart.

The atria and ventricles work as a team — the atria fill with blood, then dump it into the ventricles. The ventricles then squeeze, pumping blood out of the heart. While the ventricles are squeezing, the atria refill and get ready for the next contraction. So when the blood gets pumped, how does it know which way to go?

Well, your blood relies on four special valves inside the heart. A valve lets something in and keeps it there by closing — think of walking through a door. The door shuts behind you and keeps you from going backward. Two of the heart valves are the mitral valve and the tricuspid valve. They let blood flow from the atria to the ventricles. The other two are called the aortic valve and pulmonary valve, and they're in charge of controlling the flow as the blood leaves the heart. These valves all work to keep the blood flowing forward. They open up to let the blood move ahead, then they close quickly to keep the blood from flowing backward.

The Stomach

The stomach is an organ of digestion. It has a saclike shape and is located between the esophagus and the intestines. The human stomach is a muscular, elastic, pear-shaped bag, lying crosswise in the abdominal cavity beneath the diaphragm. It changes size and shape according to is position of the body and the amount of food inside. The stomach is about 12 inches (30.5 cm) long and is 6 inches. (15.2 cm) wide at its widest point. The stomach's capacity is about 1 qt (0.94 liters) in an adult.

Food enters the stomach from the esophagus. The connection between the stomach and the esophagus is called the cardiac sphinter. The cardiac sphincter prevents food from passing back to the esophagus. Heart burn is the sensation when stomach juices (gastric juice) is allowed to seep through the sphincter into the esophagus. Once the food enters the stomach, gastric juices are used to break down the food. Some substances are absorbed muscle lining of the stomach. The other end of the stomach empties into the duodenum. The duodenum is the first section of the small intestine. The pyloric sphincter separates the stomach from the duodenum.

The stomach is composed of five layers. Starting from the inside and working our way out, the innermost layer is called the mucosa. Stomach acid and digestive juices are made in the mucosa layer. The next layer is called the submucosa. The submucosa is surrounded by the muscularis, a layer of muscle that moves and mixes the stomach contents. The next two layers, the subserosa and the serosa are the wrapping for the stomach. The serosa is the outermost layer of the stomach.