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Circulatory System

• The heart is your hardest working organ. It pumps from the moment you are born… to the moment you are dead. The heart has four chambers that help it move the flow of blood. The chambers are called the Right Atrium, Right Ventricle, Left Atrium, and Left Ventricle. The purpose of the circulatory system is to move blood around the body. The blood carries oxygen and nutrients away from the heart and carbon dioxide and wastes back. You might be wondering, “So what is the flow of blood?”. I’m here to show you just that. Keep in mind when talking about the heart the left is really right and the right is really left because we are viewing the heart from the front and not the back. Okay, let's get started.

In the heart, we start at the right atrium. Keep in mind that the point of the atria are to hold the blood in the heart before getting pumped by the ventricles. The blood at this point is not oxygenated. The blood first enter the right atrium through the “Superior Vena Cava” and the “Inferior Vena Cava”. The SVC brings blood from the upper half of the body while the IVC brings blood from bottom half.

After that happens the right atrium contracts causing the Tricuspid valve to open so the blood can flow in the the right ventricle. You may be asking, “What is the point of the valves in the heart?” The point of the valves in the heart are to stop blood from flowing backward so it can all move in one direction.

Next the right ventricle contracts so that the pulmonary valve opens, allowing blood to pump into the pulmonary artery. From there the pulmonary artery pushes the blood into the lungs where it can oxygenated.

After being oxygenated, the blood returns to the heart through the pulmonary veins into the left atrium.

When the left atrium contracts, the Mitral valve opens allowing blood to flow into the left ventricle. Next the left ventricle pumps the blood through the aortic valve to the aorta. The aorta is the most important artery in the body because it distributes all the oxygen rich blood the rest of the body.

The blood then travels to every part of the body, distributing nutrients and oxygen whilst picking up waste, through the arteries. When it's time for the blood to come back to the heart to be oxygenated, it comes through veins, back to either the SVC or the IVC. And then the cycle restarts.

Quick Recap:

• Atria - Hold blood.
• Ventricles - Pump blood.
• Valves - Prevent blood from flowing in the other direction.
• Arteries - Move blood away from heart.
• Veins - Bring blood back to the heart.

Respiratory System

• You may think the respiratory system is just breathing in and out. Partly you are correct. The respiratory system's job is to take in air into the lungs and to facilitate the diffusion of Oxygen into the bloodstream according to www.teachpe.com.

Now the process of respiration. It’s actually not quite simple. First your diaphragm has to contract therefore expanding the chest.

This causes a negative pressure where the lungs are housed so the lungs expand. The expansion of the lungs causes a decrease in air pressure of the lungs. You should know by now that air will flow from an area of high pressure to an area of low. Knowing this principle you should understand that the air from the environment is drawn into your body.

The air then from the nose is filtered and heated in the nasal cavity.

After that the air passes down the throat, into the trachea, where it is divided in half by the bronchus. If you didn’t know the bronchus divides air between the two lungs.

Next the air passes into smaller tubes called bronchioles and then finally the air empties into the lungs.

The air then enters the alveoli, tiny sacs in the lungs, where where oxygen deposited into the bloodstream and where carbon dioxide is withdrawn.

The diaphragm then relaxes causing the chest cavity to withdraw. The lungs also become smaller which increases the air pressure in them causing the air to go back into the environment. And that’s it! That is the process of the respiratory system.

Quick Recap:

• Diaphragm relaxes muscles for air to enter the body.
• Nasal Cavity - Filters and Heats up air in the body.
• Trachea - Windpipe.
• Pharynx- Divides trachea and esophagus.
• Bronchus - Divides the trachea into two passages, one for each lung. Bronchioles - Smaller air tubes that empty air into the lung. Alveoli - Tiny sacs in the lung that deposit oxygen to the bloodstream and withdraws carbon dioxide to be exhaled. Lungs - Facilitate the diffusion of oxygen to the bloodstream and carbon dioxide out.
• Bronchus - Divides the trachea into two passages, one for each lung.
• Bronchioles - Smaller air tubes that empty air into the lung.
• Alveoli - Tiny sacs in the lung that deposit oxygen to the bloodstream and withdraws carbon dioxide to be exhaled.
• Lungs - Facilitate the diffusion of oxygen to the bloodstream and carbon dioxide out.

Digestive System

• Finally our last topic! Now if you’re like me you like food and sometimes you wonder where your food goes, don’t you? I mean it comes from one end and goes to the other, but what is really happening inside our body? The basic definition of the digestive system is the system that changes food into nutrients and wastes for the body. Digestion is also one of those topics that aren’t that simple. You see when you eat something two forms of digestion take place. Mechanical digestion, which includes chewing and the churning motions of your stomach. And chemical digestion, which includes, saliva and stomach enzymes.

Let's get started on the process of digestion. The first part of the digestive system is your mouth. Even before you eat something, your body will sense food and start to form saliva. After mechanically chewing with your need the saliva enzymes attack the smaller particles of food in a process we know as chemical digestion. Your tongue and the roof of your mouth may also help in mechanical digestion.

The food then moves down your throat to the pharynx and down the esophagus. The pharynx is a tube that divides the trachea from the esophagus. The esophagus is a tube that connects the pharynx to the stomach. While food goes down the esophagus it is also mechanically broke down in a process known as peristalsis which also moves the food down to the stomach.

Once the food approaches the stomach, a muscular valve called the lower esophageal sphincter relaxes and lets the food pass into the stomach. The purpose of the lower esophageal sphincter is so that no stomach or food reenters the esophagus.

Acid and enzymes from the glands near the stomach then secrete to continue to breakdown the food. The stomach muscles also then help to mix the food. After that the food that you have eaten is down turned into a creamy fluid called chyme.

The fluid is then pushed into the small intestine. With the help of more enzymes and bile from the pancreas and gallbladder the food is broken down further in the small intestine. The small intestine then absorbs the nutrients of the food into the bloodstream through the walls of the intestine.

After that the leftover waste is transported into the large intestine, commonly referred to as the colon. The waste product is then moved by peristalsis through the large intestine. Through this motion, water is absorbed and stool has formed.

Finally the leftover stool is stored in the rectum. Once the stool arrives in the rectum a signal is sent to the brain saying that the body is ready for a bowel movement. Again another valve called the anal sphincter relaxes and opens allowing the stool to pass through the anus and out of the body. A fun fact is that unlike most of the valves in the body the anal sphincter is one that is a voluntary action.

Although these are the main organs of the digestive system there are still a few accessory organs that help tremendously in the process of digestion. These organs are the pancreas, liver, and gallbladder. The pancreas is the main producer of digestive enzymes used in the intestines. The enzymes help with the digestion of fats, protein, and carbohydrates. Next is the liver. The liver produces bile which helps with the digestion of fats and the elimination of wastes in the body. The liver also stores nutrients as well as filtering chemicals and toxins. The gallbladder stores and releases bile. When fatty food enters the small intestine bile is released.

Quick Recap:

• Mouth - First part of mechanical digestion.
• Saliva - A chemical made by the body to assist mechanical digest.
• Pharynx - A tube that divides the trachea from the windpipe.
• Esophagus - The tube in between the pharynx and the stomach which also contributes to mechanical digestion.
• Stomach - Where food is primarily digested using stomach acid and enzymes from other glands.
• Liver - Produces bile, stores nutrients, and filters chemicals and toxins.
• Gallbladder - Stores bile and releases it when needed (fatty foods).
• Pancreas - Main producer of digestive enzymes.
• Small Intestine - Absorbs nutrients from the food through the walls of the intestine.
• Large Intestine - Absorbs water from the leftover food and forms stool.
• Rectum - Where stool is store.
• Anus - Where stool leaves the body.
• Lower Esophageal Sphincter - A muscular valve that prevented food and stomach acids from leaving the stomach into the esophagus.
• Anal Sphincter - A valve that prevents stool from leaving the rectum. Only voluntary valve.

Hope you enjoyed!