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Systems of the Human Body 2: Providing Fuel and Transportation

Science, Grade 6

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Table Of Contents: Systems of the Human Body 2: Providing Fuel and Transportation

1. Food and Nutrients

2.1. Food and Cellular Energy
Your body relies on what you eat and drink to maintain healthy tissues and to generate the energy used by cells. That energy is in the form of ATP (adenosine triphosphate), a molecule that contains high energy bonds. When those bonds are chemically broken, they release energy needed for cellular functions, such as muscle contraction. Not all foods can generate the same amount of energy in our bodies. We measure the energy value of food in calories.
2.2. Nutrients
Food contains different kinds of nutrients, which are substances that help maintain the body. There are six categories of nutrients: carbohydrates, fats, proteins, vitamins, minerals and water.

2. Types of Nutrients

3.1. Simple Carbohydrates
Nearly all the carbohydrates we eat come from plants. The simplest and smallest of carbohydrates are glucose and fructose. Found in many fruits, glucose and fructose provide a source of fuel in making the ATP needed for muscle contraction, nerve impulse conduction and nearly every cell function.
3.2. Complex Carbohydrates
A wide range of dairy products contain more complex carbohydrates, such as lactose, which is composed of two simple sugars bound together. Many foods derived from plants, such as grains and rice, contain starch, a complex carbohydrate made up of many simple carbohydrates bonded together. Complex carbohydrates are a very high-energy resource in the foods you eat.
3.3. Fats
Although many think of fats as bad for the body, they have several essential roles. Fats are a source of energy, and they are part of the structure of cell membranes. Fats also protect body tissues. Of course, too much fat can cause problems, especially when it leads to heart and artery disease.
3.4. Cholesterol
Fats help your body process cholesterol, which your body needs to produce hormones and maintain cell membrane structure. Cholesterol is found in animal fat, cheese, and eggs. However, too much cholesterol can contribute to heart disease.
3.5. Saturated and Unsaturated Fat
Saturated fat, which is present in animal meats and fried foods such as potato chips, is unhealthy for the body because it causes an increase in bad cholesterol. Unsaturated fats, present in a variety of nuts and fish oil, are better because they help to increase good cholesterol.
3.6. Proteins
We get most of the protein in our diet from animal sources, legumes and nuts. Proteins provide essential support to several parts and processes of the body. They support the structure of the body in muscles and connective tissues, and contribute to growth and repair. Proteins also act as enzymes in chemical reactions.
3.7. Proteins are Composed of Amino Acids
The simplest form of protein is the amino acid. There are many types of amino acids in your body. The most complex proteins are made up of many repeating units of amino acids.
3.8. Vitamins
Vitamins are essential components to your diet because they support the functions of carbohydrates, fats and proteins. They are only needed in small quantities, and a healthy, balanced diet can provide all the vitamins you need.
3.9. Water-Soluble Vitamins
Vitamins include two classes of molecules: water-soluble and fat-soluble vitamins. Water-soluble vitamins include vitamins C and B complex. Vitamin C is important in the process of inflammation, how your body fights infectious disease, and in maintaining the strength of our connective tissues. Vitamin B complex helps the body convert food into fuel which is used to produce energy.
3.10. Fat-Soluble Vitamins
Fat-soluble vitamins include vitamins A, D, E and K, which each support a variety of functions in your body. Vitamin D, when absorbed into your system with calcium, helps maintain the strength and integrity of your bones.
3.11. Minerals
Our bodies need a wide range of minerals, such as potassium, sodium, and magnesium, to help support body structure and functions. Calcium and phosphorus, which are in rich supply in our bones, are the most plentiful. You can get all of the most important minerals from a balanced diet that includes fruits, vegetables and meat or some other source of protein.
3.12. Water and the Human Body
The human body is 50-60% water by weight. There is water in blood as well as within and between cells in body tissues. Humans can’t live without water. Keeping the body hydrated is an important way to keep organs functioning normally.
3.13. Healthy Diets and Food Labels
With a proper diet, you will consume a balanced amount of nutrients. The U.S. Department of Agriculture (USDA) provides guidance on the components of a healthy diet. The Choose My Plate program was developed by the USDA in 2010 to help us make better daily food choices. The Food and Drug Administration monitors food and drink labels, which give us an idea of how to judge and manage how many nutrients we consume from different food products.

3. Pause and Interact

4.1. Review
Use the whiteboard text tool to fill in the table with examples for each nutrient category.

4. Digestive System - Fuel from Food

5.1. Digestive System Functions
Your digestive system processes the food and drink you consume. Food is broken down physically and chemically as it travels through the digestive system. Nutrients are absorbed into your bloodstream, and remaining wastes are excreted from your body.
5.2. Organs of the Digestive System
The organs of the digestive system are connected, making a long pathway called the digestive tract. The digestive tract starts with the oral cavity of the mouth, which connects directly with the esophagus. The esophagus ends at the stomach, where food is deposited for processing. The food then moves through the small intestines that connect with the liver and pancreas which aid in the digestive process. Lastly, digested material enters the large intestine before being excreted from the body as fecal waste.
5.3. Mouth and Oral Cavity
The mouth plays an important role in digestion. Food is mechanically broken down by the motion of your tongue and your teeth, which breaks the food into smaller particles and mixes it with saliva.
5.4. Esophagus
The esophagus is a muscular passageway that connects the mouth and throat to the stomach. Food is moved in one direction toward the stomach by the process of peristalsis – a series of muscle contractions.
5.5. Stomach
In your stomach, food is stored and processed so that your body can gain access to the nutrients in the food. Food is mechanically broken down and churned physically with stomach juices, or gastric juices, to begin the chemical digestion of proteins. In this process, the stomach releases the enzyme pepsin into the very acidic environment of the stomach. Pepsin chemically breaks down the proteins into amino acids, which your body needs for many important functions.
5.6. Pancreas
The pancreas is a very important gland that is critical to human life. It produces a wide variety of enzymes that aid in the processing of foods. The enzymes are released into the small intestine to cause chemical breakdown of carbohydrates, fats and proteins.
5.7. Liver
The liver is a very large gland that performs many functions. In digestion, it produces and releases bile along a series of ducts connected directly to the small intestine. There is also a duct that connects with the gall bladder, where bile can be stored until it is needed. Bile is then released after a big meal into the small intestine to physically breakdown large fat droplets in foods as part of the digestive process.
5.8. Small Intestine
The small intestine is about 20 feet long. Consumed materials that are partially processed move through the intestine. After being mixed with enzymes from the pancreas and bile from the liver, these materials are fully digested and the nutrients are absorbed into the walls of the small intestine.
5.9. Large Intestine
The large intestine serves as a storage organ designed to help form the feces. It absorbs water and small amounts of nutrients, such as Vitamin K, into the bloodstream.

5. Process of Digestion

6.1. Mechanical Digestion
Food is broken apart physically to make it easier for chemical digestion to occur. This process starts with chewing our food and mixing it with saliva and is followed by a physical churning that takes place in the stomach.
6.2. Chemical Digestion
Food is chemically digested by enzymes that break chemical bonds between food molecules. This process makes food molecules less complex and easier to absorb. Chemical digestion of carbohydrates begins in the mouth with the release of the enzyme amylase within the saliva. Chemical digestion of proteins starts in the stomach. The majority of chemical digestion, however, occurs in the small intestine.
6.3. Digestive Enzymes
Enzymes released by glands of the digestive tract, such as the salivary glands, pancreas and the intestines, act to break down large molecules into their simplest forms.
6.4. Pancreatic Enzymes
The greatest number and variety of digestive enzymes are released by the pancreas. Pancreatic enzymes digest carbohydrates, proteins and lipids in our foods. Carbohydrates are broken down to simple sugars, and proteins are broken down to amino acids. Fats are broken down to triglycerides and fatty acids. These end products of digestion can then be absorbed in the body to sustain life.
6.5. Absorption of Nutrients
End products of digestion and many other molecules, including water, are absorbed through the lining of our digestive tract into the bloodstream. Most of this absorption happens within the small intestine. These nutrients are transported to vital organs in support of body functions and other chemical reactions.

6. Pause and Interact

7.1. Review
Use the whiteboard tools to create a flow chart that displays and describes the path a food molecule takes during the process of digestion.
7.2. Digestive System
Click on the Terms button. Then click and drag each term to the correct box. Use the reset button to clear the terms and start over. Use the gear button to customize the draggable terms.

7. Respiratory System - The Need for Oxygen

8.1. Functions of the Respiratory Tract
In order to function, the human body needs a constant supply of oxygen and a process for removal of carbon dioxide waste. The respiratory tract is made up of a system of conducting tubes that connect the atmospheric air with the lungs. In the lungs, the inhaled oxygen-rich air is exchanged for carbon-dioxide rich air that is exhaled from the body.
8.2. The Need for Oxygen
Every cell in the human body needs oxygen. A steady supply of oxygen is critical to supporting highly active tissues and cells, which have a constant need for energy. This energy can only be produced in high quantities by cells when oxygen is present. For example, nerve cells of the brain will begin to break down and die if they are without oxygen for four minutes!
8.3. Organs of the Respiratory Tract – From Mouth to Lungs
Air enters through the nose and mouth, and then travels through the throat known as the pharynx. Air then passes along the area of the vocal cords, the larynx, before entering the main air tube known as the trachea. From there, air goes through separate tube connections, called bronchi, into the right and left lung. Most of the sounds we make in speaking happen when we exhale air across our vocal cords, which are muscular tissues.
8.4. Lung Structure
Within the lungs, the two main bronchi each branch into many smaller tubules (bronchioles). The bronchioles branch into even smaller air sacs known as alveoli.
8.5. Organs of the Respiratory Tract – The Lungs
The exchange of oxygen for carbon dioxide in the lungs occurs across the air sacs called alveoli that have walls rich in capillaries. These sacs provide surfaces where gases can diffuse back and forth between the bloodstream and the air space. Specifically, oxygen in newly inhaled air within the alveolar air space will diffuse into the bloodstream; while carbon dioxide, rich in the blood coming into the lungs, will diffuse from the bloodstream into the air space to be exhaled from the body.
8.6. Process of Respiration – How You Breathe
The process of respiration is driven by your breathing. When you inhale, your ribcage moves up and out and the diaphragm contracts to create a vacuum. Air rushes through your nose and mouth, through your conducting tubes, and into your lungs as inspiration. When you exhale, the diaphragm relaxes and air is forced out of the lungs as expiration.
8.7. Smoking and Health
Smoking or breathing in other pollutants can cause a breakdown in the elastic nature of the lungs and the trapping of air. This can lead to a dangerous condition of chronic bronchitis and emphysema. These conditions, including asthma, for which the cause is mainly unknown, are labeled as chronic obstructive pulmonary diseases (COPD).
8.8. Emphysema
In emphysema, air gets trapped over time. The air spaces get bigger and bigger, causing the air space walls to break down and cease to function. When these walls of tissue stop working, the respiratory process is interrupted or incomplete.
8.9. Lung Cancer
Lung cancer is common in smokers. Cancer occurs when pollutants cause a mutation, or change, in the lining of the bronchi. This change leads to an uncontrolled growth of abnormal cells, which can spread over many parts of the body and disrupt body functions.

8. Pause and Interact

9.1. Review
Use the whiteboard tools to create a flow chart that shows the path of oxygen during the process of respiration.
9.2. Respiratory System

9. Cardiovascular System - Transporting Fuel and Waste

10.1. Functions of the Cardiovascular System
Blood represents the only tissue in the body that is all fluid in nature. The heart and blood vessels serve as avenues to transport blood throughout the body. Your blood carries necessary nutrients and oxygen to body tissues, and transports metabolic waste and carbon dioxide away from body tissues.
10.2. Organs of the Circulatory System
At the center of the cardiovascular system is the heart which creates the pressure necessary to pump blood to all parts of the body through the blood vessels. There are three types of blood vessels: arteries, capillaries and veins. These blood vessels transport the blood to and from organ systems.
10.3. Anatomy of the Heart
The highly specialized, muscular heart serves as a pump that moves blood to the lungs and the rest of the body. The heart has four chambers. There are right and left atrial chambers and right and left ventricular chambers. Each atrium is separated from each ventricle by a cuspid valve that serves to keep blood moving in one direction.
10.4. Heart Atria and Ventricles
The right and left atria receive the blood into the heart. The right atrium receives blood from the body, and the left atrium receives blood from the lungs. The two ventricles send the blood out of the heart. The right ventricle sends blood to the lungs. The left ventricle sends blood to the body.
10.5. How the Heart Works
The heart manages the blood flow through its four chambers. The right side of the heart, the right atrium, receives oxygen-poor blood from the body and passes it through to the right ventricle. The right ventricle then pumps the blood to the lungs. The lungs remove the carbon dioxide from the blood and replenish the oxygen. The oxygen-rich blood then returns from the lungs to the left side of the heart, the left atrium. The left atrium passes it on to the left ventricle. The left ventricle pumps blood back out to the rest of the body.
10.6. Blood Circulation Loops
Two separate circulation loops exist in the human body: the pulmonary loop and the body, or systemic, loop. The pulmonary loop is the system of vessels that conducts blood from the heart to the lungs and then back to the heart to oxygenate the blood. The systemic loop conducts blood from the heart to all parts of the body to distribute oxygen and nutrients, and then back to the heart.
10.7. Arteries
Arteries carry oxygenated blood toward body systems, away from the heart. Your arteries are lined with thick layers of tissue because of the high pressure of arterial blood and the need for strong structural support. The largest artery in the human body is the aorta, which branches directly off the chamber of the left ventricle of the heart.
10.8. Capillaries
Arteries branch out into more and more vessels until they reach the thinnest and smallest of vessels known as capillaries. The walls of capillaries are so thin that gases and other molecules can pass easily across their walls into and back from cells and tissues in the area. This is how the blood distributes the oxygen and nutrients to your body’s cells.
10.9. Veins
Veins carry blood back toward the heart. These vessels have thinner walls than arteries because blood is under much lower pressure. Venous blood has been depleted of nutrients and oxygen. It is rich in carbon dioxide and returns back to the right side of the heart, where it will be pumped to the lungs for oxygen.
10.10. Blood Pressure
Blood pressure is a measure of the force blood exerts against the wall of a vessel in units of millimeters of mercury (mmHg). Typical blood pressure is measured across the wall of an artery in the arm and is a reflection of high pressure after heart contraction (systole) and lower pressure with heart relaxation (diastole). Therefore, blood pressure is reported as systolic over diastolic and is normally around 120 over 80 mmHg.

10. Pause and Interact

11.1. Review
Use the whiteboard tools to add arrows and labels to the image. Indicate the flow of blood through the heart.
11.2. Cardiac System

11. Blood

12.1. Components of Blood
Blood is composed of plasma, white blood cells, red blood cells and platelets. Plasma makes up more than half of blood's volume. It is the fluid part of blood, which is mostly water. Plasma also contains nutrients, waste products and protein molecules that give plasma its yellow color. Red and white blood cells make up a little less than half of blood's volume.
12.2. White Blood Cells
One type of blood cell is the leukocyte, or white blood cell. Leukocytes are important defense system cells. They are subdivided into cells with or without granules.
12.3. White Blood Cells with Granules
White blood cells with granules include neutrophils, eosinophils and basophils. Neutrophils, the most common leukocyte, are the most important first line of defense against infections. Eosinophils provide important defense against parasites. Basophils are the least numerous type of leukocyte, but are important in inflammation responses.
12.4. White Blood Cells without Granules
White blood cells without granules include lymphocytes and monocytes. Lymphocytes are very important cells of the body’s immune system. Monocytes help engulf foreign particles such as bacteria.
12.5. Red Blood Cells and Platelets
Erythrocytes, called red blood cells, are not really cells because they do not contain a nucleus. They are highly flexible and contain a very large number of hemoglobin molecules that bind and transport oxygen. Platelets are small, simple cell fragments with a cell membrane around them that are important in the formation of blood clots that help to reduce bleeding.
12.6. Blood Types
Very specific markers known as blood antigens exist on the surface of red blood cells. Antigens carry inherited characteristics and give rise to a person’s specific blood type. Based on the presence or absence of these antigens, an individual’s blood type is defined as A (A antigens present), B (B antigens present), AB (both A and B antigens present), or O (neither A nor B antigens present).
12.7. Blood Donation and Transfusion
Your blood type, as well as other antigen typing, is very important if you ever have to receive a blood transfusion or wish to donate blood. The blood types of donor and receiver must match or the body’s organs might reject the blood and create serious medical problems.
12.8. The Lymphatic System of Vessels and Nodes
Some of the fluid in capillaries moves into the surrounding tissues. The lymphatic system of vessels helps drain this fluid and return it back to the bloodstream. The lymph moves slowly in one direction, toward the heart. Along the way, lymphatic vessels are interrupted by specialized filtration units known as lymph nodes.
12.9. Lymph Nodes
Lymph nodes are rich in lymphocytes designed to filter out foreign material such as bacteria. When you have a sore throat, the lymph nodes below your jaw become enlarged. The lymphocytes are responding to viruses or bacteria being filtered from the fluid draining from your throat into these nodes.

12. Pause and Interact

13.1. Review
Use the whiteboard tools to create a concept map showing the components of blood.

13. Heart Health

14.1. Heart Disease
Heart disease is the number one cause of death in the U.S., most frequently due to coronary artery disease. This disease is the result of an accumulation of thick deposits of fat and calcium on the arterial walls. These deposits block blood flow, cutting off the supply of oxygen to the heart.
14.2. Hypertension – High Blood Pressure
Hypertension is blood pressure that exceeds the normal value of 120/80 mm/Hg and can come about as a result of a variety of factors. In many cases, the underlying cause is not clear. However, poor choices in diet and lifestyle can play major roles in promoting high blood pressure. Obesity, high fat and salt diets, stress, alcohol consumption and smoking are just some of the factors that contribute to hypertension. High blood pressure puts a great strain on the heart because it must pump more forcefully to keep blood moving in the right direction.
14.3. Keeping the Heart Healthy
Regular exercise, proper nutrition, weight control and stress management are just some of the more common ways to help promote a healthy heart. People who exercise regularly have much more efficient hearts and a corresponding blood pressure that reduces stress on heart function.

14. Excretory System - Transporting Waste

15.1. Functions of the Excretory System
The organs of the excretory system help to keep blood volume, body fluids and salts in balance while also helping to eliminate wastes.
15.2. Organs of the Excretory System
The kidneys and the bladder are the main organs of the excretory system. Our kidneys lie in the back of our abdomen and have a rich supply of blood vessels and filtration units. Once urine is formed in the kidneys, it travels down tubes known as ureters to the urinary bladder. Here, urine may be stored until it is released under voluntary control from the body through the tubular urethra.
15.3. Kidney Structure
The kidney is made up of an outer region known as the cortex and an inner region known as the medulla. The kidney is designed to filter the blood and remove waste materials. Therefore it has a very rich supply of blood. Within each kidney, there are over one million mini-filtration and tubular structures called nephrons. The nephrons filter blood, conserve water and form the urine.
15.4. Formation of Urine
Blood enters each of the nephron structures within a specialized capillary bed known as the glomerulus. Here, fluid and other very small particles are forced across the wall of the capillary into the elaborate system of nephron tubules. Nearly 85% of the fluid in the nephrons is reabsorbed back into the bloodstream. What is left in the kidney is waste liquids that become concentrated into urine. Although 180 liters of fluid per day is filtered across both kidneys, 99% of it is reabsorbed. So we only excrete about 1 to 2 liters of urine each day.
15.5. Urinalysis and Kidney Disease
The kidneys are an integral part of several organ systems. Medical testing of urine, called urinalysis, can detect traces of abnormal or illegal substances. The presence of substances in the urine, indicates that they were within the bloodstream, which is important medical information.
15.6. Excretion by Skin, Lungs and Digestive Tract
In addition to the kidneys, fluid may be excreted by the skin, lungs and digestive tract. Water is released as humidified air when we exhale from our lungs. Fluid may also be excreted with the feces from the digestive tract, especially in conditions of infection when diarrhea can lead to excessive loss of body fluids.

15. Pause and Interact

16.1. Review
Use the whiteboard text tool to fill in the functions, organs and potential diseases for each of the systems.
16.2. Excretory System

16. Vocabulary Review

17.1. Vocabulary Matching Review
Blood represents the only tissue in the body that is all fluid in nature. The heart and blood vessels serve as avenues to transport blood throughout the body. Your blood carries necessary nutrients and oxygen to body tissues, and transports metabolic waste and carbon dioxide away from body tissues.

17. Virtual Investigation

18.1. Blood Typing
A person’s blood type can be classified into different types according to the presence or absence of certain antigens. In this lab, you will investigate two of the most commonly used blood classification systems—the ABO blood group and the Rh factor. You will perform blood type tests in order to answer or resolve problems. Three different scenarios are presented—an accident victim in need of a transfusion, a blood donor, and a paternity question.If you would like to explore more background information about blood types, click on the more info button. This section covers the topics of ABO blood group, Rh factor, blood donors and recipients, the blood type test, and blood type inheritance. Use the data sheet to record your observations and results.

18. Assessment

19.1. Human Body 2
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