Topic: Human Body Systems

Below is a list of key ideas related to Human Body Systems. For each key idea, you will find a list of sub-ideas, a list of items, results from our field testing, and a list of student misconceptions. After clicking on a tab, click on it again to close the tab.

Oxygen, carbon dioxide, and molecules from food are carried to or from cells of the body by means of the circulatory system.

Students are expected to know that:

  1. The circulatory system is made up of a variety of blood vessels, which carry blood throughout the body.
  2. Blood stays within a system of blood vessels: arteries, veins, and microscopically small blood vessels called capillaries.
  3. Larger diameter blood vessels branch into progressively smaller blood vessels and eventually into microscopically small blood vessels known as capillaries.
  4. Blood carries needed molecules (e.g., simple sugars, amino acids, fatty acids, and oxygen) to cells of the body and carries carbon dioxide and other waste molecules away from cells of the body.
  5. Small molecules such as amino acids, simple sugars, fatty acids, oxygen, and carbon dioxide (but not large molecules like proteins, complex carbohydrates, and fat molecules) can cross the capillary walls.
  6. Small molecules can pass through capillary walls but not through the walls of other blood vessels.
  7. Capillaries are spread out throughout the entire body (and are in very close proximity to each of the cells of the body) so that needed molecules can get to the cells and waste materials can be removed from the cells.
  8. All cells receive molecules from food by way of the circulatory system.

Boundaries:

  1. The terms capillaries, veins, and arteries will be defined for students when they are used in the items.
  2. Students are not expected to know the names of waste molecules other than carbon dioxide.
  3. Students are not expected to know that white blood cells can pass (by squeezing) through capillary walls.
  4. Students are not expected to know the names or functions of the components of blood (e.g., red blood cells, white blood cells, plasma).
Percent of students answering correctly (click on the item ID number to view the item and additional data)
Item ID
Number

Knowledge Being Assessed

Grades
6–8

Grades
9–12

Select This Item for My Item Bank

BF051004

Blood carries oxygen to cells and carries carbon dioxide away from cells.

56%

64%

BF135001

Blood stays within blood vessels and moves to all parts of the body.

51%

58%

BF122003

Blood stays within blood vessels and moves to all parts of the body.

49%

56%

BF075004

Blood carries both oxygen molecules and simple sugar molecules to cells of your leg muscles.

46%

58%

BF134001

Molecules from food and molecules of oxygen are carried by a network of arteries, veins, and microscopically small blood vessels (capillaries) to the rest of the body.

46%

56%

BF018005

Small molecules like amino acids can pass through capillary walls but large molecules like proteins cannot.

42%

55%

BF136001

Small molecules like amino acids can pass through capillary walls, but large molecules like proteins cannot.

43%

47%

BF016005

Oxygen is carried by blood to cells of the body, but carbon dioxide is not carried by the blood to cells of the body.

41%

48%

BF095004

Capillaries are found in body organs such as the brain, lungs, and intestines, and capillaries are also found inside external parts of the body such as arms, legs, hands, and feet.

35%

40%

BF056006

Capillaries allow small molecules like amino acids to pass through their walls but not large molecules like proteins. Molecules do not pass through the walls of large blood vessels.

35%

38%

BF144002

Molecules from food travel from the mouth to the digestive tract and then travel through a series of blood vessels to the cells in the rest of the body.

31%

39%

BF057007

Molecules pass through the walls of microscopically small blood vessels but not through the walls of large blood vessels.

28%

30%

BF126001

Neither large molecules like proteins nor small molecules like amino acids can pass through the walls of arteries and veins.

14%

14%

Frequency of selecting a misconception

Misconception
ID Number

Student Misconception

Grades
6–8

Grades
9–12

BFM040

Air is distributed through the body in air tubes (Arnaudin & Mintzes, 1985; Catherall, 1982).

46%

39%

BFM031

Molecules from food are distributed by way of special tubes, not by way of the circulatory system, to the rest of the body (Catherall, 1982).

43%

38%

BFM070

Blood does not carry simple sugar molecules to the cells of the body.

38%

31%

BFM065

Blood flows freely through the walls of blood vessels.

35%

33%

BFM010

Carbon dioxide, oxygen, water, and molecules from food pass directly through the walls of arteries and veins to and from other parts of the body rather than through the walls of the capillaries (Minstrell, 2005).

32%

33%

BFM057

Capillaries are found only in internal organs, such as the lungs and the intestines (AAAS Project 2061, n.d.).

30%

28%

BFM051

Anything can pass through the walls of capillaries (AAAS Project 2061, n.d.).

25%

22%

BFM056

Capillaries are found only in the extremities, such as the hands and feet (AAAS Project 2061, n.d.).

23%

23%

BFM053

Blood does not carry oxygen to the cells of the body (AAAS Project 2061, n.d.).

25%

17%

BFM050

Nothing can pass through the walls of capillaries (AAAS Project 2061, n.d.).

12%

13%

BFM064

Molecules from food move directly from the mouth to the rest of the body without going through any kind of tubes.

8%

5%

BFM063

Molecules of oxygen move directly from the mouth and nose to the rest of the body without going through any kind of tubes.

8%

5%

BFM027

Food is free in the body (no links to digestive structures) (Carvalho et al., 2004).

8%

5%

Frequency of selecting a misconception was calculated by dividing the total number of times a misconception was chosen by the number of times it could have been chosen, averaged over the number of students answering the questions within this particular idea.

Most of the carbohydrates, fats, and proteins from the food humans eat must be broken down into smaller molecules before they can enter cells to be used for energy and building materials.

Students are expected to know that:

  1. Most of the food that humans eat is made up of large molecules (fats, proteins, and complex carbohydrates) that are too big to get to the cells of the body where they can be used for energy and building materials.
  2. These large molecules are made up of subunits, which are smaller molecules of the same type that are linked together.Fatty acids are subunits of fats, amino acids are subunits of proteins, and simple sugars are subunits of complex carbohydrates.Carbon dioxide is not a subunit of fats, proteins, or complex carbohydrates.
  3. Some molecules from food (e.g., simple sugars, fatty acids, and amino acids) are already small enough to get to the cells of the body without being broken down into smaller molecules.
  4. Digestion is the process of breaking larger molecules into their subunits. The subunits are called the products of digestion.
  5. Digestion does not include the breaking down of food into molecules of carbon dioxide and water.
Boundaries:
  1. Students are not expected to know that glycerol is also a subunit of fats.
  2. Students are not expected to know the chemical formulas of complex carbohydrates, fats, proteins, simple sugars, fatty acids, or amino acids.
  3. Students are not expected to know the term “macromolecules.”

Lungs take in oxygen molecules and eliminate carbon dioxide molecules.

Students are expected to know that:

  1. The air that is taken in through the lungs contains oxygen molecules that react chemically with molecules from food. The carbon dioxide molecules that are produced when molecules from food react with oxygen molecules leave the body through the lungs.
  2. The lungs are connected to the nose and the mouth by means of a tube that carries air. This tube is separate from the tube that carries food to the stomach.
  3. The tube that carries air between the mouth and nose and lungs branches into progressively smaller tubes, and these branching tubes end in many small pouches. These branching tubes and pouches make up the internal structure of the lungs.
  4. The small pouches are in close enough proximity to the capillaries so that oxygen molecules and carbon dioxide molecules can move between the pouches of the lungs and the circulatory system (through the capillary walls).
  5. The large number of small pouches in the lungs creates a large surface area for oxygen molecules and carbon dioxide molecules to move across. When the number of functioning pouches is reduced, the surface area of the lungs and the capacity of the lungs to exchange oxygen molecules and carbon dioxide molecules are also reduced.
  6. Oxygen molecules move from the small pouches of the lungs to the capillaries, and carbon dioxide molecules move from the capillaries to the small pouches of the lungs. As a result, the blood in vessels approaching the lungs has more carbon dioxide and less oxygen than the blood in vessels that has just left the lungs. Note: “move” is being used to represent the net flow of molecules.

Boundaries:

  1. Students are not expected to know the size or capacity of the lungs or the mechanics of how a person breathes.
  2. Students are not expected to know the terms “trachea” or “alveoli.”
  3. Students are not expected to know how oxygen is carried in the blood (i.e., by red blood cells or hemoglobin in the red blood cells).
  4. Students are not expected to know how carbon dioxide is carried in the blood (i.e., that some of the carbon dioxide is carried by hemoglobin, some as dissolved carbonate ions, and some as dissolved carbon dioxide gas).
  5. Students are not expected to know that oxygen molecules and carbon dioxide molecules move in both directions (both from the small pouches of the lungs to the capillaries and vice versa).
Frequency of selecting a misconception

Misconception
ID Number

Student Misconception

Grades
6–8

Grades
9–12

BFM044

The heart is the mixing place for air and blood (Catherall, 1982).

38%

41%

BFM042

Blood gets oxygen from the lungs, but does not transfer carbon dioxide to the lungs (Minstrell, 2005).

24%

19%

BFM078

The lungs do not eliminate carbon dioxide from the body.

20%

16%

BFM069

The respiratory system and the circulatory system are not connected.

12%

9%

BFM077

The lungs do not take in oxygen for the body to to use.

7%

5%

Frequency of selecting a misconception was calculated by dividing the total number of times a misconception was chosen by the number of times it could have been chosen, averaged over the number of students answering the questions within this particular idea.

Oxygen, carbon dioxide, and molecules from food are carried to or from cells of the body by means of the circulatory system.
-and-
Molecules from food are broken down into smaller molecules in the digestive tract and then enter the circulatory system by way of capillaries located in the lining of the digestive tract.

These items have been aligned to more than one key idea. To view the sub-ideas click on a key idea below.

  • Oxygen, carbon dioxide, and molecules from food are carried to or from cells of the body by means of the circulatory system.

    Students are expected to know that:

    1. The circulatory system is made up of a variety of blood vessels, which carry blood throughout the body.
    2. Blood stays within a system of blood vessels: arteries, veins, and microscopically small blood vessels called capillaries.
    3. Larger diameter blood vessels branch into progressively smaller blood vessels and eventually into microscopically small blood vessels known as capillaries.
    4. Blood carries needed molecules (e.g., simple sugars, amino acids, fatty acids, and oxygen) to cells of the body and carries carbon dioxide and other waste molecules away from cells of the body.
    5. Small molecules such as amino acids, simple sugars, fatty acids, oxygen, and carbon dioxide (but not large molecules like proteins, complex carbohydrates, and fat molecules) can cross the capillary walls.
    6. Small molecules can pass through capillary walls but not through the walls of other blood vessels.
    7. Capillaries are spread out throughout the entire body (and are in very close proximity to each of the cells of the body) so that needed molecules can get to the cells and waste materials can be removed from the cells.
    8. All cells receive molecules from food by way of the circulatory system.

    Boundaries:

    1. The terms capillaries, veins, and arteries will be defined for students when they are used in the items.
    2. Students are not expected to know the names of waste molecules other than carbon dioxide.
    3. Students are not expected to know that white blood cells can pass (by squeezing) through capillary walls.
    4. Students are not expected to know the names or functions of the components of blood (e.g., red blood cells, white blood cells, plasma).
  • Molecules from food are broken down into smaller molecules in the digestive tract and then enter the circulatory system by way of capillaries located in the lining of the digestive tract.

    Students are expected to know that:

    1. Digestion takes place in body organs (e.g., mouth, stomach, intestines) that collectively are known as the digestive tract.
    2. The food humans eat moves from the mouth to the stomach by way of a tube that is separate from the tube that carries air to and from the lungs.
    3. The breakdown of food into smaller molecules usually involves a combination of mechanical processes (mechanical digestion) and chemical reactions (chemical digestion).
    4. During mechanical digestion, more of the carbohydrate, fat, and protein molecules from food come in contact with digestive enzymes, which increases the number of carbohydrate, fat, and protein molecules that are chemically broken down.
    5. Examples of mechanical digestion include chewing food in the mouth and mixing food in the stomach.
    6. Molecules that result from the digestion of carbohydrate and protein molecules leave the digestive tract and enter the circulatory system by way of the capillaries located in the lining of the digestive tract.
    7. Not everything that we eat is digested: In some cases mechanical digestion is incomplete (e.g., inadequate chewing of food) so that digestive enzymes cannot come in contact with the molecules from food. In other cases, the body does not have the digestive enzymes needed to break down the molecules that we eat (e.g., cellulose). In still other cases, some of the molecules from food do not have to be digested because they are already small enough to enter the circulatory system and cells of the body.
    8. Undigested fats, proteins, complex carbohydrates or other undigested material that is too large to be used by the cells of the body leave the body at the end of the digestive tract.

    Boundaries:

    1. Students are not expected to know he terms “alimentary canal,” “esophagus,” “small intestine,” or“large intestine.”
    2. Students are not expected to know that most chemical digestion and absorption occurs in the small intestine.
    3. Students are not expected to know the different types of digestive enzymes or the specific role they play in chemical digestion.
    4. Students are not expected to know when digestion involves primarily chemical reactions or primarily mechanical processes.
    5. Students are not expected to know that stomach acid and bile are also molecules involved in chemical digestion.
    6. Students are not expected to know the role of microorganisms in digestion.
    7. Students are not expected to know that fatty acids enter the blood stream through the lymphatic system.
    8. Students are not expected to know that dipeptides are molecules that are small enough to enter capillaries.
Percent of students answering correctly (click on the item ID number to view the item and additional data)
Item ID
Number

Knowledge Being Assessed

Grades
6–8

Grades
9–12

Select This Item for My Item Bank

BF123003

Molecules from food are absorbed into microscopically small blood vessels (capillaries) located in the walls of the digestive tract and then pass into larger blood vessels that carry the molecules to other parts of the body.

39%

49%

BF012006

Molecules from food get from the digestive tract to the cells of the brain and the cells of the skin by way of the circulatory system.

36%

43%

BF127001

The circulatory system carries products of protein digestion from the digestive tract to cells of both the brain and cells of the skin.

34%

43%

BF039008

After a boy eats a sandwich, there are fewer molecules from food in the blood approaching the digestive tract and more molecules from food in the blood moving away from the digestive tract.

33%

41%

BF129001

The circulatory system carries amino acids from the digestive tract to cells of both the brain and the skin.

35%

37%

BF130001

The circulatory system carries simple sugars from the digestive tract to cells of both the brain and the skin.

33%

38%

BF128001

The circulatory system carries products of carbohydrate digestion from the digestive tract to cells of both the brain and the skin.

34%

37%

BF131001

The circulatory system carries products of digestion from the digestive tract to cells of both the brain and the skin.

32%

40%

BF132001

Molecules from food are absorbed through the walls of microscopically small blood vessels (capillaries). These molecules then move through the circulatory system to all parts of the body.

31%

33%

BF137001

Molecules from food in the digestive tract are absorbed through the walls of capillaries. These molecules then move through the circulatory system to all parts of the body.

29%

24%

BF038004

Amino acids enter the circulatory system from the digestive system by passing through the walls of microscopically small blood vessels (capillaries), but proteins do not.

23%

30%

Frequency of selecting a misconception

Misconception
ID Number

Student Misconception

Grades
6–8

Grades
9–12

BFM031

Molecules from food are distributed by way of special tubes, not by way of the circulatory system, to the rest of the body (Catherall, 1982).

40%

36%

BFM051

Anything can pass through the walls of capillaries (AAAS Project 2061, n.d.).

36%

37%

BFM067

Molecules from food are absorbed through the walls of large blood vessels such as veins and arteries (Minstrell, 2005).

28%

32%

BFM028

The digestive system and the circulatory system are not connected (Buckley, 2000; Carvalho et al., 2004).

24%

22%

BFM080

Molecules from food do not get to the cells of the body by way of the circulatory system.

23%

22%

Frequency of selecting a misconception was calculated by dividing the total number of times a misconception was chosen by the number of times it could have been chosen, averaged over the number of students answering the questions within this particular idea.

Most of the carbohydrates, fats, and proteins from the food humans eat must be broken down into smaller molecules before they can enter cells to be used for energy and building materials.
-and-
Molecules from food are broken down into smaller molecules in the digestive tract and then enter the circulatory system by way of capillaries located in the lining of the digestive tract.

These items have been aligned to more than one key idea. To view the sub-ideas click on a key idea below.

  • Most of the carbohydrates, fats, and proteins from the food humans eat must be broken down into smaller molecules before they can enter cells to be used for energy and building materials.

    Students are expected to know that:

    1. Most of the food that humans eat is made up of large molecules (fats, proteins, and complex carbohydrates) that are too big to get to the cells of the body where they can be used for energy and building materials.
    2. These large molecules are made up of subunits, which are smaller molecules of the same type that are linked together.Fatty acids are subunits of fats, amino acids are subunits of proteins, and simple sugars are subunits of complex carbohydrates.Carbon dioxide is not a subunit of fats, proteins, or complex carbohydrates.
    3. Some molecules from food (e.g., simple sugars, fatty acids, and amino acids) are already small enough to get to the cells of the body without being broken down into smaller molecules.
    4. Digestion is the process of breaking larger molecules into their subunits. The subunits are called the products of digestion.
    5. Digestion does not include the breaking down of food into molecules of carbon dioxide and water.
    Boundaries:
    1. Students are not expected to know that glycerol is also a subunit of fats.
    2. Students are not expected to know the chemical formulas of complex carbohydrates, fats, proteins, simple sugars, fatty acids, or amino acids.
    3. Students are not expected to know the term “macromolecules.”
  • Molecules from food are broken down into smaller molecules in the digestive tract and then enter the circulatory system by way of capillaries located in the lining of the digestive tract.

    Students are expected to know that:

    1. Digestion takes place in body organs (e.g., mouth, stomach, intestines) that collectively are known as the digestive tract.
    2. The food humans eat moves from the mouth to the stomach by way of a tube that is separate from the tube that carries air to and from the lungs.
    3. The breakdown of food into smaller molecules usually involves a combination of mechanical processes (mechanical digestion) and chemical reactions (chemical digestion).
    4. During mechanical digestion, more of the carbohydrate, fat, and protein molecules from food come in contact with digestive enzymes, which increases the number of carbohydrate, fat, and protein molecules that are chemically broken down.
    5. Examples of mechanical digestion include chewing food in the mouth and mixing food in the stomach.
    6. Molecules that result from the digestion of carbohydrate and protein molecules leave the digestive tract and enter the circulatory system by way of the capillaries located in the lining of the digestive tract.
    7. Not everything that we eat is digested: In some cases mechanical digestion is incomplete (e.g., inadequate chewing of food) so that digestive enzymes cannot come in contact with the molecules from food. In other cases, the body does not have the digestive enzymes needed to break down the molecules that we eat (e.g., cellulose). In still other cases, some of the molecules from food do not have to be digested because they are already small enough to enter the circulatory system and cells of the body.
    8. Undigested fats, proteins, complex carbohydrates or other undigested material that is too large to be used by the cells of the body leave the body at the end of the digestive tract.

    Boundaries:

    1. Students are not expected to know he terms “alimentary canal,” “esophagus,” “small intestine,” or“large intestine.”
    2. Students are not expected to know that most chemical digestion and absorption occurs in the small intestine.
    3. Students are not expected to know the different types of digestive enzymes or the specific role they play in chemical digestion.
    4. Students are not expected to know when digestion involves primarily chemical reactions or primarily mechanical processes.
    5. Students are not expected to know that stomach acid and bile are also molecules involved in chemical digestion.
    6. Students are not expected to know the role of microorganisms in digestion.
    7. Students are not expected to know that fatty acids enter the blood stream through the lymphatic system.
    8. Students are not expected to know that dipeptides are molecules that are small enough to enter capillaries.
Percent of students answering correctly (click on the item ID number to view the item and additional data)
Item ID
Number

Knowledge Being Assessed

Grades
6–8

Grades
9–12

Select This Item for My Item Bank

BF003005

If a person could not digest food anymore, the person would lose weight because most of the molecules from food could not be used for building materials.

32%

38%

Frequency of selecting a misconception

Misconception
ID Number

Student Misconception

Grades
6–8

Grades
9–12

BFM058

If food could not be digested, it would stay in the body and would not be eliminated (AAAS Project 2061, n.d.).

42%

40%

BFM059

Digestion helps us use food but it is not necessary for us to use food (AAAS Project 2061, n.d.).

19%

17%

BFM060

Digestion does not affect the way food is used by the body (AAAS Project 2061, n.d.).

6%

5%

Frequency of selecting a misconception was calculated by dividing the total number of times a misconception was chosen by the number of times it could have been chosen, averaged over the number of students answering the questions within this particular idea.

Oxygen, carbon dioxide, and molecules from food are carried to or from cells of the body by means of the circulatory system.
-and-
Molecules from food are broken down into smaller molecules in the digestive tract and then enter the circulatory system by way of capillaries located in the lining of the digestive tract.
-and-
Lungs take in oxygen molecules and eliminate carbon dioxide molecules.

These items have been aligned to more than one key idea. To view the sub-ideas click on a key idea below.

  • Oxygen, carbon dioxide, and molecules from food are carried to or from cells of the body by means of the circulatory system.

    Students are expected to know that:

    1. The circulatory system is made up of a variety of blood vessels, which carry blood throughout the body.
    2. Blood stays within a system of blood vessels: arteries, veins, and microscopically small blood vessels called capillaries.
    3. Larger diameter blood vessels branch into progressively smaller blood vessels and eventually into microscopically small blood vessels known as capillaries.
    4. Blood carries needed molecules (e.g., simple sugars, amino acids, fatty acids, and oxygen) to cells of the body and carries carbon dioxide and other waste molecules away from cells of the body.
    5. Small molecules such as amino acids, simple sugars, fatty acids, oxygen, and carbon dioxide (but not large molecules like proteins, complex carbohydrates, and fat molecules) can cross the capillary walls.
    6. Small molecules can pass through capillary walls but not through the walls of other blood vessels.
    7. Capillaries are spread out throughout the entire body (and are in very close proximity to each of the cells of the body) so that needed molecules can get to the cells and waste materials can be removed from the cells.
    8. All cells receive molecules from food by way of the circulatory system.

    Boundaries:

    1. The terms capillaries, veins, and arteries will be defined for students when they are used in the items.
    2. Students are not expected to know the names of waste molecules other than carbon dioxide.
    3. Students are not expected to know that white blood cells can pass (by squeezing) through capillary walls.
    4. Students are not expected to know the names or functions of the components of blood (e.g., red blood cells, white blood cells, plasma).
  • Molecules from food are broken down into smaller molecules in the digestive tract and then enter the circulatory system by way of capillaries located in the lining of the digestive tract.

    Students are expected to know that:

    1. Digestion takes place in body organs (e.g., mouth, stomach, intestines) that collectively are known as the digestive tract.
    2. The food humans eat moves from the mouth to the stomach by way of a tube that is separate from the tube that carries air to and from the lungs.
    3. The breakdown of food into smaller molecules usually involves a combination of mechanical processes (mechanical digestion) and chemical reactions (chemical digestion).
    4. During mechanical digestion, more of the carbohydrate, fat, and protein molecules from food come in contact with digestive enzymes, which increases the number of carbohydrate, fat, and protein molecules that are chemically broken down.
    5. Examples of mechanical digestion include chewing food in the mouth and mixing food in the stomach.
    6. Molecules that result from the digestion of carbohydrate and protein molecules leave the digestive tract and enter the circulatory system by way of the capillaries located in the lining of the digestive tract.
    7. Not everything that we eat is digested: In some cases mechanical digestion is incomplete (e.g., inadequate chewing of food) so that digestive enzymes cannot come in contact with the molecules from food. In other cases, the body does not have the digestive enzymes needed to break down the molecules that we eat (e.g., cellulose). In still other cases, some of the molecules from food do not have to be digested because they are already small enough to enter the circulatory system and cells of the body.
    8. Undigested fats, proteins, complex carbohydrates or other undigested material that is too large to be used by the cells of the body leave the body at the end of the digestive tract.

    Boundaries:

    1. Students are not expected to know he terms “alimentary canal,” “esophagus,” “small intestine,” or“large intestine.”
    2. Students are not expected to know that most chemical digestion and absorption occurs in the small intestine.
    3. Students are not expected to know the different types of digestive enzymes or the specific role they play in chemical digestion.
    4. Students are not expected to know when digestion involves primarily chemical reactions or primarily mechanical processes.
    5. Students are not expected to know that stomach acid and bile are also molecules involved in chemical digestion.
    6. Students are not expected to know the role of microorganisms in digestion.
    7. Students are not expected to know that fatty acids enter the blood stream through the lymphatic system.
    8. Students are not expected to know that dipeptides are molecules that are small enough to enter capillaries.
  • Lungs take in oxygen molecules and eliminate carbon dioxide molecules.

    Students are expected to know that:

    1. The air that is taken in through the lungs contains oxygen molecules that react chemically with molecules from food. The carbon dioxide molecules that are produced when molecules from food react with oxygen molecules leave the body through the lungs.
    2. The lungs are connected to the nose and the mouth by means of a tube that carries air. This tube is separate from the tube that carries food to the stomach.
    3. The tube that carries air between the mouth and nose and lungs branches into progressively smaller tubes, and these branching tubes end in many small pouches. These branching tubes and pouches make up the internal structure of the lungs.
    4. The small pouches are in close enough proximity to the capillaries so that oxygen molecules and carbon dioxide molecules can move between the pouches of the lungs and the circulatory system (through the capillary walls).
    5. The large number of small pouches in the lungs creates a large surface area for oxygen molecules and carbon dioxide molecules to move across. When the number of functioning pouches is reduced, the surface area of the lungs and the capacity of the lungs to exchange oxygen molecules and carbon dioxide molecules are also reduced.
    6. Oxygen molecules move from the small pouches of the lungs to the capillaries, and carbon dioxide molecules move from the capillaries to the small pouches of the lungs. As a result, the blood in vessels approaching the lungs has more carbon dioxide and less oxygen than the blood in vessels that has just left the lungs. Note: “move” is being used to represent the net flow of molecules.

    Boundaries:

    1. Students are not expected to know the size or capacity of the lungs or the mechanics of how a person breathes.
    2. Students are not expected to know the terms “trachea” or “alveoli.”
    3. Students are not expected to know how oxygen is carried in the blood (i.e., by red blood cells or hemoglobin in the red blood cells).
    4. Students are not expected to know how carbon dioxide is carried in the blood (i.e., that some of the carbon dioxide is carried by hemoglobin, some as dissolved carbonate ions, and some as dissolved carbon dioxide gas).
    5. Students are not expected to know that oxygen molecules and carbon dioxide molecules move in both directions (both from the small pouches of the lungs to the capillaries and vice versa).
Percent of students answering correctly (click on the item ID number to view the item and additional data)
Item ID
Number

Knowledge Being Assessed

Grades
6–8

Grades
9–12

Select This Item for My Item Bank

BF133001

Molecules from food and molecules of oxygen move from the mouth and the nose to cells of the body through a series of blood vessels, including veins, arteries, and microscopically small blood vessels (capillaries), that extend throughout the body.

32%

33%