CTS Guide: Organs and Systems of the Human Body, pp. 104-105- Section IV Research Summaries

Organization of the Body

  • Children recognize that the body is made up of external parts before they appear to understand internal structures. Studies of children’s ideas related to the organization of the human body reveal that between the ages of 8 and 10 children begin to understand that the body is made up of organs that work together to maintain life (Driver et al. 1994).

  • Carey (1985): Young children may think of the human body as a single entity, but by age 10 they begin to understand that it has different functional parts that work together to maintain life.

Digestive System

  • Allen (2014): A common misconception is that the stomach is larger and lower in the body than it really is. Students’ drawings show that it takes up most of the abdomen, with the center of the stomach roughly where the navel is.

  • Millar (2011): While most students recognize the stomach as part of the digestive system, its role is not well-understood. Many students perceive the stomach as the main place where digestion occurs.

  • Teixeira (2000): The word ‘tummy’ is commonly used by children up to age 10 to refer in a non-organ-specific way to the abdominal area. Children up through age 10 10 may not recognize that food is pushed through the digestive tract by waves of muscle contraction (peristalsis), believing instead that gravity and body movements such as walking and bending are responsible for moving food through the digestive tract.

  • Driver et al (1994): Some elementary students have a primitive notion of the digestive system as the palce where “lumps of food” are broken down, juices or acids dissolve the food, and “goodness” is somehow extracted from it. Few children aged 9-12 knew that after food is changed in the stomach it is then broken down into even simpler substances that are carried to tissues throughout the body.

  • Several conceptual difficulties were unrevealed among college biology students about the relationship between digestion and cellular respiration. For example, some students knew that glucose came from food but did not know how it got into cells after food was digested. One student emphatically stated that the bloodstream does not deliver glucose to cells, it only delivers oxygen (Songer 1994).

  • In a study of 131 South African biology teachers, 52.9% of teachers sampled thought digestion provided the energy needed for metabolism in animals (Sanders 1993).

  • In a study conducted by Mintzes (1984), the youngest children up to age seven related the stomach to breathing, blood, strength, and energy. When they are about seven years old, children begin to understand that the stomach helps to break down or digest food and that later the food is transferred somewhere else after being in the stomach.

  • An early study showed that students think that digestion (rather than cellular respiration) is the process that releases useful energy from food. It was thought that perhaps students incorrectly link two ideas: that digestion breaks down food, and that organisms get energy directly from food (Simpson 1984).

Circulatory System

  • Allen (2014):  Allen and other researchers noted common misconceptions about the heart, circulation, and blood including 1) the heart filters or cleans the blood; 2) arteries carry ‘clean’ blood, while veins carry ‘dirty’ blood; 3) arteries only carry oxygenated blood, while veins only carry deoxygenated blood (applying a ‘rule of thumb’ that ignores the direction of blood flow relative to the heart, and also ignores arteries and veins carrying blood to and from the lungs);and 4) deoxygenated/venous blood is blue in color and arterial blood is red.

  • A common belief is that the reason the our breathing rate increases during exercise is so that the heart can pump more oxygen from our lungs to the muscles (Allen, 2014).

  • ·Several studies have described misunderstandings students have about blood and the circulatory system. Some of these misunderstandings even persist up to the college level and include the idea that our heart filters, stores, and makes blood  (Özgür, 2013).

  • Bartoszeck, Machado and Amann-Gainotti (2011): Misunderstandings about the human circulatory system that are commonly observed in science classrooms include the idea that the heart is located on the left side of the chest (rather than in the center), and that it has a cartoon-like or emoji-like heart shape.

 Nervous System

  • Johnson and Wellman (1982): Children and adults, when questioned about the brain and activities that involve the brain, most knew the brain as an internal organ and some regarded the mind as additional to the brain. The brain was regarded as a mental organ necessary for thinking, dreaming, remembering, and knowing facts. However, the brain was not always recognized as needed for overt behaviors. Young children associate the brain with feelings (emotions) but not with senses. Only older children associated the brain with both voluntary and involuntary acts. Elementary age children recognize the brain as needed for many activities. By age 10 most children recognize the brain as helping other body parts function. By age 14 the brain was recognized as essential for all behaviors. 

  •  Gellert (1962) and Cary (1985): Elementary age children have little knowledge of nerves.

Muscles and Skeleton

  • Bartoszeck, Machado and Amann-Gainotti (2011):  When children up to age 15 were asked to draw what is inside the human body, most drew organs but very few drew muscles, and when muscles were drawn, they were commonly only depicted in the limbs. 

  • It is a common misunderstanding among students of all ages that bone is not alive, even when it is inside an organism. This may come from their experience in seeing bones in skeletons and associating skeletons with death (Caravita and Falchetti, 2005).

  • Tunnicliffe and Reiss (1999): Students struggle up to age 20 to appreciate that bones do not exist as separate, individual structures, but are connected to make a functional skeleton . While young children recognize that the skeleton supports and protects, older children understand that the skeleton is necessary for movement.

  • Movement is a common criterion students use to decide if something is living (Driver et. al 1994). Because students recognize that muscles are used for movement, they may more readily identify muscles as living tissue. There is little evidence that school age children recognize that muscles are invilved in the digestive, circulatory, and respiratory systems.

  • Caravita and Tonucci (1987): Children do not relate muscles to meat.

Respiratory System

  • Bartoszeck, Machado and Amann-Gainotti (2011): At age 11 students are aware that there are “air tubes” that link the mouth to the lungs and that humans have 2 lungs in their chest. However, some students also believe that there are similar ‘air tubes’ that connect the lungs to the heart and that this is how oxygen from air enters the blood.

Excretory System

  • Din-Yan (1998): In a study of high school biology students understanding of the excretory process, few viewed exhalation as an excretory process. There was a prevalent view that undigested food (feces) is removed by the excretory system which suggests that students do not understand the idea of metabolic waste. Some students viewed secretions, such as saliva, as an excretory process which suggests confusion about the roles of secretion and excretion in biological processes.