Topic: Digestive system

Author: Elżbieta Szedzianis

Target group

7th grade students of an eight‑year elementary school.

Core curriculum

4. Digestive system and nutrition. Student:

1) enumerates and identifies (on a schematic drawing, a drawing, a model, according to a description, etc.) elements of a digestive system; presents their functions and defines the connection between the construction of these elements and their function;

2) identifies (on a schematic drawing, a drawing, a model, according to a description, etc.) types of teeth and describes their meaning in mechanical processing of food; presents the reasons for caries and how to prevent it.

Lesson aim

The students describe the build of the digestive tract and its functions.

Key Success Criteria

• you will name the organs of a digestive system and show where they are located in your body;

• you will explain what mechanical digestion involves;

• you will talk about the functions of the digestive system.

Key competences

• communicating in the mother tongue;

• communicating in a foreign language;

• Mathematical competence and basic competences in science and technology; 

• digital competence;

• learning to learn;

• Social and civic competences.

Methods/forms of work:

Work with text, work with film, a talk, Instant Information method.

Individual and group work.

Teaching measures:

• abstract;

• interactive whiteboard or traditional blackboard;

• tablets/computers;

• metodnik (type of a teacher’s book).

Lesson plan overview (Process)

Introduction

1. The teacher gives the topic of the lesson, then, using an accessible language, explains to the students the aim of the lesson, and shows them the success criteria.

2. He asks the students to recall the meaning of terms like “organ system”, “organ”, “cellular nutrition”, and to name the organs that belong to the digestive system.

Realization

1. The teacher presents the illustration that shows the digestive system. He then asks the students to identify the organs that belong to the digestive system and write their names on the board. Then, the students look for descriptions of these organs the were not able to name in the abstract. They also write them down on the board.

2. The students show the position of each of the organs on their bodies. The teacher emphasises the placement of the liver.

3. He then asks the students to explain the notion “digestive tract” and “digestive system”. He helps the students out by asking them, whether the food “enters” the liver, the pancreas and the salivary glands.

4. Students complete interactive exercises.

5. The teacher divides students into groups. Their task is to write a single sentence that explains the functions of the digestive system. They should do it in such a way that a six‑year‑old could understand the explanation. When the time for this exercise is up, the group representatives read out their sentences. The teacher writes down on the board that sentence that, in his opinion, was the best one when it comes to its content and phrasing.

6. The students watch a fragment of the following movie from the Internet titled „Było Sobie Zycie - Kubki Smakowe I Zęby (Wyciąg)” (3:30–4:00). The teacher then asks them to write down the connection between the build and the functions of all the types of teeth that are mentioned in the fragment of the movie, according to the following pattern: feature of the build - function that stems from it.

7. The teacher explains that the mechanical digestion takes place in the oral cavity and stomach. He asks the students what it means exactly.

8. The teacher shows the students a movie from the Internet titled „Peristaltic Wave in the Gastric Antrum”, and asks them to comment on it.

Summary

1. The students, applying the method of “instant information”, describe the digestive tract.

2. The students assess the knowledge they gained using the teaching aid called metodnik. The teacher explains ideas that are not clear for the students.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Digestive system

The digestive system is responsible for the intake and the digestion of food, as well as the absorption of the nutrients in that food. It is composed of the digestive tract, through which food passes (and in its final part the undigested food elements), and the glands that are connected with the tract: salivary glands, liver and pancreas.

Food processed by the teeth is mixed by the tongue with saliva – the product of the salivary glands. The amount of saliva depends on the pH and the consistency of the food. Acidic and dry food increases the amount of saliva produced. The mucus in saliva softens the processed food, glues it together, facilitates the forming of chunks of food and swallowing them. In the saliva there are also bactericidal substances that kill germs which reach the oral cavity with the food; substances that neutralize acidic ingredients (to protect the enamel) and digestive enzymes.

Oral cavity is connected with the throat. It is a joint section of both the digestive and the respiratory tract. Behind the throat there is the larynx, an organ that belongs to the respiratory system. Usually, the entrance to the larynx remains open (when we talk or breathe). When we swallow, the entrance to the larynx becomes closed by a cartilage called epiglottis. It prevents the food from accessing the respiratory system and causes it to pass straight to the oesophagus.

Oesophagus is a muscled tube that leads to the stomach. The smooth muscles that are present in the oesophagus and throat contract regularly, causing peristalsis that moves food into the stomach.

Stomach is situated in the abdominal cavity, below the sternum, towards left. It is a type of a tank with the capacity of 1,5 litre in which food is stored (for up to 8 hours) and chemically processed. The stomach wall has glands that secrete gastric juice, which consists mainly of digestive enzymes and hydrochloric acid. The latter destroys swallowed microbes and causes the muscles of the stomach wall to contract, which facilitates the mixing of food with the digestive enzymes and the movement of food towards the intestine. The mucus produced in the stomach protects its walls from damage caused by the acidic gastric acid and the digestive glands (self‑digestion).

The middle part of the digestive tract, and also its longest part, is the small intestine that is over 6 m long, and which initial part is called duodenum. It is situated in the abdominal cavity, right below the stomach. Here, the next stage of digestion takes place. The walls of the small intestine have glans that secrete, among other things, digestive enzymes.
Liver and pancreas are equipped with pipes which open into the duodenum.

Liver is the biggest gland of the body, and it is situated in the upper part of the abdominal cavity, to the right. It produces and secretes bile, which flows to the gallbladder, where it is temporary stored and thickened. Intense metabolic processes take place in the liver, which is why the blood that flows through it is heated up and then distributed throughout the entire body. This is how the liver participates in keeping stable body temperature. The liver is a type of filter through which the food that was absorbed from the intestine to the blood passes through. Before it reaches the cells, it has to be clean from poisons, e.g. alcohol and ingredients of medicines.

Pancreas is a gland that is situated below the stomach and has two important functions: endocrine - it produces hormones, and exocrine - it produces digestive enzymes.

Nutrients are absorbed in the intestine. The interior surface of the intestine is wrinkled. There are numerous finger‑like projections present in the intestine - the intestinal villi, which are covered by even smaller projections - microvilli. The folds of the villi create a huge surface for absorption - it is close in size to the surface of a tennis court (around 300 square metres). Inside the villi, there are villus capillaries and villus lacteals (lymph capillary), which absorb nutrients. The final place the digested food reaches are the cells of the body. Food is transported there via blood.

The border between the small intestine and the last part of the digestive tract - large intestine - is where caecum is, which is joined to the appendix. In herbivore mammals, the caecum is well‑developed, as it is where cellulose is digested. In case of humans (as an example of an omnivore), this organ is reduced and it is a dead‑end pouch (vestigial organ). Sometimes, when the appendix receives nutrients and they are stored there for some time, they start fermenting and an inflammation begins. Treatment in such cases involves surgical extraction of the infected organ.

In the large intestine there around 500 types of bacteria, which create a specific intestinal microflora. They digest the ingredients that are not absorbed by humans. This process creates a liquid mass from which water is taken out and faecal mass is formed. Thanks to peristaltic movements of the large intestine these masses are moved towards the last part of the large intestine - rectum and through anus, they are expelled from our body.

• Digestive system is responsible for the intake, digestion and absorption of nutrients and the expulsion of undigested food.

• Digestive system consists of digestive tract and digestive glands connected with it.

• The movement of food along the digestive tract takes place thanks to peristaltic movements.

• The stomach's food is mixed and crushed and partially digested

• The first part of the small intestine is called duodenum, and it is where bile and enzymes of the pancreas are transferred.

• In the small intestine the nutrients are digested and absorbed.

• The large intestine is where the water and mineral salts are flushed out and where faecal mass is formed.