Topic: Motor system - bones and joints

Author: Elżbieta Szedzianis

Target group

7th‑grade students of elementary school

Core Curriculum

3.Locomotor system. Student:

2) presents bone functions; determines the physical and chemical structure of the bones as well as plans and performs experiments demonstrating the role of chemical components in bones;

3) presents the role and interaction of muscles, tendons, bones and joints in performing movements.

Lesson objectives

Students describe the structure and functions of bones and joints.

The criteria for success

• you will list the chemical components of the bones and explain how to detect them;

• you will describe the structure and shapes of bones;

• you will present the relationship of bone structure and its function;

• you will describe the construction of the joint and its functions;

• you will discuss the types of joints.

Key competences

• communication in the mother tongue;

• communication in foreign languages;

• mathematical competence and basic competences in science and technology; 

• digital competence;

• learning to learn;

• social and civic competences.

Methods/forms of work

Problem strategy: work with text, brainstorming, demonstration, substitute observation.

Individual work.

Teaching aids

• abstract;

• interactive or traditional board;

• Tablets / computers;

• rag doll;

• boiled chicken bones;

• chicken bone drenched in acetic acid;

• torch;

• laboratory bench.

Before the lesson

One week before the lesson, the teacher prepares chicken bones. He places one of the thinner forearm bones in a jar with a 10% vinegar solution. The second bone is retained for the presentation.

Lesson plan overview

Introduction

1. The teacher shows students a rag doll and tries to set it in different poses. Asks the proteges questions:

• Why can not you set the doll?

• What would it need to keep the position?

2. The teacher presents the subject and the purpose of the lesson in a language that the student understands and displays the criteria for success.

Realization

1.) The teacher gives the students a long chicken bone. He asks them to describe its construction using the interactive illustration. The lecturer explains that in the bones of mammals there is bone marrow instead of air bags.

2.) The teacher asks students to explain what function the periosteum has.

3.) The teacher initiates a brainstorm, asking students what the function performed in the body by the bone depends on. The teacher writes down on the board all the responses of the students. Then, together with the students, he analyzes the ideas written down and together they list three main factors determining the bone function: its chemical composition, shape and location.

4.) The teacher demonstrates the bone dipped in vinegar and discusses its properties. Then he burns another bone in the fume cupboard. He asks students to form observations and interpret results.

5.) Students watch an illustration depicting different types of bones and analyze „Table 1”. The teacher explains the names of individual bones, and the students determine their position in the skeleton and describe their shape. They also discuss their functions.

6.) The teacher asks students to explain the protective function of the bones. He draws attention to the appearance of cranial sutures, and students explain their functions.

7.) The students are watching a movie called „Joint operation” and then perform interactive exercise No. 2.

8.) Students analyze the illustration showing types of joints and discuss their function.

Summary

1.) Students perform interactive exercise No. 1.

2.) The teacher displays success criteria. Students name one success that they achieved thanks to the lesson.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Motor system - bones and joints

Even though bones are created at a foetal stage of our life, their development finishes when human being reaches full sexual maturity. The bones themselves cannot move, thanks to their close cooperation with muscles they allow the body to move. They are, in fact, a passive element of the motor system. They are the scaffolding and support for the muscles, they protect the organs, store minerals and participate in the creation of blood.

Bones can have many shapes which depend on the functions they have within the body and the pressure they are put through by the muscles and other bones. When it comes to their shape, we divide bones into: long bones, short bones, flat bones and irregular bones.

Long bones are composed of diaphysis and epiphysis on both sides. The diaphysis is composed of cortical bone, whereas the epiphysis is composed of cancellous (spongy) bone. Cortical bone is surrounded by the marrow cavity filled with jelly‑like substance – bone marrow. In the diaphysis the marrow consists mainly of fat, whereas in the epiphysis it is red and participates in the production of blood - it produces certain blood cells.

On the outside the diaphysis is covered with a membrane made of connective tissue – periosteum. This is where we found blood vessels and neural cells which are responsible for innervation of the bone. On the inside, the periosteum is surrounded by bone cells which participate in the development and the regeneration of the bone. Thanks to them broken bones mend, and the elements of the bone are changed every 10 years. Cylindrical build of the diaphysis allows the bones to be impervious to be crushed or torn apart, whereas the sponge‑like structure allows bones to be sturdy and rigid, despite having a small mass.

Mechanical features of a bone are the result of not only its physical build, but also of its chemical structure. Stroma of the bone tissue decides on theses features. It includes:

• organic compounds, mainly proteins (collagen fibres), which make bones elastic,

• minerals, mainly calcium carbonate and calcium phosphate, which make bones hard.

In children, the bone matrix is dominated by proteins, which makes the bones more elastic and harder to break. As we grow old, the ratio of inorganic to organic compounds changes. Bones of adults and older people lose minerals (they become demineralized), they also have less collagen, which makes them easier to break.

Bones of a human can be connected in a mobile or immobile form. Immobile bone connections are mainly the stitches, which make it impossible for the bones to move. Mobile bone connections are the joints.

Joint is formed by bones that fit with each other because of the shape of their epiphysis. The place where the bones touch are covered with cartilage that absorbs shocks and lessens friction. The outer part of the epiphysis is covered by a joint socket, which prevents the bones from moving and prevents the joint from becoming dislocated. The joint socket is filled with synovial fluid which protects the bones from grinding away and getting damaged.

Joints can vary depending on the place where they are in the body and their functions.
We divide them in accordance with:

• the number of bones that create the joint: simple joints are composed of 2 bones (shoulder joint), complex – that consist of more than 2 bones (carpal joint);

• the shape of the joint surfaces and the scope of movements: ball and socket joints (shoulder), which allow movements in many directions and hinge joints (elbow), which are only able to flex and extend.

• Bones can have various shapes, depending on what their function is.

• Physical and chemical composition decides on the mechanical properties of bones.

• Minerals makes bones more hard, whereas proteins make them more elastic.

• Periosteum covers the outside of the bones, nourishes them and helps them regenerate.