Lesson Notes By Weeks and Term v4 - JHS 2
THE HUMAN BODY SYSTEM
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THE HUMAN BODY SYSTEM
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Subject: Science
Class: JHS 2
Term: 2nd Term
Week: 1
Grade code: B8.3.1.1.3
Strand code: 3
Sub-strand code: 1
Content standard code: B8.3.1.1
Indicator code: B8.3.1.1.3
Theme: SYSTEMS
Subtheme: THE HUMAN BODY SYSTEM
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Teeth are important for chewing food properly, speaking clearly, and smiling with confidence. In Ghana, many learners buy sweets, biscuits, toffees, soft drinks, and “ice water” or take sugary tea and porridge. When teeth are not cleaned well, these foods can lead to plaque, tooth decay, and gum disease, causing pain, bad breath, difficulty eating, and sometimes missing school due to toothache. Understanding the causes and prevention helps learners protect their health and reduce medical costs for families.
A. Basic Tooth and Mouth Terms Teeth: Hard structures in the mouth used for biting and chewing. Enamel: The hard outer covering of the tooth. It protects the tooth but can be damaged by acids. Dentine: The layer under enamel; softer than enamel and sensitive. Pulp: Inner part with nerves and blood vessels; when decay reaches here, pain becomes severe. Gums (gingiva): Soft tissues that hold teeth in place and protect the roots. Bacteria: Tiny living organisms in the mouth. Some are harmless, but some cause disease. B. What is Plaque and How Does It Form? Plaque is a sticky, colourless or pale yellow film made up of bacteria, food particles, and saliva that forms on teeth—especially: near the gum line, between teeth, on the back teeth (molars).
Step-by-step formation of plaque After eating (especially sugary or starchy foods like bread, biscuits, gari soakings with sugar, toffees), small food particles remain on teeth. Bacteria in the mouth feed on these particles. As bacteria multiply, they produce a sticky layer that attaches to teeth—this is plaque. If plaque is not removed daily, it becomes thicker and harder to remove.
Important note: Plaque can begin forming again within hours after brushing. That is why daily cleaning is necessary. C. Tooth Decay (Dental Caries): What It Is and How It Happens Tooth decay is the destruction of the tooth structure (enamel → dentine → pulp) caused mainly by acids produced by bacteria.
How tooth decay happens (cause-and-effect chain) You eat sugary/starchy foods (e.g., sweets, soft drinks, sweetened tea, biscuits). Bacteria in plaque feed on the sugar and produce acid. The acid attacks the enamel and removes minerals (this is called demineralisation). Over time, a hole forms in the tooth called a cavity. If untreated, decay reaches the pulp, causing severe pain, infection, and sometimes swelling.