Lesson Notes By Weeks and Term v4 - JHS 1

Lesson Video

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Performance objectives

• Identify and label the parts of the alimentary canal.
• Describe the journey of food through the digestive system.
• Explain the role of different organs in digestion.
• Draw and label the human digestive system.

Lesson summary

The human body is made of systems that work together to keep us alive. One very important system is the digestive system (also called the alimentary canal plus other organs). In Ghana, learners eat foods like banku, kenkey, fufu, boiled yam, plantain, rice, beans, meat, fish, eggs, oranges, palm oil, etc. This lesson helps learners understand what happens to food as it moves through the mouth, stomach, small intestine and large intestine—from chewing to absorption and finally removal of waste. This knowledge supports good feeding habits, hygiene, and health (e.g., preventing stomach upset, constipation, and worm infestation).

Lesson notes

2.1 Key Terms (Definitions) Digestion: The process of breaking down food into small soluble substances that can be absorbed into the blood and used by the body. Alimentary canal: A long tube running from the mouth to the anus through which food passes. Main parts: mouth → oesophagus → stomach → small intestine → large intestine → rectum → anus Mechanical digestion: Physical breakdown of food into smaller pieces (e.g., chewing, churning in stomach). Chemical digestion: Breakdown of food using enzymes and other chemicals (e.g., saliva, stomach acid, bile, pancreatic enzymes). Enzymes: Special proteins that speed up digestion (e.g., amylase for starch). Absorption: Movement of digested nutrients from the intestine into the bloodstream. Egestion: Removal of undigested food as faeces through the anus (not the same as excretion). Peristalsis: Wave-like muscular movement that pushes food along the alimentary canal.

2.2 Parts of the Digestive System and Their Functions (Indicator Focus Areas) A. Mouth (Ingestion + Start of Digestion) What happens to food in the mouth? Ingestion: Food enters the body. Chewing (mechanical digestion): Incisors cut (e.g., biting bread). Canines tear (e.g., meat). Premolars/molars grind (e.g., boiled yam, plantain). Mixing with saliva: Saliva moistens food to form a soft ball called bolus (easy to swallow). Chemical digestion begins: Saliva contains amylase enzyme which starts breaking down starch into simpler sugars (e.g., starch in yam, cassava, plantain, bread, rice).

Worked Ghanaian example (starchy food): If you chew boiled yam for some time, it may taste slightly sweet. This is because amylase begins changing starch into maltose (a sugar).

B. Oesophagus (Transport) The bolus moves down the oesophagus by peristalsis. No major digestion happens here; it is mainly a passage.

Evaluation guide

• Identify the parts of the alimentary canal in a drawing of the digestive
• system.
• Research and describe what happens to food e.g. a piece of boiled
• yam / cassava / plantain / cocoyam / bread, egg, meat, orange, palm oil