CIE iGCSE Co-ordinated Sciences-B7.2 Digestive system- Study Notes- New Syllabus
CIE iGCSE Co-ordinated Sciences-B7.2 Digestive system – Study Notes
CIE iGCSE Co-ordinated Sciences-B7.2 Digestive system – Study Notes -CIE iGCSE Co-ordinated Sciences – per latest Syllabus.
Key Concepts:
Core
- Identify in diagrams and images the main organs of the digestive system, limited to:
(a) alimentary canal: mouth, oesophagus, stomach, small intestine (duodenum and ileum) and large intestine (colon, rectum and anus)
(b) associated organs: salivary glands, pancreas, liver and gall bladder - Describe the functions of the organs of the digestive system listed in 7.2.1, in relation to:
(a) ingestion – the taking of substances, e.g. food and drink, into the body
(b) digestion – the breakdown of food
(c) absorption – the movement of nutrients from the intestines into the blood
(d) assimilation – uptake and use of nutrients by cells
(e) egestion – the removal of undigested food from the body as faeces
CIE iGCSE Co-Ordinated Sciences-Concise Summary Notes- All Topics
Main Organs of the Digestive System
1. Alimentary Canal (Digestive Tube)
The alimentary canal is a continuous tube through which food passes, is digested, absorbed, and waste is egested.
Organ & Key Function
| Organ | Key Function |
|---|---|
| Mouth | Ingestion; mechanical digestion by chewing; chemical digestion starts with saliva. |
| Oesophagus | Transports food from mouth to stomach via peristalsis. |
| Stomach | Stores food; mechanical digestion (churning); chemical digestion by enzymes and acid. |
| Small Intestine | Duodenum: chemical digestion with bile & pancreatic juice. Ileum: absorption of digested food into blood. |
| Large Intestine | Colon: absorbs water & minerals; forms faeces. Rectum & Anus: stores and egests faeces. |
2. Associated Organs (Accessory Glands)
These don’t carry food, but produce and release digestive enzymes and other substances into the alimentary canal.
Organ & Role
| Organ | Role |
|---|---|
| Salivary Glands | Produce saliva with amylase to start starch digestion. |
| Pancreas | Secretes pancreatic juice containing enzymes (amylase, lipase, proteases) into duodenum. |
| Liver | Produces bile to emulsify fats and neutralize stomach acid. |
| Gall Bladder | Stores and releases bile into the small intestine. |
🔑 Key Definitions
- Ingestion: Taking in food through the mouth.
- Digestion: Breaking down food into small, soluble molecules.
- Absorption: Moving nutrients from gut into blood.
- Egestion: Removing undigested waste as faeces.
🌟 Quick Tip
Alimentary canal → tube food passes through (mouth → anus).
Associated organs → glands helping digestion (salivary glands, pancreas, liver, gall bladder).
Functions of Digestive Organs
1. Ingestion – Taking in food and drink
Mouth: Takes in food; mechanical digestion by teeth (mastication) breaks food into smaller pieces; saliva lubricates and starts starch digestion (amylase).
Salivary glands: Secrete saliva to moisten food and start chemical digestion of starch.
2. Digestion – Breakdown of food
Types of digestion:
- Mechanical digestion: Teeth chew food; stomach churns food.
- Chemical digestion: Enzymes break down large molecules into soluble forms.
Organ & Role in Digestion
| Organ | Role in digestion |
|---|---|
| Oesophagus | Moves food to stomach via peristalsis. |
| Stomach | Produces gastric juice: pepsin for protein digestion; HCl kills bacteria; churning mixes food into liquid (chyme). |
| Duodenum | Receives pancreatic juice for protein, starch, and fat digestion; bile emulsifies fats (physical digestion) and neutralizes stomach acid. |
| Ileum | Epithelial enzymes finish chemical digestion; villi increase surface area for absorption. |
| Pancreas | Secretes enzymes into duodenum: amylase, lipase, proteases. |
| Liver | Produces bile (emulsifies fats); deaminates excess amino acids. |
| Gall bladder | Stores and releases bile into duodenum. |
3. Absorption – Movement of nutrients into blood
| Organ | Key function |
|---|---|
| Ileum | Villi absorb glucose, amino acids, fatty acids, and glycerol into blood/lymph. |
| Colon | Absorbs water and bile salts back to liver. |
4. Assimilation – Uptake and use of nutrients by cells
Liver: Glucose used for energy or stored as glycogen; amino acids used to build proteins; deamination of excess amino acids.
Nutrients from blood are transported to body cells (muscle, skin, organs) to build tissue, provide energy, or maintain metabolism.
5. Egestion – Removal of undigested food
| Organ | Role |
|---|---|
| Rectum | Stores faeces. |
| Anus | Egests faeces (undigested food + fibre). |
💡 Quick Tips
Ingestion: Mouth & salivary glands
Digestion: Stomach, duodenum, pancreas, bile/liver
Absorption: Ileum & colon
Assimilation: Liver & body cells
Egestion: Rectum & anus