The Digestive System
Structure & Function of the Digestive System
Major Organs & Functions
1. Mouth
● Chewing (mechanical digestion) by teeth breaks down food
into smaller pieces
● Saliva contains amylase, which starts breaking down starch
into maltose (chemical digestion)
2. Epiglottis
● A flap that closes over the trachea when swallowing to prevent
choking
3. Oesophagus
● A muscular tube moving food from the mouth to the stomach
via peristalsis (wave-like contractions)
4. Stomach
● Stores & churns food with gastric juices
● Hydrochloric acid kills bacteria & activates pepsin, which
starts breaking proteins into peptides
● Converts food to chyme
5. Small Intestine
● Duodenum - Digestive enzymes from the pancreas & bile from
the liver complete chemical digestion
● Illeum - Absorbs nutrients into the bloodstream via villi
6. Large Intestine (Colon)
● Absorbs water & compacts waste into faeces
7. Rectum
● Stores faeces before elimination
8. Anus
● The exit point of waste through egestion
, Accessory Organs & Their Functions
● Liver:
○ Produces bile (stored in the gall bladder) to emulsify fats
○ Bile also neutralises acidic chyme from the stomach
● Gall Bladder:
○ Stores bile & releases it into the duodenum when needed
● Pancreas:
○ Produces digestive enzymes:
■ Amylase - Starch → Maltose
■ Lipase - Fats → Fatty Acids + Glycerol
■ Trypsin - Proteins → Peptides
○ Release bicarbonate to neutralise the stomach acid
Identify The Parts of The Stomach
● Cardiac Sphincter - Entry point from oesophagus, prevents
backflow
● Fundus - The top part of the stomach
● Body - Central region
● Pylorus - Lower section leading to the small intestine
● Pyloric Sphincter - Controls flow of chyme into the duodenum
Four Layers of The Alimentary Canal
1. Mucosa - Inner lining, secretes mucus, enzymes, & absorbs
nutrients
2. Submucosa - Connective tissue with blood vessels & nerves
3. Muscularis Externa - Smooth muscle layers for peristalsis
4. Serosa - Protective outermost layer
Structure & Function of the Digestive System
Major Organs & Functions
1. Mouth
● Chewing (mechanical digestion) by teeth breaks down food
into smaller pieces
● Saliva contains amylase, which starts breaking down starch
into maltose (chemical digestion)
2. Epiglottis
● A flap that closes over the trachea when swallowing to prevent
choking
3. Oesophagus
● A muscular tube moving food from the mouth to the stomach
via peristalsis (wave-like contractions)
4. Stomach
● Stores & churns food with gastric juices
● Hydrochloric acid kills bacteria & activates pepsin, which
starts breaking proteins into peptides
● Converts food to chyme
5. Small Intestine
● Duodenum - Digestive enzymes from the pancreas & bile from
the liver complete chemical digestion
● Illeum - Absorbs nutrients into the bloodstream via villi
6. Large Intestine (Colon)
● Absorbs water & compacts waste into faeces
7. Rectum
● Stores faeces before elimination
8. Anus
● The exit point of waste through egestion
, Accessory Organs & Their Functions
● Liver:
○ Produces bile (stored in the gall bladder) to emulsify fats
○ Bile also neutralises acidic chyme from the stomach
● Gall Bladder:
○ Stores bile & releases it into the duodenum when needed
● Pancreas:
○ Produces digestive enzymes:
■ Amylase - Starch → Maltose
■ Lipase - Fats → Fatty Acids + Glycerol
■ Trypsin - Proteins → Peptides
○ Release bicarbonate to neutralise the stomach acid
Identify The Parts of The Stomach
● Cardiac Sphincter - Entry point from oesophagus, prevents
backflow
● Fundus - The top part of the stomach
● Body - Central region
● Pylorus - Lower section leading to the small intestine
● Pyloric Sphincter - Controls flow of chyme into the duodenum
Four Layers of The Alimentary Canal
1. Mucosa - Inner lining, secretes mucus, enzymes, & absorbs
nutrients
2. Submucosa - Connective tissue with blood vessels & nerves
3. Muscularis Externa - Smooth muscle layers for peristalsis
4. Serosa - Protective outermost layer
