1. Human Digestive System

2. Ingest food
Break down food
Move through digestive tract
Absorb digested food and water
Eliminates waste materials
HowStuffWorks Videos "Assignment Discovery: Breaking Down Digestion"

3. 1. Ingestion
Eating and drinking

4. 2. Digestion Bite Size Science 2 kinds Mechanical Digestion
chewing, chopping, grinding
breaks food into smaller pieces
increases surface area for:
Chemical Digestion
breaks chemical bonds within macronutrients
hydrolysis reaction (releases water)
BiologySource

5. Mouth Breaks down food into small pieces
Begins starch digestion (amylase)
Saliva produces amylase and lubricates food
Moves food into esophagus
Epiglottis covers trachea
Peristalsis moves food to stomach

6. Oesophagus (esophagus)
~ 24 cm long tube
takes food from pharynx to stomach
made up of circular, longitudinal & smooth layers of muscles
work together to push food along

7. Peristalsis circular & longitudinal muscles contract rhythmically
lubricant mucin added
together push bolus (ball of food) along in waves to stomach
Peristaltic Wave in the Gastric Antrum - YouTube

8. Stomach First opening – cardiac sphincter
Muscles churn food – more mechanical digestion
Inner layer folded into ridges called rugae that contain gastric glands
Glands produce gastric juice = pepsin + HCl
Mucous secreted that protects stomach wall
Pepsin breaks down proteins (only at pH 2)
creates chyme (thick liquid), which leaves after 2-4 hrs
Second opening – pyloric sphincter
Stomach Digestion - YouTube

9. 3. Absorption proteins, starches, sugars, fats & vit. Small Intestine:
~ 7 m long
chyme leaves stomach into duodenum
jejunum middle section
illium passes chyme into lg intestine
lined with finger-like villi (inc SA)
each villus had artery, vein & lymph vessels to it
nutrients absorbed into blood by diffusion or active transport

10. Large Intestine (aka the colon)
~ 1.5 m long
absorbs water from wastes
e. coli bacteria further break down wastes (produce methane)
other bact. produce vitamin B & K which get absorbed

11. 4. Elimination Large Intestine, Rectum & Anus
Rectum - last cm of LI
stores wastes (toxins)
when fills with wastes nerves send message to brain to empty
wastes exit through anal sphincter
low cellulose (fibre) diet results in less elimination, so toxins in rectum for longer
increased risk of colon cancer

12. Endocrine Glands Pancreas, Liver & Gall Bladder
* chyme doesn’t enter these organs but they help in digestion*
Pancreas produces:
insulin lowers blood glucose
glucagon raises bld glucose
pancreatic juices & NaHCO3:

13. Digestive Enzymes (Pancreas)
neutralize chyme & contain digestive enzymes
break down macromolecules
Ex:
Protease – protein into a.a.
Lipase – fat into glycerol and 3 fatty acids
Maltase, Sucrase, Lactase – sugars into glucose

14. Liver & Gall Bladder Liver:
produces bile which contains salts to break down lg fat globules (inc. SA)
stores carbs and vitamins
detoxifies
Gall Bladder:
stores bile until needed
Digestive System.notebook