2.3 - The digestive organs

• Biologie
• Middelbare school
• havo
• Leerjaar 2

2.3 - The diestive organs

Today's lesson

 HW review

 The digestive organs

HW review

Oral cavity, pharynx and oesophagus

-digestion begins in oral cavity

-chewing breaks food into small

pieces 

-salivary glands make saliva

-saliva has water, mucus, and enzyme

-Enzyme in saliva breaks down starch

-Swallowing: Food via pharynx to 

oesophagus - uvula and epiglottis closed

-Peristalsis moves food to stomach

Why is your stomach rumbling? 

-peristalsis

-muscle activity 

- circular and longitudinal muscles

- mechanical digestion

-stomach constantly moving

-Empty stomach and intestines make a louder sound!

In your stomach

Digestive juices are added

-pyloric sphincter

-temporary storage area

-Gastric glands make gastric juices

-Gastric juices are made up of water, hydrochloric acid and enzyme

-Hydrochloric acid kills bacteria

-Gastric juices start to digest proteins

Duodenum, Liver, Gall Bladder and Pancreas

2 important liquids added in the first part (the duodenum)

• Bile made in the liver, stored in the gall bladder
• Bile emulsifies fats, NO digestion - increases surface area of fats for enzymes to act upon
• Pancreas makes pancreatic juices - different enzymes to digest proteins, carbohydrates and fats

small intestine 

• is very long-> 6 meters
• contains intestinal glands that make intestinal juice
• Intestinal juice digests proteins and carbohydrates
• has many fingerlike projections-> Villi
• Large total surface area -> making  absorption go faster

Characteristics of villi

• One cell layer thick (thin walls for faster absorption)
• Good blood supply (fast transport of nutrients to the rest of the body)

Appendix

It has no function but can become infected and has to be removed.

Large intestine

• About one and a half meters long
• Mainly fibre, dead cells, bacteria and water
• Water absorbed in the blood 
• No all food can be digested - cellulose from cell walls (plants)
• waste product becomes more solid-> faeces

Where does faeces collect?

• in the RECTUM
• when enough is collected the brain signals for elimination
• Anus - a sphicter (circular muscle) relaxes and rectum empties
• this is called a bowel movement