Module 3.1 Digestion

Module 3.1 Digestion

1. The mouth

   • The types of teeth
     • Incisors
       • The four teeth at the front they bite of pieces small enough to chew on
     • Canines
       • The canine teeth have no significant function
     • Premolars & Molars
       • These teeth grind the food into tinier and tinier pieces as you chew
   • Chewing and bitting is a form of mechanical digestion the process starts at the teeth
   • Saliva
     • Saliva is a watery liquid, it has a chemical that turns any starch in the food into glucose, since glucose is easily absorbed

2. Oesophagus

   • Bolus
     • A slimy ball of food
   • Peristalsis
     • The process of rhythmic contracting and relaxing of the oesophagus's muscles. This keeps food moving though the oesophagus
   • A long muscular tube starting at the mouth ending at the stomach

3. Types of digestion

   • Mechanical
     • Food is sliced, crushed and torn by your teeth, although no new substance is made
   • Chemical
     • Large, complex substances are broken down to simpler chemicals

4. Digestive tract

   • A pathway of organs that food goes though. It stars at the mouth end at the anus

5. Digestion

   • The process in which breaks down food into usable form to make its nutrients available

6. Stomach

   • Gastric juice
     • Hydrochloric acid
       • A very strong acid that kills many bacteria that may have been swallowed with the food
     • Mucus
       • A layer of mucus on the lining of the stomach stopping the stomach from digesting itself.
     • Digestive juices
       • Contain chemicals that begin the digestion of protein
     • Produced by special cells in the stomach wall
   • The stomach is shaped as a bag, its found in the left side of the upper abdomen.

7. Small intestine

   • Duodenum
     • This is the first part of the small intestine. The walls are muscular they continue to churn and squeeze the food, this breaks the food down even more. Two tubes do enter the duodenum they carry chemicals crucial for digestion from the pancreas and liver
   • Ileum
     • Villi
       • Villi are microscopic 'fingers' that line the ileum
       • Villi very much increase the surface area of the small intestine's wall, and also greatly increase the amount of nutrients being absorbed.
       • Inside villus are tiny blood vessels named capillaries. Since capillaries and villi are only a cell thick the nutrients move a microscopic distance to enter the blood
     • The ileum is the lower part of the small intestine. Here digested food are absorbed by the body
   • This is the longest part of the digestive tract at 6 metres long and 3cm diameter
   • Nutrients that pass though the intestine
     • Fatty acids and glycerol
       • This is from the digestion of fats
     • Amino acids
       • From digestion of proteins
     • Glucose
       • The digestion of carbohydrates

8. Pancreas

   • Pancreatic juice
     • Contains chemicals that help with digest fats, protein, and carbohydrates
   • Pancreas is not part but connected to the digestive tract

9. Large intestine

   • Anus
     • The anus is a sphincter muscle, stools are let out though the anus. Its at the end of the digestive tract
       • Stool is poo
   • This is the final section of the digestive tract. The large intestine is 1.5 meters long and 6 or 7 cm in diameter
   • Water is reabsorbed into the body

10. Liver

    • The liver is the largest internal organ. It performs over 500 chemical processes

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