There are many types of human teeth that have different shapes and sizes that have different roles in mechanical digestion
Diagrams of types of human teeth
- Incisors: Bite and cut food
- Canines: Tear, hold, and bite food
- Premolars: Flat larger teeth that chew and grind food
- Molars: Flat large (larger than premolars) teeth that grind and chew food
Structure of human teeth
Diagram of human tooth
- Enamel: The hardest tissue of our body which coats the crown of the teeth (the part of the tooth about the gum)
- Dentine: The tissue between the enamel and the cement that has small hollow canals. When the enamel wears off, food accumulates in these canals and cause sensitivity by stinging nerves and cells
- Pulp: The center of the tooth that is soft and contains nerves, blood vessels and connective tissue
- Cement: The tissue coating the tooth root and is about as hard as bone
- Gums: Connective tissue coated by a mucous membrane surrounding teeth and the alveolar bone (a bone located on the jawbone to hold teeth in sockets in the bone)
Dental Decay
- Some bacteria form plaque (a sticky thin layer) with the saliva coating the teeth and the area it connects with the gum
- Plaque is initially soft, but becomes later tartar, which cannot be removed just by brushing
- Bacteria in plaque can produce acids from respiration for sugar which can harm your teeth by dissolving the enamel and later the dentine
- Plaque can also spread to beneath the gums, causing damage to tooth roots and the bones that support teeth. This may cause tooth diseases and teeth loss
To avoid dental decay, you can...
- Eat less high-sugar foods
- Brush regularly with toothpaste
Enzymes and where they are secreted
Amylase
- Enzyme which breaks starch down into simpler sugars
- Produced in the mouth, and then the pancreas which secretes amylase in the duodenum
Protease
Lipase
- Enzyme which breaks down fats to fatty acids and glycerol
- Produced in the pancreas which secrets lipase in the duodenum
Functions of Hydrochloric acids in gastric juice
- Hydrochloric acid is present in the gastric juice in the stomach
- Kills bacteria in food by denaturing the enzymes in their cells and making it unable to function
- Maintains an acidic pH level for which are more suited the protease enzymes in the stomach and allow them to work faster
Explanation of functions of Hydrochloic acids in gastric juice with the use of low pH
- Kills enzymes in harmful organisms in consumed food
- Creates an appropriate pH level which allows protease to function well
The role of bile
- Bile is an alkaline liquid which helps digest food
- As it is alkaline, it neutralises the hydrochloric acid from the stomach, which makes it easier for enzymes the small intestine to work (as they have higher optimum pH they work best at)
- It emulsifies (breaks down) fats into smaller droplets and increases their surface area for lipase to break down fats into fatty acids and glycerol
Importance of villi
- Villi are fingerlike projections that line the walls of the ileum (second part of the small intestine)
- They increase the surface area for absorption of water and food molecules, making absorption more efficient
- Villi have more microvilli on its surface which makes absorption even faster
- Villi have very thin walls to allow diffusion of water and food molecules to happen faster (as the molecules travel less distance)
- Contain blood capillaries that transport glucose and amino acids through the blood after they diffuse from the small intestine
- Lacteal (vessels) absorb and transport fatty acids and glycerol from the villi out of the small intestine in the lymph (a colourless liquid) and into the bloodstream
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