Digestion: The breakdown of large insoluble molecules into smaller soluble ones
- Physical:
Teeth break down large food pieces into small food pieces creating a larger surface area for enzymes to act on
- Chemical:
Digestive enzymes break down large insoluble food molecules into smaller soluble food molecules
The functions of different body parts in digestive
- Mouth:
Chewing is an example of mechanical digestion
- Salivary glands:
Saliva moistens the food to make a bolus for swallowing. Salivary amylase begins the chemical digestion of starch
- Oesphagus:
A wave of muscle contractions [peristalsis] pushes the bolus into the stomach
- Stomach:
Muscular contractions continue mechanical digestion. Acid kills bacteria. Pepsin begins the digestion of proteins
- Duodenum:
Bile from the liver and gall bladder neutralizes acid and emulsifies facts. Pancreatic amylase and lipase digests carbs and fats. Tripsin digests polypeptides to amino acids
- Ileum:
Lower half of small intestine absorbs nutrients into the blood via villi
- Large intestine:
Water is reclaimed and returned to the blood, leaving semi-solid faeces. This is stored in the rectum
- Egestion:
Faeces (containing undigested food, dead cells and other waste) is forced out of the anus
SUMMARY:
- One long tube
- with three accessory organs (alimentary cancal, pancreas and gall bladder)
- Begins with the mouth and ends with the anus
- Anything ingested, after digestion is absorbed into the bloodstream or elimnated as feaces
Peristalsis:
Smooth muscles contract to move food through
The Alimentary Canal is controlled by the Automatic Nervous System
2 muscle layers working together:
- Circular
muscle layer: In rings around gut
- Longitudinal
muscle layer: Fibres running along the length of the gut
Circular muscles contract and longitudinal muscles relax the lumen is narrower
Longitudinal muscles contract and the circular muscles relax the lumen is wider
1. Contraction of longitudinal muscles expand the lumen in front of the food giving it more space to move into
2. Contraction of circular muscles behind the food propels it forwards
In small intestine the process of peristalsis mixes the food with enzymes and forces the products of digestion to come into contact with the wall of the intestine
References:
https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.niddk.nih.gov%2Fhealth-information%2Fdigestive-diseases%2Fdigestive-system-how-it-works&psig=AOvVaw3RziBuxOjdQbnxOAXzrCJN&ust=1625198119611000&source=images&cd=vfe&ved=0CAoQjRxqFwoTCODmoPf8wPECFQAAAAAdAAAAABAJ
Drafted by Venetia (Biology)