Below are a few points I have written about the digestive system:
• Digestion is the process of extracting nutrients and energy from the food we consume
• It (digestion) occurs in a six - seven metre tubed called the alimentary canal, digestive track/gut, which runs from the mouth to the anus where waste is expelled.
• Along the way, food is broken down into smaller and simpler substances that can pass into the bloodstream and travel through various parts of the body (which is where they can dissolve in the water in the cells)
• Two main types of digestion:
- mechanical, which occurs in the mouth where the food is physically broken down.
- chemical, which occurs through various stages along the alimentary canal where enzymes (catalyst) break down the food.
Mouth (1 minute):
• Food is grinded into smaller pieces (by the teeth), mixed with saliva and made into a small lump called bolus.
Oesophagus (3 secs):
• 25 cm tube connecting the mouth to the stomach
• The peristalsis moves the bolus (small lump) down the oesophagus by wave-like contractions and expansion of muscles (like squeezing a marble through a rubber tube, narrow than the marble)
• The trachea/windpipe branches off and leads to the lungs. When food is swallowed, the top of the windpipe extends slightly and a flap called epiglottis folds over its entrance (to the lungs) to stop the food from 'going down the wrong way'.
Tuesday, 11-08-10
Stomach (2 - 4 hours):
• The stomach is a J-shaped organ that has a capacity of about 2 litres.
• The muscles in the stomach mixes the food with gastric juice.
• Gastric juice contains the enzyme pepsin, which helps break down large protein molecules and fats.
• Hydrochloric acid in the stomach helps this enzyme and kills harmful bacteria.
• Sphincters are rings of muscles that control the entrance and exit to and from the stomach.
• A sphincster on top of the stomach prevents acid and other stomach contents from rising into the oesophagus. The one at the bottom protects the next part of the digestive tract from acid.
Pancreas:
• The pancreas is not part of the alimentary canal. Instead, it is part of a 15 cm multipurpose 'side attachment'.
• It produces pancreatic juice that contains:
- more enzymes that help digest carbohydrates, fats and proteins
- a chemical, insulin, that controls the amount of sugar in the bloodstream and how cells use energy (Diabetes is an example when the pancreas does not produce enough insulin)
- an alkali (a liquid which neutralises the acidic stomach chyme)
• Chyme is a partly digested, semi-liquid food.
Gallbladder:
• The gallbladder is a smal muscular sac about 8 cm long that stores bile (a green liquid that helps breaks down fats into smaller particles), produced by the liver. It can hold about 50 mLs of bile.
Liver:
• The liver is a living 'chemical factory' that is involved in over 500 chemical processes.
• It is the largest internal organ, weighing 1.5kg.
• It consists of two parts/lobes and has an extensive blood supply.
• The function of the liver include:
- the conversion of glucose into glycogen (stored in the liver and muscles and can be converted back into glucose when needed in the body)
- the storage of vitamins and minerals
- production of blood-clotting chemical
- the break-down of poisons (like alcohol)
- the production of around 700 - 1000 litres of bile per day.
- the production of heat, which is transferred around the body by the blood
Duodenum:
• The duodenum is the start of the small intestine
• 10cm along its length, two small tubes come together (from the pancreas and liver/gall bladder)
• These small tubes allow chemicals (such as bile) and enzymes to enter the small intestine.
Small Intestine (1 - 4 hours):
• The small intestine is the longest part of the digestive tract, with a length of 4 - 6 metres.
• It is called 'small' because of its narrow width of about 3 - 4 centimetres.
• It contains muscles that churns (mixes) food and produces enzymes that continue the digestion of carbohydrates, proteins and lipids.
• The walls of this intestine are lined with tiny bumps called villi.
• The villi allows more nutrients to pass through as digested food moves through.
Large Intestine (10 hours - several days):
• The large intestine is about 1.5 metres long and about 6 - 7 centimetres wide.
• It is made up of five parts:
- caecum
- appendix
- colon
- rectum
- anus
• Undigested waste passes into the large intestine, where water and a few remaining minerals are absorbed.
• Stools (lumps of faeces) form and are expelled later from the body, through the anus.
• 1/3 of faeces is made up from intestinal bacteria.
• Although these bacteria help break down fibre (and reduce the amount of faeces), they also contribute to the smell.
Tuesday, 17-08-10
The research I have done for today could not save.
Wednesday, 18-08-10
The food you eat (and it's nutrients) cannot be used by the body in its own form. The food or liquids you consume need to be broken down both mechanically and chemically, by the digestive system, into smaller molecules. These molecules (nutrients) are absorbed and is transported throughtout the body by the blood. These nutrient molecules nourish our cells and provide a source of energy for us.
'The collection and elimination of waste products also is an important part of digestion. Undigestible parts of foods (fibre), older cells that line the digestive tract, and some water, are eliminated from the body as faeces. Thus, maintaining a healthy digestive system is extremely important for your general health and well-being.'
Not only does it provide nutrients (from our food) to the body but it also gets rid of the undigested food. The way our body gets rid of these leftovers is through stool - clumps of faeces.
The digestive system provides nutrients for our body which are used for growth, energy or repairing anything that's wrong.
Next to the nervous system, in terms of functioning, the digestive system is the 2nd most important system of our body.
Friday, 20-08-10
