Unit 1: Human nutrition (1)
a) How the human body is organized
We are multicellular organisms. We have three vital functions: nutrition, interaction and reproduction. Our cells are organized into:
Cells >>> Tissues >>> Organs >>> Systems
- Nutrition: In nutrition we use the digestive system (to obtain nutrients from food), the respiratory system (to absorb oxygen and eliminate carbon dioxide), the circulatory system (to distribute substances through the blood) and the excretory system (to eliminate waste).
- Interaction: in interaction we use our sense organs, the nervous systems(that processes the information and create a response) and the locomotor system (that respond the orders through the effectors).
- Reproduction: we use the reproductive system.
b) Food and nutrition
Nutrients are healthy substances obtained from food. They are carbohydrates, fats, proteins, vitamins, minerals and water.
- Carbohydrates give us energy
- Fats give us energy that is stored in our skin.
- Proteins help to the formation of cells and tissues.
- Vitamins and minerals regulate and protect our body.
- Water is essential, without it our body cannot function.
There are three groups of food:
- Energy giving food: Contain carbohydrates and fats (oil, butter, cereals…).
- Body building food: Contain proteins (meat, fish, chicken, eggs, milk…).
- Body regulating food: Contain vitamins and minerals (fruit and vegetables).
A healthy diet must contain a sufficient amount of each nutrient.
c) The digestive system and how it works:
- We have two different parts, the digestive tract (made up of the mouth, pharynx, oesophagus, stomach, small and large intestine and anus) and the accessory organs that produce substances that support digestions. They are the salivary glands (that produce saliva), the liver (that produces bile) and the pancreas (that produces pancreatic juice).
- The digestion takes place in various places:
- In the mouth and the oesophagus the food is mixed with the saliva and form a structure called bolus that reaches the stomach.
- In the stomach, the walls produce juices and the food is partially digested.
- In the small intestine the intestinal juices are mixed with the bile and the pancreatic juice and the nutrients are absorbed through the blood capillaries. Water is absorbed in the large intestine and the waste (faeces) is expelled from the anus.
d) Food safety
- Food decomposes quickly because of bacteria that produce substances that make us ill.
- We can preserve food in different ways:
Freezing: Storing food at very low temperatures.
Salting: Storing food in large quantity of salt.
Vacuum sealing: We store food in bags removing all the air from them.
In these cases microorganisms can´t live.
- When the food is in bad condition can produce poisoning. We can avoid food poisoning if we:
Check the expiry date.
Wash our hands, raw vegetables or fruit before eating them,
You have to cook or freeze some food (eggs, sushi…) before eating it.
Check that the food is in good condition and store it in a fridge. Don´t refreeze the food.
