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.
