10．Humans have five senses：sight，hearing，smell，taste and touch．They collect information for the brain．For example，the eyes collect information on pictures and the ears collect information on sounds．
Sometimes a person loses a sense．Their other senses become better．For example，a blind person has much better senses of hearing and touch．
Sight
The eyes can only see with light．Light carries the picture of something into the eyes so humans can see it．But do you know that the picture is upside down？The brain has to turn the picture the right way up again．
Hearing
Sounds travel through the air like waves （波）．Human ears are like cups．They catch sound waves for the brain and the brain translates them as different sounds．
Smell
Humans smell with their noses．Most people can recognize about 10，000 kinds of smell．This is amazing!Humans each have five million receptor cells （感受細胞）in their noses．Noses are not only for smelling．They also clean and warm the ail that people breathe in．How does the nose prevent the dirty air from getting into the body？Well，it sneezes（打噴嚏）！
Touch
There are receptor cells for the sense of touch all over the body．This is different from the other senses．Touch receptor cells are in the lowest part of the skin．They help the body to have all kinds of feelings like pain，cold and heat．Some parts of the body （like the finger） are more sensitive（敏感的）than other parts of the body （like the back） because they have more touch receptor cells．
Taste
People can taste food because they have about 10，000 taste buds（味蕾）on their tongues．Old taste buds die and new ones come out every two weeks．But when people get older，this happens less often．That's why old people often complain their food is tasteless．Scientists also find that smokers have fewer taste buds．Do you want food to taste good？Well，don't smoke!
For hundreds of years，people knew the basic tastes were sour，sweet，salty and bitter（苦）．In 2002，a fifth taste，umami（delicious taste） joined the list．Now，a study from Purdue University in the US found that fat could actually be the sixth basic taste．
To be considered a basic one，a taste needs to beable to active certain receptor cells in the mouths．A study has shown that humans have fat receptors in the mouths．Not long after that，a scientist made a study to test a second question：can people taste the difference between fat and other tastes？
Richard Mattes gave the testers six different kinds of things．Each kind had a taste：sweet，salty，sour，bitter，umami or the newcomer-fat．Mattes asked the people to pick out tastes by their differences．This was to test whether or not fat would be picked out from the group．Most of tlie testers could clearly find out the different taste of fat．
Then how does fat taste？"It's terrible．"Mattes said．"However，the taste can be pleasant in a small amount，just as we enjoy the bitterness of chocolate．"
| senses | （111）
parts of the body/collectors/organs | facts about the senses |
| sight | eyes | Pictures of real things are completely different in（112）brainfrom those carried by light into the eyes． |
| hearing | ears | Sound waves caught by ears must go through a process like（113）translatingso that we can hear different sounds． |
| smell | nose | The fhnctions of nose are smelling，cleaning and warming the air people breathe in．Sneezing is the way to（114）take outthe dirty air we breathe in． |
| touch | （115）
skin | People feel pain，cold and heat（116）because ofthe fnction of the receptors．So the more touch receptors we have，the more sensitive we are． |
| taste | tongue | Old taste buds die and new ones come out every 2 weeks．
Losing a certain amount of taste buds（117）causesthat the old and the smokers have a bad sense of taste．They can't enjoy tasty food like others． |
| （118）basic tastes | sour sweet salty bitter umami |
| one newly found taste | A scientific study has proved people have fat receptors
in the mouth．One（119）
more
study shows：people can clearly（120）tell
the taste of fat from other tastes． |
