TOUCH
* Our skin is the organ we use to touch.
* Our body is covered in the skin. It is the largest organ in the human body.
* Our skin can tell us if something fells soft or hard, hot or cold, rough or smooth.
* Sensory nerves send this information to our brain.
TOUCH
The middle layer of sky, called the dermis, contains nerves and tiny clood vessels. These nerves detect sensations, such as temperature, pain and texture and send this information to our brain.
SMELL AND TASTE
SMELL
* Our nose is the organ we use to smell.
* Air enters the nose through the nostrils.
* The olfactory nerve sends information to our brain which tell us what we can smell.
* We ca smell about 10,000 different odours.
TASTE
* Our tongue is the organ we use to taste.
* Our tongue is convered in taste buds. These identify different tastes.
* Nerves send information about the different tastes to our brain.
* We can identify four basic tastes: sweet, salty, bitter and sour.
SMELL AND TASTE
* Our sense of smell detects chemicals in the air. When the air enters our nose through our nostrils, these chemicals come into contact with nerve receptors. The nerve receptors send this information along the ofactory nerve to our brain.
* The receptor cells for taste are on the tongue inside each taste bud. The receptors detect different tastes (bitter, sour, salty and sweet).
THE DIGESTIVE SYSTEM
The digestive system allows our body to get nutrients it needs. Digestion begins in the mouth. The food then travels down the oesophagus and into the stomach. The small intestine separates the nutrients from the waste. The nutrients pass to the circulatory system and travel to all the body cells. The waste passes to the large intestine and leaves the body through the anus.
THE CIRCULATORY SYSTEM
The circulatory system sonsist of the heart, blood vessels and blood. It moves blood through the heart and around the body. Blood gives our cells the oxygen and nutrients they need. Blood also collects waste products, such as carbon dioxide, and takes them to the parts of the body which expel them.
THE RESPIRATORY SYSTEM
The respiratory system is made up of a group of organs that help us breathe. We breathe in oxygen and breathe out carbon dioxide.
Air enters our lungs through the nose, mouth, trachea and bronchi. Oxygen then passes into our blood through the alveoli. Carbon dioxide from our blood passes into our lungs, also through the alveoli. When we breathe out, the carbon dioxide leaves our lungs.
The diaphragm is a strong muscle below the lungs which contracts when we breathe in and relaxes when we breathe out.
THE EXCRETORY SYSTEM
Our excretory system excretes waste from our body. Two organs called kidneys clean waste from our blood. The waste combines with water to make urine. Urine travels down two tubes called ureters and collects in a bag called the bladder. When the bladder is full, the urine leaves the body through the urethra.
Our body also eliminates waste through the skin. This waste is in the form of a liquid called sweat.
THE DIGESTIVE SYSTEM 3r
The digestive system is a group of organs that work together to help us digest food.
+ We take in food through our mouth.
+ It passes down into our stomach and intestine.
+ The intestine separates the nutrients from the waste and expels the waste from our body.
+ The nutrients are passed to the circulatory system, where they move around the body.
THE RESPIRATORY SYSTEM 3r
The respiratory system is a group of organs that work together to help us breathe.
+ We breathe in air through our nose and mouth.
+ The air goes down into our lungs.
+ Oxygen is passed to the circulatory system, where it moves around the body.
+ We breathe in oxygen and breathe out carbon dioxide.
How our eyes and ears work
Our brain is the control centre of our body. It reads signals from our eyes and ears and tell us what we can see and hear.
How do we see things?
1. Light reflects off an object and enters the eye through the pupil.
2. The light goes through the lens and makes an image on the retina at the back of the eye. The image is upside down.
3. The retina sends the information to the brain.
4. The brain reads the signals and tells us what we can see.
How do we hear things?
1. Sound waves enter through the outer ear.
2. The waves hit the eardrum in the middle ear and make it vibrate.
3. This makes the liquid in the inner ear move and send signals to the brain.
4. The brain reads the signals and tells us what we can hear.
