【Science】Structure and Function of the Human Body (6th Grade)
Hello everyone! Let's work together to learn about the "Structure and Function of the Human Body."
Inside our bodies, amazing processes are happening every second without rest—like digesting food, breathing, and circulating blood. Once you understand how your body works, you’ll likely feel even more appreciative of yourself.
It might seem a bit tricky at first, but we’ll take it one step at a time using everyday examples, so don't worry!
1. How Respiration Works: Taking in Oxygen, Releasing Carbon Dioxide
We breathe naturally without even thinking about it. Respiration has the vital role of taking oxygen into the body and getting rid of carbon dioxide, which we don't need.
Airflow
Air inhaled through the nose or mouth passes through the trachea (windpipe) and is sent to the lungs located in the chest.
The lungs contain many tiny sacs called "alveoli." This is where oxygen from the air is taken into the blood, and carbon dioxide from the blood is released into the air.
Experiment Tip! Changes in Limewater
Exhaled air (expiratory air) contains more carbon dioxide than the air we inhale (inspiratory air).
To prove this, we use "limewater" in science experiments.
・When carbon dioxide passes through limewater, it turns cloudy white.
Fun Fact:
The air we breathe out isn't completely devoid of oxygen. It just has slightly less oxygen and slightly more carbon dioxide compared to the air we breathed in.
Key Points:
・We take in oxygen and release carbon dioxide.
・This process takes place in the lungs.
2. Digestion and Absorption: Creating Fuel for Energy
The food we eat cannot be absorbed by the body in its current form. It must be broken down into pieces small enough to be taken in as nutrients. This process is called "digestion," and the uptake of these nutrients is called "absorption."
The Path of Food (Digestive Tract)
- Mouth: Teeth break down food into smaller pieces. Here, it mixes with "saliva."
- Esophagus: A tube that sends food down to the stomach.
- Stomach: Further dissolves food into a liquid/mushy state.
- Small Intestine: This is the most important part! It is where nutrients are absorbed.
- Large Intestine: Absorbs water from the remaining waste and turns it into feces (stool).
The Power of Saliva
Saliva has the ability to turn "starch," found in foods like rice, into "sugar." This is why rice tastes sweet when you chew it for a long time.
In science tests, you will often see "iodine solution", which reacts to starch.
・If starch is present = It turns blue-black.
・If it has been broken down by saliva and there is no starch = No color change occurs.
Key Points:
・Nutrients are absorbed in the small intestine, while water is absorbed in the large intestine.
・Saliva converts starch into sugar.
3. Blood Circulation: The Delivery Truck of the Body
The oxygen taken in through breathing and the nutrients obtained through digestion are carried throughout the body by the blood. The pump that keeps this blood moving is the "heart."
How the Heart Works
The heart is a powerful pump made of muscle. The rhythmic "thump-thump" motion is called the "heartbeat." Because the heart pumps, blood is able to circulate continuously throughout the entire body.
Checking Your Pulse
The "thumping" feeling you can detect on your wrist or neck is your pulse. This is the heart's heartbeat transmitted through the blood vessels. When you exercise, your body needs more oxygen and nutrients, so your heart beats faster, and your pulse rate increases.
Common Misconception:
Some people think "blood is made in the heart," but that is wrong! The heart acts strictly as a pump to push blood through the body.
Key Points:
・The heart acts as a pump, sending blood throughout the entire body.
・Blood carries oxygen and nutrients, while collecting waste products.
4. Excretion: The Body's Cleaning Service
As the body produces energy, waste (unnecessary substances) is created. The mechanisms to get these out of the body are also very important.
Kidneys and Liver
- Liver: Works to change harmful substances in the body into less harmful ones.
- Kidneys: Filter out waste from the blood to create "urine."
The urine created in the kidneys passes through the ureters, is stored in the bladder, and is then excreted from the body.
Analogy:
Think of the kidneys like a "filter" or a "water purifier" that removes dirt and impurities from the blood!
Summary: Everything in the Body is Connected!
Finally, let's look at what we learned today as one big process:
- The mouth, stomach, and intestines turn food into nutrients and absorb them.
- The lungs take in oxygen from the air.
- The heart pumps blood, carrying those nutrients and oxygen to the entire body.
- The body uses these to stay energetic and active!
- Waste products are removed by the kidneys (and other organs), and carbon dioxide is exhaled through the lungs.
What do you think? Our bodies aren't just parts working separately; they are all cooperating to support our "life."
It might be hard to memorize all these terms, but try to review them while imagining these things happening right inside you. I'm rooting for you!