How We Separate and Study Blood
You’ve probably tried swinging a bucket of water in circles – the water stays in the bucket instead of spilling out. This happens because of centrifugal force, the same force that pushes things outward when they spin.
Scientists used this idea to create a special machine called a centrifuge. Here’s how it works:
- It spins test tubes very fast
- The spinning force pushes heavier parts to the bottom
- Lighter liquid stays at the top
When we spin blood in this machine:
- The heavy red blood cells sink to the bottom (they make up about 45% of blood)
- A thin white layer forms in the middle (white blood cells and platelets, about 1%)
- The yellowish liquid part (plasma) stays on top (about 55% of blood)
If we look at blood under a microscope after adding a special dye:
- We see lots of red blood cells (they carry oxygen)
- We also spot a few white blood cells (they fight infections), which stain darker because of the dye
This helps doctors study blood to check for health problems. The centrifuge makes it easy to separate the different parts of blood so we can examine each one.
What They Look Like:
- When blood is spun in a centrifuge, red blood cells sink to the bottom because they’re heaviest
- These cells have a special shape called a “biconcave disc” – like a donut that’s not fully punched through (thinner in the middle than at the edges)
- This unique shape helps them do their job better
Why They’re Important:
- Their main job is to carry oxygen from your lungs to all body parts
- When carrying oxygen, they’re bright red
- After delivering oxygen, they turn dark red
- A special chemical called hemoglobin makes this color change possible
Fun Facts About Red Blood Cells:
- For every white blood cell, there are 500 red ones!
- Your body makes over 1 million new red blood cells every second (mostly in your bones)
- They live for about 120 days before your liver and spleen remove them
- In tiny blood vessels (capillaries: ), they line up single file to move through
Science Bonus:
The hemoglobin in red blood cells changes when it picks up oxygen in your lungs, turning into oxyhemoglobin (that’s what makes them bright red). After delivering oxygen to your body, they return to their darker color.
Sickle Cell Anemia: A Serious Blood Condition
- This is an inherited disease (passed from parents to children) that can’t spread between people
- What happens:
- Red blood cells change from their normal donut shape to a crescent (sickle) shape after releasing oxygen
- These sickle cells clump together and block small blood vessels
- Effects on the body:
- Causes severe pain
- Can damage organs like the liver, heart, lungs and brain
- May lead to shorter life expectancy
- Treatment options:
- Pain medication helps manage symptoms
- Bone marrow transplants can cure it but aren’t always possible
- Where it’s common:
- Mostly affects people in sub-Saharan Africa
- In Nigeria, about 2 in every 100 babies are born with it
- Current research:
- Scientists like Dr. Joy Okpuzor in Lagos are studying moringa leaves
- They hope to find new treatments from this plant
White Blood Cells: The Body’s Defenders
- Where they’re found:
- When blood is spun, they appear in a thin light layer between red cells and plasma
- How they look:
- They don’t have a fixed shape like red cells
- Their shape keeps changing as their insides move around
- What they do:
- Protect the body from germs (bacteria, viruses, etc.)
- Germs can enter through cuts, nose, mouth, lungs or digestive system
- How they work:
- Rush to where germs enter the body
- Some types actually “eat” and destroy harmful bacteria
- Work in large groups to fight infections
Key Differences Between Blood Cells:
- Red blood cells: Carry oxygen, have fixed shape, much more numerous
- White blood cells: Fight infections, change shape, fewer in number
- Both are crucial for keeping the body healthy!
How Our Body Fights Infections and What Blood Plasma Does
White Blood Cells: Our Infection Fighters
Remember when you got cuts as a kid and they formed scabs? That was your white blood cells working hard to protect you! Here’s how it works:
- When germs enter through a cut:
- White blood cells rush to the area
- They “eat” the harmful bacteria and viruses
- After fighting, the white cells die
- What happens next:
- Dead white cells form pus at the wound
- A scab forms to seal the wound and keep more germs out
- Not everyone gets scabs in the same places – it depends on your injuries!
Important Question:
If someone has fewer white blood cells:
- Yes, it’s easier for germs to invade
- Because there are fewer “soldiers” to fight infections
Cool Fact:
Some white blood cells make antibodies – special markers that help identify germs for destruction.
Blood Plasma: The Body’s Delivery System
- What it is: A yellowish liquid that makes up most of your blood
- What it carries:
- Red and white blood cells (like a river carrying boats)
- Important nutrients from food (glucose, vitamins, fats, minerals)
- Small amounts of waste like carbon dioxide
- Why it matters: Delivers everything cells need to stay alive and work properly
Science Bonus About Glucose:
- Comes from digested carbohydrates
- Used by cells for energy (through respiration)
- We’ll learn more about this in the next chapter
Key Points to Remember:
- White blood cells sacrifice themselves to protect us
- Plasma is like the body’s transportation network
- Everything in blood works together to keep us healthy
Why Donate Blood?
When people lose blood due to injuries, surgeries, or illnesses, they often need blood transfusions to survive. This blood comes from generous blood donors—healthy adults who volunteer to give some of their blood to help others.
Key Facts About Blood Donation:
- Amount Donated: About 470 mL (less than half a liter) per donation
- Frequency: Donors can safely give blood up to 4 times a year
- Global Impact: Over 100 million donations are made worldwide annually
- Special Day: World Blood Donor Day celebrates donors and raises awareness
Matching Blood Types
Not all blood is the same—people have different blood types. Before a transfusion:
- Doctors carefully match the donor’s blood to the patient’s blood type.
- This ensures the body won’t reject the new blood.
From Donation to Transfusion:
- Collection: Blood is drawn from a donor’s arm.
- Storage: The blood is tested, preserved, and stored in a blood bank.
- Delivery: When needed, it’s sent to hospitals or emergency sites.
- Transfusion: The blood is given to the patient through an IV drip.
Why It Matters:
- One donation can save up to 3 lives!
- Blood cannot be artificially made—it only comes from donors.
- Donating is safe, quick, and makes a huge difference.