*Digestive System — From Bite to Finish*
Today I want to share a topic from my biology book: _digestive system_. How it works and everything I know so far.
First, we all eat food but we never really think about the process of digestion. You know it’s really amazing. This process starts from our _mouth_ and ends at the _anus_.
*Flowchart: Digestive System*
Mouth → Oral cavity → Pharynx → Oesophagus → Stomach → Small intestine → Large intestine → Anus
*How it starts:*
It starts in the mouth where teeth chew food and saliva breaks it down. The tongue pushes it to the pharynx, then the oesophagus carries it to the stomach. The stomach mixes it with acid and enzymes to make a soupy liquid.
Next, the small intestine does the main job. It absorbs nutrients like glucose and vitamins into the blood using tiny villi. The large intestine just takes back water and forms waste, which leaves through the anus.
It’s crazy how our body does all this silently every day. Learning this made me appreciate biology more, and I hope my PSC community finds it cool too!
_— Amna, Explorer Volunteer_
*Nephrons — The Kidneys’ Real MVPs*
I’m a bio student and today while going through my biology book I hit the chapter on nephrons. I had no idea something that tiny could do so much.
Nephrons are the main filters inside your kidneys. Each kidney has about a million of them, and they work 24/7 without us noticing. Here’s how they work: when blood enters a nephron, it first dumps everything out into a tube. That means water, salts, sugar, urea, all of it gets filtered out at once.
But nephrons are smart. They act like a picky shopper and take back only what your body needs. Glucose, most of the water, and important minerals get reabsorbed into your blood. Whatever is left becomes urine.
If nephrons stop working, your blood doesn’t get cleaned and your body can’t balance fluids. That’s why kidney problems are so dangerous. It’s amazing how these microscopic parts keep us alive every day.
Wanted to share this with my PSC community because learning how our bodies work is pretty cool.
_— Amna, Explorer Volunteer_
I’m excited to share that I’ve officially started my journey as an Explorer Volunteer with Pakistan Science Club. I’ve already completed 1 mission and earned 2 badges after updating my profile and submitting my personalized poster on the PSC portal. Looking forward to contributing more to science promotion in Pakistan!
*How Your Heart Has Electricity ⚡❤️*
*Topic*: Human Physiology | *PSC Tag*: Circulatory System, Bio-Physics
*The Weird Fact First*
Your heart beats _without_ your brain telling it to. Even if doctors took your heart out and put it in a saltwater bath with oxygen, it would keep beating for a while. Why? Because your heart makes its own electricity.
*The 1-Minute Breakdown*
1. *Your heart’s power station: SA Node*
In the top-right of your heart is a tiny patch called the *SA node* — the “natural pacemaker.” Think of it as a drummer setting the beat. It fires an electric signal ∼70 times per minute when you’re chilling.
2. *The wiring*:
The signal spreads like a wave through special muscle fibers:
`SA node → Atria contract → AV node → Bundle of His → Ventricles contract`
That’s why you hear “lub-dub.” Lub = atria, Dub = ventricles.
3. *No brain needed*:
Your brain can _speed up_ or _slow down_ the heart using nerves, like during exam stress vs sleep. But the beat itself starts in the heart. That’s why a brain-dead patient can still have a heartbeat.
*Try This Safe Experiment*
*You need*: Just yourself + a timer
1. Sit quietly. Find your pulse on your wrist. Count beats for 15 sec, multiply by 4. That’s resting BPM.
2. Do 20 jumping jacks. Check pulse again.
3. Wait 1 minute, check again.
*What you proved*: The SA node responded to signals from your brain + adrenaline. You just did a mini cardio lab without any equipment.
