Fracture – Rebuilding Bone

Posted by on Aug 18, 2013 | 1 comment

In honor of my dear mother, today we’re looking at repair of a broken bone.  Get well soon, Mama!  Hang in there, Daddy!

Disclaimer: I’m not a doctor – just a bioengineer who happens to find pathophysiology fascinating.  If you find an error, please let me know!  Also, NONE of my drawings are to scale.

Today we turn to a common ailment: broken bones.  Because, as I learned, reading about how bones get fractured freaks me out1, we’ll jump in right after Jill has broken her arm.  Sorry we weren’t there to stop it, Jill.

 

Sorry, Jill.

Sorry, Jill.

Jill's broken elbow.

Jill’s broken elbow.

 

Steps to repairing this bone:

  1. as does any trauma to the eye.  I’m too empathetic!  If you want to see a post about injured eyes on Pathology Storybook, you’ll need to write it yourself. []
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Sickle Cell and Malaria – A Double-Edged Sword

Posted by on Jul 29, 2013 | 4 comments

And now for the exciting conclusion to these two posts.  

Disclaimer: I’m not a doctor – just a bioengineer who happens to find pathophysiology fascinating.  If you find an error, please let me know!  Also, NONE of my drawings are to scale.

In this post, we looked at how one tiny change in a person’s DNA caused her to suffer from sickle cell anemia.  We learned that, untreated, about 50% of children with sickle cell anemia die before their fifth birthday.  If you understand natural selection, you’ll recognize this as a puzzle: if sickle cell anemia is so deadly, why are there so many people still affected by it?  Let me explain the puzzle a little further.

For almost all traits, a person has two copies of instructions: one from her father and one from her mother.  Sickle cell disease is autosomal recessive – which just means that both parents must pass on the sickle cell trait for the child to be sick.  People who only received the trait from one parent aren’t sick, but can pass the disease on to their children.

In this case, Mom and Dad are both carriers of a genetic disease.  Statistically, 1/4 of their children will be completely healthy, 1/2 of their children will be healthy carriers of the disease, and 1/4 of their children will be sick.

In this case, Mom and Dad are both carriers of a genetic disease. Statistically, 1/4 of their children will be completely healthy, 1/2 of their children will be healthy carriers of the disease, and 1/4 of their children will be sick.

In most cases where an autosomal recessive trait is deadly early in childhood, the disease dies out.  A child affected by the disease won’t live to have children of his own, and thus won’t pass down the bad information.  With no one to pass it on, the disease stops.

But, sickle cell disease hasn’t followed that pattern. 

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Malaria – An Ancient Struggle

Posted by on May 13, 2013 | 0 comments

Before we discuss why sickle cell anemia has persisted for so long, let’s take a detour to learn about once of the most ancient human diseases: malaria.  

Disclaimer: I’m not a doctor – just a bioengineer who happens to find pathophysiology fascinating.  If you find an error, please let me know!  Also, NONE of my drawings are to scale.

Malaria: scourge of the human race since time immemorial.  The disease is mentioned by the ancient Chinese, Egyptians, Greeks, and Sumerians as far back as 2700 BC.  Some Biblical scholars even believe that Peter’s mother-in-law was suffering from malaria before Jesus healed her.

Unlike the ancient scholars who attributed malaria to the “bad air” (mala aria) of the swamps, we now know that malaria is spread by mosquitoes (who, as it so happens, absolutely love swamps.  You were close, ancient scholars).  But what happens after that terrible bite?  How does malaria make you sick?

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Sickle Cell – The Power of the Little Guy

Posted by on Apr 28, 2013 | 1 comment

Today, we’ll be learning about sickle cell anemia.  
Disclaimer: I’m not a doctor – just a bioengineer who happens to find pathophysiology fascinating.  If you find an error, please let me know!  Als0, NONE of my drawings are to scale.

Sickle cell anemia is the ultimate morality tale about the importance of the little guy: in the 3 billion letters that make up your genome, one letter determines if you’re healthy or sick.  Inheriting the wrong gene for hemoglobin can cause extremely painful episodes, recurring infections, and even death.  Let’s see how it happens.

It all starts with what scientists like to call the Central Dogma of Biology.  It says that information comes from your DNA, gets translated into amino acids, which get strung together to form proteins.  DNA is the instructions, amino acids are like LEGOs, and the proteins are like the resulting LEGO dinosaur.

The central dogma of biology: DNA provides the instructions for the order of amino acids (LEGOs), which fold to create a protein (or dinosaur).

The central dogma of biology: DNA provides the instructions for the order of amino acids (LEGOs), which fold to create a protein (or dinosaur).

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Hives – A Body on High Alert

Posted by on Feb 16, 2013 | 3 comments

Today, we’ll be following an anaphylactic reaction to an allergen.  

Disclaimer: I’m not a doctor – just a bioengineer who happens to find pathophysiology fascinating.  If you find an error, please let me know!  Als0, NONE of my drawings are to scale.

An allergy starts out very innocently.  Everything is humming along: white blood cells patrolling the blood stream, stomach merrily digesting shellfish, or medicine destroying bacteria.

Meet Jill.

Hello!

Hello!

Jill’s taking a particular antibiotic for the first time, and it’s working great: fighting bacteria just like it’s supposed to.

Unfortunately, her white blood cells are getting curious. 

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