Sunday, September 14, 2014

fun med facts #2

As you will soon see, this week we spent studying the eyes, face, and parts of the ear. Here are some fun facts I thought others would find interesting:

1. Baby Vision. 

In fetal development, the lens and surrounding structures continue to develop after birth! Check out this crazy vision simulator card to see how awful a new baby's vision is, even after months! According to on of my professors, there was even a study conducted where a brand new baby would only nurse or respond when the mother's voice was heard, meaning that the baby recognized it from the womb as well. How cool is that?  This also explains why you have to get in babies faces to talk to them.

(image from here)

2. Red Eyes in Your Photographs

As shown below, the back of the eye is made up of an "inner" retina, a "middle" choroid layer (with blood vessels), and the outer sclera (the white of your eye). 

As you may already know, the pupil constricts when there's a lot of light in the room so that you can see better (known as the pupillary reflex). When your camera flashes bright, the pupil doesn't have time to close fast enough and the light bounces through the pupil and reflects off of the capillaries (blood vessels) in the back of your eye causing it to appear red in the photo! How cool is that? 

(photo from here)

3. Eye Color

Have you ever wondered anatomically why your eye color is the color it is? (Yes genetics contributes, but after your genetics are already in place, why is your eye blue/brown/hazel/green ??) 

**awesome Image available from this website, GO CHECK OUT THE REST of his images! Awesome!)

Real quick, in case you forgot, the colored part of your eye is called the iris. The black dot is called the pupil, and it's a hole. So now look at the following image and orient yourself. The circled part of the image is the top half of the iris, and then there's a space under it (the pupil), and then the bottom half of the iris is not in the image. So the stroma of iris is basically the middle of the iris. When a person has a lot of pigmented cells in that stroma (melanin) then they have brown eyes. When that person's melanin is either not migrating forward to the stroma and remains in the back of that iris, or it's never produced at all the person will have blue eyes. Hazel and green are supposedly just mixtures of the two.

(Image from here)

And guess what? Just like how babies' lens continue to develop after birth, their melanocytes don't have to produce melanin (brown pigment) until later after birth either. So eye color can change from blues to browns or hazel colors in kids. 

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