Lymphocyte

We just learned that there are three types of blood cells, white blood cells, red blood cells and platelets.

Let's learn a little more about the white blood cells.
There are 5 different types of white blood cells!

One of the types of white blood cells is called a Lymphocyte.

Remember we learned that lymph is a white liquid carried in the lymph capillaries and then the lymphatic vessels, and the lymph nodes help clean out all the bad stuff in the lymph.

Lymphocytes are types of white blood cells that help fight off bad diseases, and in the white lymph liquid there is more of this type of cell than any of the other ones.

There are 3 different types of lymphocytes: T cells, B cells and NK (natural killer) cells and they each have a different job to help fight the bad diseases that attack the body.


(from: wikipedia - lymphocyte)


Kid Facts - Blast from the past: Vitreous Body

Platelet

We just learned about the Red Blood Cell and the White Blood Cell.

The third type of blood cell is the Platelet, also called thrombocytes.

The name thrombocyte comes from the Greek words θρόμβος (thrombos) which means clot, and κύτος (kytos) which means cell.
Platelets get carried around in the veins and arteries, and if they see that there is some damage to the body, like a hole in the vein or artery then they will try and patch up the hole.

A bunch of platelets will work to connect to each other, and when they work to block up a hole like this it is called a clot.

So when you have a cut and are bleeding, the platelets come and make a blood clot and help fix up the cut.


(from: wikipedia - platelet)


Kid Facts - Blast from the past: Macula

Red Blood Cell

We just learned about the White Blood Cell.

Another type of blood cell is the Red Blood Cell, also called RBC, red cell, red blood corpuscle, haematid, erythroid cell, or erythrocyte.

Most of the weird science names come from other languages, like corpuscle comes from the Latin word "corpus" for body, haematid comes from the Greek word "hema" for blood, and erythrocyte comes from the Greek words "erythros" for red plus "kytos" for hollow vessel.

Remember there are three types of blood cells: White Blood Cells, Red Blood Cells, Platelets.

There are more red blood cells than the other two type of blood cells, with TRILLIONS of RBCs in the body.

The job of these blood cells is to take oxygen from the lungs to the body, going along the veins and arteries of the circulatory system.

They are shaped a little like a frisbee or a bowl, and they don't have a middle part called a nucleus like most other cells.
Just like the white blood cells, these are made in the bone marrow, and a grown up person makes over 2 million of these RBCs per second!
They go around the body and do their job for about 4 months, and then they get recycled back into the body and replaced by new ones.


(from: wikipedia - red blood cell)


Kid Facts - Blast from the past: Sclera

White Blood Cell

We just learned that there are three types of Blood Cell red blood cells, white blood cells and platelets.

Let's learn a little about White Blood Cells, also called WBCs, leukocytes or leucocytes.

These cells in the blood help fight against diseases or other bad things in the body.
This could be a type of virus or some kind of germs that got into the blood.

White blood cells are made in the bone marrow.
If there are a lot of white blood cells in the body, this can be a way for doctors to tell if someone is sick.
Looking at a liter of blood, if there are between 4,000 and 11,000 white blood cells then this is ok.
If there is a lot more or a lot less, then it is a sign the person is sick.

There are a lot of different types of white blood cells and they all have different jobs for fighting off anything that might be trying to hurt your body.


(from: wikipedia - white blood cell)


Kid Facts - Blast from the past: Optic Nerve

Blood Cell

We just learned about the Haematopoiesis.

The bone marrow that uses haematopoiesis makes Blood Cells, also called hematopoietic cells, hemocytes or hematocytes.

Remember we learned before that the Greek word for blood is hema, so that is why all of those other names start with hema.

Blood cells come in three types: Red blood cells, white blood cells and platelets.


(from: wikipedia - blood cell)


Kid Facts - Blast from the past: Lens

Haematopoiesis

We just learned about the Bone Marrow.

The bone marrow that makes blood cells is part of Haematopoiesis which comes from the Greek words αἷμα (aima) "blood" and ποιεῖν (poieín) "to make", so it means "to make blood".

A normal human body can make from one hundred billion to a trillion blood cells every day!


(from: wikipedia - haematopoiesis)


Kid Facts - Blast from the past: Retina

Bone Marrow

We just learned about the Lymph Nodes.

Another part of the lymphatic system is Bone Marrow.

When we think about our bones, we think of them as hard solid.
But inside our bones is something called bone marrow.

This bone marrow is soft, and is mostly white with some yellow and red.

When we think about blood, we just think of it red liquid, but there are really two types of blood cells called red and white blood cells.
Marrow is where these blood cells in the body are made, and even though we think of the outside of our bones as solid there are really small arteries and veins there that bring the fresh blood cells out of the bone marrow to go to the rest of the body.


(from: wikipedia - bone marrow)


Kid Facts - Blast from the past: Cornea

Lymph Nodes

We just learned about the Lymphatic Vessel.

Another part of the lymphatic system is the Lymph Node.

So we know that lymph is carried in the lymph capillaries and then the lymphatic vessels.
The lymphatic vessels bring the lymph to the Lymph Node.

This is a kidney bean shaped small part of the body that helps filter out bad stuff in the lymph.
It keeps the bad stuff in the lymph node and lets the other liquid lymph go back out to circulate.

The lymph nodes try to fight off the bad stuff collected inside them, and if there is too much bad stuff collected, then your lymph nodes can fill up and get swollen.

Sometimes if you are sick, you can feel on the side of your neck and feel a little lymph node bump sticking out.
Doctors can feel that area and if your lymph nodes are swollen that is a sign you are probably sick and they can do some other tests to try and figure out what sickness you have.

An adult has about 450 lymph nodes in their body, so the lymph gets carried all over and collected in these lymph nodes.


(from: wikipedia - lymph node)


Kid Facts - Blast from the past: Eye Color

Lymphatic Vessel

We just learned about the Lymph Capillary.

Another part of the lymphatic system is the Lymphatic Vessel.

These are like the veins and arteries in the body, but they carry lymph around the body.

The lymph is either brough to something called a lymph node, lymph duct or to a blood vein.

There are two types of lymphatic vessles:
- afferent lymph vessels: Bring lymph to a lymph node
- efferent lymph vessels: Bring lymph away from a lymph node


(from: wikipedia - lymphatic vessel)


Kid Facts - Blast from the past: Iris

Lymph Capillary

We just learned about Lymph.

Another part of the lymphatic system is the Lymph Capillary.

These are tiny little tubes a lot like the capillaries that carry blood, but they carry lymph instead, and they are a little smaller.

Remember that there are a bunch of left over liquids in the body that all make up what we call lymph.
The lymph gets sucked into these tiny capillaries that are all over the body.

These tiny tubes are like little collectors picking up all the lymph that gets left behind by the blood vessels or other organs, to carry it along the lymphatic system.


(from: wikipedia - lymph capillary)


Kid Facts - Blast from the past: Pupil

Lymph

Let's learn more about the Lymphatic System.

One of the first things to learn about the lymphatic system is Lymph.

The word lymph comes from an ancient Roman goddess of water named Lympha.

Lymph is a liquid that is sent all around the body in little tubes, a lot like blood is carried all over the body.

Every time the heart pumps it pushes blood out to all the parts of the body, and then pulls it back to the heart to get more oxygen and nutrients.
When the blood is pulled back, it leaves behind a lot of things like proteins and other liquids that just float around in the body.

The digestive system also leaves some things like fatty white liquids and other things behind after digestion.

Lymph is all of these left over liquids that get sent back around the body through the lymphatic system.
It can be made of proteins, fats, bacteria or other liquids.


(from: wikipedia - lymph)


Kid Facts - Blast from the past: Eyes

Lymphatic System

We just learned about Presbyopia.

We've learned a whole lot about Eyes, from the Cornea, Pupil, Iris and Retina to the Rods, Cones and Fovea!

Let's move on now and learn about something else, called the Lymphatic System.

This is a part of the body that helps make new blood cells, and also helps fight off diseases.
It's part of both the circulatory system and immune system, and goes through the whole body.

The lymphatic system isn't as well known as other parts of the body like the bones or muscles, but it was discovered over 300 years ago, so scientists have been studying it for a long time to figure out how the body works.


(from: wikipedia - lymphatic system)


Kid Facts - Blast from the past: Tonsils

Presbyopia

We just learned about the Astigmatism.

Another kind of refractive error is Presbyopia.

This is something that usually happens to older people, when the lens of the eye gets harder.
When that happens the eye focuses light behind the retina instead of right on it.

If someone has this presbyopia, they usually can't read small printed words, and a lot of times they have to hold things away from them to see them better.



(from: wikipedia - presbyopia)


Kid Facts - Blast from the past: Parotid Gland

Astigmatism

We just learned about the Far Sightedness.

Another type of refractive error that makes the eye not see as well is Astigmatism.

This happens when the cornea at the front of the eye is not shaped right, causing light to get focused in the wrong place and not where it is supposed to go on the back of the retina.


(from: wikipedia - astigmatism)


Kid Facts - Blast from the past: Labial Commissure of Mouth

Far Sightedness

We just learned about the Near Sightedness.

Another type of refractive error that people can have is called Far Sightedness, also called hypermetropia.

If someone is far-sighted that means they can see far away very well, but they can't see up close very well.
An easy way to remember that is that if you are "far-sighted" you are good at seeing far away.

A lot of people become far sighted when they get older, and they can not see up close as well as they used to.
This is one of the reasons that old people will hold something out in their hand with their arm stretched out as far as it can go, because they can see far but not up close.

Older people will also get what are called "reading glasses" meaning that they only wear them when they need to look at something up close like when reading a book.

If someone is young and far sighted then it usually means there is a problem with the shape of their eyeball, or their lens or cornea are not the right shape.
This makes the light coming into the eye not focus on the retina, but focus past it, so it doesn't send the right signals to the brain.

For old people it is because the eye muscles are weaker and can't focus the lens as well as they used to.


(from: wikipedia - far-sightedness)


Kid Facts - Blast from the past: Frenulum of Lower Lip

Near-Sightedness

We just learned about the Refractive Error.

One of the types of refractive errors is Near-Sightedness, also called myopia.

If someone is near-sighted that means they can see up close very well, but they can't see far away very well.
An easy way to remember that is that if you are "near-sighted" you are good at seeing nearby.

Of all the types of eye problems, more people are near-sighted than any other problem, about 1.5 billion people!

When light comes into the eye, the lens is supposed to try and make it focus right on the retina.
The lens is like a magnifying glass, and if it doesn't focus just right then it won't get a clear enough picture.

If the lens is focusing all of the light into a point before the retina, then this causes near-sightedness.
An eye doctor can make glasses to change the direction of the light coming into the eye so that it focuses right on the retina and helps the eye see near and far.


(from: wikipedia - near-sightedness)


Kid Facts - Blast from the past: White Roll

Refractive Error

We just learned about the Myokymia.

Another part of how the eye works is a Refractive Error.

Some people have better vision than others and can see farther, closer or more clearly.

The reason some people have problems seeing is because the shape of the eyeball is not perfect, or because a person is old and their eye muscles aren't working as well as they used to.

The eye needs to be able to focus on things far away or up close, and switch between the two.
If you use a camera sometimes you can see that it is blurry at first and then focuses.

Refraction means how the eye changes the direction and size of the light coming into the eye.

All of the different parts of the eye have to work together to get the picture right and send it to your brain.
If one of them is not right, then your eyes have a refractive error and you can wear glasses to see better.


(from: wikipedia - refractive error)


Kid Facts - Blast from the past: Philtrum

Myokymia

We just learned about the Rheum.

Another part of the eye is a Myokymia, which is a type of eye spasm where the eyelid twitches.

Sometimes without doing it on purpose the upper or lower eyelid might twitch a little.
It usually goes away after a while, and is usually caused by not getting enough sleep or not drinking enough water.

If it is really bad and doesn't go away for months, then it is called a blepharospasm.


(from: wikipedia - blepharospasm)


Kid Facts - Blast from the past: Vermillion Border

Rheum

We just learned about the Eyelash.

Another part of the eye is Rheum.

This is what some people call sleep, sleepy seeds, sleepy bunds, sleepy sand, eye goop, sleep dust or sleepy dirt.

Sometimes when you wake up in the morning there is some hard crusty thing by the inside corner of your eye.
It is hard almost like a piece of sand, and you can wipe it away.

This is called rheum, and it is just the oils that come from your glands building up and drying by your eye.
These oils are coming out all day long, but when you blink they get spread out on your eye or they dry up.
When you sleep you aren't blinking so it dries up and gets crusty.

In the old days people made up a person called the Sandman that comes around and sprinkles sand on the eyes of kids to bring them good dreams.
When you wake up in the morning, that's the leftover sand from the sandman.


(from: wikipedia - sandman)


Kid Facts - Blast from the past: Cupid's Bow

Eyelash

We just learned about the Bulbar Conjunctiva.

Another part of the eye is the Eyelash, also called the cilium.

The hair on the eyelids helps protect the eyes from dust and other things that might fly into it.
There are three layers of eyelids on the edge of the eyelids.

Eyelashes grow on the body even before a person is born.
They do not keep growing forever, they stop after growing out a little.
These hairs take about 7 to 8 weeks to grow, and after a while they will fall out and new ones will grow in the same place.


(from: wikipedia - eyelash)


Kid Facts - Blast from the past: Lips