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Anemia pathophysiology
Created by Nauroz Syed.
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- The URL of the next video Microcytic, normocytic, and macrocytic anemias gave me the 404 error (https://www.khanacademy.org/science/health-and-medicine/hematologic%20system%20diseases/anemia/v/rn-microcytic-normocytic-macrocytic-anemias). I have not known where to effectively report this problem (so KA staffs can fix the URL) so I just asked here.(24 votes)
- Awesome. Thanks for finding this! I'll fix it right away.(10 votes)
- Are there any specific pathogens that destroy red blood cells and result in a destruction anemia?(4 votes)
- You may want to look up malaria. Malaria is a disease caused by a unicellular parasite (not bacteria, there is a very large difference). In part of the life cycle of malaria, the parasite infects red blood cells and can reproduce asexually in the cell, eventually causing the red blood cells to burst. With thousands of these parasites infecting blood cells, proliferating, and then bursting red blood cells, you can imagine it's a very serious disease (but also quite interesting. The importance of this disease is huge, especially in third world countries).
Another relevant disease you may want to look up is meningococcus, a bacteria that is known for causing meningitis, a life threatening disease. Many college students are highly recommended to get the vaccine for this to prepare for life in the dorms.(10 votes)
- When, why and how do erythroblasts mature?(3 votes)
- *When:* RBCs are produced when the blood's oxygen levels are low (e.g. blood loss, high altitude, exercise, etc.). Your kidneys send out a hormone called erythropoietin, which makes the bone marrow produce RBCs.
*Why:* More RBCs increases the oxygen levels.
*How:* They come from stem cells in the bone marrow, then lose their nucleus.(5 votes)
- After 120 days what triggers allow the degradation of a red blood cell. What give away the "age" of the cell. Does it leak some material over time?(2 votes)
- Answer to first question: At the end of a red blood cell's lifespan, it becomes senescent. This, in its simplest form, is defined as the progressive decay or degeneration of biological function characteristic. Consequently, the cell is removed from circulation. This is all triggered by the cell itself, in a process known as eryptosis. By making changes in its plasma membrane, the erythrocyte makes itself susceptible to increased mortality.
Answer to second question: Cellular aging is typically determined by the measurement of how well or quickly cells resist stress, react to damage, or lose functions.
Answer to third question: No, it does not. If a red blood cell did leak during its lifespan, vital oxygen molecules would have been lost in the bloodstream. In turn, if this was common in most if not all of a person's blood cells, the person would die from an inadequacy of oxygen reaching designated destinations in the body.(2 votes)
- At2:08in the video
what would cause the Kidney to stop producing EPO(2 votes) - Is hemoglobin formed during the formation of the erythrocyte?(1 vote)
- The Homatrpoetic Stem Cell produces all cells in the blood?(1 vote)
- how dangerous is anemia or does it depend on the type? And can it be cured easily or agian, does it depend on the type?(1 vote)
- Depends on the type. Hemorrhagic anemia can be more life threatening because of hypovolemia or low volume, and really should be treated with blood transfusions. Iron-deficient anemia is "less" dangerous, but can still lead to major complications (remember hemoglobin transports oxygen in the blood)(1 vote)
- red marrow is converted into yellow marrow at adolesence is there decrease in blood count ?coz red marrow is responsible for rbc production(1 vote)
- Where do the nucleus and other organelles go when erythroblast mature (or are they destroyed)?(1 vote)
- They are destroyed. Ironically, the cells are carrying oxygen,O2, and they have no mitochondria which need O2 to make ATP. So, all the O2 they collect in the lungs is delivered to other cells in the body that have all the normal organelles. The red blood cells or erythrocytes survive by anaerobic respiration. Neat!(1 vote)
Video transcript
Voiceover: So, as their
name suggests, red blood cells are actually red, and
they're found in the blood. There's a little blood
vessel, and that's the blood inside. Blood cells are found in
the blood, but this is actually the end of the story, right? Because red blood cells,
even though they're found in the blood, they're
actually not made there. They're actually made inside bone. This is a picture of a
bone, not a very good one. But that's a picture of a
bone, and inside the bone you have this cavity in
the center of the bone. So much so, that if you
took a slice of the bone, like that, and you were to
look into it, look kind of like head-on to it, you'd
see that, on the outside of bone, there's this hard
part, this hard, white part that we all know about. But, in the center, there's
this red, spongy tissue. That stuff, that red,
spongy tissue, is called bone marrow. Bone marrow. Bone marrow is where all of
the different blood cells are made, including red blood cells. That's where they're made. This isn't the start of
the story, because the bone marrow is instructed by
the kidney to make the red blood cells. Here's the kidney, and
the kidney releases this molecule, this hormone,
called erythropoietin. That's often abbreviated E P O. So, "erythro-" means
red, and erythropoiesis a very similar word, means
"to make red blood cells". So, erythropoietin is a
hormone that's released from the kidney, that
tells the bone marrow to make red blood cells. But how does it do that? Inside the bone marrow,
there's this cell, the main cell, if you will, of
the bone marrow is called this cell, right here,
it's called a hematopoietic Hematopoietic. stem cell, all right? Stem cell. This stem cell gives rise
to all of the different blood cells, whether it's
red blood cell, a white blood cell, or a platelet,
they all originate from a hematopoietic stem cell. So, erythropoietin,
released from the kidney, once again, instructs the
hematopoietic stem cell to form a red blood cell. So the hematopoietic stem
cell then develops into an immature red blood cell. That's what I'm drawing in over here. It's a pretty big cell, right? Inside the cell, there's
a nucleus, that's a nucleus right there. The nucleus contains DNA,
so that's the cell's DNA. This immature red blood
cell, this precursor red blood cell is called an erythroblast. Erythroblast. And the erythroblast,
it's an immature cell, it eventually it matures into
a mature red blood cell. A mature red blood cell
is called an erythrocyte. "Erythro-," again, means
red, "-cyte" means cell. So, those are red blood cells. As you can tell, the
erythrocyte looks pretty different from an erythroblast. For one thing, there's
no nucleus inside the erythrocytes, and hence it has no DNA. No DNA. Also, you can see that
the erythrocyte has no organelles, so it has no
mitochondria, no ribosomes, it's given all of that stuff up. So, what does the erythrocyte have inside? Well, the erythrocyte has,
inside of it, lots and lots of hemoglobin. Hemoglobin. And what is hemoglobin? Hemoglobin is a protein
that binds to oxygen. We know that red blood
cells serve the function of carrying and delivering oxygen. It's hemoglobin that allows
the red blood cells to serve that function,
because it's the hemoglobin that actually binds to the oxygen. You can see that red
blood cells are pretty committed to their job of
carry oxygen, because they empty their cell of
pretty much anything else, fill themselves up of
hemoglobin, so that all they do is carry oxygen. All-in-all, this is what the
life-cycle of a red blood cell looks like, and
this blood cell will live for 120 days before it's
taken out of commission. We were talking before about anemia. Anemia. And how anemia refers to
a decrease, a shortage in the number of red blood cells. So there are too few red
blood cells in the body. There are many different causes of anemia. So much so, that we
could probably spend the entire week talking about
the different causes of anemia, but the people
who first described anemias asked themselves
a very important question. They asked themselves,
"Is the decrease in the "number of red blood cells
because there's a problem "in making the red blood
cells, or is it a problem "of normal, healthy red
blood cells being destroyed?" So, in essence, they drew
a line down the middle of this diagram, I'm
going to do that again. They drew a big line down the middle of this diagram, where
above this line, you're looking at anemias that
are caused by a problem with underproduction. Underproduction. Below this line, you're
looking at a problem where healthy, normal red blood
cells are being destroyed. So you're looking at a
problem of destruction. Destruction. We're going to go through
the different types of underproduction anemias
and the different types of destruction anemias in great
detail, but for right now, I'd like to just graze over
the different types briefly. I like to use really bright
colors, so that's good, some minty green. Let's start off with the kidney. If, let's say, a person
was suffering from renal failure, from kidney failure,
and they weren't able to produce as much erythropoietin,
that would cause an under-stimulation of
this entire process, right? That would certainly lead
to an underproduction anemia. What about, moving on,
what if the bone marrow was sick because it was
infected by a virus? What if it was too sick to
produce red blood cells? Or what if it was taken over by a tumor? Or fibrosis, scar tissue? And it didn't have enough
room to produce red blood cells, that would
lead to an underproduction anemia, and what if this
erythroblast, looking at this erythroblast, you see
it has this huge nucleus, and it has lots of DNA in the center. What if we didn't have
enough precursors to make all of this DNA? That would prevent us from making as many erythroblasts and as many erythrocytes. That would be a cause of
an underproduction anemia. Finally, getting to this
erythrocyte, we said that it was filled, chock-filled, of hemoglobin. Hemoglobin has lots of
different components to it. What if there was a
shortage of one of those components, or a problem
making the hemoglobin? That would be one of
the most common causes of an underproduction anemia. Those are the different
causes of underproduction anemia. What if we had healthy
red blood cells, in good quantities, being released
into the blood, but our immune system started
to attack the red blood cells, started to destroy
the red blood cells? That would be a cause
of a destruction anemia. What if, instead of our
immune system attacking the red blood cells, what
if pathogens, such as viruses and bacteria
started to attack the red blood cells? That would be another cause
of a destruction anemia. Finally, I'm going to complete
the rest of this blood vessel, what if we had a
situation like this, where you have this blood vessel,
and there's a hole in it, a tear and the blood
just starts to escape and hemorrhage out? Well, that loss of red
blood cells, because of the loss of blood would be another cause of a destruction anemia. So that's an overview, a
very brief overview of the different types of anemias
that we're going to talk about in greater detail
later, but one point that I'd like to leave you with, is
that this division is pretty intuitive, and there's a
hint that we can find in lab values that helps us to
determine whether we're looking at an underproduction anemia or a destruction anemia. If we have a destruction
anemia, you can imagine that the bone marrow and
the kidney would work extra hard. They would ramp up their
processes to compensate for that loss. They would try to pump out more and more red blood cells. You would start to see,
in fact, immature red blood cells being released
into the blood, because the bone marrow's working
so hard and so fast to release new red blood cells. Those are young red blood
cells, kind of a step between the erythroblasts
and the erythrocytes, are called reticulocytes. Reticulocytes. You'd see a lot of reticulocytes,
specifically greater than 3%, because 3% is the amount that you normally see in blood. If you see greater than
3%, you can assume that we have a destruction anemia. In an underproduction
anemia, your bone marrow or kidney could be the
problem, so they're not able to compensate by increasing
their production of young red blood cells,
so you'd see a decrease in the reticulocyte count. Instead of having 3%,
which we said was normal, you'd have less than 3%. That's one really quick
and easy way to tell the difference between whether
you're looking at an underproduction anemia
or a destruction anemia.