hi let's talk about erythrocytes erythrocytes or red blood cells are by concave discs that are
helpful for carrying oxygen and carbon dioxide throughout the cardiovascular system there are
approximately five million red blood cells in every micro liter of blood and on average
these are between 7 to 8 micrometers in diameter when you think about the average diameter of a
capillary bed as about 10 micrometers you can imagine that these red blood cells are going
through capillary beds single-file probably of most importance to a red blood cell is
the protein hemoglobin hemoglobin is a hetero tetramer meaning that it is a protein comprised
of four subunits each subunit containing a human group where oxygen can reversibly
bind there are approximately 280 million hemoglobin molecules in every erythrocyte and
erythrocytes as a cell are highly specialized they're not like other cells of the body as
such they lack nuclei they lack mitochondria they are very reduced in terms of their overall
cellular organization but they do have a lot of haemoglobin probably the most efficient way of
thinking of an erythrocyte is as a little bag of hemoglobin hemoglobin accounts for about a third
of the mass of an erythrocyte and if you were to dehydrate an erythrocyte or take away all
the water hemoglobin would be approximately 96% of the mass of an erythrocyte because
hemoglobin is important for transporting oxygen we might therefore conclude that the primary duty
of an erythrocyte is to transport oxygen and we would be correct in that assumption erythrocytes
have a shelf life it's approximately 120 days after that time erythrocytes are filtered out
by organs such as the spleen erythrocytes may be produced on demand to meet the body's needs
for oxygen we think of erythrocytes as being hypoxia dependent meaning whenever levels of
blood oxygen decrease there are specialized peptide hormones such as erythropoietin or
EPO and transcription factors such as hypoxia inducible factors or H ifs that are secreted
within the kidneys released within the blood and red blood cells or erythrocytes are produced this
process takes approximately ten days from start to finish so one might imagine that
if they were to board an aircraft at sea level and be transported to a high altitude such as
Denver Colorado that within their kidneys they would start to release erythropoietin
and these hypoxia inducible factors that would within 10 days help to elevate the hematocrit
hematocrit is a fancy word that means the percentage of red blood cells that are available
by having an elevated hematocrit the blood is capable of transporting more oxygen to help the
body meet its energetic needs erythrocytes function through the reversible binding of
oxygen to the heme groups of hemoglobin there are four Hulme's within hemoglobin and that represents
the opportunity for oxygen to be loaded on to that molecule within the erythrocyte also erythrocytes
have the capacity of carrying carbon dioxide perhaps in the form of bicarbonate ion or carbonic
acid or even as carbon dioxide as we've discussed previously in the carbonic acid bicarbonate ion
buffer system hemoglobin hemoglobin is a cooperation between two major elements the
heme groups the center of which contains iron and various globin proteins the polypeptides
they comprise hemoglobin may be varied and we refer to them with Greek letters Alpha
Beta Delta Gamma and so on the two most frequent subunits that we find in hemoglobin are alpha and
beta subunits and so there's a particular type of hemoglobin called hemoglobin a which often
time is referred to as adult hemoglobin which comprises about 97 to 98 percent of the total
of adult hemoglobin with regards to hematocrit whenever the volume of red blood cells Falls an
individual might be suffering from anemia Hey meaning without an amia blood literally meaning
without blood anemia is a very large concept that can be broken down into many different
types of anemias of various ideologies or causes all of these ideologies have one thing in common
and that's the reduced capacity of the blood to carry oxygen these ideologies may be dietary in
nature an individual might not be getting enough iron in their diet so that they're not forming
enough heme groups it might be a physiological limitation for that individual to absorb the
iron or to even biologically incorporate it into other molecules the anemia might be a disorder of
the successful production of healthy red blood cells or it might be as simple as a hemorrhage
where the volume of blood decreases and following that plasma bounces back rather rapidly but if
you recall Ipoh EPO takes about ten days in order to manufacture more red blood cells and
so an individual following hemorrhage might be somewhat anemic on the other side of the
spectrum an individual might be polycythemia and that is having an elevated hematocrit
to the point of danger with too many red blood cells an individual is at risk for spontaneous
coagulation which would lead to ischemia which could possibly lead to necrosis and possibly
death on the surface of erythrocytes are a number of different molecular enhancements they may be
proteinaceous they may be lipid as' in nature they might be associations of lipids and sugars and
all of these molecular enhancements serve various functions oftentimes we might categorize or group
an individual's blood by these surface elements and one of the more popular ways of doing so is
with the ABO blood group with the ABO blood group there are certain surface membrane antigens
either A or B or both a and B or the complete lack of those surface membrane antigens which
help us to categorize the blood so there are four major blood types type a Type B type a B
and Type O there are two surface antigens and their various distributions that help
us to type within the ABO blood group those surface antigens are the a and the B antigen
and an individual might have only the a antigen in which case they are type A they may have only the
B antigen in which case they are type B they may have both antigens in which case they are type a
B or they may have neither antigen in which case they are Type O or originally thought of as zero
complementing these surface antigens our serum antibodies for whichever antigen the individual
does not have so for instance an individual who has type a has serum anti-b antibodies
an individual who has type B has serum anti a antibodies an individual who has type a B as no
anti a or anti-b antibodies and an individual who is Type O has both anti a and anti-b antibodies
now an antibody is a protein with variable sites that can interact with antigens and an antibody
may bind or a gluten eight molecules together or an antibody may call in what's known as a
complement response or reaction in which case the cell and all surrounding tissues can be destroyed
by the immune system in the case of the ABO blood group these antibodies are agglutinative
and what can happen is if someone is not careful when performing a transfusion of blood or blood
products there can be a cross reaction so for instance if an individual who is Type A receives
blood products from a donor who has type B we can have a looot nation likewise if an individual who
is Type B receives blood products from someone who's Type A we can have a glutton nation if an
individual is type a B they're considered the universal recipient they can receive blood from
any of the blood types in an individual who is Type O they can only receive blood from other
individuals who are Type O they receive blood from individuals that are a B or a B they're going have
agglutination responses these individuals who are Type O our special however because
they're erythrocytes don't have any surface ISO antigens meaning they can be donated to
any of the other blood types in a whereas type a B was seen as the universal recipient type O
as a blood type is the universal donor another form of blood typing involves a surface antigen
known as the Rh factor the Rh factor was first isolated in rhesus monkeys that's why we call
it the Rh factor and an individual either has the Rh factor meaning they are Rh positive or
they do not have the Rh factor in which case they are Rh negative as you can imagine this
can be layered onto the [ __ ] blood type as well so an individual might be a positive or a
negative or a positive or a negative and so on and so forth the largest clinical significance
of the Rh factor involves mothers who are Rh negative so what can happen is a woman who is
Rh negative might conceive a child with a partner who has Rh positive and it's therefore conceivable
that the fetus and the subsequent embryo might be Rh positive well what can happen is during
the first pregnancy in the placenta where we have mixing of mother and child's blood this
Rh negative mother is exposed to the Rh factor for the first time and she might start producing anti
RH antibodies and in subsequent pregnancies these anti RH antibodies can travel across the placenta
and into the bloodstream of the developing fetus and embryo and mount an immune response against it
they could be deadly thankfully science has engineered a cure for this in the form of a
substance called Rogan with rhogam a woman who is Rh negative receives a series of injections
and this prevents her body from ever forming these anti Rh factor antibodies and so she
can proceed with this pregnancy and subsequent pregnancies without jeopardizing the health of
the developing child the condition of having these anti RH antibodies attacking a developing embryo
is known as hemolytic disease of the newborn and it has been nearly eliminated thanks to
the development of Rogan so we've discussed red blood cells their components their functions their
clinical applications let's go on in future lessons to see how other constituents of the
blood such as leukocytes or white blood cells and thrombocytes may also function thank you