PHIS 206 Lecture Notes - Lecture 15: Buffy Coat, Erythropoiesis, Urobilin
2 May 2018
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Lecture 15: The Blood
Blood Components
• Erythrocytes = red blood cells (RBCs)
• Buffy Coat contains other cellular components
• Plasma contains proteins and electrolytes
• Blood is a tissue - got different cell types - liquid tissue
• Plasma = 55% of whole blood (majority) (yellowy straw color)
• Buffy coat = less than 1% of whole blood
• Erythrocytes = 45% of whole blood (red)
• Fraction of red blood cells (percentage of blood volume that is red blood cells) =
hematocrit (or crit)
• Red blood cells hold the oxygen
Hemoglobin
• Two sets of parts
o Large globular proteins (two alpha chains, two beta chains)
o Heme Groups (that bind iron) - one for each chain
• Structure of ring around iron (porphyrin ring basis of the color) gives red color
• Red blood cells have hemoglobin
• Made up of 4 pieces - 4 large proteins
• Constantly recycled
• Hemoglobin red because heme group
• Urobilin is the reason your urine is yellow
• Stercobilin is the reason why poop is brown
Differentiation
• Stem cells “progenitors” differentiate into cells that become the cells that become the
erythrocyte
• Along the way, all internal cellular machinery is lost
• As a result, RBCs have very limited lifespan (100-120 days)
• This differentiation process is known as erythropoiesis (differentiates to become blood
cell)
• Red blood cells pretty much just full of hemoglobin, don't have mitochondria, nuclei, etc
→ shell of hemoglobin
• Stem cells are cells that haven't decided what they want to become yet
• Understand process of erythropoiesis
Erythropoiesis
• Oddly enough, the kidney plays a major role in triggering/regulating erythropoiesis
• The hormone erythropoietin (EPO) is released by the kidney, and stimulates the
progenitor stem cells to differentiate
• When kidney notices your oxygen content is too low, it releases erythropoietin (EPO)
•
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