Unit 3: Blood Part D Flashcards
Erythrocytes (Red Blood Cells)
Most numerous blood cell. Makes up >99% of
blood cells.
Ø ~ 5 billion RBC’s per ml of blood
Describe the shape of erythrocytes
Flattened, biconcave disk-shaped cells that lack
nucleus and organelles.
Ø specialized for gas transport.
ØShape can change due to disease (e..g. crescent
shaped in sickle-cell anemia; spherocytosis, cells
now round spheres instead of flattened disk)
What is the lifespan of RBCs?
Short-lived (~120 days) – rapidly produced in bone marrow
Explain the basic process of erythropoiesis
in the bone marrow the committed progenitor cell will differentiate through several stages into large nucleated erythroblasts
as they mature the nucleus condenses and the cell shrinks in diameter
in the last stage before matuaration the nucleus is pinched off and phagocytized by bone marrow macrophages
final immature cell; reticulocyte
Explain the significance of the reticulocyte
the final immature cell form of a RBC
leaves the marrow and enters circulation where it matures into a erythrocyte in abt 24 hrs
What do RBC contain?
Hemoglobin; transports o2
large complex protein
What is adult Hemoglobin (Hb) composed of?
Adult Hb (HbA) is composed of two a-globin and two b-globin protein chains, each of which bound to an iron containing heme group.
Globin
protein chains; binds and transports CO
Heme
Red pigment molecule
porphyrin ring surrounding an iron (Fe 2+) atom that reversibly binds to O 2
There are 4 hemes per Hb molecule, so each Hb
transports 4 O 2
Gives blood its red colour which can be
seen through skin as a pink colour especially in areas of thin skin like like the lips.
Describe the process of Iron metabolism and Hemoglobin Synthesis
Ø Iron from diet actively transported into blood
(excess stored in liver as ferritin)
Ø Transported in plasma by transferrin
Ø Iron is taken up in the bone marrow and used
to synthesize heme –> hemoglobin –> RBCs
Ø RBCs live 120 days and are then broken down
in spleen
Describe the breakdown products of RBC and their fates
Heme:
§ iron removed and stored in liver (as ferritin), muscle, & spleen to be recycled for future use.
§ Porphyrin ring: converted to bilirubin – excreted in bile (& therefore feces) as well as urine metabolites of bilirubin give feces and urine their colour).
§ Globin: converted to amino acids and recycled
What is jaundice? include symptoms
excess bilirubin in blood (due to excess RBC breakdown, liver dysfunction, or
blockage of bile excretion)
Symptoms include yellow skin and sclera of eye.
Why is jaundice common in neonatal infants
Common in neonatal infants because their livers are not yet fully functional (phototherapy oxidizes bilirubin and allows for excretion)
Hematocrit (Hct)
the % of blood volume that is erythrocytes
What is the average in hematocrit in women and men?
On average ~42% (women) and 47% (men
How is hematocrit determined?
Determined by Complete Blood Count (CBC).
Ø Blood is centrifuged (spun in a test tube at high speeds to separate formed elements from plasma); result is a blood column separated into 3 layers:
i. RBCs packed at the bottom of the tube.
ii. Middle layer of WBCs (also known as the buffy coat)
iii. Upper layer of plasma.
ØPercentage of the blood column that is packed RBCs = hematocrit
identify the clinical relevance of a high hematocrit value
High hematocrit can indicate dehydration or a condition such as polycythemia vera, which causes the body to produce too many
blood cells (both RBCs and WBCs), in which case hematocrit may be elevated to 60—70%
Anemia
low hemoglobin content of blood, which
decreases its ability to carry oxygen
Why does anemia occur?
Occur due to blood loss (hemorrhage); accelerated rate RBC destruction, or decreased RBC production
Hemolytic anemias
cells rupture at abnormally high rate; can
be hereditary or acquired
ex- Hereditary spherocytosis
Parasitic infections (acquired) such as malaria – parasite infects RBCs, proliferates and ruptures cells.
Hereditary spherocytosis
defective cytoskeletal elements change cell shape to a sphere that ruptures easily in response to osmotic changes
Sickle cell anemia
genetic disorder affecting amino
sequence hemoglobin beta chain
abnormal hemoglobin causes crescent shaped cells that cause blockages and reduced blood flow to tissues
Describe how accelerated blood loss causes anemia
cells are normal in size and hemoglobin content but low in number
ex- hemolytic anemias
sickle cell
parasitice
Describe how decreased red cell production causes anemia
defective red blood cell or hemoglobin synthesis in the bone marrow
Aplastic Anemia
bone marrow has few stem cells, so all blood
cell production is reduced (including RBCs)
Stem cells in bone marrow can be reduced by cancer treatments (radiation/chemotherapy) and some drugs
Iron Deficiency Anemia
low iron levels due to dietary
deficiencies, blood loss (e.g. menstruation), inability to absorb iron (e.g. Celiac’s disease which damages absorptive surface of
intestine)
less iron –> less heme –> less hemoglobin
Vitamin Deficiency Anemia
Dietary deficiency or trouble absorbing Folic acid, Vitamin C, or Vitamin B12 leads to abnormal RBC production (fewer cells,
& larger cells)
