Unit 3: Blood Part D

Question 1

Erythrocytes (Red Blood Cells)

Answer 1

Most numerous blood cell. Makes up >99% of
blood cells.
Ø ~ 5 billion RBC’s per ml of blood

Question 2

Describe the shape of erythrocytes

Answer 2

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)

Question 3

What is the lifespan of RBCs?

Answer 3

Short-lived (~120 days) – rapidly produced in bone marrow

Question 4

Explain the basic process of erythropoiesis

Answer 4

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

Question 5

Explain the significance of the reticulocyte

Answer 5

the final immature cell form of a RBC

leaves the marrow and enters circulation where it matures into a erythrocyte in abt 24 hrs

Question 6

What do RBC contain?

Answer 6

Hemoglobin; transports o2
large complex protein

Question 7

What is adult Hemoglobin (Hb) composed of?

Answer 7

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.

Question 8

Globin

Answer 8

protein chains; binds and transports CO

Question 9

Heme

Answer 9

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.

Question 10

Describe the process of Iron metabolism and Hemoglobin Synthesis

Answer 10

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

Question 11

Describe the breakdown products of RBC and their fates

Answer 11

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

Question 12

What is jaundice? include symptoms

Answer 12

excess bilirubin in blood (due to excess RBC breakdown, liver dysfunction, or
blockage of bile excretion)

Symptoms include yellow skin and sclera of eye.

Question 13

Why is jaundice common in neonatal infants

Answer 13

Common in neonatal infants because their livers are not yet fully functional (phototherapy oxidizes bilirubin and allows for excretion)

Question 14

Hematocrit (Hct)

Answer 14

the % of blood volume that is erythrocytes

Question 15

What is the average in hematocrit in women and men?

Answer 15

On average ~42% (women) and 47% (men

Question 16

How is hematocrit determined?

Answer 16

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

Question 17

identify the clinical relevance of a high hematocrit value

Answer 17

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%

Question 18

Anemia

Answer 18

low hemoglobin content of blood, which
decreases its ability to carry oxygen

Question 19

Why does anemia occur?

Answer 19

Occur due to blood loss (hemorrhage); accelerated rate RBC destruction, or decreased RBC production

Question 20

Hemolytic anemias

Answer 20

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.

Question 21

Hereditary spherocytosis

Answer 21

defective cytoskeletal elements change cell shape to a sphere that ruptures easily in response to osmotic changes

Question 22

Sickle cell anemia

Answer 22

genetic disorder affecting amino
sequence hemoglobin beta chain

abnormal hemoglobin causes crescent shaped cells that cause blockages and reduced blood flow to tissues

Question 23

Describe how accelerated blood loss causes anemia

Answer 23

cells are normal in size and hemoglobin content but low in number

ex- hemolytic anemias
sickle cell
parasitice

Question 24

Describe how decreased red cell production causes anemia

Answer 24

defective red blood cell or hemoglobin synthesis in the bone marrow

Question 25

Aplastic Anemia

Answer 25

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

Question 26

Iron Deficiency Anemia

Answer 26

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

Question 27

Vitamin Deficiency Anemia

Answer 27

Dietary deficiency or trouble absorbing Folic acid, Vitamin C, or Vitamin B12 leads to abnormal RBC production (fewer cells,
& larger cells)