Red Blood Cells

Question 1

erythrocyte

Answer 1

• live about 120 days
• flexible biconcave disks, lack a cell nucleus, mitochondria, ribosomes, and they cannot synthesize proteins
• 4.5-6x10^6 men

4-5x10^6 women

-at end of lifespan, become senescent, mis-shapen and removed by macrophages in the spleen or liver (extravascular) or destroyed in blood stream (intravascular)

Question 2

hemoglobin

Answer 2

• a molecule that can bind to oxygen.
• 14-17g/dL men
• 12-15g/dL women
• 4 globin chains + 4 heme
• give RBCs their color
• synthesis happens during the erythroblast stage in bone marrow

Question 3

normochromic

Answer 3

RBC staining (due to hemoglobin) is deeper at the periphery of the cell and fades at the center (central pallor).

Question 4

hypochromic

Answer 4

cells that stain with decreased intensity (because of less hemoglobin)

Question 5

Rouleaux formation

Answer 5

• in the absence of significant blood flow, RBCs stack due to Plasma proteins—fibrinogen, C-reactive proteins, globulins, albumin
• reversible

Question 6

hematocrit

Answer 6

• aka Packed cell volume
• Volume occupied by RBCs in blood (normal is 45% men; 40% women)
• 42-49%men
• 38-46%women
• increased hematocrit -> increased blood viscosity -> thrombotic complications e.g. clogged capillaries

Question 7

Mean Corpuscular Volume

Answer 7

• average volume of single RBCs. Normal MCV is ~85 femtoliters (fl).
• decreased in iron deficiency anemia
• 83-99 fL (femto = 10^-15)
• nucleus (lost before reticulocyte) is about 40 pg

Question 8

microcytic anemia

Answer 8

• iron deficiency
• reduced MCV

Question 9

macrocytic anemia

Answer 9

• cobalamin (vit B12) deficiency
• vit B12 needed for DNA synthesis/replication so cells don’t divide fast enough
• increased MCV

Question 10

Mean Corpuscular Hemoglobin:

Answer 10

• average mass of hemoglobin in each RBC (in picograms)
• 30pg/cell
• 32-36 g/dL

Question 11

Mean Corpuscular hemoglobin concentration

Answer 11

• average concentration of hemoglobin in a given volume of packed RBCs

[Hb]/hematocrit

Question 12

reticulocyte %

Answer 12

.5-1.8%, men

.5-2.2% women

50,000-75,000/microliter

Question 13

decreased reticulocyte

Answer 13

hematopoeisis deficient

Question 14

increased reticulocyte

Answer 14

increased hematopoeisis (for example, compensatory response to a bleed)

Question 15

erythropoietin

Answer 15

90% produced by kidney

• chronic renal failure (CRF) -> EPO deficiency -> anemia
• renal cell carcinoma -> increases EPO (increased hematocrit)

10% produced by liver

• hepatocellular carcinoma -> increases EPO

Decreased oxygenation causes EPO synthesis and release within minutes, peaking in 24 hours. Stimuli include hypoxia, severe anemia, high altitude, abnormal hemoglobins that bind O2 tightly and do not release it to tissues

suppresed by increased O2 content

new RBCs within 5 days of EPO stimulus

Question 16

Polycythemia

Answer 16

• elevated hematocrit due to increased RBCs or decreased plasma volume
• hematocrit > 55%

Question 17

Physiological Polycythemia.

Answer 17

• High Altitude Living increases EPO

Question 18

Secondary Polycythemia

Answer 18

occurs when EPO rises in renal or hepatocellular carcinoma, EPO doping, or due to chronic hypoxia (e.g. lung or heart disease).

Question 19

Polycythemia Vera

Answer 19

is a disease due to over-production of RBCs because of clonal expansion of “abnormal” pluripotent stem cells. The resulting erythroblasts may be hypersensitive to EPO, but the EPO level may be low.

Question 20

O2 concentration

Answer 20

• decreases 10% per 1000m over sea level

Question 21

Microcytic Hypochromic Anemia

Answer 21

non-viable or a barely viable red blood cell that is both pale (hypochromic) because of reduced hemoglobin, and small (microcytic)

Question 22

ferritin

Answer 22

intracellular protein serves to store iron in a non-toxic form, to deposit it in a safe form, and to transport it to areas where it is required

• iron + apoferritin (protein)
• apoferritin is a shell with a central cavity to store iron, six channels go to the cavity. Fully saturated, can hold up to 4500 iron atoms
• releases iron easily

Question 23

Clinical Features of Iron Deficiency

Answer 23

• pale conjunctiva
• fatigue
• tachycardia
• koilonychia- spoon-shaped nails
• glossitis- sore or swollen tongue
• angular stomatitis- fissuring at lip corners
• gastric atrophy
• esophageal strictures- narrowing of esophagus
• melena- back stool
• pica- craving for starch, clay or ice

Question 24

treatment of iron deficiency

Answer 24

• ferrous salts
• ascorbic acid ncreases absorption and toxicity
• supplement on empty stomach
• avoid antacids

Question 25

orthochromaticblast

Answer 25

stage before reticulocyte, when nucleus is shed

Question 26

iron storage

Answer 26

• liver removes and stores excess iron ~1000mg
• ferriton is main form of storage (65%), hemosiderin (33%)
• human body contains 3-4g of iron
• hemoglobin 1800-2500mg
• liver 0-1000mg
• blood 3mg
• iron deficiency results in accumulation of protoporphyrin IX in RBCs

Question 27

hemosiderin

Answer 27

• dense aggregate of ferritin crystals formed inside lysosomes of macrophages and hepatocytes so it’s membrane bound

Question 28

heme

Answer 28

• one iron molecule per heme. Iron is added as last step in the pathway

Question 29

protoporphyrin IX

Answer 29

important precursor to heme

Question 30

iron absorption

Answer 30

• In stomach Ferric (Fe3+) -> ferrireductase -> ferrous (Fe2+)
• ferrous absorbed easier
• antibiotics reduce absorption
• absorption takes place in duodenum
• acidic compounds (ascorbic acid/vit C) increase release of iron from food

Question 31

iron deficiency anemia

Answer 31

• decreases hemoglobin synthesis which decreases:
• MCV, mean corpuscular volume
• MCHC, mean corpuscular hemoglobin concentration
• total arterial O2 concentration
• which increases:
• total iron binding capacity
• free erythrocyte protoporphyrin (bc protoporphyrin IX accumulates)