2 - Erythropoiesis

Question 1

Erythropoiesis

Answer 1

Formation and life cycle of RBC

Question 2

Where does RBC form before birth? (3 Stages)

Answer 2

Mesoblastic stage – 3rd week, nucleated red blood cells form in Yolk sac and mesothelial layers of placenta
Hepatic stage – 6 weeks, Liver & Spleen
Myeloid stage – 3rd monthonwards, bone marrow becomes principal source of RBC

Question 3

Where does RBC form after birth? (3 stages)

Answer 3

Up to 5 years –Bone marrow in all bones
Age 5 to 20/25 – Marrow of longbones (Femur, tibia)
Age 25+ - Marrow of membranous bones(vertebrae, sternum, ribs, cranial bones)

Question 4

Yellow Marrow

Answer 4

Fat droplets and cells

Question 5

Red Marrow

Answer 5

Erythropoiesis

Question 6

Stages of Erythropoiesis

Answer 6

1 = Haemocytoblast in bone marrow
2 = Common myeloid progenitor (proerythroblast)
3 = Early, late erythroblast and normoblast
4 = Reticulocyte

Question 7

Erythrocyte size + stain

Answer 7

7.8um diameter, stain with EOSIN, volume of 90cumm

Question 8

Reticulocyte what are they and percentage

Answer 8

Haveribosomal RNA which shows as dark markings, 1% of red cells are reticulocytes

Question 9

Proerythroblast what are they

Answer 9

Can differentiate into other blood cells e.g megakaryocyte, myeloblast

Question 10

Myeloblast what do they develop into

Answer 10

Developinto granulated white cells (granulocytes)

Question 11

Granulocytes what are they

Answer 11

Part of the innate immune system, neutrophils make up majority

Question 12

What is the RBC count for male and female

Answer 12

Male 5.2 ± 0.3 x 106 /µL

Female 4.7 ± 0.3 x 106 /µL

Question 13

Where is EPO produced?

Answer 13

Interstitial cells in kidney proximal tube

Question 14

What stimulates EPO release?

Answer 14

Hypoxia stimulates EPO secreting cells to release EPO

Question 15

What does EPO act on ?

Answer 15

Erythropoeitic stem cells

Question 16

What are the effects of EPO?

Answer 16

Rapid maturation of bone marrow cells, increased reticulocyte, stimulates maturation of erythroblasts in the red bone marrow

Question 17

Erythrocyte Sedimentation Rate

Answer 17

Non-specific marker of infection
Standard blood test
Raised indicates infection as bacteria release molecules that bind RBC together as they reduce the negative charge on the RBC caused by sialic acid

Question 18

How does RBC make ATP

Answer 18

Anaerobic glycolysis

Question 19

What is the RBC lifespan

Answer 19

120 days

Question 20

How do splenic macrophages detect old RBC

Answer 20

Cell surface antigens are different
Splenic macrophages identify and remove them
Increase in methaemoglobin in the cell

Question 21

What is the enzyme that converts heme into biliverdin in the macrophage?

Answer 21

Heme oxygenase

Question 22

What is biliverdin and what colour is it

Answer 22

Opened porphyrin ring minus iron atom

Greenish colour

Question 23

What is the enzyme that converts Biliverdin to Bilirubin

Answer 23

Biliverdin Reductase

Question 24

Unconjugated bilirubin

Answer 24

Bilirubin bound to albumin in the splenic macrophages and released into the blood

Question 25

Conjugated bilirubin

Answer 25

bound to glucuronic acid in the liver by hepatocytes to make it more soluble

Question 26

Normal level of conjugated bilirubin in the blood

Answer 26

0.1-0.3 mg/dL

Question 27

Where is bilirubin converted to urobilinogen?

Answer 27

Small intestine

Question 28

What happens to urobilinogen

Answer 28

90% in faeces

10% in portal vein to liver - to kidney - urine

Question 29

What can intestinal urobilinogen be oxidised into?

Answer 29

Stercobilin which is excreted in faeces

Question 30

Why is EPO produced where they are

Answer 30

Kidney has regulated GFR + steady oxygen
the o2 levels are not altered by exercise or BP changes
it is determined by level of haemoglobin in arterial blood

Question 31

What enzyme breaks down haem

Answer 31

Haemoxygenase enzyme

Question 32

What colour is stercobilin

Answer 32

Yellow