Red Blood Cells - creation, function and destruction

Question 1

Red blood cell name?

Answer 1

erythrocytes

Question 2

erythrocytes?

Answer 2

RBCs

• biconcave disk without nucleus
• contain pigment haemoglobin - red, transport oxygen and CO2 - acid/base balance
• 500X more numerous than WBCs
• replace at 1% per day to make up for lifespan of 100 days
• contain enzymes for glycolysis
• can’t divide or make new proteins
• maintain membrane integrity and prevent oxidation

Question 3

How are blood cells produced?

Answer 3

• embryological stem cell form blood islands in yolk sac
• cells migrate to liver then spleen then bone marrow in foetus
• at birth marrow is widely distributed - l retreats to axial skeleton by adulthood

Question 4

Bone marrow storma consists of?

Answer 4

• fibroblasts
• macrophages
• endothelium
• fat cells
• bone cells

Question 5

Growth factors of red blood cells?

Answer 5

• interleukin 3
• erythropoietin
• androgens
• thyroxine
• growth hormone

Question 6

Reticulocytes?

Answer 6

immature RBS

• no nucleus
• granulated appearance when stained

Question 7

What is reticulin?

Answer 7

remnants of mRNA left once the nucleus of a maturing RBC had been extruded - removed by spleen in 1-2 days

• useful measure of marrow response to anaemia or treatment
• stained by methylene blue on slide or automated count

Question 8

Iron in the body?

Answer 8

• 3000 - 5000 mg - 2/3 is hb
• daily diet - 10-20 mg - 1-2 mg in ferrous form (II) - higher need in pregnancy
  ferrous form (II) is transported into duodenal enterocytes (cells of intestinal lining)
• no mechanism to excrete iron - use or build up
• balance must be well maintained - transferrin regulates absorption

Question 9

What is transferrin?

Answer 9

protein in the blood that binds to iron and transports it throughout the body
- delivers iron from absorption centres in the duodenum and white blood cell macrophage to all tissues

Question 10

What is hepcidin?

Answer 10

regulator of iron into the circulation
- when abnormally high - inflamation - iron falls due to iron trapping within macrophages and liver cells and decreased gut iron absorption

Question 11

How is iron lossed?

Answer 11

• menstrual loss
• minor trauma
• GI - approx iml blood per day
• blood sampling
• very small amounts in urine/skin shedding

Question 12

What transports iron?

Answer 12

> transferrin - transport/recycling - transferrin receptors increase in iron def
ferritin - insoluble form of storage iron - better measure of iron stores

Question 13

Where is iron stored?

Answer 13

mostly in the liver, as ferritin or hemosiderin

Question 14

Folic acid/folate in body?

Answer 14

(folate - includes folic acid, vit B9, folacin)

• daily requirement - 0.1mg - approx 0.25 from diet
• absorbed in upper small bowel
• liver stores 10-20mg (100-200 days worth)
• deficiency caused by poor intake, absorption - symptoms pins and needles, yellow skin, sore tongue, mouth ulcers…

Question 15

Vitamin B12/cobalamin in body?

Answer 15

• 1 microgram required daily - animal products
• absorbed in terminal ileum
• deficiency leads to pernicious anaemia

Question 16

What transports B12/cobalamin?

Answer 16

trans cobalamin II via portal circulation to liver

Question 17

How does B12/cobalamin bind?

Answer 17

intrinsic factor bind it

- intrinsic factor produced by gastric parietal cells

Question 18

Functions of B12 and folate?

Answer 18

required in RBC production

Question 19

What is erythropoietin? (EPO)

Answer 19

hormone produced by the kidneys

• role in production of RBCs
• no body stores so switched on by - tissue hypoxia or anaemia, high altitude, epo producing tumours eg renal
• drives erythropoesis in marrow
• useful recombinant drug for renal anaemia (underproduction) and myelodysplasia (increased drive to erythropoeises)

Question 20

What is sypherocytosis?

Answer 20

change of shape of RBCs to being spherical - not biconcaved disk

• caused by inherited mutations
• anaemias

Question 21

Binding of haemoglobin?

Answer 21

One hb to each globin chain
needs - 2 alpha chains, 2 beta chains, (2a, 2g if foetal)
- binds to O2 at high oxygen concentrations, released easily at low O2 concentrations - acids and increased temperature delivers more O2 to tissues

Question 22

What is thalassaemia?

Answer 22

an inherited defect in globlin chain production

- deformities in facial bones

Question 23

What causes sickle cell disease?

Answer 23

one amino acid chain change in beta chain

- valine replaces the glutamic acid on the sixth chain

Question 24

What does the glycolytic pathway end with? and what used for?

Answer 24

lactate and pyruvate

for: - membrane integrity - prevent oxidation of enzymes and Fe(II), maintains gradients of K+ and Ca++

Question 25

What do enzyme deficiencies of pyruvate or G6PD result in?

Answer 25

anaemia by haemolysis - increased RBC breakdown

Question 26

Release of O2 form haemoglobin?

Answer 26

2,3 DPG

• right shift in O2 dissociate curve
• enters global chain releasing O2
• increased 2,3 DPG in exercise, anaemia, high altitude

Question 27

Store of O2 for intermediate use in muscle?

Answer 27

myoglobin

• one hb unit, one goblin chain
• last resort oxygen reserve in muscle - only gives up oxygen in severe cases

Question 28

pH of blood?

Answer 28

7.35 - 7.45

Question 29

Why is acid-base balance important?

Answer 29

• enzymes have an optimum pH
• cell membranes become leaky in acidosis
• neurones become less able to transmit in acidosis - hyperactive in alkalosis

Question 30

What does the blood buffer system consist of?

Answer 30

• carbonic acid (H2CO3)
• bicarbonic anion (HCO30-)
  maintains blood pH

> when basic substance enters

Question 31

Increase in H+ result?

Answer 31

bicarbonate ions remove hydronium ions - neutralising blood - forming carbonic acid and water

Question 32

Increase in OH- result?

Answer 32

carbonic acid reacts with hydroxide ions producing bicarbonate ions and water - removing hydroxide ions

Question 33

Blood buffer equilibrium?

Answer 33

co2 + h20 h2co3 h+ + hco3-

Question 34

What catalyses blood buffer reactions?

Answer 34

carbonic anhydrase

Question 35

Haemoglobin function in blood buffer capacity?

Answer 35

(30% due to this)

• low pH decreases Hb affinity for O2
• H+ combines with Hb after loss of 02

Question 36

What causes RBC loss?

Answer 36

as RBC age - membrane more rigid, loss of glycolytic enzymes, neoantigens exposed on cell surface

• some lost from GI tract, into soft tissues, menstural loss
• some destroyed within body

Question 37

Recycling of RBCs?

Answer 37

spleen/liver

• free hb mopped up by liver using haptoglobin - excess appears in urine
• globin chains broken up into amino acids
• iron bound to transferrin and returned to macrophages
• porphyrin ring becomes bilirubin - bound to albumin and conjugated to glucuronide - excreted in bile