Red Blood Cells - creation, function and destruction Flashcards
Red blood cell name?
erythrocytes
erythrocytes?
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
How are blood cells produced?
- 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
Bone marrow storma consists of?
- fibroblasts
- macrophages
- endothelium
- fat cells
- bone cells
Growth factors of red blood cells?
- interleukin 3
- erythropoietin
- androgens
- thyroxine
- growth hormone
Reticulocytes?
immature RBS
- no nucleus
- granulated appearance when stained
What is reticulin?
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
Iron in the body?
- 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
What is transferrin?
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
What is hepcidin?
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
How is iron lossed?
- menstrual loss
- minor trauma
- GI - approx iml blood per day
- blood sampling
- very small amounts in urine/skin shedding
What transports iron?
> transferrin - transport/recycling - transferrin receptors increase in iron def
ferritin - insoluble form of storage iron - better measure of iron stores
Where is iron stored?
mostly in the liver, as ferritin or hemosiderin
Folic acid/folate in body?
(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…
Vitamin B12/cobalamin in body?
- 1 microgram required daily - animal products
- absorbed in terminal ileum
- deficiency leads to pernicious anaemia
What transports B12/cobalamin?
trans cobalamin II via portal circulation to liver
How does B12/cobalamin bind?
intrinsic factor bind it
- intrinsic factor produced by gastric parietal cells
Functions of B12 and folate?
required in RBC production
What is erythropoietin? (EPO)
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)
What is sypherocytosis?
change of shape of RBCs to being spherical - not biconcaved disk
- caused by inherited mutations
- anaemias
Binding of haemoglobin?
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
What is thalassaemia?
an inherited defect in globlin chain production
- deformities in facial bones
What causes sickle cell disease?
one amino acid chain change in beta chain
- valine replaces the glutamic acid on the sixth chain
What does the glycolytic pathway end with? and what used for?
lactate and pyruvate
for: - membrane integrity - prevent oxidation of enzymes and Fe(II), maintains gradients of K+ and Ca++
What do enzyme deficiencies of pyruvate or G6PD result in?
anaemia by haemolysis - increased RBC breakdown
Release of O2 form haemoglobin?
2,3 DPG
- right shift in O2 dissociate curve
- enters global chain releasing O2
- increased 2,3 DPG in exercise, anaemia, high altitude
Store of O2 for intermediate use in muscle?
myoglobin
- one hb unit, one goblin chain
- last resort oxygen reserve in muscle - only gives up oxygen in severe cases
pH of blood?
7.35 - 7.45
Why is acid-base balance important?
- enzymes have an optimum pH
- cell membranes become leaky in acidosis
- neurones become less able to transmit in acidosis - hyperactive in alkalosis
What does the blood buffer system consist of?
- carbonic acid (H2CO3)
- bicarbonic anion (HCO30-)
maintains blood pH
> when basic substance enters
Increase in H+ result?
bicarbonate ions remove hydronium ions - neutralising blood - forming carbonic acid and water
Increase in OH- result?
carbonic acid reacts with hydroxide ions producing bicarbonate ions and water - removing hydroxide ions
Blood buffer equilibrium?
co2 + h20 h2co3 h+ + hco3-
What catalyses blood buffer reactions?
carbonic anhydrase
Haemoglobin function in blood buffer capacity?
(30% due to this)
- low pH decreases Hb affinity for O2
- H+ combines with Hb after loss of 02
What causes RBC loss?
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
Recycling of RBCs?
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
