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Blood cells- OB/Biochem > Red Blood Cells > Flashcards

Red Blood Cells Flashcards

1
Q

erythrocyte definition

A

A red blood cell, which in humans is typically a biconcave disc without a nucleus

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2
Q

How can erythrocytes be visualised in blood?

A
  1. smear blood on slide, add H&E- stain pink due to protein haemoglobin- no blue as they have no nuclei
  2. scanning EM
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3
Q

3 shapes of red blood cells, what causes the differences?

A

discocyte, stomatocyte, echinocyte

shape depends on water content, due to the osmotic effects of solutes- especially ions

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4
Q

discocyte explained

A

the shape that a rbc takes when not subjected to external stress

7.5-8.7 μm in diameter and 1.2-2.2 μm in thickness

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5
Q

stomatocytes structure

A

erythrocytes with a slit-like central pallor, giving the appearance of a coffee bean- bowl shape

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6
Q

how are stomatocytes formed?

A

lost its biconcave structure due to membrane defect

stomatocytosis often due to alterations in membrane permeability, leading to increase in cell volume

form in low blood acidic pH

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7
Q

Echinocyte structure

A

red blood cell with an abnormal cell membrane characetrised by many small, evenly spaced thorny projections

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8
Q

synonym for echinocytes

A

Burr cells

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9
Q

Why are echinocytes formed?

A

Echinocytosis- reversible condition of red blood cells

often occurs during sampling blood due to EDTA ( an anticoagulant) producing the artefact.

also associated with disease- such as cirrhosis, and vitamin E deficiency

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10
Q

Inner structure of erythrocytes

A
  • annucleate
  • no mitochondria- rely solely on anaerobic respiration
  • haemoglobin
  • enzymes
  • ions
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11
Q

advantages of being annucleate

A
  • better surface- volume ratio, thus improves gas exchange
  • improved deformability- able to fit through capillaries
  • less work for heart as a pump, as the red blood cells have a smaller mass
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12
Q

How many kg does the heart pump per minute?

A

3kg of erythrocytes

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13
Q

disadvantages of being anucleate

A
  • no further protein synthesis or repair- cells wear out
  • requires vast new replacement cell production
  • terminally differentiate, therefore cannot adapt to changes in conditions
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14
Q

turnover of erythrocyte

A

120 DAYS

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15
Q

How do erythrocytes survive without mitochondria?

A
  • energy required is very small, only for ion pumps
  • solely depend upon glucose- glycolysis
  • glycolytic intermediate- 2,3 bisphosphoglycerate is produced by erythrocyte enzyme. This shifts the curve to enable oxygen to dissociate
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16
Q

Haemoglobin brief structure

A

globin protein- alpha 2 and beta 2 (tetramer)

haem prosthetic group- one Fe2+ per haem

forms 2/3 of the body’s iron

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17
Q

haemoglobin function

A

binds to oxygen, enabling it to be carried around the body

carbon dioxide binds to the haemoglobin, forming carbaminohaemoglobin

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18
Q

How else is carbon dioxide transported around the body?

A

via the bicarbonate buffer system

  1. co2 diffuses into the red blood cells
  2. carbonic anhydrase converts the co2 into carbonic acid
  3. carbonic acid is unstable, so dissociates into bicarbonate ions and hydrogen ions
  4. since carbon dioxide is quickly converted into bicarbonate ions, a concentration gradient is maintained, enabling co2 to continually diffuse into cells
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19
Q

How does carbon dioxide become released?

A
  1. bicarbonate ion transported out of red blood cell into the plasma, in exchange for a chloride ion (known as the chloride shift)
  2. when the blood reaches the lungs, the bicarbonate ion is transported back into the red blood cell in exchange for chloride
  3. H+ dissociates from the haemoglobin and binds to the bicarbonate ion, forming carbonic acid intermediates
  4. carbonic anyhydrase then converts the carbonic acid back into CO2
  5. CO2 then expelled during exhalation
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20
Q

Intracellular K+ and Na+ conc

A

na+ = 6mM

K+ = 100-140 mM

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21
Q

Extracellular K+ and Na+ conc

A

Na+= 140mM

K+ = 3.5-5 mM

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22
Q

How is this maintained?

A

Na+ - K+ ion exchanger present in cell membrane

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23
Q

How do red blood cells flow through blood vessels?

A
  • erythrocytes deform to squeeze through arterioles and capillaries
  • occupy the central axis of the vessel- plasma rich at circumference
  • blood is viscoelastic- meaning it changes shape with flow rate
  • form a rouleaux- pile up on each other
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24
Q

anomalous viscosity of blood definition

A

The measure of the resistance of blood to flow- the thickness and stickiness of blood.

Viscosity of blood increases with decreased velocity

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25
Q

Why is blood flow low in small vessels?

A

adherence of RBCs to each other, forming a rouleaux and to vessel walls

shear forces no longer enough to deform the RBC, so they appear my rigid

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26
Q

what factors increase the viscosity of blood? + explained

A

Hematocrit- one unit increase in haematocrit can cause up to a 4% increase in blood viscosity

red blood cell aggregation- rouleaux formation

plasma viscosity- depends on water content and macromolecular components

low temperatures

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27
Q

Where does the energy fro viscoelasticity come from?

A

primarily due to the elastic energy that is stored in the deformation of red blood cells

energy transferred to the blood from the heart is partially stored in the elastic structure, whilst the remaining energy is stored in the kinetic motion of the blood

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28
Q

How do rouleauxs form?

A

At rest or very small shear rates, the cells aggregate and stack together in an energetically favourable manner.

due to the attraction of charged groups on the surface of cells and the presence of fibrinogen and globulins

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29
Q

different physiological solution conditions and their osmotic effects on erythrocytes

A

isotonic- rouleaux

hypotonic- lysis

hypertonic- shrivelled, crenated cells

30
Q

What causes the cells to burst?

A

cell membrane contains aquaporins, which allows fluid to cross the membrane

31
Q

How much water permeates the rbc?

A

250 times the cell volume

32
Q

Brief erythrocyte membrane structure

A

anchoring proteins- spectrin, ankyrin, band 3

glycoproteins with external carbohydrate

33
Q

How are the anchoring proteins bound together?

A

spectrin dimers form a lattice bound to underlying actin filaments and ankyrin

this anchors the spectrin lattice to the glycophorins and band 3 proteins- enable red blood cells to maintain their shape

34
Q

Ankyrin function

A

protein that links the bilayer to the membrane skeleton through the interaction of cytoplasmic domains

35
Q

spectrin function

A

cytoskeletal protein that lines the intracellular side of the plasma membrane

maintains plasma membrane integrity and cytoskeletal structure

36
Q

Band 3 function

A

anion transport protein- mediates the exchange of chloride and bicarbonate ions across plasma membranes

37
Q

What shortens the life span of red blood cells?

A

abnormal shape, accelerated clearance

38
Q

Explain abnormal shape

A

Mutated haemoglobin- thalassaemias, sickle cell anaemia

cytoskeletal proteins altered- hereditary spherocytosis

39
Q

Explain accelerated clearance

A

overactive phagocytosis in spleen and liver, due to autoimmune disease or the macrophages are too active

40
Q

What causes erythrocyte ageing?

A

inactivation of cellular enzymes and many membrane transporters

increased haemoglobin oxygen affinity and decreased cellular deformability of aged red blood cells

products of proteolytic degradation of Band 3 accumulate

41
Q

How are aged erythrocytes removed from circulation?

A

Bind immunoglobin G

erythrophagocytosis

42
Q

Erythrophagocytosis stages

A
  1. ageing red blood cell undergoes changes in its plasma membrane
  2. selectively recognised by macrophages
  3. leads to phagocytosis in the spleen and liver
43
Q

How is a low RBC count prevented?

A

erythopoiesis is the same rate as eryptosis

44
Q

anaemia definition

A

condition which leads to a decrease in the total amount of RBCs, haemoglobin or a lowered ability of the blood to carry oxygen around the body

45
Q

anaemia symptoms

A

tiredness, weakness, shortness of breath, poor ability to exercise

46
Q

Causes of anaemia

A

impaired RBC production, increased RBC destruction, blood loss

47
Q

how are anaemias differentiated + 3 divisions of anaemia

A

different diseases dependent on the shape of blood cell- microcytic, normocytic, macrocyctic

48
Q

Anaemia due to lack of…

A

Iron and vitamins- B12 or folate

49
Q

Example of B12 deficiency anaemia

A

pernicious anaemia- immune system attacks healthy cells in the stomach

prevents the body absorbing vitamin B12 from food

50
Q

Causes of ion deficiency anaemia

A

lack of iron in diet, o heavy periods

51
Q

Folate and B12 function

A

work together to during the purine and thymidylate syntheses and dna synthesis

52
Q

sickle cell anaemia explained

A

An individual inherits two abnormal copies of the haemoglobin gene- in chromosome 11

leads to sickle shaped red blood cells

low oxygen tension promotes sickling and damage to the cell membranes, which decreases elasticity

53
Q

How does sickle cell disease damage organs?

A

causes a vaso-occlusive crisis that causes the obstruction of capillaries and restrict blood flow to an organ

splenic sequestration crisis- vaso-occlusion increases the risk of infection from encapsulated organisms- leads to an acute, painful enlargement of the spleen

54
Q

process that produces more erythrocytes

A

hematopoeisis

55
Q

process of hematopoeisis stages

A
  1. all blood cells arise from a single hemopoietic stem cell in the bone marrow
  2. give rise to two majr lineages of progenitor cells- myeloid an lyphoid
  3. myeloid cells divide into different types of colony forming units- the erythroid lineage of erythrocytes
  4. each of these progenitor cell lineages produce precursor cells that gradually assume the morphologic characteristics of the mature, functional cell type they become
56
Q

where does the process of hematopoeisis take place?

A

red bone marrow

57
Q

key features of stem cells

A
  1. self renew

2. differentiate to next stage

58
Q

Who investigated the pluripotency of cells in the bone marrow?

A

Till and McCullough

59
Q

Explain Till and McCullough experiment

A
  1. irradiated a female mouse, killing her bone marrow
  2. inserted a cell suspension containing male red blood cells, male bone marrow and male spleen into the female mouuse
  3. within 8-14 days, the spleen was shown to be full of erythrocytes, suggesting that the red blood cell population had been repopulated
60
Q

list sources of haemopoietic stem cells

A

adult bone marrow, liver in foetus, embryonic yolk sac, umbilical cord

61
Q

erythropoiesis definition

A

the formation of a terminally differentiated red blood cell. Requires approximately a week and involves 3-5 cell divisions between the progenitor cell and the functional cell

62
Q

Changes that take place during erythropoiesis

A

cell and nuclear volume decrease

nucleoli diminish in size and disappear

gradual decrease in number of polyribosomes

increase in the amount of haemoglobin

mitochondria and other organelles slowly disappear

63
Q

important growth factor in erythropoiesis

A

Erythropoietin (EPO)

64
Q

where is EPO produced? + when?

A

The kidneys. Produced by interstitial fibroblasts

in response to cellular hypoxia (when a region of the body is deprived of oxygen)

65
Q

EPO function

A

stimulates production of mRNA for the protein components of haemoglobin

66
Q

EPO mechanism of action

A

C

67
Q

two different types of blood group

A

ABO and Rh

68
Q

explain ABO blood typing

A

presence of alpha or beta glycorproteins on the outer cell membrane

alpha and beta are dominant to i but are co dominant

69
Q

explain Rh blood typing

A

blood typing system of 49 defined blood group antigens

main antigens are D,C,E,e and c

70
Q

what does rh negative mean?

A

there’s no d

inherits two d which means has no rhesus protein

Blood cells- OB/Biochem (8 decks)

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