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POM > Red Blood Cells > Flashcards

Red Blood Cells Flashcards

1
Q

what is the difference between sickle haemoglobin and normal haemoglobin?

A

glutamate 6 in the beta chain is mutated to valine which is hydrophobic rather than hydrophilic

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2
Q

structure of haemoglobin

A

quarternary protein made from 4 protein chains, 2 alpha and 2 beta
contain 4 harm groups (fe2+) which binds to oxygen

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3
Q

where do all blood cells originate from?

A

HSCs (haematopoietc stem cells) in the bone marrow

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4
Q

which cells do HSCs give rise to?

A

HSCs give rise to common myeloid progenitor and common lymphoid progenitor cells

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5
Q

haemopoiesis?

A

formation and development of red blood cells

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6
Q

typical lifespan of rbc?

A

120 days

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7
Q

two key abilities of HSCs?

A

self-renewal - pool of HSCs is not depleted as some daughter cells remain as HSCs

ability to differentiate into mature progeny

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8
Q

common myeloid progenitor?

A

pluripotent cell type which gives rise to erythrocytes, monocytes and granulocytes

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9
Q

common lymphoid progenitor?

A

gives rise to NK cells, T lymphocytes and B lymphocytes

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10
Q

sites of haemopoiesis in human lifecycle?

A

initially at 3 weeks in yolk sac (mesoderm)
at 6-8wks gestation liver takes over and is principal source of blood until shortly before birth
children = bone marrow and this can occur in all bones
by the time we become adults, this is limited to a few bones, mainly pelvis, femur and sternum

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11
Q

when does the bone marrow develop haematopoietic activity?

A

around 10 wks gestation

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12
Q

where are HSCs and progenitor cells distributed?

A

ordered fashion among the bone marrow amongst mesenchymal cells, endothelial cells and vasculature

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13
Q

what are haematopoietic growth factors?

A

glycoprotein hormones which bind to cell-surface receptors

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14
Q

growth factor for erythropoiesis and where is it made?

A

erythropoietin, made in kidney

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15
Q

growth factors for granulocyte and monocyte production?

A

G-CSF and G-M CSF

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16
Q

growth factors for platelet production?

A

thrombopoietin

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17
Q

stages of rbc development?

A

common myeloid progenitor –> proerythroblast –> erythroblast —> erythrocyte

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18
Q

young RBCs?

A

polychromatic, have a bluish tinge due to high RNA content
this is linked to reticulocytes which is the name given to these young RBCs

19
Q

what is needed for erythropoiesis?

A

iron, folate, vitamin B12, erythropoietin

20
Q

what does low B12/folic acid cause?

A

macrocytic anaemia, RBCs are large in size
= megaloblastic anaemia

21
Q

what do low iron levels lead to? how is this caused?

A

microcytic anaemia (smaller cells)
also tend to be pale (central pallor is greater than 1/3) so are called hypochromic
caused by anaemia of chronic disease, thalassemia

22
Q

erythropoietin?

A

glycoprotein that is synthesised in response to hypoxia, stimulates bone marrow to produce more red blood cells

23
Q

major functions of iron?

A

transports oxygen in haemoglobin

formation of mitochondrial proteins, namely cytochrome a, b and c

24
Q

forms of iron? which is better?

A

ham = ferrous = fe2+ (animal-derived)
non-harm = ferric = fe3+
ferrous form is better because it’s more easily absorbed by body
ferric form requires action of reducing substances

25
Q

name a source of non-haem iron?

A

soya beans, contain phytates which further reduces absorption

26
Q

problem with excess iron consumption?

A

toxic to organs e.g. heart and liver and therefore is tightly-controlled

27
Q

how much iron absorbed per day?

A

1-2 mg per day

28
Q

what regulates iron stores?

A

hepcidin, secreted by liver in response to high-storage iron

29
Q

what are vitamin B12 and folate needed for?

A

for dTTP synthesis, this is necessary for thymidine synthesis
deficiency of either inhibits DNA synthesis

30
Q

how does vitamin B12 and folate deficiency affect rapidly dividing cells?

A

bone marrow - cells can grow but are unable to divide properly

31
Q

where is folic acid absorbed?

A

small intestine

32
Q

when do the requirements of folic acid increase?

A

pregnancy
sickle cell anaemia

33
Q

how is vitamin B12 absorbed?

A

B12 combines with intrinsic factor in (made in gastric parietal cells) stomach to form B12-IF
the B12 is first cleaved by HCl in the stomach

in the small intestine, B12-IF binds to receptors in the ileum (this is how B12 is absorbed)

34
Q

causes of vitamin-B12 deficiency?

A

inadequate intake - veganism
inadequate secretion of IF (pernicious anaemia)
lack of acid in stomach

35
Q

rbc destruction?

A

= after typical lifestyle of 120 days
the rbc is destroyed by the phagocytic cells of the spleen (macrophages)

most of RBC is recycled, iron from haem group returns to bone marrow where it is recycled

36
Q

three things erythrocyte function depends on?

A

-integrity of membrane
-haemoglobin structure and function
-cellular metabolism

37
Q

red blood cell membrane?

A

biconcave shape - aiding manoeuvrability through small red blood vessels
made up of lipid bilayer supported by protein cytoskeleton and contains transmembrane proteins
these maintain integrity of cell

38
Q

disruption of vertical linkages in membrane?

A

hereditary spherocytosis
these are cells that are spherical in shape
lack central pallor
results from a loss of cell membrane without loss of equivalent amount of cytoplasm, so cell is forced to round up
rbcs become less flexible and are forced to haemolyse by the spleen

39
Q

disruption of horizontal linkages?

A

= elliptocytes
these may also occur in iron deficiency

40
Q

G6PD?

A

important enzyme in HMP shunt
HMP shunt is tightly coupled to glutathione metabolism, which protects red blood cells from oxidant damage
e.g. of oxidant = broad beans or drugs

41
Q

G6PD deficiency?

A

x-linked inheritance, affected individuals are usually males
signs are irregularly contracted (bite) cells

42
Q

polycythaemia?

A

too many red blood cells in circulation
Hb, RBC and Hct are all elevated

43
Q

types of polycythaemia?

A

pseudo = reduced plasma volume
true = increase in total volume of red cells in circulation
can be caused by doping, appropriately increased erythropoietin (e.g. when at high altitudes, hypoxia)
or independent of erythropoietin (polycythaemia vera)

POM (15 decks)

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