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Blood cell physiology Flashcards

1
Q

Lymphocyte function

A

humoral (B cell) and cellular (T cell) immunity

B cells differentiate into plasma cells when activated by Ag –> synthesize and secrete immunoglobulins

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2
Q

Hematopoietic stem cell progenitors

A

Lymphoid multipotent cell

Myeloid multipotent cell

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3
Q

Lymphoid multipotent cell progenitor

A

Lymphocyte-colony-forming cell

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4
Q

LCFC progenitor

A

lymphoblast –> B and T lymphocytes

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5
Q

Myeloid multipotent cell progenitors

A 
Erythrocyte-colony-forming cell
Megakaryocyte-forming cell
MGCFC --> monocyte-CFC, granulocyte-CFC
Eosinophil-colony-forming cell
Basophil-colony-forming cell
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6
Q

MCFC progenitor

A

promonocyte –> monocyte

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7
Q

GCFC progenitor

A

neutrophilic myelocyte –> neutrophilic granulocyte

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8
Q

Neutrophil function

A

phagocytose bacteria

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9
Q

Eosinophil function

A

phagocytose Ag-Ab complexes and parasites

allergic responses

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10
Q

Basophil function

A

anticoagulation (platelet-activating chemotactic factors, heparin)
increases vascular permeability (histamine)
bind IgE in allergic reactions
anaphylaxis

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11
Q

Monocyte function

A

gives rise to macrophages

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12
Q

Megakaryocyte function

A

gives rise to membranous cytoplasmic fragments –> platelets

blood clot and coagulation formation (produce von-Willebrand factor, thrombospondin, platelet-derived GF)

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13
Q

Fe distribution men

A

4g
65-70% hemoglobin
10% myoglobin
20-25% storage in reticuloendothelial cells, liver

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14
Q

Fe distribution women

A

2-3g

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15
Q

Food that increases Fe absorption

A

forms soluble iron chelates
ascorbic acid
sugars
amino acids

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16
Q

Foods that decrease Fe absorption

A

phosphates
oxalates, phytates
tannates

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17
Q

Iron absorption

A

1) ferric reductase from +3 to +2 on brush border
2) enter enterocyte via DMT1
3) storage into ferritin or transported out via ferroportin
4) hephaestin coverts +2 to +3, bound to transferrin

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18
Q

Iron utilization

A

1) transferrin receptor endocytoses transferrin-iron complex
2) acidic pH of vesicle releases iron, receptor/transferrin recycled
3) Fe incorporated into Heme (made by mit) or stored as ferritin

19
Q

Fe recycle

A

1) RBC turnover in the spleen
2) macrophages destroy heme poryphyrin ring via heme oxygenase, releases Fe and protoporphyrin
3) Macrophages transport Fe to plasma transferrin, carry back to bone marrow

  • macrophages also maintain a storage pool of iron
20
Q

Iron storage

A

Ferritin

  • multi-subunit protein shell surrounding up to 4500 Fe
  • easily mobilized

Hemosiderin

  • insoluble complex derived from ferritin, lost surface protein and has aggregated
  • higher concentration of Fe than ferritin but releases it more slowly
21
Q

Regulation of iron absorption

A

Hepcidin

  • produced in the liver in response to iron demands
  • controls flow out of enterocytes, macrophages, RE and liver cells by binding to ferroportin
  • Hepcidin-ferroportin complex taken up by cell and degraded
22
Q

Role of B12 in metabolism

A

Cofactor for:

  • homocysteine –> methionine: generates THF from methyl-THF; active form needed for DNA synthesis
  • methylmalonyl-CoA–>succinyl-CoA
23
Q

Folate absorption

A

Present in food in the form of reduced polyglutamates
Requires transport and action of pteroylglutamyl carboxypepsidase associated with mucosal membranes
Mucosae of duodenum and upper jejunum are rich in dihydrofolate reductase, can methylate most or all of folate absorbed

24
Q

Anemia in B12 and folate deficiency

A

megaloblastic anemia
larger variation in size
erythroblasts in bone marrow show slowed maturation
hypersegmented neutrophils

25
Q

Normal Hb structure

A

64.5 kDa
4 globins, 4 heme groups
2 alpha, 2 beta
each Hb binds 4 oxygen molecules

26
Q

Hb synthesis

A

1) protoporphyrin combines with Fe in mit to form heme
2) globin synthesized on polyribosomes
3) globin + heme in cytoplasm

27
Q

Hb gamma chain

A

synthesis starts in 1st trimester
rises to a peak in 2nd and 3rd
falls off just before birth
gives rise to major Hb in fetus and newborn (HbF - alpha2gamma2)

28
Q

Epsilon and zeta chains of Hb

A

synthesized in embryonic yolk sac, disappears in first trimester

29
Q

Erythropoietin site of production

A

Peripheral interstitial cells in the kidney

30
Q

Integral membrane proteins of RBCs

A

Glycophorin C - anchoring

Band 3 - link plasma membrane to cytoskeleton

31
Q

Peripheral membrane proteins of RBCs

A

spectrin
protein 4.2
ankyrin

form lattice framework parallel to membrane
dynamically changes shape to accommodate passage of RBCs

32
Q

G6PD

A

provides reducing power (NADPH)

  • prevents membrane lipid oxidation
  • detoxifies oxidants
  • prevents globin oxidation & denaturation
  • the only source for reduced glutathione (only protection for oxidative stress)
33
Q

PK in RBC

A

pyruvate kinase
key glycolytic enzyme
catalyzes transphosphorylation from PEP to ADP –> yields pyruvate + ATP

34
Q

Red marrow

A

50% of adult marrow
dividing stem cells, precursors of mature blood cells
in adults - only in heads of femur and humerus & sternum, ribs, cranium, pelvis, vertebrae (flat)

35
Q

Yellow marrow

A

50% Of adult marrow
inactive
dominated by fat cells
may be reactivated

36
Q

Components of a bone marrow biopsy

A 
framework of reticulin fibers
specialized supporting fibroblasts
meshwrok of vascular sinuses
cords of hematopoietic cells
adipocytes (increases with age)
37
Q

Key cells in erythropoiesis

A

1) proerythroblast
2) basophilic erythroblast (early normoblast)
3) polychromatic erythroblast (intermediate normoblast)
4) (late) normoblast
5) reticulocytes
6) mature RBCs

38
Q

RBC maturation

A

5-7 days to form
released into bloodstream as reticulocytes
then matures in 24-48 h

39
Q

Lymphocyte maturation

A

T - differentiate and mature in thymus

B - develop in bone marrow

40
Q

Factors that affect hepcidin production

A 
Iron stores, circulating iron
- bone morphogenetic protein senses iron
- transferrin receptor, HFE (iron sensors on cell surfaces)
Erythropoiesis & hypoxia
- erythropoietin, erythroferrone
Inflammation
-IL6
41
Q

effects of hypoxia on iron availability

A

1) kidney produces epo
2) erythroblasts produce erythroferrone
3) downregulate hepcidin in hepatocytes
4) increased iron availability

42
Q

TIBC in different disease states

A

Goes up in iron deficiency (transferrin goes up)
Iron overload - increases up to 50% but not 100%
Anemia of chronic disorders - reduced TIBC

43
Q

Serum ferritin in different states

A

Anemia of chronic disorders - increased, iron trapped in cells
Low ferritin = diagnostic of iron deficiency

2 (6 decks)

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