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circulatory system > blood > Flashcards

blood Flashcards

1
Q

what are the sites of RBC degradation

A

spleen
liver
bone marrow

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2
Q

when are RBC’s degraded

A

when they display a specific oligosaccharide on their surface

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3
Q

list the adaptations of RBC’s

A
  • biconcave disc shape, increases SA which increases gas exchange
  • un-nucleated + no organelles, provides more space for Hb
  • Hb concentrated at periphery of erythrocyte, facilitates gas exchange
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4
Q

what is the cytoskeleton of RBC’s made out of

A

spectrin
actin
adducin

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5
Q

explain why RBC’s are flexible + how they maintain their biconcave shape

A

cytoskeleton (spectrin/ actin/ adducin) is attached to ankyrin which is attached to a transmembrane protein

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6
Q

explain how ABO blood groups are determined

A

CHO chains attached to glycoproteins/lipids (glycocalyx) act as antigens to determine the blood group

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7
Q

where does prenatal hemopoiesis occur

A

liver

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8
Q

where does postnatal hemopoiesis occur

A

bone marrow (sinusoids/ stroma/ myeloid cells)

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9
Q

what do all blood cells arise from

A

pluripotent hematopoietic stem cells (PHSCs)
= 0.1% of nucleated cell population of bone marrow

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10
Q

what do PHSCs give rise to

A

more PHSCs

multipotent hematopoietic stem cells (MHSCs)
- CFU-Ly
- CFU-GEMM

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11
Q

what do MHSCs give rise to

A

unipotent/progenitor cells

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12
Q

what GFs/ cytokines control erythropoiesis + what is their function

A

IL-3 / IL-9
GM - CSF (granulocyte macrophage - CSF)
steel factor
erythropoietin hormone

function is to drive stem cells from G0 to G1 stage so they can synthesize the max amount of Hb

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13
Q

till what stage in erythropoiesis can erythroblasts divide by mitosis

A

polychromatophilic erythroblasts stage (where Hb synthesis starts)

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14
Q

what are the stages of erythropoiesis

A

1- progenitor cell is CFU-E

2- proerythroblast

3- basophilic erythroblasts (abundant ribosomes to synthesize Hb)

4- polychromatophilic (Hb synthesis occurs resulting in eosinophilia + basophilia due to present ribosomes)

5- orthochromatophilic (ribosomes decrease + nucleus becomes eccentric and is expelled)

6- reticulocyte (non-nucleated, w/ remnants of ribosomes, first to be released into circulation)

7- mature erythroblast

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15
Q

what does an abnormally high % of reticulocytes in blood indicate

A

normal % = 0.5-2.5%

abnormal increase indicates increased rate of erythropoiesis in conditions where the rate of RBC destruction exceeds rate of formation, such as hemorrhage/ anemia

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16
Q

Where is erythropoietin hormone formed

A

90% in kidney
10% in liver

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17
Q

What stimulates the formation of erythropoietin

A

Hypoxia

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18
Q

What are the general factors that affect erythropoiesis

A

Hormones (erythropoietin / thyroxin / androgen / growth hormone)
Vitamin C
Bone marrow
Liver

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19
Q

What are the maturation factors that affect erythropoiesis

A

vitamin B12 + folic acid
necessary for nuclear maturation and cell division

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20
Q

what are the factors necessary for Hb formation

A

protein
iron
copper (Fe absorption from GIT)
cobalt (utilization of Fe during Hb synthesis)

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21
Q

what are the derivatives of Hb

A
  1. oxyhemoglobin (ferrous/ Fe 2+)
  2. deoxyhemoglobin/ reduced Hb
  3. carbinohemoglobin (Hb + CO2)
  4. carboxyhemoglobin (Hb + CO)
  5. methemoglobin (blood is exposed to drugs/ oxidizing agents converting ferrous iron (Fe 2+) to ferric iron (Fe 3+) which is unable to carry oxygen)
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22
Q

what are the steps of heme synthesis

A
  1. glycine + succinylcholine CoA ( ALA synthase)
  2. ALA (ALA dehydratase)
  3. porphrobilinogen (deaminase)
  4. uroporphyrinogen (decarboxylase)
  5. coproporphyrinogin
  6. protoporhyrin IX + Fe 2+ (ferrochelatase)
  7. heme
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23
Q

what inhibits ALA synthase

A

vitamin B6 deficiency

hemin (Fe 3+)

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24
Q

what does lead inhibit in heme synthesis

A

ALA dehydratase

ferrochelatase

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25
Q

what does iron deficiency inhibit in heme synthesis

A

ferrochelatase

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26
Q

effect of lead poisoning on heme synthesis

A

inhibits ALA dehydratase + ferrochelatase resulting in an increase in ALA w/o an increase in porphobilinogen (protoporphyrin)

accumulation of ALA results in neurological symptoms such as learning disorders and decreased attention span in children

other presentations include microcytic anemia/ pallor + weakness caused by anemia/ abdominal pain/ lead lines in bone + teeth x-rays

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27
Q

what differentiates porphyria’s from lead poisoning

A

both lead poisoning + porphyria’s are caused by accumulation of ALA which causes neurological symptoms

only porphyria’s have accumulations protoporphyrins (PBG) which causes photosensitivity

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28
Q

effect of iron deficiency on heme synthesis

A

inhibits ferrochelatase which introduces Fe 2+ into heme ring resulting in microcytic hypochromic anemia

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29
Q

effect of B6 deficiency on heme synthesis

A

inhibits ALA synthase

B6 deficiency is associated with ionized therapy for TB and may cause anemia

30
Q

define porphyria

A

inherited defect in heme synthesis resulting in diseases of porphyrin metabolism

characterized by dermatologic/ neurological/ psychological manifestations

porphyria symptoms are caused by toxic accumulation of heme synthesis intermediates such as:

ALA accumulation causes neurological symptoms

porphyrin accumulation causes photosensitivity, symptoms are worsened by sunlight + cytochrome P450 inducing drugs which stimulate heme synthesis pathway to increase production (alcohol + barbiturates)

31
Q

what are the types of porphyria

A

porphyria cutanea tarda
- deficiency in uroporphyrinogin decarboxylase
- late onset (4th/5th decade)
- autosomal dominant
- presentation: photosensitivity/ hyperpigmentation/ dark red pr brown urine

acute intermittent porphyria
- deficiency in porphobilinogen deaminase (increase in ALA + PBG)
- autosomal dominant
- late onset
- presentation: NO photosensitivity/ episodic psychological symptoms ( paranoia, anxiety, depression)/ abdominal pain/ dark red or brown urine

32
Q

what are the steps of heme degradation

A
  1. reticuloedothelial system
    - macrophages of spleen/ liver/ BM phagocytoses RBCs and lysosomal enzymes degrade Hb into heme + globin
    - globin broken down into AA
    - heme broken down by heme oxygenase into biliverdin + Fe 3+
    - biliverden (green) gets reduced to bilirubin (yellow) by biliverdin reductase
  2. blood
    - bilirubin-albumin complex transported in blood to liver (water insoluble)
  3. liver
    - bilirubin dissociates from albumin and binds to glucuronic acid forming conjugated bilirubin (water soluble)
    - conjugated bilirubin either gets excreted in urine / secreted in bile + small intestine
  4. GIT
    - bilirubin gets deconjugated by intestinal bacteria and metabolized into urobilinogen
    - most urobilinogen gets oxidized to stercobilin + excreted in feces
    - some urobilinogen is converted into urobilin + excreted in urine
    - some urobilinogen gets reabsorbed into enterohepatic circulation back to liver
33
Q

what proteins bind to Fe 3+ after it gets released by heme degradation

A

ferritin for storage
transferrin for transport in blood to tissues (to resynthesize heme)

34
Q

clinical picture of erythroblastosis fetalis

A
  1. anemic newborn (first 1-2 months after birth)
  2. spleen/hepatomegaly (increased production of RBCs trying to compensate for hemolyzed RBCs)
  3. nucleated blastocyst forms of RBCs in circulation (due to rapid production of RBCs trying to compensate for hemolyzed RBCs)
  4. jaundice + kernicterus (due to increased conc. of bilirubin by hemolysis)
35
Q

prevention of erythroblastosis fetalis

A

anti-D antibody administration to mother 72 hrs before delivery/ 28-30 weeks gestation

prevents sensitization of mother

36
Q

treatment of neonates w/ erythroblastosis fetalis

A

removing Rh +ve blood and replacing it w/ Rh -ve blood for the first few weeks of life (to prevent kernicterus) until anti-Rh agglutinates from mother are destroyed

37
Q

transfusion of whole blood is indicated in cases of:

A

acute blood loss
shock

38
Q

transfusion of packed RBCs is indicated in cases of:

A

chronic/severe anemia
leukemia

39
Q

transfusion of platelets concentrate is indicated in cases of:

A

thrombocytopenia
bleeding due to platelet dysfunction

40
Q

define transfusion reaction

A

when antibodies in recipient plasma bind to antigen do RBCs of donor causing agglutination + hemolysis releasing Hb into plasma

41
Q

what are the manifestations of transfusion reaction

A

allergic reaction (type II HS)
circulatory overload ?
febrile reaction ?
transfusion transmitted infection
hemolytic reaction (may result in jaundice)
kidney/renal failure

42
Q

what are the 3 causes of acute renal failure after transfusion reaction

A
  1. antigen-antibody reaction releases toxic substances from hemolyzing RBCs which causes powerful renal vasoconstriction
  2. loss of circulating RBCs + production of toxic substances from hemolysis and immune reaction cause circulatory shock where arterial BP falls and renal blood flow + urine output increase
  3. excess Hb released into circulating blood that cannot bind to haptoglobin leaks through glomerular membranes into kidney tubules + precipitates + blocks them

renal vasoconstriction + renal blockage together cause acute renal shutdown

43
Q

list the normal types of Hb

A

HbA - 2a/ 2b, 90%

HbA1c - 2a/ 2b + glucose, 4-6%

HbA2 - 2a/ 2 delta, 2-3%

HbF - 2a/ 2 gamma, <2%

44
Q

define hemoglobinopathies

A

a group of genetic disorders caused by the production of structurally abnormal Hb OR the synthesis of insufficient quantities of normal Hb OR (rarely) both

45
Q

examples of hemoglobinopathies

A

sickle cell anemia
thalassemia
methemoglobinemia

46
Q

what are the characteristics of sickle cell anemia

A

autosomal recessive disease

2 mutant B chains where glutamate at position 6 is replaced by valine forming a protrusion on B chain that fits into complementary site on B chain on another Hb molecule causing polymerization of Hb molecules at low oxygen tension causing RBC to become rigid + deformed

sickle cell RBCs are less flexible + have an increased tendency to adhere to vessel walls therefore cause micro vascular occlusions leading to localized hypoxia which results in pain + infarction/ ischemic death of tissue

47
Q

clinical picture of sickle cell anemia

A

lifelong episodes of pain (crises)

chronic hemolytic anemia w/ associated hyperbilirubinemia

increased susceptibility to infections

acute chest syndrome

stroke

splenic/renal dysfunction

bone changes due to marrow hyperplasia

reduced life expectancy

48
Q

what are the variables/factors that increase the severity of sickle cell anemia

A

factors which decrease Hb S affinity to oxygen such as:

increased pCO2
decreased pO2
decreased pH (acidosis)
increased 2,3-BPG
dehydration

49
Q

how to diagnose sickle cell anemia

A

clinical picture

gel electrophoresis

DNA sequencing

50
Q

treatment of sickle cell anemia

A

hydration

analgesics

aggressive antibiotic therapy if infection is present

transfusion if patient is at a high risk of fatal occlusion

intermittent blood transfusion w/ packed RBCs which decreases risk of stroke

hydroxyurea, an anti tumor drug which increases levels of circulating Hb F which decreases RBC sickling leading to a decreased risk of painful crises + decreased mortality

stem cell transplantation

51
Q

what is the selective advantage of individuals w/ the sickle trait (heterozygotes)

A

less susceptible to severe malaria caused by the parasite plasmodium falciparum which spends an obligatory part of its life cycle in the RBC

RBC life cycle of sickle cell is less than 20 days compared to normal 120 days therefore it prevents the parasite from growing

52
Q

what are the characteristics of methemoglobinemia

A

heme iron gets oxidized from Fe 2+ to Fe 3+ producing methemoglobin which cannot bind to oxygen

can be acquired or congenital

acquired via: oxidation by action of drugs
- nitrate sulfanilamide
- acetaminophen (paracetamol)
- sodium nitroprusside
- ROS (endogenous product)

congenital:
- substitution of histidine by tyrosine resulting in permanent oxidation of Fe forming Hb M (irreversible)
- deficiency of NADH cytochrome b5 reductase/ NADH-methemoglobin reductase which is responsible for conversion of methemoglobin (Fe 3+) to hemoglobin (Fe 2+) (reversible)

53
Q

clinical picture of methemoglobinemia

A

characterized by chocolate cyanosis, blue coloration of skin/mucous membranes + brown colored blood as a result of dark colored methemoglobin

symptoms are related to the degree of tissue hypoxia including:

anxiety
headache
dyspnea
coma + death (rare)

54
Q

treatment of methemoglobinemia

A

reversible - methylene blue, a reducing agent

irreversible repeated blood transfusion

55
Q

what are the characteristics of thalassemia

A

hereditary hemolytic disease in which an imbalance in synthesis of globin chains occurs resulting in a decreased conc. of Hb

caused by genes deletion/ nucleotide substitution or deletion

either no globin chains are produced (a0/ b0)
or globin chains are synthesized at a reduced level (a+-/ b+-)

56
Q

what are the types of thalassemia

A

B thalassemia major (2)/minor (1)
a thalassemia major (3)/minor (2)

57
Q

describe B thalassemia

A

synthesis of B globin chain is decreased (B+-) or absent (B0)

result of point mutation which affects production of functional mRNA

a globin chains cannot form stable tetramers w/o B globin chains so they precipitate and cause premature death of RBCs

results in an increase of Hb A2 (a2/ delta 2) + Hb F (a2/ y2)

there are 2 copies of the B globin gene, one on each chromosome 11
if one copy is defective = B thalassemia minor
if both copies are defective = B thalassemia major / cooley’s anemia

58
Q

clinical picture of B thalassemia

A

physical manifestations of B thalassemia appear several months after birth because B globin gene is not expressed until late in prenatal development (Hb F > Hb A)

seemingly heathy at birth but become severely anemic during 1st-2nd year of life

skeletal changes as a result of extra medullary hematopoiesis (formation + activation of blood cells outside BM as a result of hematopoietic stress)

59
Q

treatment of B thalassemia

A

regular blood transfusions

hematopoietic stem cell transplantations (curative option)

60
Q

describe a thalassemia

A

synthesis of a globin chain is decreased (a+-) or absent (a0)

result of deletional mutation

there are 4 copies of the a globin gene, two on each chromosome 16

if 1/4 a globin genes is defective = silent carrier, no physical manifestations of disease

2/4 defective genes = a-thalassemia trait

3/4 defective genes = Hb H, results in hemolytic anemia

4/4 defective genes = Hb bart, hydrops fetalis (fluid build up causing edema) + fetal death because a globin chains are required for the synthesis sis of Hb F (+ all Hb)

61
Q

which diseases are accompanied by a resistance to malaria

A

heterozygote sickle cell anemia

heterozygote a/B thalassemia

G6PD deficiency (favism)

62
Q

what are the functions of iron in the body

A

oxygen transport - component of Hb + myoglobin

cellular respiration - component of e- transport chain proteins

antioxidant - catalase, a heme enzyme, converts H2O2 —> H2O + O2 / Fe is a cofactor for catalase

*Fe 2+ reacts w/ H2O2 to form hydroxyl + hydroxide radicals which are dangerous and toxic to cells, catalase eliminates H2O2 which prevents the fenton reaction

63
Q

where is Fe absorbed and what aids its absorption

A

Fe 2+ (ferrous) is absorbed in the proximal duodenum

aided by
low pH of HCL secreted into gastric lumen
reducing agents such as vitamin C
(keep Fe in soluble ferrous form)

64
Q

what agents inhibit Fe absorption

A

tannins (tea)
phyates (grains, oats)
phosphates

*bind to Fe in intestinal lumen which prevents is absorption

+lowered gastric acidity/ increased pH

65
Q

what is the process of Fe absorption

A
  1. Fe 3+ is reduced to Fe 2+ in intestinal lumen
  2. DMT1 on enterocytes transports Fe into cell
  3. inside enterocyte Fe 2+ gets oxidized to Fe 3+ and is stored by binding to ferritin OR Fe 2+ is transported through basolateral membrane and into circulation while bound to ferroportin
66
Q

what is hepcidin + its function

A

hormone secreted by liver

controls Fe absorption into enterocytes and delivery to blood

acts by binding to + inactivating ferroportin

stimulated by increased plasma Fe conc.

67
Q

what are the proteins of Fe transport + storage

A

ferritin - oxidizes Fe 2+ to Fe 3+ and binds to it for storage inside tissues

hemosiderin - denatured form of ferritin, binds to excess Fe 3+ preventing its escape into blood

ferroxidase / ceruloplasmin - oxidizes Fe 2+ to Fe 3+ for transport

transferrin - carries Fe 3+ in blood (transport) and delivers it to tissues for heme synthesis

ferroportin - binds to Fe 2+ in enterocyte + transports it to blood

68
Q

difference between ferroportin / transferrin

A

ferroportin - from enterocyte/tissue to blood (transport)

transferrin - from blood to tissues (transport)

69
Q

causes of Fe deficiency anemia

A
  1. increased iron loss
    secondary to excessive bleeding (GIT/ menstrual sources/ hookworm infestation)
  2. decreased iron uptake
    diet low in Fe
    malabsorption due to disease associated w/ flattening of duodenal mucosal villi
70
Q

causes of iron overload

A
  1. hemochromatosis
    genetic disorder, hepcidin deficiency
    characterized by excessive intestinal absorption of dietary Fe resulting deposition of Fe in liver/ pancreas/ heart
    causes tissue damage
    primary hemochromatosis (inherited) referred to as bronze diabetes due to darkening of skin
  2. hemosiderosis
    deposition of hemosiderin in reticuloendothelial system (cells of spleen/ liver/ BM)
    caused by multiple blood transfusions/ hemorrhage
    when reticuloendothelial are saturated deposition occurs in other body parts leading to secondary hemochromatosis (acquired)
71
Q

treatment of iron overload (hemochromatosis/ hemosiderosis)

A

iron chelation therapy using deferoxamine

72
Q

laboratory determination of Fe status

A

serum iron

serum ferritin (cytoplasmic Fe storage protein gets secreted into serum, high serum ferritin = high iron level)

total iron binding capacity (reflects amount of transferrin in blood available to attach to Fe, in iron deficiency where iron level is low = TIBC is high / in iron overload where iron is high = TIBC is low)

circulatory system (4 decks)

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