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Physiology - Blood > Blood 1+2: Blood and RBCs > Flashcards

Blood 1+2: Blood and RBCs Flashcards

1
Q

We generally have how much blood (in mls) per Kg body weight?

A

60-80ml/kg

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2
Q

What are the sites of blood production in the developing fetus?

A

6 weeks to 7 months - mainly liver with spleen contributing
5th month production begins in red marrow (in all bones).
From birth through adulthood marrow is main site, lymphocytes still formed by spleen and lymphoid tissues

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3
Q

Red marrow (blood producing) is found in which bones in adult

A

Axial skeleton - mainly veterbrae, skull and upper ends of femur and humerus

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4
Q

Describe pluripotent stem cells

A

Pluripotent stem cell are uncommitted cells capable of self renewal that give rise to different lineages of progenitor cells which in turn give rise to different precursors of blood cells

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5
Q

List the production line of erythrocytes

A

Proerythroblast -> erythroblast -> reticulocyte -> reticulocyte leaves marrow into blood - looses last of polyribosomes and become -> erythrocytes

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6
Q

What hormone stimulates erythrocyte production?

A

Erythropoietin - produced by kidneys, 10-15% produced by liver and acts on stem cells to stimulate differentiation of committed progenitor cells into erythrocyte lineage

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7
Q

How long does erythropoiesis generally take

A

7 days

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8
Q

What takes place for erythroblast to become reticulocyte?

A

Cell size progressively decreases, haemoglobin content increases, nuclear condensation and finally nuclear extrusion -> thus reticulocyte is formed

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9
Q

When do reticulocytes become erythrocytes?

A

Mature 1-2 days -> then circulate for 1-2 days continuing to make haemoglobin. Then loose residual polyribosomes and become erythrocytes

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10
Q

What controls erythropoiesis?

A

Mainly EPO - produced mainly in kidneys (some in liver) mainly secreted in response to hypoxia.
Other factors such as corticosteriods, androgens, GH and thyroxine can also play a part

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11
Q

Describe haemoglobin

A

Haem: 4 iron containing porphyrin rings
Globin: Each porphyrin ring attached to polypeptide chain

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12
Q

What dietary constituents are required for haemoglobin production?

A
  • Iron
  • B12
  • Folate
  • Vit B6
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13
Q

Where is haemoglobin synthesised?

A

Haem - mitochondria
Globin - cytoplasm
combine together in cytoplasm

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14
Q

How is iron stored in the body?

A

60-70% in Hb
4-5% in myoglobin
Rest stored as ferritin or haemosiderin in liver, spleen and bone marrow

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15
Q

How is iron transported

A

Iron binds to transferrin in blood. Usually only 1/3 saturated. When saturation falls to below 15% bone marrow supply is impaired

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16
Q

How is iron balance regulated?

A

Absoprtion varies from 5-30% of ingested iron depending on body stores levels.

17
Q

How is iron lost from the body?

A

Mainly lost from the gut in exfoliated intestinal cells
Small amounts lost in sweat and urine
Women lose almost twice as much due to menstruation

18
Q

Where is most iron absorbed in gut?

A

Duodenum and upper jejunum

19
Q

What are dietary sources of Vit-B12

A

Cobalamin is synthesised by bacteria. Mostly in animal protein - liver, kidney, muscle, eggs, dairy

20
Q

How is Vit B12 absorbed

A

Intrinsic factor secreted by pareital cells of stomach, combines with B12 and is absorbed as complex in terminal ileum

21
Q

How long do body stores of B12 last?

A

3-4 years. Deficiency usually due to decreased absorption (pernicious anaemia, ileal disease, ileal resection

22
Q

What are dietary sources of folate?

A

Most foods, especially liver, yeast, vegetables, nuts

23
Q

Where in gut is folate absorbed?

A

Duodenum and jejenum

24
Q

How long do body stores of folate last?

A

Several months. Deficiency can be from decreased intake or absorption issues or increased demand (eg pregnancy)

25
Q

Megaloblastic erythropoiesis occurs why?

A

Increased B12 or folate - > delayed DNA synthesis -> delayed maturatio -> cell continues to grow without division becoming abnormally large

26
Q

Describe the shape of RBCs and physiological benefits

A

Biconcave disc - flat shape provides large SA:V ratio for rapid diffusion of respiratory gases

27
Q

How does RBC maintain high Hb concentration and thus osmotic pressure without lysis?

A

Membrane extremely low permeability to Na.

Small number of Na/K/ATPase and Ca/Mg/ATPas pumps maintain cation balance

28
Q

Describe Haemoglobin A compared with Hb F

A

Hb A - adult Hb - 2alpha units and 2beta units

Hb F - fetal Hb - 2alpha and 2 gamma units - higher affinity for O2

29
Q

Describe RBC metabolism

A

No mitochondia or ribosomes

95% anaerobic glycolysis and 5% pentose-phosphate pathway.

30
Q

What role does 2,3 DPG play in gas exchange?

A

2,3 Diphosphoglycerate is by product of RBC metabolism. Binds to Hb and reduces affinity for O2 thus promoting delivery to tissues. Hypoxic conditions produce more O2 and thus increased O2 release

31
Q

Average lifespan of RBC?

A

120 days

32
Q

How are RBCs removed from circulation?

A

Macrophages in liver, spleen and marrow - break down cell Hb

33
Q

What happens to the breakdown products of RBC?

A

Amino acids - returned to body general pool of AA

Haem - iron is released to be reused, remainder formed into bilirubin

34
Q

What are the 3 mechanisms for anaemia?

A
  1. Decrease Production
  2. Destruction
  3. Bleeding
35
Q

Decreased production of RBCs (thus anaemia) can be categorized into 2 groups…

A
  1. Decreased proliferation - low iron, low EPO, marrow failure, chronic disease
  2. Decreased maturation - B12, folate low, thalassemias

Both have low retic counts

36
Q

What happens to the retic count in destructive anaemias

A

Goes up

37
Q

What compensatory mechanisms are there for anaemia

A

Increased 2,3 DPG thus O2 release

Increased CO if low enough

Physiology - Blood (4 decks)

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