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Blood > Red Blood Cells > Flashcards

Red Blood Cells Flashcards

1
Q

Where do all blood cells originate?

A

Bone marrow

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2
Q

What type of cell are all blood cells derived from?

A

Pluripotent haematopoietic stem cells (HSCs)

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3
Q

What do HSCs divide into?

A
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4
Q

Define Haematopoiesis

A

The formation and development of blood cells

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5
Q

Function and life span of blood cells

A
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6
Q

Two essential charecteristics of HSCs

A
  • Self renew
  • Differentiate to mature progeny
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7
Q

Sites of haematopoiesis in the fetus

A
  • In the first 3 weeks of gestation, HSCs are derived from the mesoderm and primitive RBCs are formed in the vasculature of the yolk sac.
  • From 5/6-8 weeks gestation, the fetal liver becomes the main site of haematopoiesis.
  • Bone marrow starts developing haematopoietic activity approx. 10 weeks gestation onwards, also sole site for adults.
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8
Q

In what bones do haematopoiesis occur in children vs adults?

A

In children, haemopoiesis occurs in almost all bones.

By adulthood this is restricted to the bone marrow of the pelvis, vertebrae and sternum as well as the proximal ends of the long bones of the thigh and arm (femur and humerus).

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9
Q

What is erythropoiesis?

A

Formation and development of RBCs.

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10
Q

What enzyme regulates erythropoiesis?

A

Erythropoietin (epo)

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11
Q

Products of lymphoid progenitor differentiation

A
  • Mature T cells (cytokine-producing)
  • Mature B cells (antibody-producing)
  • Mature Natural Killer cells (cytokine-producing)
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12
Q

Products of myeloid progenitor differentiation

A
  • Erythroid
  • Megakaryocyte
  • Monocyte
  • Granulocytes
  • Platelets
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13
Q

Requirements for erythropoiesis

A

Iron, Vitamin B12, Folate, Erythropoietin

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14
Q

Features of Erythropoietin

A
  • Synthesised in kidney.
  • RBCs are produced under its influence; EPO acts as a growth factor to them.
  • When the kidney detects low blood oxygen levels (hypoxia), Erythropoietin interacts with the EPO receptor on red cell progenitor membranes, stimulating the bone marrow to produce more red cells. The resulting rise in erythrocytes increases the oxygen-carrying capacity of the blood.
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15
Q

What is anaemia?

A

Deficieny in the number or quality of RBCs in the body.

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16
Q

What does low vitamin B12/Iron/Folate cause?

A

Anaemia

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17
Q

What is microcytic anaemia and how is it caused?

A
  • Small RBCs.
  • Iron deficiency.
  • Risk factors include: pregnancy, childhood, low resource nation.
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18
Q

What is macrocytic anaemia and how is it caused?

A
  • Large RBCs.
  • B12/Folate deficiency.
  • Risk factors include: alcohol excess, pregnancy, vegan diet.
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19
Q

Functions of Iron

A
  • O2 transport
  • In cytochrome a,b,c for ATP production
  • In cytochrome p450 for hydroxylation reactions
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20
Q

Where does iron absorption take place?

A

Duodenum

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21
Q

Why is iron homeostasis necessary?

A
  • Excess iron is potentially toxic to organs such as the heart and liver
  • There is no physiological mechanism by which iron is excreted
  • Therefore, iron absorption is tightly controlled: only 1-2 mg per day is absorbed from diet
22
Q

Sources of B12 and Folate

A
23
Q

Detail Vitamin B12 absorption.

A
  1. Stomach:

B12 combines with Intrinsic factor (IF) (a protein) made in the gastric parietal cells

  1. Small intestine:

B12-IF complex binds to receptors in the ileum

24
Q

What are vitamin B12 and folate together needed for and what happens if there is a deficiency of them?

A
  • Vitamin B12 (cobalamin) and folate are needed for dTTP (a precursor for DNA synthesis) synthesis, necessary for the synthesis of thymidine.
  • Deficiency of vitamin B12 or folate inhibits DNA synthesis
  • Vitamin B12 and folate deficiency affects all rapidly dividing cells:
  • bone marrow: cells can grow but are unable to divide normally
  • epithelial surfaces of mouth and gut
  • gonads – nerves
25
Q

What are the body stores of folic acid?

A

~ 10 mg (3 months)

26
Q

What is the lifespan of an erythrocyte?

A

Circulates for about 120 days.

27
Q

What happens to an erythrocyte after its lifespan is over?

A

Destroyed by the phagocytic cells of the spleen (macrophages)

28
Q

What factors do erythrocyte function depend on and what happens if there is a defect in any of these?

A

–Integrity of the membrane

– Haemoglobin structure and function

– Cellular metabolism

• A defect in any of these results in shortened erythrocyte survival (haemolysis)

29
Q

What is G6PD and why is a deficiency of it dangerous?

A

Glucose-6-Phosphate Dehydrogenase is an important enzyme in the hexose monophosphate (HMP) shunt, a metabolic pathway in red cell metabolism.

  • HMP shunt is tightly coupled to Glutathione metabolism, which protects red cells from oxidant (oxidizing agent) damage
  • Oxidants may be generated in the blood stream, e.g. during infection, or may be exogenous e.g. drugs, broad beans
  • Deficiency of G6PD causes red cells to be vulnerable to oxidant damage
30
Q

Effects of G6PD deficiency

A
  • Intermittent, severe intravascular haemolysis as a result of infection or exposure to an exogenous oxidant (e.g. foodstuffs, chemicals, drugs)
  • Episodes of intravascular haemolysis are associated with the appearance of considerable numbers of Irregularly contracted cells/ ‘bite cells’
  • They usually result from oxidant damage to the cell membrane and to the haemoglobin
  • Haemoglobin is denatured and forms round inclusions known as Heinz bodies, which can be detected by a specific test
31
Q

How common is GP6D deficiency?

A

Most prevalent enzyme disorder – 400 million people worldwide

32
Q

How is G6PD deficiency inherited?

A

X-linked inheritance: the gene for G6PD is on the X chromosome so affected individuals are usually hemizygous males (but occasionally homozygous females)

33
Q

What factors may Vitamin B12 deficiency result from?

A

Vitamin B12 deficiency may result from:

  • inadequate intake e.g. veganism
  • inadequate secretion of IF: pernicious anaemia (an autoimmune disorder)
  • Malabsorption e.g. coeliac disease
  • lack of acid in stomach (achlorhydria)
34
Q

Where is folic acid absorbed?

A

The small intestine.

35
Q

When are folic acid requirements of the body increased?

A

During pregnancy and increased red cell production e.g. sickle cell anaemia, other haemolytic anaemias

36
Q

What are the different types of granulocytes?

A

Neutrophils, eosinophils, and basophils

37
Q

What types of iron are best and worst absorbed, and why?

A
  • Haem iron (Fe2+) is ferrous and best absorbed. Comes from animals.
  • Non-haem iron (Fe3+) is ferric and needs to be reduced before absorption. Comes from plants (e.g. soybeans)
  • Non-haem iron often contain phytates, which bind to the iron and reduce absorption
38
Q

The body stores of what protein carefully regulates absorption of iron in the gut?

A

Hepcidin

39
Q

What are neutrophils?

A
  • Type of granulocyte
  • Most abundant type of white blood cell
40
Q

What are eosinophils?

A
  • Type of granulocyte
  • Type of WBC; fights parasitic infection
41
Q

What are basophils?

A
  • (Largest) Type of granulocyte
  • Type of WBC; least abundant granulocyte
42
Q

What are granulocytes?

A
  • Type of WBC with small granules.
  • Derived from myeloid progenitor cells
43
Q

What is a leukocyte?

A

A WBC

44
Q

Totipotent vs Pluripotent vs Multipotent

A

Totipotent (omnipotent) stem cells can give rise to any of the 220 cell types found in an embryo as well as extra-embryonic cells (placenta).

Pluripotent stem cells can give rise to all cell types of the body (but not the placenta).

Multipotent stem cells can develop into a limited number of cell types in a particular lineage (e.g. myeloid/lymphoid progenitor cells)

45
Q

What is a reticulocyte?`

A

Newly produced, relatively immature RBCs

46
Q

Does a reticulocyte have more RNA than a mature RBC?

A

Yes

47
Q

Do cytokines increase or decrease the production of erythropoietin?

A

Decrease

48
Q

How does hepcidin act?

A

Hepcidin binds to ferroportin in the duodenum and prevents iron absorption

49
Q

What is the purpose of the biconcave disc of a RBC?

A

Biconcave shape increases manoeuvrability of the erythrocyte through small blood vessels to RELEASE oxygen.

50
Q

What is the most abundant cytoskeletal protein?

A

Spectrin

51
Q

What are spherocytes and how do they form?

A
  • RBCs with an abnormal, spherical shape and decreased flexibility
  • Spherocytes result from abnormalities in the MEMBRANE content of the erythrocyte.
52
Q

What is a thrombocyte?

A

A platelet

Blood (2 decks)

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