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Human Diseases > 5.1 Erythropoiesis > Flashcards

5.1 Erythropoiesis Flashcards

1
Q

What is haemopoiesis?

A

The production of blood cells and platelets.

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2
Q

What is erythropoiesis?

A

Production of erythrocytes.

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3
Q

How many erythrocytes do we produce every second?

A

2 million

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4
Q

Which vitamins are essential for RBC production?

A
  • B12
  • Folate
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5
Q

Which hormone regulates erythropoiesis?

A

Erythropoietin
- Produced by the kidneys, creates negative feedback loop between kidneys and blood

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6
Q

Where does erythropoiesis occur?

A

In the bone marrow

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7
Q

What is the life span of an RBC?

A

Approximately 120 days

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8
Q

What is haemolysis?

A

Destruction of RBCs

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9
Q

Where is erythropoietin produced?

A
  • 90% produced by kidneys in the renal parenchyma
  • 10% produced in the liver parenchyma
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10
Q

What are the effects of too few or too many erythrocytes?

A
  • Too few = hypoxia
  • Too many = undesirable blood viscosity
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11
Q

Which enzyme is important in the hameoglobin-oxygen dissociation curve?

A

2,3-DPG
More 2,3-DPG means Hb dissociates more easily- curve shifts right, less means dissociates less easily- curve shifts left.

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12
Q

What shape is the Hb-O2 dissociation curve?

A

Sigmoid

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13
Q

What happens if the Hb-O2 dissociation curve shifts left or right?

A

Shift to the right = oxygen more easily given to the tissues (increased DPG). Decreased affinity of Hb for oxygen.

Shift to the left = Hb holds onto oxygen and gives it away less easily (decreased DPG). Increased affinity of Hb for oxygen.

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14
Q

Describe the structure of an erythrocyte.

A
  • Concave disc shape
  • 8um diameter, minimum 3.5um in circulation
  • Able to travel through narrow vessels
  • Flexible
  • Carries oxygen via Hb (2 alpha and 2 beta chains)
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15
Q

What is hereditary spherocytosis?

A

A genetic malformation affecting the red cell membrane.
Causes life long mild-moderate anaemia.

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16
Q

What is glucose-6-phosphate dehydrogenase deficiency?

A

Glucose-6-phosphate dehydrogenase is needed to reduce oxygen free radicals.
A deficiency causes early haemolysis (RBC destruction) and lead to haemolytic anaemia.
More prevalent in areas of Africa and the Middle East.

17
Q

Outline the main causes of anaemia.

A

Underproduction:
Hereditary - haemoglobinopathies
Acquired - iron, B12 or folate deficiency, increases EPO, bone marrow failure

Increased haemolysis:
Hereditary - sickle cell anaemia, glucose-6-phosphate dehydrogenase deficiency
Acquired - immune, PNH

Acute blood loss

18
Q

What Hb levels are considered anaemia in different age groups?

A

<150g/l : newborn
<110g/l : 3 months to puberty
<115g/l : adult female
<135g/l : adult male

19
Q

What are the clinical features of anaemia?

A
  • Shortness of breath on exertion
  • Weakness, lethargy
  • Headaches
  • Cardiac failure, angina, confusion
  • Pallor of mucous membranes
  • Tachycardia
  • Cardiac failure
  • Jaundice (haemolysis or megaloblastic)
  • Skin ulcers (sickle cell anaemia)
  • Koilonychia, spoon nails (iron deficiency)

Symptoms are affected by severity, speed of onset, age, co-morbidities. Some people may be symptomless.

20
Q

What laboratory investigations are carried out for suspected anaemia?

A
  • Full blood count (MCV/MCH, WBC/platelets)
  • Reticulocyte count
  • Blood film
  • Haematinics (B12, folate and ferritin)
21
Q

How should FBC results be interpreted?

A

1) Check for evidence of bone marrow disease such as aplasia, infiltration or leukoplakia.
This is checked by looking for leukopenia and thrombocytopenia.

2) Do the RBCs appear big/full or little/empty? (Macrocytic/hyperchromic or microcytic/hypochromic). Both are bad.

22
Q

What is the most common cause of anaemia?

A

Iron deficiency

23
Q

How much of iron consumed is absorbed?

A

10%
30% in pregnancy

24
Q

Which form of iron is favoured for absorption?

A
  • Ferrous form
  • Ferric form not favoured
25
Q

What are the causes of iron deficiency?

A
  • Chronic blood loss (e.g. menstrual, GI- peptic uclers)
  • Increased demands (growth spurts, pregnancy)
  • Malabsorption (e.g. coeliac)
  • Poor diet (rare)
26
Q

What are the diagnostic measures of iron deficiency?

A

Red cell indices:
- MCV <80fl
- MCH <27pg

Blood film:
- Hypochromic (pale), microcytic (small), pencil shaped cells
- Occassional target cells

Serum ferritin:
- <15ug/l

27
Q

How is iron deficiency treated?

A
  • Ferrous sulphate 200mg TDS for 6 months (contains 67mg iron)
    Can have GI side effects.
  • Parenteral iron
28
Q

What is folate?

A
  • A water soluble form of vitamin B
  • Found in fruit and veg
  • Absorbed in small intestine
  • Overcooking destroys folate
29
Q

What is vitamin B12?

A
  • A vitamin
  • Normal diets contain excess B12, may see deficiency in vegans
  • Deficiency can cause neurological problems: peripheral neuropathy, numbness
30
Q

What is pernicious anemia?

A

An autoimmune condition where there is a decrease in the intrinsic factor that is usually found in the stomach to combine with vitamin B12.
This autoimmune condition causes B12 deficiency leading to anaemia.

31
Q

What is pernicious anaemia?

A

An autoimmune condition where there is a decrease in the intrinsic factor that is usually found in the stomach to combine with vitamin B12.
This autoimmune condition causes B12 deficiency leading to anaemia.

32
Q

How is a folate deficiency treated?

A

Folic acid prescribed.

33
Q

How is a B12 deficiency treated?

A

Intramuscular hydroxocobalamin injection every 3 months following initial loading doses.

34
Q

What are the blood group systems based on?

A

RBC antigens.
Nearly 30 different blood group systems and hundreds of individual RBC antigens have been described.
Clinically, the ABO and Rhesus blood group systems are most important.

35
Q

Describe the ABO blood group system.

A
  • Antigens are syntheisised by the sequential addition of sugar residues on a common precursor substance (H)
  • These are IgM antibodies
  • Either the A-antigen, B-antigen or O-antigen
36
Q

Describe the 4 blood groups.

A

Group A: have A-antigen and Anti-B antibodies
Group B: have B-antigen and Anti-A antibodies
Group AB: have A and B antigens and no antibodies (univeersal recipient)
Group O: have O-antigen and antiA and anti-B antibodies (universal donor)

37
Q

When is the Rhesus blood group system most important?

A

In pregnancy.

38
Q

Describe the Rhesus system.

A
  • Rhesus negative = doesn’t have D antigen
  • Rhesus positive = does have D antigen

15% of Caucasian population are rhesus negative

39
Q

Which body controls incidents related to donated blood?

A

Serious Hazards of Transfusion (SHOT) team

Human Diseases (47 decks)

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