14 - Haemopoiesis Flashcards

1
Q

A haemopoietic stem cell can differentiate into what two common progenitor cells?

A
  • Common myeloid progenitor

- Common lymphoid progenitor

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2
Q

What cell types are formed from the common myeloid progenitor?

A
  • Megakaryocyte (platelets)
  • Erythrocyte
  • Mast cell
  • Myeloblast:
    > Basophil
    > Neutrophil
    > Eosinophil
    > Monocyte –> Macrophage
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3
Q

What cell types are formed from the common lymphoid progenitor?

A
  • Natural killer (large granular lymphocyte)

- Small lymphocytes (T cells and B cells)

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4
Q

Not all the cells in the bone marrow end up in the blood, what process removes the cells that aren’t required?

A

Apoptosis

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5
Q

What hormone is responsible for common myeloid progenitor differentiation into a megakaryocyte?

A

Thrombopoietin

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6
Q

What hormone is responsible for common myeloid progenitor differentiation into an erythrocyte?

A

Erythropoietin

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7
Q

What moelcules are responsible for common lymphoid progenitor differentiation into T cells and B cells?

A

Interleukins

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8
Q

What is the lifespan of an erythrocyte?

A

120 days

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9
Q

How are erythrocytes specialised for oxygen transport?

A
  • Biconcave shape increases surface area
  • Minimal organelles to maximise space
  • No mitochondria so oxygen is not used up (only use anaerobic respiration)
  • Haemoglobin to increase affinity of oxygen binding
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10
Q

Summarise the process of erythropoiesis.

A
  1. Proerythroblast formed in bone marrow
  2. Matures to erythroblast in bone marrow, intially have a large nucleus and lots of RNA but nucleus gradually shrinks and RNA is removed (except what is needed to make haemoglobin)
  3. Nucleus is removed to form a reticulocyte
  4. Enters peripheral blood and matures to an erythrocyte
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11
Q

What precursor to RBCs can be found in the blood in a high number during recovery from blood loss?

A

Reticulocytes (final step before RBC)

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12
Q

What is erythropoietin? When and where is it produced?

A

A glycoprotein that increases the levels of RBCs. Stops apoptosis of erythrocyte progenitors.

Produced by the kidneys in response to tissue hypoxia. Made in the liver during foetal life.

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13
Q

What factor is responsible for myeloblast maturation into neutrophils?

A

Granulocyte colony stimulating factor (G-CSF)

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14
Q

What are granulocytes?

A

A sub-group of white blood cells, named due to presence of granules in the cytoplasm

  • Neutrophils
  • Basophils
  • Eosinophils
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15
Q

What is a neutrophil? What does it do?

A
  • Multi-lobed nucleus
  • 3 types of granules
  • Most abundant of granulocytes
  • First line of defence
  • Kills bacteria in multiple ways
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16
Q

What granules does a neutrophil contain?

A
  • Lysozomes
  • Matrix metalloproteinases (MMPs)
  • Gelatinase
17
Q

Other than secretion of its granules, what other functions does a neutrophil have?

A
  • Phagocytosis
  • Antigen presentation
  • Neutrophil Extracellular Traps (NETs)
  • Respiratory burst (create free radicals and superoxide to destroy bacterial DNA)
18
Q

Where does G-CSF come from and what does it do?

A
  • Secreted by many immune cells and endothelial cells
  • Released in response to inflammation
  • Acts on bone marrow to increase number of neutrophils
  • Also increases speed of maturation
19
Q

What are basophils and what do they do?

A

Granulocyte with a bilobed nucleus. Granules contain histamine and heparin.

  • Release histamine to trigger inflammation
  • Mediate hypersensitivity reactions (e.g. asthma)
20
Q

What are eosinophils and what do they do?

A

Granulocyte with a bilobed nucleus. Granules contain antihelminthic proteins (fight parasitic worms) and cell component destroying enzymes.

  • Phagocytose pathogens
  • Fight parasites
  • Role in inflammation and allergy?
21
Q

All lineages of granulocyte undergo which main steps in granulopoiesis?

A
  • Nuclear condensation and lobulation

- Formation of granules

22
Q

What is the difference between a monocyte and a macrophage?

A

Cell is a monocyte in the bloodstream but becomes a macrophage when it enters the tissue.

23
Q

What is a macrophage and what does it do?

A

Largest blood cell with unilobular horseshoe-shaped nucleus. First line of defence.

  • Phagocytose pathogens, cellular debris and senescent cells
  • Antigen presentation (‘raise the alarm’)
24
Q

What is the structure of a platelet (thrombocyte) and what does it do?

A

Very small biconcave cells. No nucleus, only cytoplasm. Contain vast amounts of protein and clotting factors. Specialised receptors on the surface for aggregation

  • Stop bleeding and mediate haemostasis
25
Q

What factor upregulates thrombopoiesis?

A

Thrombopoietin, produced by the liver

26
Q

How are platelets formed?

A
  • Common myeloid progenitor produces megakaryocytes (very large cells with multi-lobular nucleus) in bone marrow
  • Megakaryocyte sends out extensions of its membrane (proplatelets) through the vessel wall
  • These extensions break down into platelets in the blood
27
Q

What are the three types of lymphocyte produced in lymphopoiesis?

A
  • B lymphocyte
  • T lymphocyte
  • Natural killer cell
28
Q

What are B lympocytes and what do they do?

A

Mature in the bone marrow and then in Peyers patches (intestine), spleen and lymph nodes.

  • Each B cell is specific to an antigen
  • Produce antibodies
  • Can activate T cells
29
Q

What are T lympocytes and what do they do?

A

Large nucleus with a small ring of cytoplasm, indistinguishable from B cells.

  • Kill virus-infected and neoplastic cells and transplanted tissue
  • Activate B cells (IL 4)
  • Proliferate (IL 2)
30
Q

Where do T cells mature?

A
  • Start in bone marrow (or liver in foetus) and migrate to thymus to mature
  • Then migrate to secondary lymphoid organs to await activation (spleen, lymph nodes, appendix, tonsils)
31
Q

How does the site of haemopoiesis change during foetal development and after birth?

A
  • Initially the yolk sac
  • Then foetal liver and spleen
  • Bone marrow takes over around 6 months into pregnancy
  • Postnatally, only in bone marrow (most in the vertebra)
32
Q

What is plasma and what is it made up of?

A

The supporting medium for blood cells that makes up the circulating volume.

  • 92% water, 8% proteins
  • Ions
  • Proteins include: albumin, clotting factors, hormones, cytokines, antibodies etc.
33
Q

What is the difference between plasma and serum?

A

Serum is plasma without the clotting factors

34
Q

What is a low platelet count known as?

A

Thrombocytopenia