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Blood and Circulation > Lecture 5 > Flashcards

Lecture 5 Flashcards

1
Q

What is haematopoiesis?

A

The process of blood cell formation occurring in the bone marrow.

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2
Q

Where does haematopoiesis initially begin during embryonic development?

A

In the yolk sac around 3 weeks of human development.

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3
Q

What type of cells does the yolk sac contain that contribute to early haematopoiesis?

A

Mesoderm-derived cells known as haemangioblasts.

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4
Q

What do haemangioblasts differentiate into?

A

Nucleated red blood cells and endothelial cells.

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5
Q

When does haematopoiesis transition to the liver during development?

A

At a later stage of embryogenesis.

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6
Q

Where does haematopoiesis occur after birth?

A

Primarily in the bone marrow.

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7
Q

What are the two main types of cells in the bone marrow?

A

Haematopoietic cells (form blood cells) and stromal cells (provide support).

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8
Q

What is the function of stromal cells in the bone marrow?

A

They provide a specialized environment necessary for haematopoiesis.

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9
Q

What types of cells are osteoblasts and osteoclasts?

A

Cells concerned with bone formation and resorption.

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10
Q

What is the composition of compact bone?

A

About 70% hydroxyapatite (hydrated calcium phosphate).

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11
Q

What type of tissue is bone considered?

A

A specialized form of connective tissue.

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12
Q

What are Haversian canals?

A

Microscopic tubes in the compact bone that contain blood vessels and nerves.

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13
Q

What is the main cause of death after exposure to ionizing radiation?

A

Haematological failure.

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14
Q

What discovery confirmed the importance of bone marrow in haematopoiesis?

A

Transplantation of bone marrow cells could save animals exposed to radiation.

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15
Q

What is a haematopoietic stem cell (HSC)?

A

A stem cell capable of generating all blood cell types and capable of self-renewal.

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16
Q

What limits the self-renewal capability of HSCs?

A

The ‘Hayflick limit’ and telomere shortening due to the end replication problem.

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17
Q

What is a stem cell niche?

A

A microenvironment in the bone marrow that supports stem cells.

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18
Q

Where are haematopoietic stem cells found within the bone marrow?

A

In the endosteum and perivascular regions.

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19
Q

What is the role of growth factors in haematopoiesis?

A

They drive growth and differentiation of progenitor cells.

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20
Q

What growth factor is essential for erythropoiesis?

A

Erythropoietin (EPO), produced mainly by the kidneys.

21
Q

What stimulates the production of erythropoietin (EPO)?

A

Low oxygen levels in the blood.

22
Q

What is thrombopoiesis?

A

The process of platelet formation.

23
Q

What hormone regulates thrombopoiesis?

A

Thrombopoietin (TPO), primarily produced by the liver.

24
Q

How do platelets regulate thrombopoietin levels?

A

Platelets have TPO receptors and remove TPO from circulation via negative feedback.

25
Q

What triggers increased TPO production during inflammation?

A

Cytokine IL-6.

26
Q

What is the common precursor for erythrocytes and platelets?

A

The megakaryocyte/erythrocyte precursor (MEP).

27
Q

What is the function of granulocyte-monocyte colony-stimulating factor (GM-CSF)?

A

It stimulates the growth of granulocytes and monocytes.

28
Q

What type of fashion do growth factors act in haematopoiesis?

A

Paracrine and juxtacrine fashion.

29
Q

What is the role of interleukin-3 (IL-3)?

A

It stimulates the growth of most haematopoietic cell types.

30
Q

How does infection affect haematopoiesis?

A

It increases growth factor production due to leukocyte activation, enhancing haematopoiesis.

31
Q

What is a progenitor cell?

A

A cell derived from a stem cell that is on a committed pathway to differentiate into specific blood cells.

32
Q

What is the Hayflick limit?

A

The number of times a normal cell population will divide before stopping due to telomere shortening.

33
Q

What is a colony in the context of in vitro bone marrow culture?

A

A visible cluster of cells derived from a single progenitor cell.

34
Q

What is semi-solid media used for in cell culture?

A

To support the growth of progenitor cells, allowing colony formation.

35
Q

Which growth factor stimulates platelet production and is produced by liver cells?

A

Thrombopoietin (TPO).

36
Q

How are the early stages of erythrocyte and platelet production connected?

A

Both share a common pathway through the megakaryocyte/erythrocyte precursor (MEP).

37
Q

What type of tissue origin do bones have?

A

Mesodermal/mesenchymal origin.

38
Q

What characterizes cancellous bone?

A

A less dense, spongy structure compared to compact bone.

39
Q

What is the significance of the endosteum in haematopoiesis?

A

It is a niche location for haematopoietic stem cells within the bone marrow.

40
Q

What happens to HSCs during serial transplantation?

A

Their capacity for self-renewal eventually declines.

41
Q

What are the roles of osteoblasts and osteoclasts?

A

Osteoblasts build bone, while osteoclasts resorb bone.

42
Q

What component comprises most of the rigid structure of bone?

A

Hydroxyapatite, a form of hydrated calcium phosphate.

43
Q

What does paracrine signaling entail?

A

The diffusion of signals from a producer cell to a responder cell nearby.

44
Q

What does juxtacrine signaling involve?

A

Direct contact between the signaling cell and the responder cell.

45
Q

What cytokine is associated with increasing liver TPO production during inflammation?

A

IL-6.

46
Q

What are examples of growth factors with broad activity in haematopoiesis?

A

Interleukin-3 (IL-3).

47
Q

What historical evidence supports bone marrow’s role in blood formation?

A

Animal studies showing that transfusion of bone marrow, but not blood or lymphoid tissue, saves animals after radiation exposure.

48
Q

What do progenitor cells require to grow and differentiate in vitro?

A

Specific growth factors and cytokines.

49
Q

Why is erythropoiesis important at high altitudes?

A

To increase red blood cell production due to lower oxygen availability.

Blood and Circulation (6 decks)

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