Lecture 1 - Haemopoeisis

Question 1

Haematopoiesis

Answer 1

Ensures the appropriate cell types in the appropriate numbers when needed

Question 2

RBCs: vertical and horizontal interactions

Answer 2

Vertical interactions - anchoring proteins

Horizontal interactions - proteins located just under the membrane, interacting with and cross-linking anchoring proteins

Question 3

What shape do RBCs take when travelling through vessels?

Answer 3

Torpedo shape, more efficient for vessel travel, no round shape bouncing around

Question 4

Strengths for the RBC adaptations

Answer 4

Efficient and stable - maximises oxygen transport

Lots of space - more haemoglobin

Unattractive to infecting organisms (no DNA, mitochondria, ribosomes etc.)

Question 5

Weaknesses of the RBC adaptations

Answer 5

No protein synthesis

No ATP/reducing power can be produced

Question 6

RBC slicing damage repair: why is it required, what may cause it, and what is the process behind it?

Answer 6

If a RBC gets damaged, haemoglobin (an extremely toxic and oxidative substance) pours into the bloodstream

Cuts from fibrin … smtn sepsis (rewatch leccy)

The cytoskeleton will repair by sealing the cell, using the vacuole when necessary

Question 7

RBC membrane damage repair: why is it required, what may cause it, and what is the process behind it?

Answer 7

The membrane loses parts as damage occurs, increasing the risk of internal contents leaking

Heat, antibody, pH, etc…

The cell shrinks as membrane parts diffuse

Question 8

RBCs: how many, what lifespan, and how many are produced per day?

Answer 8

20-30 trillion in the body

Lifespan up to 120 days

Produce 4000 million per day on average – can vary greatly

Question 9

WBCs

Answer 9

Fight infection in the body

Survive around 5-10 days on average, but may be much less during infection

Make 10,000 million per day

Question 10

Platelets: what are they, how long do they survive, and how many are produced per day?

Answer 10

Small cell fragments that promote clotting

Survive minutes to days

Produce 400,000 million/day

Question 11

petechiae

Answer 11

Caused by low platelet quantity - capillaries not sealed by platelets, blood leaks

Question 12

Cytokines

Answer 12

Small peptide hormones that affect haemoptysis

Question 13

Acute leukaemia

Answer 13

a stem cell mutation leads to cells failing to mature and increasing their number through uncontrolled self-renewal

Question 14

Stem cell niche

Answer 14

Environment of cytokines, adhesive proteins, and stromal cells

Stem cells struggle to survive outside of this niche - acts as a way to prevent cancer

With around 19-20 generations of division one stem cell produces up to half a million mature cells

Question 15

Proliferating cells summary

Answer 15

Proliferating cells have many cycles of replication before they mature – this allows a huge number to be formed from a single stem cell

Proliferating cells cannot self-renew so the system is protected from forming cancers

Many proliferating cells die – this allows number to be controlled by reducing death rate

The cell types formed may be directed by reducing death selectively.

Question 16

Erythropoietin

Answer 16

Ensures red cell number is sufficient for oxygen delivery to tissues

Secretion controlled by blood oxygen in the kidney - too low, +EPO, high enough, -EPO

Question 17

Granulocyte colony stimulation factor

Answer 17

Ensures that the neutrophil number and function are sufficient to fight infection without overproduction

Acting mainly on late granulocyte precursors it enhances the survival of the precursors and increases maturation rate and granule formation to increase output and function massively

It is produced when the body detects infection or inflammation: G-CSF is released by endothelial cells causing increased neutrophil formation release and infection

Question 18

Thrombopoietin

Answer 18

Increases platelet production

To ensure that there are always enough platelets to prevent haemorrhage

Acting mainly on megakaryocytes it enhances the survival of megakaryocyte precursors within the proliferating pool to increase number and rate of maturation

Like G-CSF it can be produced in response to inflammation, but mainly the Tpo is produced in fairly constant amounts by the liver – control is achieved because mature platelets are able bind the Tpo and destroy it. This means if platelet numbers are high the level of Tpo is reduced, but if platelet numbers are reduced e.g. after bleeding, the Tpo level rises to stimulate production!

Question 19

Importance of cell death

Answer 19

the ability to respond rapidly to increase cell production depends on cell death

Under normal circumstances, up to 40% of cells produced in bone marrow spontaneously die

This may seem really wasteful, but it is in fact crucial to the whole system of blood cell production - Cell death provides us with the flexibility to adapt to sudden change in need