haemopoiesis + the spleen Flashcards

1
Q

blood cell precursors

A

“blasts” = nucleated precursor cells (erythro-, myelo-)

megakaryocytes = platelet precursor, polyploid

reticulocytes = immediate red cell precursor, “polychromasia”

myelocytes = nucleated precursor between neutrophils + blasts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

division of haemopoitic stem cells

A

divides in asymmetrical fashion
- one of daught cells is identical to parent (self-renewal)
- other is different -> progenitor

self-renewal = property of stem cells, lost in descendants

in adults, most haemopoietic stem + progenitor cells are bone marrow based
- more primitive progenitors (stem cells) are quiescent/dormant during steady-state haemopoiesis - might only divide every few weeks

overlap between developmental events - proliferation + maturation can occur simultaneously

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

embryonically where do stem cells originate?

A

mesoderm
- circulating committed progenitors detectable as early as week 5

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

where is a bone marrow sample taken in adults vs kids

A

adult - posterior iliac crest
kids - tibia

stem cells are mobilised from marrow into blood for collection + transplantation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

bone marrow compartments

A

cellular
- haemopoietic cells
- non-haemopoietic cells - adipocytes, fibroblasts, osteoclasts, osteoblasts

  • connective tissue matrix
  • vascular elements
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

bone marrow venus sinuses - “sinusoids”

A

arteriole drain into “sinus” - wide venous vessels, which open into larger central sinuses
- in contrast to capillaries, sinuses are larger + have discontinous membrane

  • fenstrations (gaps) in endothelial cells
  • discontinous basement membrane - adventitial cells can open gaps further
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

release of mature cells from marrow

A

formed blood cells can pass through fenestration in endothelial cells to enter circulation
- release of red cells is assoc with sinusoidal dilation + increase blood flow

neutrophils actively migrate towards sinusoid

megakaryocytes extend long branching processes called proplatelets into sinusoidal blood vessels (pop off platelets)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

red vs yellow marrow

A

red = haemopoietically active

yellow = fatty, inactive
- increase in yellow marrow with age - results in reduction in marrow cellularity in older individuals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

myeloid:erythroid ratio

A

relationship of neutrophils + precursors to proportion of nucleated red cell precursors
- can change e.g. reversal in haemolysis as a compensatory response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

cell maturation regulators

A

RBC - erythropoietin

neutrophil - G-CSF (granulocyte-colony stimulating factor)

megakaryocytes - thrombopoietin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

how can we identify normal, more mature non-lymphoid cells?

A

morphology
cell surface antigens - glycophorin A = red cells
enzyme expression - myeloperoxidase = neutrophils

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

how can we identify normal progenitors/stem cells?

A

(morpholofically indistinguishable cells)

cell surface antigens -> immunophenotyping (CD34)

cell culture assays

animal models - not practical in routine diagnostic practice

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

immunophenotyping

A

identify patterns of protein (antigen) expression unique to a cell lineage
use antibodies (in combination) specific to different antigens

-> to see how many stem cells are harvested - they are “marked”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

spleen

A

secondary lymphoid organ
not usually palpable unless substantially enlarged

communications
- diaphragmatic surface
- visceral surface - left kidney, gastric fundus, tail of pancreas, splenic felxture of colon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

blood supply of spleen

A

supplied by splenic artery - branch of coeliac axis

drained by splenic vein - forms portal vein with SMV

rupture is a surgical emergency
- trauma
- a diseased spleen is more prone to rupture

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

structure + function of spleen

A

encapsulated organ
parenchyma includes red pulp + white pulp

sinusoids are: fenestrated, lined by endothelial cells, supported by hoops of reticulin

acts as filter for blood
- detects retain + eliminate unwanted, foreign or damaged material
- facilitate immune responses to blood borne antigens

17
Q

white pulp of spleen

A

white pulp comprises the periarteriolar lymphoid sheath (PALS) - CD4+ lymphoid cells
- this is expanded by lymphoid follicles - may show reactive changes as in lymph node

  • antigen reaches white pulp via the blood
  • APCs in the white pulp present antigen to immune reactive cells
  • when stimulated by antigen, T + B cell responses may occur
18
Q

hyposplenism causes

A

most commonly - spenectomy (need for immunisation)

coeliac disease
sickle cell disease
sarcoidosis
iatrogenic

19
Q

blood features of hyposplenism

A

mainly from reduced red pulp function
- Howell-jolly bodies
- siderocytes

may also be some immune deficiency - esp if spleen removed in childhood

20
Q

causes of splenomegaly

A

infection
congestion - portal
-> hepatic cirrhosis, cardiac failure, portal/splenic vein thrombosis

haematological disease
- lymphoma/leukaemia
- haemolytic anaemia
- myeloproliferative disorders

inflammatory conditions
others - amyloid, tumours

21
Q

splenomegaly presentation

A

dragging sensation in LUQ
discomfort when eating, early satiety
pain if infection

hypersplensism triad
- splenomegaly
- fall in one or more cellular components of blood
- correction of cytopenias by splenectomy