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Med 2024-2028 > TOB L6 > Flashcards

TOB L6 Flashcards

1
Q

Define Haematopoiesis

A

process by which the body produces blood cells.

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2
Q

Describe the sites of haematopoiesis

A
  1. Foetal blood cells form initially in yolk sac
  2. From the second trimester (second period of 3 mont, heamaeopoiesis takes place primarily in liver and from the third trimester (third period of 3 months), bone
  3. In adults, blood cell formation takes place in red marrow of sternum, pelvis, vertebrae, ribs, skull
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3
Q

Describe how hormones regulate mature blood cell development from progenitors

A

Red Blood Cells (eryhtocytes)
Erythropoietin - EPO

Platelets - Thrombopoietin (TPO)

Myeloid Cells - Granulocyte colony-stimulating factor (G-CSF) and granulocyte/macrophage colony-stimulating factor (GM-CSF);IL3

Lymphoid Cells: various interlukins

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4
Q

Blood Cell Statistics

A

Typical individual
Ranges vary between populations and laboratories

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5
Q

Describe the structure and function of the red blood cell membrane proteins

A

Band 3 proteins exchanges Cl- + HCO3-
(crucial for CO2 uptake

Spectrin - cytoskeletal protein - associates with transmembrane proteins to stabalise membranes

Glycosylated membrane proteins (such as glycophorins) contain antigenic sites - important in blood typing systems

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5
Q

Describe the structure, function and adaptations of red blood cells

A

Anucleate cells
Densely filled with haemoglobin
Flexible
Biconcave disks
Narrow diameter
Large SA for gas exchange
Deliver O2 to tissues, return CO2 to lungs
Lack of organelles make glycolysis their main source of ATP

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6
Q

Describe the control of erythropoiesis

A

Reduced pO2 (partial pressure of oxygen) is detected by interstitial peritubular cells of the kidney, stimulating them to produce EPO

EPO stimulates maturation of nucleated precursors (erythroblasts) in bine marrow + release of mature RBCs into circulation

A rise in RBCs is accompanied by rise in pO2, therefore EPO production falls (positive feedback?)

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7
Q

Describe the structure of haemoglobin

A

Tetramer - two pairs of globin chains, each with its own haem group

Haemoglobin exists in two configurations

Oxyhaemoglobin
Deoxyhaemoglobin

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8
Q

Diagram of Oxygen-Haemoglobin Dissociation Curve

A
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9
Q

RBC / Haemoglobin deficiencies - Anaemia

A

Blood loss (e.g. trauma)
Decreased RBC production (iron or Vitamin B12 deficiency
Reduced haemoglobin / increased RBC destruction

Thalassemia - inherited mutations in alpha and beta haemoglobin chains

Sickle cell anemia

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10
Q

Outline different causes of anaemia

A

RBC / Haemoglobin Deficienceis anaemia: General category where no of red blood cells / amount of haemoglobin within them is lower than normal. Due to nutritional deficiencies, chronic disease etc

  1. Blood loss (e.g. trauma): significant blood loss due to trauma (surgery, gastrointestinal bleeding). Losing large vol of blood reduces overall rbc in circualtion
  2. Decreased RBC production (Iron / Vit b12 deficiency): reduced production of rbc caused by nutritional deficiencies includng iron deficiency anemia (inadequate iron for haemoglobin production) or vitamin B12 deficiency anemia (insufficient vit b12 for RBC maturation)
  3. Increased RBC destruction/ recduced Hb: blood cells prematurely destroyed / issue with haemoglobin within RBC. This can be due to conditions such as:
  • THALASSEMIA: inherited genetic disorder
    mutation to genes responsible for producing alpha + beta Hb chains. Mutations result in abnormal haemaglibin - leads to anemia
  • SICKLE CELL ANEMIA: inherited genetic disorder
    mutation in beta Hb chain
    Cuases RBC to take on sickle shape when they release oxygen - leads to anemia
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11
Q

Describe patterns of haemoglobin synthesis

A
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12
Q

Describe sickle cell aneamia

A

A single nucleotide polymorphism (SNP) in the haemoglobin beta chains leads to polymerisation of the HbS. under low oxygen conditions the RBC will take on this sickle shape, resulting in the loss of cell flexibility and increased fragility.

As a result, sufferers cannot carry as much oxygen. This can result in ischemia…

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13
Q

Describe how damaged RBCs are removed by reticuloendothelial system (RES)

A
  1. RBC live 120 days
  2. No nucleus/other organelles, therefore unable to synthesise new compounds to replace damaged ones
  3. Damaged RBCs destroyed by fixed phagocytic macrophages in spleen + liver
  4. Break down products are then recycled + waste is excreted
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14
Q

What is the reticuloendothelial system composed of?

A

Monocytes
Macrophages of lymph nodes, spleen, liver (kupfer cells)

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15
Q

State which lymphoid organ surveils the blood

A

spleen is the only lymphoid organ that surveils the blood

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16
Q

Describe the process of haemoglobin catabolism

A
  1. Macrophages in the spleen, liver or red bone marrow phagocytose damaged RBCs
  2. The globin and the heme portions of haemoglobin are split apart in the reticuloendothelial system
  3. Globin is broken down into amino acids which can be reused to synthesise sother proteins
  4. The iron is removed from the heme and transferred to the bone marrow via transferrin, leaving biliverdin (non-iron portion of the haem). It is a green pigment
  5. Biliverdin reduced to bilirubin (yellow pigment)
  6. Bilirubin enters blood + transported to liver, where it forms component of bile
  7. In the large intestine, gut commensal bacteria converty bilirubin to urobilinogen
  8. Urobilinogen is ultimately excreted in faeces in form of brown pigment - called stercobillin - gives faeces brown colour
  9. Some urobilinogen absorbed back into blood and then converted to a tellow pigment called urobilin and is excreted in urine
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17
Q

State the role of the spleen

A

spleen is the only lymphoid organ that surveils the blood

site for antibody production and lymphocyte activation

It provides a reservoir for platelets

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18
Q

State the function of transferrin

A

It is a plasma protein that transports iron in the blood.

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19
Q

Diagram of Haemoglobin Catabolism

A
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20
Q

Describe the structure, function and adaptation of platelets

A

Small, round particles produced from cytoplasm of megakarocytes in bone marrow

  1. Anucleate
  2. Stored in spleen
    3 Principal inflammatory mediator released by platelets - Serotonin
  3. Derived from bone marrow megakarocytes
  4. Platelets cytoplasm cntains alpha granules + dense granules

Alpha granules: contain fibrinogen, von Willebrand’s factor and other large molecules
Dense granules: contain small molecules such as ADP and calcium, important in platelet adhesion

Appear blue with Wright’s / Giemsa stain

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21
Q

What colour do platelets appear to be with Wright’s / Giemsa stain?

A

BLUE

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22
Q

Define thrombopoiesis

A

Formation of platelets in bone marrow

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23
Q

Describe the control of thrombopoiesis

A

Controlled by hormone thrmbopoietin
Produced constitutively (released constantly all the time) by liver + kideys

Under influence of of thrombopoietin, myeloid stem cells develop into megakarocyte colony forming cells that develop into precursor cells called megakaryroblasts
Megakaryoblasts transform into magakaryocytes

TPO acts in bone marrow to stimulate megakaryocytes to increase in size by undergoing DNA replication without dividing. Platelets bud off / ligate from enlarged cells

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24
Q

How do we stop thrombopoeisis from happening / switch it off?

A

Thrombopoietin is primary regulator of platelet production
TPO can bind to receptors on platelets
Upon binding to plateletsm hormone is removed from circulation + destroyed
This reduces bioavailability of hormone in blood as platelet number rise (-ve feedback) platelet destroys the hormone which prevents further formation of platelets

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25
Q

Define thrombocytopenia

A

Abnormally low platelet levels

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26
Q

Describe the process of clotting

A
  1. Following damage to blood vessel walls, the exposure of platelets to underlying collagen activates the intrinsic pathway (contact activation pathway)

Extrinsic pathway (tissue factor pathway) stimulated by trauma, requires a thrombin “burst”
Rupture of vessels exposes tissue factor (found in subendotheloial tissue) to Factor VII, which becomes activated

These factors intersect in the common pathway.
Activated Factor X (Factor Xa) converts prothrombin to thrombin, which in turn converts fibrinogen to fibrin

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27
Q

Describe the process of primary haemostasis

A
  1. Platelets weakly adhere to exposed collagens via glycoprotein (GP) la/lla receptors. Stronger adhesion (to collagen) occurs via binding of von Willebrand factor (vWF) to the platelet GP Ib/IX.V heterotrimeric receptors
  2. GP IIB/IIIa receptors on activated platelets act to increase platelet aggregation
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28
Q

Compare the binding in strong and weak adhesion

A

Weak adhesion to collagen fibres = binding to GP la/lla

Strong adhesion to collagen fibres = binding of von Willebrand factor (vWF) to platelet GP Ib/IX/V heterotrimeric receptors

28
Q

Describe the process of secondary haemostasis

A

Secondary haemostasis leads to polymersiation of fibrin which traps platelets and RBCs, forming a clot

by clotting cascade

29
Q

Describe the clotting cascade in secondary haemostasis

A
  1. Intrinsic pathway is activated by damage to endothelium
    Exposure to collagen activates FXII which activates FXI
  2. The extrinsic pathway is activated when blood escapes from vascular system
    Tissue Factor (expressed by smooth muscle + fibroblasts) binds to
    and activates circulating FVII
  3. These processes both activate FX, initiating the common pathway, leading to fibrin-cross linking
30
Q

Describe the retraction and removal of the clot

A

Contraction of platelet actin and myosin filaments reduce the size of the clot

As the damaged endothelium is repaired, the clot is dissolved by plasmin (Fibrinolysis)

31
Q

Define coagulation

A

Process of blood clotting

32
Q

State disorders of coagulation

A

Haemophillia A - results from mutations / deletions in Factor VIII gene

Von Wilebrand disease - common inherited bleeding disorder involving vWF. Severity of bleeding varies between different types

Vitamin K: important co-factor in formation of clotting factors. Deficiencies lead to bruising + uncontrolled bleeds.
Anti-coagulant warfarin inactivates vit k dependent clotting factors

33
Q

Define innate immunity

A

Immediate + non specific, transient (lasting for short time perioid) response to infection

34
Q

Define Adaptive immunity

A

LESS TRANSIENT, SLOWER

Humoral responses involve secretion of immunoglobulins (antibodies) by B cells
Cell mediated responses involving the killing of infected cells by T cells

35
Q

What are leukocytes?

A

White blood cells

36
Q

Describe the structure, function and adaptations of leukocytes

A
  1. Have nuclei + full complement of organelles
  2. Do not contain haemoglobin
  3. Classified as granular or agranular
37
Q

Describe the classification of leukocytes

A

WBC

38
Q

Describe the difference between innate and adaptive / acquired immunity

A

Innate immunity is an immediate, non specific, transient response to infection

Adaptive / acquired immunity is divided into two:
1. Humoral: Involves secretions of immunoglobulins by B cells into extracellular fluids
2. Cell mediated immunity - involve killing infected cells by T cells

39
Q

Table comparing Neutrophils, Eosinophils, Basophils, Natural killer cells, monocytes

A
40
Q

What is the lifespan of neutrophils?

A

1-4 days

41
Q

How common are neutrophils

A

Most common (60% of WBC)

42
Q

Describe the structure of the nucleus neutrophils

A

Multi-lobed (2-5 lobes) - sometimes called polymorphonuclear cells

43
Q

State the function of neutrophils

A

To be recruited + migrated out of circulation to site of infection(chemotaxis) + destroy foreign material by phagocytosis

44
Q

Where are nuetrophils developed?

A

Neutrophils develop in the bone marrow
under the control of G-CSF

45
Q

Describe the lifespan of monocytes

A

Variable lifespan

46
Q

How common are monocytes?

A

3-5% of WBC

47
Q

Describe the nucleus of monocytes

A

Kidney shaped

48
Q

State the function of monocytes

A

Differentiate into macrophages in tissues.

Respond to inflammation + act as antigen presenting cells

They are:

  1. Phagocytic
  2. Pinocytic
    (pinocytosis - ingestion of small amounts of fluid)
49
Q

What is the lifespan of eosinophils?

A

8-12 days

50
Q

How common are eosinophils?

A

1-3% of WBC

51
Q

Describe the nucleus of eosinophils

A

Bi-lobed

52
Q

State the function of eosinophils

A
  1. Combating helminth infections (helminths - parasitic worms)
  2. Mediating hypersensitivity (allergic) reactions - when body exposed to allergens, eosinophils recruited to site of allergic reaction
  3. Phagocytosing antigen-antibody complexes
53
Q

Histology of eosinophils in the colonic mucosa

A
54
Q

What is the lifespan of basophils?

A

Basophils have a half-life of 2.5 days

55
Q

How common are basophils?

A

account for
0.2-1% of circulating leucocytes.

56
Q
A
57
Q

Describe the nucleus in basophils

A

Bi-lobed

58
Q

State the function of basophils

A

Important in type 1 hypersensitivity reactions (eg. exposure to allergens).
ALLERGIC REACTIONS

59
Q

Describe the nucleus of natural killer cells

A

Large nuclei

60
Q

State the function of natural killer cells

A

Produce rapid response to viral infection

Recognition of “stressed” cells:include those undergoing cellular stress, tumour cells, cells with DNA damage. When detecting these stressed cells, initiate a response to eliminate them

61
Q

Compare natural killer cells to cytotoxic T cells

A

Mechanism of killing similar to cytotoxic T cells, albeit with less
specificity.

62
Q

Describe how adaptive immunity is divided into two systems

A
  1. Humoral immunity: Secretion of immunoglobulins (antibodies) by B lymphocytes into extracellular fluids (humors)
  2. Cell mediated immunity:
    T lymphocyte-mediated destruction of infected cells
62
Q

Which cells are involved in adaptive immunity?

A

Lymphocytes
(T lymphocytes and B lymphocytes)

63
Q

State an adaptation of B lymphocytes

A

“shuffle” DNA which encodes for immunoglobulins (antibodies) to create variety of antibodies which are able to recognise a variety of antigens

When B cell presented with foreign antigen it recognises, it proliferates (under control of T helper cells) to form plasma cells which produce antibodies specific to that antigen

64
Q

State the role of memory B lymphocytes

A

Expand following re-exposure to antigen

65
Q

State the role of B lymphocytes

A
  1. B lymphocytes are presented with foreign antigen it recognises
  2. Proliferates (under control of T helper cells)
  3. Forms plasma cells
  4. Plasma cells produce antibodies specific to antigen
66
Q

State the origin of T lymphocytes

A

Bone marrow
Mature in thymus (or spleen in adults)

67
Q

State the role of T helper cells

A

CD4+ (T helper): induce proliferation + differentiation of T cells + B cells + activate macrophages

CD8+ (T cytotoxic): -induce apoptosis (controlled cell death) in cells infected by virus
1. Release perforin (protein).
2. Punches holes (forms pores) in plasma membrane of infected cell 3. CD8+ T cells release granzymes into pores 4. Granzymes reach target cells, activate series of intracellular processes, leads to cell destruction

Med 2024-2028 (56 decks)

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