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PA10315 > Blood > Flashcards

Blood Flashcards

1
Q

How much blood does an average human have?

A

5 litres.

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2
Q

What is the ideal pH range?

A

7.35-7.45.

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3
Q

What are some of the roles of blood?

A

Transport of oxygen, CO2, nutrients and excretory products; regulation of the body in ways such as delivering hormones and diversion of blood in homeostasis and temperature control;protection such as the role of leukocytes in infection.

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4
Q

What is a hematocrit used for?

A

Rapid assessment of blood composition using centrfuging.

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5
Q

How are blood cells generated?

A

The bone marrow - from hematopoietic stem cells. These are undifferentiated cells capable of producing the precursors of different blood cells.

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6
Q

How do platelets look different from other types of blood cell?

A

They are cell fragments and do not have a nucleus. They are also discoid shaped.

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7
Q

What is the production of platelets controlled by?

A

Thrombopoietin - this is a hormone that is mainly produced by the liver and activates megakaryocytes, therefore stimulating platelet production.

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8
Q

How is the number of platelets in the blood regulated?

A

If the platelet count is normal, the platelets will be bound to thrombopoietin. If the count is low, TPO (thrombopoietin) is free and unbound so more platelets can be produced.

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9
Q

How are platelets activated?

A

If the epithelial layer is damaged, proteins underneath (including collagen and connective tissue) are exposed. The platelets attach to the collagen and become activated.

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10
Q

What is thromboxane A2 and what does it do?

A

It’s a signalling molecule that can feedback and activate more platelets. It can cause the platelets to aggregate - positive feedback. It also results in the contraction of vascular smooth muscle, resulting in vasoconstriction.

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11
Q

What benefit does platelets aggregating have?

A

It creates a plug at the site of injury.

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12
Q

Give a summarised description of the platelet plug formation.

A

Unactivated platelets contain secreting granules. Glycoprotein receptors on the surface of the platelet bind onto the site of damage directly onto the collagen or onto a sub-endothelial protein. Activation occurs (shape change) which triggers the release mechanism. Signalling molecules are released into the extracellular environment, including ADP and serotonin. These activate neighbouring platelets, and triggers a change in shape to become more dendritic. If fibrinogen receptors are activated, it causes them to bind to fibrinogen and the platelets become attached together.
Fibrinogen forms the bridges between aggregating platelets

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13
Q

What is erythropoiesis?

A

The formation of blood cells that happens in the bone marrow.

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14
Q

What is anaemia?

A

The decreased ability to transport oxygen due to a reduced number of RBCs/haemoglobin per RBC or both options. There may be a dietary deficiency of iron, bone marrow failure, poor production of EPO or increased destruction of RBCs.

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15
Q

What are monocytes?

A

Cells that can differentiate into a second cell type called a macrophage. They are the largest of the blood cells and have an irregular, often lobed nucleus. They contain 5 granules.

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16
Q

What do neutrophils look like?

A

They have a distinct nucleus (not round) and they are lobular and granular.
have a distinct nucleus with 2-5 lobes

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17
Q

What are lymphocytes?

A

Natural killer cells that lyse target cells.
They have a large nucleus and a small number of granules with lysosomal enzymes
include B cells, T helpers and natural killer cells
Provide protection against specific pathogens

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18
Q

What are basophils?

A

They are involved in allergic reactions and contain histamine and heparin. Skin rash and anaphalactic shock.

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19
Q

What is eryhthropoietin and what does it do?

A

It is a hematopoietic growth factor that stimulates the production of erythrocytes.

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20
Q

How are platelets formed from megakaryocytes?

A

They fragment into platelets.

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21
Q

What are the two main stages in blood clotting?

A

Primary haemostasis and secondary haemostasis. The plug is formed in primary and the plug is stabilised and transformed into a clot by a fibrin network in the second stage.

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22
Q

What is haemotoma?

A

The accumulation of blood in tissues - forms a bruise.

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23
Q

How do platelets adhere to collagen fibres?

A

Via an intermediate protein called von Willebrand factor (vWF). It forms a bridge between the damaged blood vessel and the circulating platelet.

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24
Q

What are the three main steps in platelet action?

A

Platelet activation, platelet aggregation and platelet plug formation.

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25
Q

What proteins are in platelets that enhance plug formation?

A

Actin and myosin that can contract in activated platelets.

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26
Q

How is the formation of the platelet plug prevented from spreading to the healthy body?

A

Healthy endothelial cells synthesise Prostacyclin and nitric oxide.
These are inhibitors of platelet activation/aggregation

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27
Q

How is a clot formed?

A

Vessel damage exposes subenodthelial layer, and contact of blood with underlying layer activates a cascade of enzymes that result in the activation of Thrombin. Thrombin cleaves fibrinogen into fibrin - these bind together to form a loose meshwork.

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28
Q

What does thrombin do?

A

It is a protease enzyme that cleaves proteins - it cleaves fibrinogen to form fibrin.

29
Q

What is the extrinsic pathway?

A

The principle pathway that is activated in clotting. The factors needed to activate the pathway are outside of the blood.

30
Q

What is the intrinsic pathway?

A

A minor component that is amplified by the extrinsic pathway and only requires factors in the blood in order to be activated.

31
Q

What feeds back to the intrinsic pathway?

A

Thrombin - it activates components in the intrinsic pathway to generate even more thrombin.

32
Q

Where does thrombin bind?

A

A site on the N terminus of the thrombin receptor (PAR - protease activated receptor).

33
Q

How is the blood clot dissolved?

A

Plasminogen activators are secreted by healthy endothelial cells that cause plasminogen to be cleaved into plasmin (an enzyme) that attacks fibrin to cause the fibrin fragments to become soluble (by cleaving them into soluble fibrin fragments). The binding of tPA to fibrin is important as this increases the activity of the enzyme and tPA catalyses the conversion of plasminogen into plasmin.

34
Q

What does this trigger

A

Release of Adp and serotonin

35
Q

What is platelet aggregation

A

positive feedback
attachment of platelets to each other recruits more platelets
results in formation of a platelet plug

36
Q

What is a summary of the platelet plug formation?

A

Platelets adhere to the damaged surface. There is platelet activation, aggregation and plug formation. THe plug is enhanced by actin/myosin that contract. Smooth muscle in the blood vessel wall will also contract and decrease blood flow to the site of damage.

37
Q

What other chemicals do platelets release when they adhere

A

thromboxane A2

38
Q

What does thromboxane do

A

(cause contraction of smooth muscle, leading to vasoconstriction- indirectly? )
promote platelet aggregation

39
Q

function of neutrophils

A

They are found in the blood but leave and enter tissues during inflammation. Granules have enzymes for breakdown of engulfed particles and they produce inflammatory mediators. They have amoeboid movement.

40
Q

Eosinophils features

A

2/3 lobed nucleus
granules spherical and larger than in neutrophils and stain with acid dytes. They have some phagocytic action and have a role in allergy and asthma.

41
Q

Action of eosinophils

A

Some phagocytic action, or release toxic chemicals

Role in allergy and asthma

42
Q

Monocyte features

A

Largest BC
Fine granules
Irregular, often lobed nucleus

43
Q

What are monocytes

A

Phagocytes that circulate in the blood and migrate into tissues where they develop into macrophages

44
Q

What are the progenitors of platelets and how do they form

A

Megakaryocytes, form when cytoplasmic portions of large bone marrow cells pinch off

45
Q

What about the structure of platelets increases its enhances plug formation

A

Contains high levels of actin/myosin and a cyoskeleton that can contract in activated platelets

46
Q

what is thrombocytopenia and why does it happen

A

bleeding disorder due to a low platelet count

Happens when the pathway leading to platelet activation is disrupted

47
Q

What are erythrocytes?

A

They are red blood cells involved in the transport of CO2 and O2. They contain haemoglobin and have a biconcave shape.

48
Q

Intrinsic pathway detailed

A

XII converted into XIIa when comes into contact with collagen
XIIa catalyses activation of XI into XIa, which in turn activates IX to IXa
This last factor activates X to Xa, which converts prothrombin to thrombin

49
Q

Extrinsic pathway detailed

A

Pathway begins with transcription factor located on outside of subendothelial cells which are exposed
TF on these cells bind to factor VII, forms activated VIIa
Complex formed by these then activates factor X

50
Q

In an uninjured blood vessel..

A

Thrombin bound to thrombomodulin (bound to the endothelial cell) activates protein C, which blocks the clotting response

51
Q

Where is the majority of blood cell production from in an adult?

A

The ribs, sternum, vetrebrae, pelvis, ribs and cranial bones.

52
Q

What are the progenitor cells for platelets?

A

Megakaryocytes - these are cells with a multi-lobed nucleus.

53
Q

What else happens due to the activation and aggregation of platelets?

A

There is a discharge of mediators that result in the contraction of vascular smooth muscle to result in vasoconstriction.

54
Q

What is erythrocyte production controlled by and what is it called?

A

The production is called erythropoiesis and it occurs in the bone marrow. It is controlled by a hormone called erythopoietin (EPO) which is produced by the kidney.

55
Q

What happens if there is low oxygen delivery to the kidneys?

A

The kidneys secrete more erythropoetin which results in more production of erythrocytes in the bone marrow. There is an increase in blood Hb concentration, along with the blood carrying capacity.

56
Q

What are the 6 leukocytes?

A

Basophils, neutrophils, eosinophils, monocytes, macrophages and lymphocytes.

57
Q

What are the 5 types of phagocytes?

A

Basophils, neutrophils, eosinophils, monocytes, macrophages.

58
Q

What are the three types of granulocytes?

A

Basophils, neutrophils, eoisinophils.

59
Q

What are the sub divisions of lymphocytes?

A

B cell involved in antibody production, T helper cell that regulate antibody production and immune reactiosn and Natural Killer cells that lyse target cells.

60
Q

What is the process for blood cell production?

A

A pluripotent stem cell differentiates into a lymphoid or myeloid stem cell that will give rise to specific types of blood cell. Myeloid stem cells differentiate into erythrocytes, neutrophils, monocytes, eosinophils, basophils and megakaryocytes.

61
Q

What is platelet aggregation?

A

When platelets change shape and stick together.

62
Q

What happens to activated platelets?

A

They release the contents of secretory vesicles that contain ADP and serotonin to activate nearby platelets.

63
Q

What is a clot?

A

The transformation of blood into a gel. It occurs around the platelet plug.

64
Q

How is thrombin activated during clot formation?

A

Prothrombinase compelx forms on the surface of the activated platelet and leads to the activation of prothrombin. This is cleaved into active thrombin that cleaves fibrinogen to form fibrin.

65
Q

What is the PAR receptor?

A

A receptor found on platelets called the protease activated receptor.

66
Q

What does thrombin do to the PAR receptor?

A

It binds to the N terminus of the receptor and cleaves the terminus. This can now bind and activate the thrombin receptor.

67
Q

How is the clotting response prevented in uninjured vessels?

A

Thrombin is bound to thombomodulin that activates protein C, which blocks the clotting response.

68
Q

How is the liver involved in the blood?

A

It produces and modifies blood proteins that are used in the clotting pathway. Bile salts from the liver facilitate the absorption of lipids, including vitamin K which is required for the synthesis of prothrombin and several other clotting factors.

69
Q

What does the term tethered ligand mean?

A

The ligand of the receptor is part of the receptor itself - it activates itself.

PA10315 (47 decks)

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