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Science for Paramedics > Blood and the clotting cascade > Flashcards

Blood and the clotting cascade Flashcards

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Biology 101 flashcards
1
Q

What is the medical definition of blood?

A

Blood is a specialised connective tissue that circulates in the cardiovascular system and delivers oxygen and nutrients to cells and tissues. It also removes waste products like carbon dioxide and metabolic byproducts.

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2
Q

What percentage of our bodyweight is blood?

A

8%

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3
Q

How much of total blood volume is plasma?

A

55%

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4
Q

What is the composition of plasma?

A

Approx. 90% water, about 10% proteins & less than 1% of various solutes.

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5
Q

What is the composition of plasma proteins and where are they all made?

A

Albumin (60%)
Globulin (36%)
Fibrinogen (4%)

The liver

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6
Q

What is albumin and why is it important for the body?

A

Albumin is a carrier protein that will take lipid soluble substances around the body.

Most of the blood is made up of water, lipid soluble substances need assisstance moving through it - albumin binds to the lipids and carries them around the body. For example:
-Vitamins like calcium
-Lipid soluble drugs such as propranolol
-Benzodiazepines
-Hormones like steroids

Albumin is also the key component to maintaining osmotic pressure by pulling water back into the vascular system. (The body can’t do anything without pressure, all physiology is dependent on movement of solutes across membranes)

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7
Q

What are globulins are what are they for?

A

Globulins are plasma proteins and are involved in your immune response, they carry various ions and transport fats around, there are 3 types; gamma, alpha & beta.

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8
Q

What is fibrinogen?

A

An inactive protein that needs to be activated to produce fibrin which is a chief component in forming blood clots.

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9
Q

What percentage of the blood is solutes and what do they include?

A

<1% - Gasses like O2, ions, nutrients and waste.

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10
Q

What is the composition of blood?

A

55% plasma
<1% buffy coat
45% erythrocytes

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11
Q

What makes up the buffy coat of blood?

A

Platelets and leukocytes

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12
Q

What are platelets are what are they useful for?

A

Platelets are small blood cells & cell fragments produced in bone marrow with a life span is around 5-9 days. The surface of platelets contain proteins that allow them to stick to other proteins. Platelets are essential when forming a platelet plug which is a vital step in stemming bleeding.

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13
Q

What is the lifespan of erythrocytes?

A

Approx. 120 days

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14
Q

Which protein helps erythrocytes keep their shape?

A

Spectrin

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15
Q

What is the pH of blood?

A

7.35 – 7.45

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16
Q

How much will the blood volume of a pregnant woman have increased by in the 20th week of pregnancy?

A

50%

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17
Q

What are the three steps to haemostasis?

A

Vascular constriction
Platelet aggregation
Coagulation

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18
Q

What happens during vasoconstriction as part of haemostasis?

A

When vascular damage happens the smooth muscle constricts around the vessel. This means less blood flows through the vessel in an attempt to limit the blood loss in the area.

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19
Q

What happens during platelet aggregation as part of haemostasis?

A

Vessel walls contain collagen, and when collagen fibres become damaged the circulating platelets will respond by sticking to the ends of the collagen fibres. When the platelets do this they form a platelet plug which will stop up the hole the blood is leaking from. This usually happens within 30-60 seconds. This might be enough to stop the bleeding and the reaction will stop there.

This is primary haemostasis

20
Q

What is the clotting cascade?

A
21
Q

How does platelet aggregation lead to fibrin and what is the purpose of it?

A

When the platelet plug forms it releases prothrombin activator, which activates prothrombin (prothrobin is hanging about in the blood stream) and turns it into thrombin. (Thrombin will cut up proteins, namely fibrinogen which is in the plasma already)
Thrombin will cut up the plasma protein fibrinogen into fibrin. This will reinforce the platelet plug until the connective tissue can be replaced and the hole can be glued shut.

22
Q

What is a Complete blood count (CBC) AKA Full blood count (FBC)?

A

This checks the counts and characteristics of all formed elements – white blood cells, haemoglobin & haematocrit. It also counts the amount of platelets. This is generally what will be done for our emergency patients

23
Q

Which clotting factors are involved in the core extrinsic pathway of the clotting cascade?

A

Tissue factor (Factor III)
VII + VIIa

24
Q

Which clotting factors are involved in the core intrinsic pathway of the clotting cascade?

A

XII + XIIa
XI + XIa
IX + IXa
VIII + VIIIa

25
Q

What stimulates the extrinsic pathway of the clotting cascade?

A

Tissue and platelet injury

26
Q

What stimulates the intrinsic pathway of the clotting cascade?

A

The exposure of blood to a negatively charged surface
Endotheial vessel damage

27
Q

What clotting factors are involved in the common pathway?

A

X + Xa
V + Va
Prothrombin (Factor II)
Thrombin (Factor IIa)
Fibrinogen (Factor I)
Fibrin (Factor Ia)

28
Q

Which clotting factors are vitamin K dependant?

A

II (Prothrombin)
VI
IX

29
Q

What are the 3 steps to the cell-based model of the clotting cascade?

A

1) Activation
2)Amplification
3)Propagation

30
Q

What happens during the activation and amplification phases of the cell-based model of clotting cascade?

A

Activation: Initial generation or exposure of tissue factor from the extrinsic pathway at the wound site and its interaction with factor VIIa is the primary phisiological event in initiating clotting leading to activation of thrombin.

Amplification: The small amount of thrombin generated then activates factors V (into Va), XI (into XIa), and XIII (into XIIIa) (all from the core intrinsic pathway) in a feedback manor leading to amplification of thrombin generation. This in turn also activates the platelets. All this activation leads to the next step - propigation which occurs on activated platelets

31
Q

What carries factor clotting factor VIII, why?

A

Von Wilderband factor, it prevents factor VIII from rapidly degrading i.e. increases its half life

32
Q

What releases factor VIII from von Willebrand factor?

A

Thrombin (factor IIa)

33
Q

What happens during the propigation phase of the cell-based model of clotting cascade?

A

Factor VIIIa combines with factor IXa to produce the very powerful tenase complex resulting in factor X activation into Xa. Xa and Va then combine to form the pro-thrombinase complex. Pro-thrombinase rapidly converts prothrombin (factor II) into thrombin (factor IIa) which subsequently forms fibrin (factor Ia) from fibrinogen (factor I)

34
Q

What does fibrin get broken down into?

A

Fibrin degrodation products (FDPs) e.g. D-Dimers

35
Q

What breaks down fibrin?

A

Plasmin

36
Q

What is plasmin derived from, and what activates it into plasmin?

A

Plasminogen - it is activated by tissue Plaminogen Activator (tPA)

37
Q

What is thrombin-activateable fibrinolygis inhibitor (TAFI)?

A

A molecule activated by thrombin (factor IIa) that slows down fibrinolysis

38
Q

What are the anti-thrombotic pathways?

A

The body’s way of controlling the clotting cascade

39
Q

What is the protein-C/protein-S anti-thrombotic pathway?

A

As clotting formation progresses, thrombin (factor IIa) binds to thrombomodulin, an integral membrane protein on the surface of epithelial cells.
The thrombin-thrombomodulin complex activates protein-C to form activated protein-C.
Together with protein-S as a co-factor, activated protein-C inhibits factors Va and VIIIa, halting coagulation.

40
Q

Was is the TFPI anti-thrombotic pathway?

A

Tissue Factor Pathway Inhibitor circulates in the plasma at low concentrations and inhibits factor X activation in two main ways:
Inhibiting Xa directly
Inhibiting tissue factor-factor VIIa complex

41
Q

What is the C1 esterase inhibitor anti-thrombotic pathway?

A

C1 esterase inhibitor is a protease inhibitor which inhibits factors XIa and XIIa as well as the complement proteases c1r and c1s

42
Q

What is the antithrombin antithrombic pathway?

A

Antithrombin is a circulating protease inhibitor which neutralises most of the factors in the clotting cascade inhibiting formation of factors Xa, IXa and IIa (thrombin)

43
Q

What are the four anti-thrombotic pathways?

A

Protein-C/protein-S
Tissue Factor Pathway Inhibitor (TFPI)
C1 esterase inhibitor
Antithrombin

44
Q

What is plasmin activator inhibitor (PA1)?

A

An inhibitor of tPA which in turn inhibits plasmin formation and decreases fibrinolysis - encouraging continued clotting

45
Q

What is alpha-2 antiplasmin?

A

A direct inhibitor of plasmin which decreases fibrinolysis - encouraging continued clotting

Science for Paramedics (18 decks)

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