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General Health and Disease (GHD) > Blood > Flashcards

Blood Flashcards

1
Q

Functions of blood?

A 
Carriage of physiologically active compounds
Clotting
Defence
Carriage of gas
Thermoregulation
Maintenance of ECF pH
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2
Q

Composition of blood?

A

Consists of plasma, red blood cells, white blood cells and platelets.

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3
Q

Plasma? Characteristics?

A

4% body weight, 95 % water
Circulates biologically active compounds, composition kept within strict limits in health
Plasma proteins subdivided into 3 categories:

Albumin: most abundant
Globulin - Subdivided into 3 categories;
alpha and beta globulins
Fibrinogen and other clotting factors

Plasma proteins not taken up by cells, and generate and regulate oncotic pressure

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4
Q

Colloid Oncotic Pressure? Description?

A

Capillary wall allows the transport of ions, glucose and water from the interstitial space to the vessel lumen

The concentration of fluid remains unchanged while volume of plasma and interstitial fluid is altered

Interstitial fluid acts as a fluid resevoir

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5
Q

Erythrocytes? Characteristics?

A 
Most abundant blood cell 
(4 - 6 x10*12 per litre), 
120 day lifespan.
Highly flexible 
Biconcave
Non-nucleated
Diameter 7-8um 
Contain haemoglobin: gas transport.
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6
Q

Red Blood Cell Formation? Process and enhanced hormone prod?

A

Controlled and accelerated by erythropoietin
Secretion - 85% kidney
15% liver hepatocytes

Pluripotent stem cells form erythroblasts stimulated by erythropoietin

Erythropoietin is enhanced when o2 delivery to kidney is reduced;

  • hypox
  • haemorrage
  • anaemia
  • lung disease
  • cardiac dysfunction
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7
Q

Haemoglobin - iron stores? development? ferritin?

A

RBC synthesise haemoglobin at the erythroblast stage of development.
Essential dietary requirements: iron, folic acid, vit B12
Iron stores:
70% haemoglobin
5% muscle myoglobin
25% hepatocytes, bone marrow, spleen (stored as ferritin).

Ferritin also found in soln in blood. Reflects iron status of individual.
Women - 8.5mmol/L , Men 10mmol/L

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8
Q

Haemoglobin breakdown? Process?

A

Haemoglobin is released from degraded RBCs which becomes globin and is broken into aas

The haem either froms new RBCs, or converted to bilirubin

Bilirubin is carried in the blood by albumin (unconjugated), and enters the liver and becomes conjugated with glucuronic acid

Some is excreted in the urine or secreted into the bile and excreted in the faeces

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9
Q

Leukocytes? Types, Characteristics and Formation?

A

Nucleated
5 x 10*10 per litre
Involved in defense against pathogens

WBCs form granulocytes, monocytes and lymphocytes

Granulocytes can differentiate to neutro, eosino and baso

Lymphocytes can differentiate to B cells and T cells

T cells differentiate to helper and killer cells

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10
Q

Neutrophils? Characteristics?

A

68% of WBC population, half-life 6 hours (need to produce 100 billion per day for normal function!)

Phagocytic, and can also entrap bacteria in NETS (Neutrophil Extracellular Traps)

Form first line of defence.

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11
Q

Eosinophils? Characteristics?

A

1.5% although number will increase rapidly during allergic response

Attack pathogens too large for neutrophils and other defense cells

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12
Q

Basophils? Characteristics?

A

0.5%, Release histamine and heparin - trigger inflammation.

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13
Q

Monocytes? Characteristics?

A

5%, largest WBC, life span 72 hours in circulation. Migrate to spleen, liver, lungs and lymph nodes - macrophages

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14
Q

Macrophages? Characteristics?

A

Mature monocyte that has migrated from the blood to the connective tissue where it may reside for up to 3 months. Phagocytic.

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15
Q

Lymphocytes? Characteristics?

A

25%
Adaptive immunity
B and T cells

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16
Q

Platelets? Characteristics?

A

Membrane bound cell fragments (from megakaryocytes)
Formation governed by Thrombopoietin
10 day span

Adhere to damaged vessel walls and exposed connective tissue (via Von Willibrand Factor) to mediate blood clotting
DO NOT adhere to healthy intact endothelium.

17
Q

Haematocrit? Range? Viscosity?

A

Male: 40-54%
Female: 37-47%

Plasma 1.8 and blood 3-4

Factors temperature and flow rate

18
Q

Steps involved in haemostasis? Overview?

A
  • Vasoconstrict
  • Platelet plug
  • Clot cascade
  • Clot retraction
  • Fibrinolysis
19
Q

Platelet plug? Characteristics?

A
  • Starts with a damaged vessel and vasoconstrict
  • Adherence of platelets via their receptors to the Von Willebrand factor present on the outer-surface of the vessel, unknown to the platelet
  • This activates the platelet which enables it to secrete TXA2, ADP and 5-HT
  • These substances then chemokines then attract other platelets which bind to to the other platelets
  • This creates +ve feedback to create the platelet plug

The opposing BV wall secrete anticoags to reduce the formation of the plug

20
Q

Platelets? Characteristics?

A
  • Released from megakaryocytes governed by IL-6 and IL-11
  • Canalicular system: platelets have channels that allow nutrients to enter
  • Surface glycoproteins

Secretions:

  • dense (TXA2, CA, ADR, 5-HT and ADP)
  • alpha (PDGF, fibrinogen, herparin antag)
  • lysosomal

Essential for clotting - most cascade reactions take place on the platelet membrane.

21
Q

Clotting? Characteristics?

A

Convert the blood around the site of damage into a plug with a solid gel like consistency

Circulating soluble plasma proteins called fibrinogen are converted to insoluble polymer strands of fibrin which form a mesh, trapping blood cells and preventing blood loss.

Conversion of fibrinogen to fibrin is the final step in a cascade of reactions which can either follow an intrinsic or extrinsic pathway.

22
Q

Intrinsic pathway? Process?

A

XII activated by collagen or other activator
Act XII activates XI
Act XI activates IX
Act IX activates X

Act X converts prothrombin to thrombin (activates XI)
Thrombin converts fibrinogen to fibrin by activating XIII to cross-link fibrin

Each step needs Ca as a co-factor

23
Q

Extrinsic pathway? Process?

A

Damage exposes tissue factor III which activates VII, both of these then activate IX, which then activates X (activates VII)

TFPI inhibits the formation of Act X

Act X converts prothrombin to thrombin (activates XI)
Thrombin converts fibrinogen to fibrin by activating XIII to cross-link fibrin

Each step needs Ca as a co-factor

24
Q

Factor XIII? rls?

A

Transglutaminase which links glutamine to lysine residues

25
Q

Importance of calcium? not cows milk? for clotting?

A

Main cofactor for activation of platelet factors

26
Q

Clot stabilisation Characteristics?

A

Circulating, soluble fibrinogen forms stable insoluble fibrin mesh

Catalysed by thrombin
Polymerisation via h-bonds

XIII creates cross-links allowing stabilisation, which surrounds the platelet plug

27
Q

Clot retraction? Characteristics?

A

Actin & myosin in platelets contract drawing edges of wound together (thrombin stimulates release of intracellular Ca++)

28
Q

Fibrolytic system? Characteristics?

A
  • Thrombolytic system
  • Clot breakdown via plasmingoen/plasmin which digest fibrin
  • Tissue plasminogen activator (t-PA) released by endothelial cells – activates plasminogen to plasmin leading to breakdown of fibrin, fibrinogen and Factors V and VIII.
  • Fibrin binds increases t-PA enzymatic activity but inhibited by PAI-1
29
Q

Anti-clotting drugs? Mechanisms?

A
  • Prostacyclin and NO
  • Heparin: binds and act antithrombin, which neutralises IX and XII
  • Thrombomodulin: binds thrombin (Protein C + co-factor, protein S, inactivate clotting factors V and VIII and catalyses formation of plasmin from plasminogen)
  • TFPI: inhibits VII
30
Q

Dental-related drugs? Problems?

A
  • Aspirin and Warfarin
  • No clotting after extraction
  • Warfarin is a vit K reductase inhibitor

General Health and Disease (GHD) (31 decks)

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