Guyton Phys 36: Hemostasis And Blood Coagulation

Front 1

hemostasis definition

Back 1

prevention of blood loss

Front 2

hemostasis mechanisms

Back 2

1) vascular constriction 2) platlet plug 3) blood clot 4) growth of fibrous tissue

Front 3

trauma causes what reaction in vessel wall

Back 3

smooth muscle contraction

Front 4

mechanisms of smooth muscle contraction in vessel wall

Back 4

1) local myogenic spasm 2)local autacoid factors from platelets and injured tissues 3) nervous reflexes

Front 5

what are the nervoud impulses initiated by in vessel wall contraction

Back 5

pain nerve impulses from injured vessel or nearby tissues

Front 6

what is reponsible for most vasoconstiction of small vessels

Back 6

platlets releasing thromboxane A2

Front 7

size, number, and origin of platlets

Back 7

1-4 uL in diameter; 150,000-300,000 per uL; megakaryocytes in marrow

Front 8

active factors in platelet cytoplasm

Back 8

1) actin/myosin and thromosthnin 2) ER and golgi reminants 3) mitochondria 4)prostaglandin synthesis 5) fibrin stabilizing factor 6)growth factor

Front 9

platelet cell membrane

Back 9

glycoproteins on surface (repulses normal endothelium); phospholipids (activate stages of blood clotting process)

Front 10

platelet half life

Back 10

8-12 days (most removed by spleen)

Front 11

what happens to platelets when exposed to a damaged vascular surface

Back 11

swell, numerous pseudopods form, contractile proteins contract and release granules, become sticky and adhere to collagen or protein called con Willebrand factor, secrete lots of ADP, enzymes form thromboxane A (ADP and thromboxane activate other platelets)

Front 12

what occurs when platelet levels are diminished

Back 12

thousands of small hemmorrhagic areas develop under the skin and thoughout internal tissues

Front 13

how quickly does a blood clot form

Back 13

15-20 seconds if vascular wall trauma severe, 1-2 if minor

Front 14

how long until the blood clot retracts

Back 14

20 minutes to one hour (if not too large of a vessel or opening)

Front 15

2 potential fates of a blood clot

Back 15

1) invaded by fibroblasts 2) dissolve

Front 16

3 steps of clotting

Back 16

1) complex cascade resulting in prothrombin activator 2) Prothrombin catalyzed into thrombin (Ca++ needed) 3)thrombin converts fibrinogen to fibrin

Front 17

rate-limiting factor in blood coagulation

Back 17

usually formation of prothromin activator

Front 18

platlet involvemnt with prothrombin

Back 18

prothrombin attaches to platelet receptors bound to damaged tissue

Front 19

Prothrombin info (class, weight, concentration, origin)

Back 19

alpha2-globulin plasma protein; MW 68,700; 15 mg/dL; made in liver (vit K required)

Front 20

Fibrinogen info (weight, concentration, origin)

Back 20

MW 340,000 (large weight/size prevents leakage into interstitial fluids); 100-700 mg/dL plasma concentration; made in liver

Front 21

What can high capillary permeability cause

Back 21

fibrinogen leaks into interstitial fluids and clots form

Front 22

Thrombin action

Back 22

has weak proteolytic capabilities and removes 4 low MW peptides from fibrinogen creating fibrin monomer; activates fibrin-stabilizing factor; direct effect on prothrombin (positive feedback - also acts on factors responsible for prothrombin activator - factors 8-12)

Front 23

bonds of early fibrin monomers

Back 23

weak noncovalent hydrogen bonding (no cross-links)

Front 24

Fibrin-stbilizing factor origin, activation, and action

Back 24

in normal plasma globulins and released by platelets; thrombin activates; causes covalent bonds and cross-links between fibrin monomers

Front 25

blood clot definition

Back 25

meshwork of fibrin fibers running in all directions and entrapping blood cells, platelets, and plasma

Front 26

Why are platelets necessary for clot retraction

Back 26

attach to fibrin fibers and bond everything together; also release procoagulant substances including fibrin-stabilizing factor; have contractibility capability; Ca++ stored in platelets accelerate process

Front 27

Two pathways for prothrombin activator formation

Back 27

1) extrinsic pathway - trauma to vascular wall and tissues 2) intrinsic pathway - within blood itself

Front 28

Step 1 of extrinsic pathway

Back 28

Release of tissue factor aka tissue thromboplastin (phospholipids plus lipoprotein complex)

Front 29

Step 2 of extrinsic pathway

Back 29

activation of factor 10 by a complex of factor 7 and tissue factor in presence of Ca++

Front 30

Step 3 extrinsic pathway

Back 30

Factor 10a combines with tissue phospholipids and factor 5 ( V is not active until positive feedback) to form prothrombin activator (in presence of Ca++, converts prothrombin to thrombin)

Front 31

Step 1 intrinsic pathway

Back 31

blood trauma causes factor 12 activation and release of platelet phospholipids (including platelet factor 3)

Front 32

Step 2 of intrinsic pathway

Back 32

Factor 11 activated by 12 (requires kininogen and accelerated by prekallikrein)

Front 33

Step 3 intrinsic pathway

Back 33

Factor 9 activated by 11

Front 34

Step 4 intrinsic pathway

Back 34

Factor 10 activated by 9 with 8 and platelet phospholipids and platelet factor 3

Front 35

What facor is missing in hemophillia

Back 35

usually factor 8, sometimes (15%) factor 9

Front 36

Step 5 intrinsic pathway

Back 36

same as last step on extrinsic pathway: activated 10 combines with 5 and platelet/tissue phospholipids to form prothrombin activator

Front 37

How can blood be prevented from clotting when removed from a person

Back 37

keep Ca++ below threshold for clotting: add citrate ions (deionize) or oxalate ion (precipitate)

Front 38

What pathway is activated after blood vessel rupture

Back 38

both intrinsic via platelet/factor 7 interaction and extrinsic via tissue factor

Front 39

speed of extrinsic vs intrinsic pathway

Back 39

15 seconds vs 1-6 minutes

Front 40

What prevents clotting

Back 40

1)smooth endothelial walls 2)layer of glycocalyx on endothelium (mucopolysaccaride) repells clotting factors 3)thrombomodulin on endotheial membrane binds thrombin (activates protein C which inactivated factors 5 and 8)

Front 41

most important anticoagulants

Back 41

fibrin fibers and antithrombin III (aka antithrombin-heparin cofactor)

Front 42

how much thrombin do fibrin fibers absorb

Back 42

85-90%

Front 43

where is heparin found naturally in the body

Back 43

in capillaries, especially mast cells of lung and liver (receive venous blood from body, heparin prevents the growth of clots they may receive)

Front 44

Heparin action

Back 44

highly neg charge; combines with antithrombin III (increases effectiveness from 100 fold to 1000 fold; also removes factors 7,9, 10, and 11)

Front 45

plasmin (from plasma proteins as plasminogen)

Back 45

digests fibrin fibers and some other protein coagulants - fibrinogen, factors 5, 7, and 8, prothrombin

Front 46

plasmin activation

Back 46

tissue plasminogen activator (t-PA)

Front 47

vitamin K required for formation of what clotting factors

Back 47

prothrombin, protein C, and factors 7,9, and 10

Front 48

component of factor 8 deficient in hemophilia

Back 48

smaller component (most important for intrinsic pathway)

Front 49

component of factor 8 deficient in von Willebrand's diease

Back 49

loss of large component

Front 50

treatment for thrombocytopenia

Back 50

spleen removal

Front 51

cause of roughened endothelial surface

Back 51

arteriosclerosis, infection, or trauma

Front 52

treatment of thrombitic occusion

Back 52

genetically engineered t-PA (best within first hour of onset)

Front 53

occurance of thrombosis in bed ridden patients

Back 53

1 in 10

Front 54

disseminated intravascular coagulation

Back 54

clotting mechanism activated in widespread areas of circulation (common in septicemia)

Front 55

length of heparin effectiveness

Back 55

1.5-4 hours (broken down by heparinase)

Front 56

Coumarin (warfarin)

Back 56

decreases levels of prothrombin, factors 7, 9, and 10 (competes for vit K active sites))

Front 57

prothrombin time

Back 57

indication of prothrombin concentration in blood (normal about 12 s)