Blood Physiology Flashcards
(167 cards)
1
Q
Describe blood
A
Blood is the only fluid tissue in the body. It is a specialised connective tissue of mesoderma origin in which formed elements are suspended in a non-living fluid matrix called plasma
2
Q
Other names for blood and why?
A
Fluid of life: because it carries oxygen from the lungs to the cells and CO2 from the cells to the lungs
Fluid of growth: because it carries nutritive substances from the digestive system to the tissues of the body and hormones from the endocrine glands to where they’re needed.
Fluid of health: because it protects the body against disease and gets rid of unwanted substances by transporting them to excretory organs like kidney.
3
Q
Characteristics of blood
A
Colour:
- Scarlet red: oxygenated
- Dark red: deoxygenated
pH: 7.35 - 7.45
Temperature: Slightly higher than normal body temperature.
Density:
- For males: 1.052 - 1.063
- For females: 1.050 - 1.058
Volume:
- For females: 4 - 5L
-For males: 5 - 6L
- 4 - 5 times more viscous than water
Weight: 100mls of blood weighs about 106g
Osmolarity: 300mOsm for 0.3Osm
About 6 - 8% of tbw
Salinity: 0.85%
4
Q
Functions of blood
A
*Transport functions
- Distributed O2 from the lungs to the cells of the body.
- Carries metabolic wastes from the cells to the organs of excretion
- Transports nutritional substances from the GI tract to the tissues of the body.
- Transports hormones from their site of synthesis to where they’re needed in the body.
- Regulatory functions
- Body fluid
_ Body pH - Regulates blood pressure
- Body temperature
- Body protection
- Protective functions
- Activates plasma protein and platelets
- Synthesis of antibodies
- Haemostasis
_ Fights against diseases
5
Q
Composition of blood
A
- Plasma (60%)
- Formed elements (40%)
6
Q
Composition of blood
A
- Plasma (60%)
- Formed elements (40%)
7
Q
Characteristics of white blood cells
A
Larger in size
Nucleated
Short lifespan
Irregular in shape
Colourless
8
Q
Describe Basophils
A
- Make up <1% of WBC (least abundant)
- Produce inflammatory and allergic reactions
- They store and synthesize histamine which is important in allergic reactions
- Basophils enter the body tissues to become mast cells which help blood flow to injured tissues by releasing histamine
9
Q
Describe Monocytes
A
- Largest of WBC
- Dark kidney bean-shaped nucleus
- Highly phagocytotic
- Accounts for about 2 - 8% of TWBC counts
- Fights off bacteria, fungi and mycobacterium such as mycobacterium tuberculosis.
- Migrate to the tissues to become macrophages and bear various names depending on their locations.
10
Q
Characteristics of neutrophils
A
- Also called polymorphs
- Phagocytosis, contains several lysosomes
- Diapedesis
- Stain light purple with neutral dye
- Has several lobes in nucleus
- Granules are small and numerous in the cytoplasm (gives a coarse appearance)
- 50-70% of total WBC count
- Highly mobile/ very active
- Lifespan is 12-48 hours
- Its number increases with bacterial infection, burns, inflammation and stress.
- Neutrophil granules contain enzymes such as elastase, proteases, metalloproteinase, myeloperoxidases which are involved in the destruction of bacteria.
- Major function is to engulf and phagocytose bacteria and also involved in acute inflammation.
11
Q
Characteristics of WBC
A
- Colourless
- Nucleated
- Short lifespan
- Larger size
- Irregular in shape
- Phagocytosis
- Diapedesis (extravasation): can exit circulatory system through capillary bed
- Capable of ameboid movement
- ## Chemotaxis (attracted to certain chemicals like those from damaged cells).
12
Q
Primary cytokine responsible for erythrocyte production?
A
Erythropoietin (EPO)
13
Q
Where are leucocytes formed?
A
The red marrow of many bones
Lymphatic tissue
14
Q
Types of WBC
A
*Granulocytes
- Neutrophils
- Eosinophils
- Basophils
*Agranulocytes
- Lymphocytes
- Monocytes
15
Q
Normal total WBC count
A
2,500 - 11,000 / cubic mm
16
Q
Differential count of WBC?
A
Gives the relative percentage of each white blood cell.
17
Q
Absolute value of WBC
A
Gives the actual number of each white blood cell / cubic mm
18
Q
Describe neutrophils
A
- Also called polymorphs
- Stain bright purple with neutral dye
- Granules are small & numerous - coarse appearance
- Several lobes in nucleus
- Phagocytosis, many lysosomes present
*Lifespan of 12 - 48 hours
- About 50 - 70% of TWBC
- Major function is to engulf and phagocytose bacteria and also involve in acute inflammation
- Very active / mobile
- Numbers increase when there’s bacterial infection, inflammation, burns & stress.
- Diapedesis
*Neutrophil Granules contain enzymes such as myeloperoxidases, elastases, proteases, metalloproteinase which are involved in destruction of bacteria
19
Q
Eosinophils
A
- Also known as acidophiles
- Can be found in the lining of respiratory and digestive tract
- 1 - 4% of TWBC
- Main function is protection against infections caused by parasitic worms and involvement in allergic reactions
- Granules are large and numerous
- Nuclei with two lobes
- Number increases with worm infestation
- Help initiate and sustain inflammation and can activate T-cells.
- Chemotoxic, can kill parasites
- Responds to diverse stimuli including tissue damage, allergens, allograft, tumour & infections
- Lifespan of 8 - 12 days
20
Q
Constituent of plasma
A
Water: 90 - 92%
Plasma proteins: 6-7% (Albumin, globulin, clotting proteins)
Organic molecules: Glucose, amino acids, fatty acids
Electrolytes: Na, K, Ca, Cl, HCO3
Others: Urea, Lactic acid, CO2, O2, Creatinine
21
Q
Describe plasma
A
Plasma is a straw coloured sticky fluid matrix, the liquid component of blood and on which formed elements is suspended.
22
Q
Function of plasma
A
*Haemostasis - blood coagulation
- Transport mechanism: alpha albumin, beta globulin transports hormones, enzymes, gasses, urea, etc.
*Defense mechanism of blood: immunoglobulin
*Acid-base balance
*Maintenance of osmotic pressure in blood
*Makes blood viscous
- Provides suspension stability of RBC
- Reserve proteins
23
Q
Characteristics of albumins
A
- Is the most abundant plasma protein (60%)
- Single polypeptide chain with 585 amino acids and 17 disulphide bonds
- Plasma level of albumin is about 3.5 - 5.0 g/dl
- Half-life of 20 days
- Important blood buffer
- Carries some substances through the circulation
- Maintains osmotic pressure of the blood
24
Q
Characteristics of Globulins
A
25
How much albumin is produced per day and where?
The liver produces 12g of albumin per day which accounts for 25% of total hepatic protein synthesis and 50% of secreted protein
26
Can measurement of serum albumin concentration be used to assay liver function test?
Yes, but only when the kidney is functioning properly i.e not excreting albumin
27
What can be used to assay liver function test?
Measurement of serum albumin concentration provided the kidney is functioning properly
28
Diameter of RBC
7.2 - 7.5 micrometer
29
Life span of RBC
120 days
30
Average number of RBC
5 million / cubic mm
Or
5 million / microlitre of blood
31
Characteristics of RBC
* Flexible, biconcave cells that are thinner at the center and thicker at the edges.
* Larger surface to volume ratio which help them bend and twist to pass through narrow capillaries very easily.
* Diameter of ~ 7.5 micrometer
* Mature RBC lack nucleus and organelles
* Lack mitochondria
* Major forms of cells
* Lifespan of 120 days
* Each RBC has 280 million Haemoglobin
* Average number of RBC are 5 million / cubic mm or 5*10^6 /microlitre
* Thickness of about 2 micrometer
32
What's the reaction that occurs in RBC
CO2 + H20 --CA ---> H2CO3 ---> HCO3 + H+
33
What does Carbonic anhydrase do?
It is an enzyme present in the membrane of RBC. It increases the conversion of CO2 in the blood to bicarbonate ion by 5000 folds
34
Mean Cell Volume (MCV)
Also known as Mean corposcular volume is the measure of the average volume of a RBC. It calculates the average volume of a RBC in fentoliters fl (×10^-15 l)
35
What is the normal MCV
85 +/- 8 fl
36
If you relate PCV to total RBC count, what cell indices will you get?
MCV because MCV = PCV/ TRBC count (×10^12 per l)
37
Normal range of RBC in males and females
Females: 4.5 - 5.5 million / cubic mm or microlitre
Males: 5-5.5 million / cubic mm or microlitre
38
What is macrocytic anaemia
This is when the RBC are bigger than normal as a result of abnormal increase in MCV as seen in deficiency of cyanocobalamin (vit B12)/folic acid (vit B9), liver disease, alcoholism and drugs (chemotherapy & antiretrovirals).
39
What leads to macrocytic anaemia?
Deficiency of cyanocobalamin/folic acid, lover diseases, alcoholism and drugs (chemotherapy and antiretrovirals).
40
If a patient comes in with liver disease, what will be the size of the patient's RBC?
> 7.5 micrometer
41
What is microcytic anaemia?
Microcytic anaemia is a condition where the RBC are smaller than normal as a result of a decrease in MCV as seen in iron deficiency anaemia, lead poisoning and thalassemia.
42
Mean Cell Haemoglobin
Also known as Mean corposcular haemoglobin. It is the average content (mass) of haemoglobin per RBC
43
If you relate haemoglobin to total RBC count, what cell indices will you get?
MCH in pictogram
MCH (pg) = Hb (g/l) ÷ RBC count (× 10^12 / l)
44
What is MCH measured in?
Pictogram (10^-12 g)
45
What is the normal MCH
29.5 +/- 2.5 pg
46
What is the normal size of the central pallor of RBC?
About ⅓ of the entire RBC
47
Clinical correlate of MCH
Abnormal decrease in MCH is seen morphologically as hypochromic as seen in iron deficiency anaemia
48
Mean Cell Haemoglobin Concentration
Also known as Mean Corposcular Haemoglobin Concentration (MCHC).
It is the measure of the average concentration of haemoglobin in a given volume of packed RBC.
49
What is the normal MCHC?
33 +/- 2g/dl
50
Haemolytic anaemia
This is a form of anaemia that occurs as a result of the breaking down / lysing of RBC e.g Sickle cell anaemia
51
Clinical correlate of MCHC
Increased MCHC is commonly as a result of smoking cigarettes and occasionally in autoimmune disorders known as cold agglutinin disease and other forms haemolytic anaemia.
It could also be as a result of wrong Hb/PCV values.
52
How do you calculate MCHC?
MCHC (g/dl) = Hb (g) ÷ PCV (dl)
53
What are the cell indices?
* Mean cell volume
* Mean cell haemoglobin
* Mean cell haemoglobin concentration
* Red cell distribution width
54
What is RDW?
Red cell distribution width is a test that shows the variability in the size of red blood cells.
55
Clinical correlate of RDW?
A normal RDW shows that the RBC are similar in sizes.
However, a higher RDW shows that there's variation in the sizes of the RBC and that clues us to early nutritional deficiency which may not have been noted with the other tests alone.
56
Haematopoiesis / Haemopoiesis
Production of blood cells
57
Where is red blood cell first produced?
During the early week of the embryonic life it's produced in the yolk sac
58
When does the production of red blood cells start?
3rd week of embryonic life. Around day Day 18 - Day 20
59
Explain where RBC are produced in the body from shortly after birth to puberty
RBC are produced in the marrows of all bones till about 5 years.
From 5 years to puberty it is restricted to the marrow of long bones.
Then at puberty RBC are produced in the marrows of membraneous bones like ilium, scapula, sternum, vertebrae, skull, mandible, ribs because the marrow of long bones would have been replaced by yellow fat.
60
What is hypoxia?
This is a condition where the tissues (especially the blood) are deprived of adequate supply of oxygen.
61
Stimulants of erythropoiesis
* Hypoxia
* Alkalosis
* Cobalt salts
* Beta-adrenergic stimulants & adenosine
62
At what stage does pyknosis occur?
At the late normoblast stage
63
What is pyknosis?
Pyknosis is the process by which the nucleus disintegrates and disappears in the late normoblast stage of a RBC.
64
At what stage does nucleoli of the RBC disappear?
The early normoblast stage
65
What notable events occur at the early normoblast stage?
* Nucleoli disappears
* Chromatin network condenses
* The condensed chromatin network become dense
* It is also called basophilic erythroblast
66
How many RBC are made per sec?
2 million RBC
67
What is RBC indices?
Set of tests carried out to check the physiological state of RBC in the body and is usually used to diagnose the type of anaemia or cause.
68
How does cobalt salt stimulate erythropoiesis
Cobalt ions (Co(2+) ) stabilize the hypoxia-inducible transcription factors (HIFs) that increase the expression of the erythropoietin (Epo) gene.
69
How many days does it take for the development and maturation of RBC from proerythroblast?
7 days
70
What's the normal percentage of reticulocytes in babies?
2% - 6%
71
Minor blood groups
Laugh wan : Lewis
Kill : Kelly
Me : MN
Kidd : Kidd
Duffy. : Duffy
72
Major blood group
A
B
O
Rh
73
ABO blood group was discovered by?
Karl Landsteiner in 1901
74
The genes that determine A and B phenotype are found where?
Chromosome 9p
75
Where are leucocytes formed?
Red marrow of many bones
Lymphatic tissue
76
Lifespan of leucocytes
About 13 - 20 days
77
Describe lymphocytes
* Smallest WBC
* Make up about 25 - 40% of TWBC count
* Large nucleus / small amount of cytoplasm
* They are of two types: T - Lymphocytes, B - Lymphocytes
* B - Lymphocytes produce gamma globulins (immunoglobulin) responsible for humoral immunity. They produce antibodies against specific antigens
* T - Lymphocytes produce cytokines and are responsible for cellular immunity. The attack infected or cancerous cells.
78
Classification of white blood cell disorders
* Disorder of cell number:
. cytosis/philia (increase in number)
. cytopenia (decrease in number)
* Disorder in function & morphology
79
Leucopenia
A reduced number of white blood cell count < 2,500 / cubic mm
80
Leucocytosis
An increased number of WBC in the peripheral blood > 11,000 / cubic mm
81
Causes of Leucocytosis
* Neutrophilia (commonest cause)
* Eosinophilia
* Basophilia
* Lymphocytosis
* Monocytosis
82
What is neutrophilia
Increase in the number of neutrophils and/or its precursors > 7,000 / cubic mm
83
Causes of neutrophilia
* Infections (pyogenic bacteria: pus-making bacteria)
* Inflammations produced by toxins, infectious agents, neoplasms or burns.
* Following haemorrhage
* Chronic granulocytic leukemia
* Other myeloproliferative disorders
84
Define eosinophilia
Increase in number of eosinophils in the peripheral blood > 400 / cubic mm
If eosinophilic count is > 600 / cubic mm further investigation is required
85
What is immunity
The ability of the body to resist almost all forms of invasion
86
What is the immune system
The immune system consists of group of cells, molecules and organs that collectively defend the body against invasion by organisms, tumor cells and foreign substances
87
Classification of immune system
* Innate immunity
* Adaptive (acquired) immunity
88
Components of immune system
* Organs: Thymus, Bone marrow, lymph nodes, spleen
* Molecules: immune modulators; cytokines
* Cells: white blood cells, antigen-presenting cells
* Antibodies/immunoglobulin
* Complement system
89
What is innate immunity?
It is a nonspecific type of immunity. This refers to the body's in-born ability to resist invasion by organisms or foreign substances.
90
Adaptive immunity
Refers to a specific type of immunity developed in response to a specific antigenic challenge
91
Examples of innate immunity
* Surface barriers/mucosal immunity: skin, secretions of gastrointestinal, respiratory and genitourinary tract
* Normal microflora that live on the body and generally don't cause any harm but prevent the growth of pathogenic organisms in those areas
* Natural killer cells: Large granular lymphocytes that destroy viruses and tumor cells in the body
* Complement system: set of protein that promote destruction of organisms.
* Phagocytic cells: Neutrophils and macrophages that engulf invading microorganisms
92
What are antigens?
Substances capable of eliciting immune response
93
Most potent antigens are ____
Complex proteins or polypeptides
94
Antibodies/ immunoglobulins
These are gamma-globulins produced by the plasma cell (differentiated B - cells) in response to antigenic challenge.
95
Memory
This is the ability of the immune system to remember a previous encounter with an antigen so that a second exposure to that same antigen produces more rapid and powerful response.
96
What cells are responsible for cellular immunity?
T - lymphocytes
97
What cells are responsible for humoral immunity?
B - lymphocytes
98
What is CD?
Cluster of Differentiation are a set of protocols used in the identification and investigation of cell surface molecules found on white blood cells.
99
What are the subset of lymphocytes
* T lymphocytes
+ Cytotoxic T cells
+ Helper T cells: T-helper 1 & T-helper 2
+ Suppressor cells
+ Memory T cells
* B lymphocytes
+ Plasma cells
+ Memory B cells
100
Function of cytotoxic T cell
Killer cell in cellular immunity
101
Function of T-helper cell 1
Activates T-cell in cellular immunity
102
Function of T-helper cell 2
Activates B-cell in humoral immunity
103
Function of Suppressor cell
Regulates both humoral and cellular immunity
104
Function of memory T cell
Keeps record of events of cellular immunity and facilitates secondary immune response to repeated antigenic challenge
105
Function of plasma cell
Produces antibodies (immunoglobulin)
106
Function of memory B cells
Keeps record of events of humoral immunity and facilitates secondary immune responses to repeated antigenic challenge.
107
How are lymphocytes assigned CDs
Lymphocytes are assigned clusters of differentiation based on their reactions to a panel of monoclonal antibodies.
108
_____ can serve as receptors on the surface of white blood cells
Clusters of differentiation (CD)
109
What is the cluster of differentiation for B lymphocytes
* CD 45+
* CD 19+
* CD 20+
* CD 24+
110
What is the CD for all leukocytes
CD 45+
111
What is the CD for T lymphocytes
* CD 45+
* CD 3+
112
What is the CD for cytotoxic T cells
* CD 45+
* CD 3+
* CD 8+
113
What is the CD for T-helper cell
* CD 45+
* CD 3+
* CD 4+
114
How does HIV affect the white blood cells?
Enters the T-helper cell through the CD 4 molecule and multiplies itself within the cell, destroys the cell and propagates itself.
115
What are APCs
Antigen Presenting Cells are specialized cells that process antigens detected in the body and presents them to the immune system.
116
Examples of the APCs in the body
* Macrophages: large phagocytic cells found in the body, especially lymph nodes
* Dendritic cells: The most potent APCs. Involved in the trapping of antigen.
* B cells
*
117
Most potent dendritic cells in the body
* Follicular dendritic cells in lymph nodes
* Langerhans dendritic cells in the skin
* Dendritic cells in the spleen
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How do APCs work
The antigens are engulfed or trapped by the APC and are digested. Their antigenic products are coupled to human leucocyte antigen (HCL)/ major histocompatibility complex (MHC) molecules on the surface of the APC for onward presentation to the immune system.
119
What are cytokines
Cytokines are cell-signaling protein molecules secreted by the cell for intercellular communications.
120
What are MHC
Major histocompatibility complex are genes located on the short arm of human chromosome 6.
The gene's products are expressed on the surface of the cell and are called major histocompatibility complex (MCH) or human leucocyte antigens (HLA)
121
What's the difference between class I molecules of MHC and class II molecules?
* Class I molecules are expressed by all nucleated cells while class II molecules are expressed by macrophages, B cells and other APCs
* Class I molecules are coupled to peptide fragments generated from proteins synthesized inside the cell while class II molecules are coupled to peptide products of extracellular antigens.
* Class I molecules present antigens to cytotoxic T cells.
122
Examples of cytokines in immune system
Immunomodulatory molecules such as interferons and interleukins
123
Causes of eosinophilia
* GIT disorders
* Allergy (atopic, drug sensitivity & pulmonary eosinophilia)
* Malignancy (Hodgkin's lymphoma, NHL (Non-hodgkin's lymphoma) & MPD (Myeloproliferative disorders)
* Hypereosinophilic syndrome
* Infestations (Parasites)
* Drugs
* Skin disorders
124
Causes of basophilia
* Hypersensitivity to food and drugs
* Inflammatory conditions (rheumatoid arthritis & ulcerative colitis)
* Chronic myeloid leukemia & other MPD
* Infections such as brucellosis, infectious hepatitis, tuberculosis, syphilis, thyrotoxicosis (usually only relative)
* Chronic lymphocytic leukemia
125
Causes of lymphocytosis
* Acute infections
PRIMA
P - Pertussis
R - Rubella
I - Infectious mononucleosis
M - Mumps
A - Acute infectious lymphocytosis
126
Causes of monocytosis
TBB MTTK
T - tuberculosis
B - Brucellosis
B - bacterial endocarditis
M - Malaria
T - Typhus
T - Trypanosomiasis
- Kala-azar
Hodgkin's lymphoma
Monocytic & myelomonocytic leukemia
127
Describe platelets
* Membrane-bound cell fragments
* Formed in the bone marrow from cell fragmentation of large cells called megakaryocytes
* 200 billion produced per day
* Lack nucleus
* Platelet count is about 100,000 - 400,000 / cubic mm
* Circulating lifespan of 7 - 10 days
* Play important role in haemostasis
* Produce and release factors that aid in blood clotting: thromboxane A2 (platelet aggregation), thromboplastin (promotes blood coagulation), serotonin (enhances vasoconstriction).
128
What is haemostasis?
Process of stopping blood flow out of injured blood vessel
129
Mechanisms involved in haemostatis
* Vasoconstriction
* Platelet plug formation
* Blood coagulation
130
Factors contributing to the vasoconstriction
* local myogenic spasm
* Thrombaxane A2
* Serotonin
* Neural reflexes in response to pain and trauma
131
Explain vasoconstriction
This is the immediate response of blood vessels to vascular injury
Vasoconstriction is as a result of contraction of smooth muscles in the vascular wall which leads to reduced diameter of blood vessels thus reducing blood flow.
132
Explain platelet plug formation-1
Damage to the endothelial cells lining the blood vessels cause the release of Von Willebrand's factor which makes the endothelial cells sticky. The stickiness of the endothelial cells promote the adhesion, activation & aggregation of platelets.
The Von Willebrand factor serves as abridge between the glycoprotein on the platelet and the collagen in the damaged blood vessel
The Von Willebrand factor also acts as a carrier for factor VIII, maintaing the normal level of factor VIII by increasing the half-life fivefold.
133
What happens in platelet plug formation-2
* Conformational changes: platelets change in shape and become larger extending projections that facilitate contact with other platelets
* Degranulation: platelets release the contents of their granules: ADP, thrombaxane A2, serotonin.
134
Functions of the contents of platelet granules
ADP: causes aggregation of platelets which leads to free platelets sticking to platelets already stuck to the vascular wall.
Thrombaxane A2: Vasoconstriction & platelet aggregation
Serotonin: Vasoconstriction
135
What happens in platelet plug formation-3
Platelets stick to the damaged vascular walls and aggregate to form a plug that seals the injured blood vessel
136
Blood coagulation
Series of enzymatic reactions that leads to the formation of a clot.
137
Source of factor V
Liver & platelets
138
What factors are from liver?
Factors 1,2,5,7,9,10,11,12,13
139
What factors are found in bone and gut
Factor 4
140
Clotting factor found in platelets
3,5,8
141
Clotting factor found in damaged cells
Factor 3
142
Clotting factor in endothelium
Factor 8
143
Sources of clotting factors
* Bone and gut
* Endothelium
* Liver
* Damaged cells
* Platelets
144
There are how many Vit K dependent clotting factors
6
145
Mention the Vit K dependent clotting factors
(1972 = 10, 9, 7, 2), protein C & S
Factors X, IX, VII, II, Protein C, Protein S
146
Why is vit K important in clotting factors
Needed as a cofactor for the enzyme that catalyzes the conversion of Glutamic acid to Gama carboxylicglutamic acid residues, a step needed for the release of the 6 clotting factors into circulation.
147
Why is vit K given to neonates at birth?
To prevent bleeding because they don't yet have the normal intestinal flora that synthesis vit K
148
What is the trigger for the extrinsic pathway?
Tissue thromboplastin (protein-phospholipid mixture) released by damaged tissue cells.
149
What is the trigger for the intrinsic pathway?
Contact of blood with the collagen of the exposed vascular wall.
150
Difference between intrinsic and extrinsic pathway
* Trigger: E - tissue thromboplastin from damaged tissue cells. I - contact of blood with collagen of the exposed vascular wall.
* Time taken: E - rapid process occuring within 12-15secs. I - slow process occuring with 5-10mins
* Size of clot: E - small clot is formed. I - large clot is formed.
151
Function of calcium in blood coagulation
* Necessary for acceleration of almost all the steps in the cascade enzymatic reactions in the coagulation pathway
* The intrinsic pathway, all but the first two steps require Ca for potentiation (step 3)
* In the extrinsic pathway, all but the first step requires Ca for potentiation (step 2 &3)
152
In the intrinsic pathway, what do you need to activate factor X?
Factor VIIa activates factor X in the presence of Ca.
153
In the extrinsic pathway what activates factor X?
Factor IX in the presence of Ca, plasma phospholipid and factor VIII activates factor X (Xa)
154
What makes up blood clot
* Platelet plug
* Fibrin meshwork
* Plasma
* Entrapped blood cells
155
When does clot retraction occur?
Between 20 - 60 mins of initiation of blood coagulation.
156
Factors that promote clot retraction
* Fibrin-stabilizing factor (laki-lorand factor)
* Contractile proteins of platelets such as: Thrombosthenin, myosin, actin molecules
157
Fibrinolytic system
Consists of series of enzymatic reactions for the breakdown of fibrin
158
Major enzyme of the fibrinolytic system
Plasmin
159
What does plasmin do in the fibrinolytic system
Dissolves clot and digests fibrin strands.
160
How is plasmin formed
Formed from plasminogen by the action of tissue plasminogen activator (t-PA) or urokinase plasminogen activator (u-PA)
161
Clotting disorders
* Liver disease e.g cirrhosis, hepatitis, hepatocellular carcinoma
* Vit K deficiency
* Thrombosis
* Embolism
* Consumptive coagulopathy (Disseminated Intravascular Coagulation DIC)
* Haemophilia A
* Haemophilia B
* Haemophilia C
* Thrombocytopenia
* Von Willebrand disease
162
Haemophilia A
X-linked, defective factor VIII, mostly seen in males
163
Haemophilia B
X-linked, defective factor IX
164
Haemophilia C
Defective factor XI
165
Thombocytopenia
Decreased number of circulating platelets
166
Vit K deficiency in clotting disorders
Blood will lack vit K-dependent clotting factors (factors X, IX ,VII, II, Protein C, Protein S).
167
Disseminated Intravascular Coagulation (DIC)/ Consumptive coagulopathy
Condition characterized by occurrence of blood coagulation throughout the body resulting in depletion of clotting factors and platelets thus leading to uncontrolable bleeding.
