Download Chapter 10 Blood

Blood
Keri Muma
Bio 6
Functions of Blood
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Transport
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Regulation
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Oxygen and nutrients to the cells
Waste away from cells
Hormones
Maintain body temperature by absorbing and
distributing heat
Protection
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Prevents infection
Blood clotting prevents blood loss
Composition of Blood
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Plasma – 90% water along with dissolved compounds
 Proteins – albumin, antibodies, clotting proteins
 Electrolytes – sodium, potassium, calcium, magnesium,
chloride, bicarbonate
Formed elements – erythrocytes, leukocytes, platelets
Components of Plasma
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Proteins in plasma – maintain osmotic
pressure
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Albumin – 60% of plasma proteins
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Globulins
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Transports substances such as bilirubin and bile salts
α , β – transports hormones, cholesterol, and iron;
angiotensinogen and clotting factors
Gamma globulins - antibodies
Fibrinogen
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Precursor for the clotting protein fibrin
Erythrocytes
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Erythrocytes (red blood cells)
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Biconcave shape
Contains no nucleus or organelles
Enzymes in cytoplasm:
Glycolytic enzymes to carry out glycolysis
 Carbonic anhydrase – converts CO2 to HCO3Last ~120 days and are then destroyed by the spleen or liver
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Erythrocytes
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Function – to transport oxygen and to a lesser extent
carbon dioxide
Contains hemoglobin
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Made of 4 globin polypeptides and 4 heme groups
Erythrocytes
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Erythropoiesis – production of new erythrocytes (~3
million per second)
Occurs in the red bone marrow
Rate of production is controlled by erythropoietin produced
by the kidneys in response to blood oxygen levels
Erythrocytes
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Anemia - decrease in oxygen carrying ability
of the blood
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Causes:
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Decreased number of RBC (low hematocrit)
Deficient or abnormal hemoglobin
Deficiency in iron or vitamin B12
Kidney disease, decrease in EPO
Blood loss
Malaria, sickle-cell anemia
Erythrocytes
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Polycythemia – increased numbers of
erythrocytes / hematocrit
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Causes: cancer, high altitudes, lung and heart
disease, dehydration
Leukocytes
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Leukocytes – white blood cells
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Protect against infection and initiates inflammation
Destroy cancerous cells
Tissue repair
Types of Leukocytes
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Granulocytes – granule containing cells with
lobed nuclei
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Neutrophils (60 – 70%)
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Eosinophils (1-4%)
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Phagocytes
First on the scene of infection
and triggers inflammation
Associated with allergies and
parasite infections
Basophils (< 1%)
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Contain and release histamine
Types of Leukocytes
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Agranulocytes
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Monocytes (2 - 6%)
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Travel into the tissue and mature
into macrophages
Lymphocytes (25 – 33%)
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Specific immune defenses
B cells & T cells
Hematopoiesis
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All blood cells arise from a common stem
cell found in the red bone marrow
Summary:
Platelets
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Platelets (a.k.a thrombocytes)
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Irregular shaped cell fragments
from megakaryocytes
Play a role in blood clotting
Platelets
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Hemostasis –prevents the loss
of blood when blood vessels are
damaged
3 phases:
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Vascular spasm
Platelet plug formation
Coagulation
Hemostasis
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Platelet plug formation
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Broken or damaged blood
vessels cause platelets to
become sticky and cling to the
site
Release chemicals that attract
other platelets (ADP)
Release chemicals that cause
vasoconstriction: serotonin,
epinephrine, thromboxane A2
Platelet plug formation
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Normal endothelial cells release prostacyclin and
NO to inhibit platelet aggregation
Hemostasis
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Vascular spasms
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Blood vessels constrict to diminish blood flow and
loss
Coagulation
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Formation of a network of fibers
that seals the blood vessel
Involves a clotting cascade
Coagulation
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Clotting cascade
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Involves 12 clotting factors
Requires the presence of Ca2+ and platelet factor
3 (PF3) produced by aggregating platelets
Summary of events:
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An initial inactive clotting factor, found in the
plasma, is activated by exposed collagen
This activates the next factor and so on….. Until
thrombin converts fibrinogen into fibrin
Clotting Cascade
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Intrinsic Pathway
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Initiated when Hageman
factor is activated by
exposed collagen
Extrinsic Pathway
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Factor X is activated by
thromboplastin released
by damaged tissues
Clotting Cascade
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Role of Thrombin
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Converts fibrinogen to
fibrin
Activates stabilizing
factor (XIII)
Enhances conversion
of more thrombin from
prothrombin
Enhances platelet
aggregation
Coagulation
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Clot retraction
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Vessel repair
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Platelets trapped in the clot contract and squeeze
serum out
Platelets attract fibroblasts that repair blood
vessel
Clot dissolution
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Thrombin and tissue plasminogen activator (tPA)
converts plasminogen into plasmin which breaks
down fibrin
tPA
breaks down
Plasminogen
Plasmin
Fibrin
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Clotting disorders
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Thromboembolism – clots forming in intact
vessels
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Imbalance in clotting – anticlotting mechanisms
Slow moving blood
Release of thromboplastin from damaged tissue
Hemophilia – deficiency in one of the clotting
factors (usually VIII), excessive bleeding
Thrombocytopenia – deficiency in platelets
Impaired liver
Lack of vitamin K
Summary: