lecture 8 blood
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8/9/2019 Lecture 8 Blood
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THE BLOOD
General Function of the Blood
y Transportation
molecules: O2, CO2, hormones heat
y Protection
phagocytes
antibodies
coagulantsy Regulation
regulating ECF pH
osmolarity
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1. Properties of Whole Blood
A. Components
y plasma
y formed elements:
erythrocytes (RBC)
leukocytes (WBC)
plateletes (thrombocytes)y hematocrit
B. Physical characteristics
y color
y density (specific gravity)
y viscosityy pH
y ~7% of body mass
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2. Plasma
A. Chemical composition
93% H2O
7% solutes:
86% proteins
11% inorganic solutes
3% nonprotein organic substancesB. Plasma proteins
functions
cell nutrition
carries
pH buffers clotting factors
water distribution
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albumin
globulins alpha-1 globulin
alpha-2 globulin
beta globulins
gamma globulins
fibrinogen2. Erythrocytes
A. Characteristics
8 µm diameter and 2 µm maximum thick
deformable, biconcave disks
anuucleated/no organelles
male, 5.4 million/µl; female, 4.8 million/µl
pale red color (hemoglobin)
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B. Oxygen-carrying capacity
y hemoglobin (Hb)
normal values: male, 16gm/dl; female,
14gm/dl 4 hemes + 1 globin
two types of Hb
- type A1 (2 E chains, 2 F chains)
- type A2 (2 E chains, 2 H chains)- type F (2 E chains, 2 K chains)
sickle cell disease - altered DNA templates
of F chains
hemoglobin H disease - altered DNA
templates of E chains oxyhemoglobin (98% O2): oxygen-carrying
capacity: ~20ml O2/dl blood (1 gm of Hb can
combine with 1.34 ml O2)
deoxyhemoglobin
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C. Hematopoiesis: Erythropoiesis
y organs that produce RBCs
liver, spleen, etc. (only in the fetus)
red bone marrow (both in the fetus and adult)
humerus, femur, ribs, sternum, skull, vertebrae,
pelvis, etc.y regulation of RBC production
erythropoietin
hypoxia
- low blood volume
- anemia- poor blood flow
- pulmonary disease
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y vitamins and iron: essential requirements
vitamin B12 and folic acid
65% of iron supply is in Hb iron is stored bound to ferritin and transported by
transferrin
D. Fate and destruction of RBCs
y life span: 100-120 days
y iron recycled, formation of bilirubinE. Erythrocyte disorders
y anemias
insufficient numbers (< 37% hematocrit, aplastic
anemia) decreased Hb content (<12gm/dl)
abnormal Hb (thalassemias)
y polycythemia - too many RBCs (6.2 million/µl)
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F. Blood Types
y membrane glycoproteins (antigens) on surface of RBCprovide unique antigenic identity
y RBC antigens (agglutinogens) and plasma antibodies
(agglutinins) promote agglutination
y three strong antigens in RBC: A, B, and D
The ABO blood group contains four major blood types
Type A: A antigen + anti-B
Type B: B antigen + anti-A
Type AB: A & B antigens + no antibodies
Type O: no antigens + anti-A and anti-B Rh blood group
D antigen (Rh factor) on surface of RBCs
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3. Leukocytes: White blood Cells (WBCs)
lack of pigmented molecules (no color)
total cell count: 7,000-11,000/mm3
diapedesis
chemotaxis
two main categories:
granulocytes agranulocytes
A. Granular leukocytes
neutrophils
most numerous WBCs (50-70%)
very motile and phagocytic most granules are lysosomes containing
hydrolytic enzymes
numbers increase during bacterial infections
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y eosinophils
1-5% of WBCs more numbers in connective tissues: lung,
mammary glands
not actively phagocytic
lysosomes contain oxidase, peroxidase, and
phosphatase
main functions: detoxification of foreign proteins
and other substances
y basophils
0-1% WBCs more numbers in loose connective tissues
granules contain heparin and histamine
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B. Agranular leukocytes - lack visible granules
lymphocytes
20-40% of WBCs T-lymphocytes
the most numerous lymphocytes in the blood
participating in cell-mediated immunity
B-lymphocytes
participate in humoral or antibody-mediatedimmunity
y monocytes
1-6% of WBCs, largest in size
differentiate into macrophages actively phagocytic
contain a variety of digestive enzymes
very effective in destroying bacteria, detoxifying
harmful chemicals, cleaning up cellular debris
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C. Leukopoiesis
y pluripotential hemopoietic stem cell (PHSC) makescommitment to a pathway in the bone marrow
granulopoiesis
stimulated by leukocyte-inducing factor
regulated by colony stimulating factors (CSFs)y lymphopoiesis
regulated by lymphokines (interleukins)
y life span of WBCs
neutrophils: a few minutes to a few days
lymphocytes: years
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4. Thrombocytes (Platelets)
y cytoplasmic fragments of megkaryocytes (2-4 µm in
diameter)
y 150, 000-350,000/µl
y contain chemicals needed in clotting process
y life span: ~ 10 days
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5. Hemostasis: Mechanisms to Prevent Blood Loss
A. Vasoconstriction reduces blood flow
respond to sympathetic reflexes
release of vasoconstrictors by platelets
B. Platelet aggregation
initiated by ADP released from the injured blood vessel
platelets release ADP, serotonin, thromboxane A
pseudopodia (footlike extentions)
plug formed by platelets provide the framework for
coagulation
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C. Coagulation
a process by which liquid blood becomes gel
thrombin needed to convert fibrinogen to fibrin (3 stages)
Stage I: formation of a prothrombin converting factor
extrinsic pathway
intrinsic pathway
Stage II: conversion of prothrombin to thrombin Stage III: conversion of fibrinogen to fibrin
D. Clot retraction
retraction is induced after stabilization of clot
via thrombosthernin, a contractile platelet factor ATP required for the process
serve to bring ruptured edge together, open the
occluded vessel, increase blood flow and promote
tissue repair
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E. Fibrinolysis: degradation of clots
y fibrin is broken down into soluble fragments by
plasminy plamin is derived from plasminogen
y a balance between deposition of fibrin and fibrinolysis
limits coagulation to the area of vascular injury