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