Introduction Bloodmade up of plasma and formed elements Bloodcomplex transport medium that performs vital pickup and delivery services for the body Bloodkeystone of bodys heatregulating mechanism ID: 926975
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Slide1
Chapter 17
Blood
Slide2Composition of Blood
Introduction
Blood—made up of plasma and formed elements
Blood—complex transport medium that performs vital pickup and delivery services for the body
Blood—keystone of body’s heat-regulating mechanism
Slide3Composition of Blood
Blood volume
Young adult male has approximately 5 liters of blood
Blood volume varies according to age, body type, sex, and method of measurement
Slide4Formed Elements of Blood
Red blood cells (erythrocytes)
Description of mature red blood cells (RBCs)
Have no nucleus and are shaped like tiny, biconcave disks
Do not contain ribosomes, mitochondria, and other organelles typical of most body cells
Primary component is hemoglobin
Most numerous of the formed elements
Slide5Formed Elements of Blood
Function of RBCs
RBCs’ critical role in the transport of oxygen and carbon dioxide depends on hemoglobin
Carbonic anhydrase—enzyme in RBCs that catalyzes a reaction that joins carbon dioxide and water to form carbonic acid
Carbonic acid—dissociates and generates bicarbonate ions, which diffuse out of the RBC and serve to transport carbon dioxide in the
blood plasma
Slide6Formed Elements of Blood
Red blood cells (erythrocytes) (cont.)
Hemoglobin
Within each RBC are approximately 200 to 300 million molecules of hemoglobin
Hemoglobin is made up of four globin chains, each attached to a heme molecule
Hemoglobin is able to unite with four oxygen molecules to form oxyhemoglobin to allow RBCs to transport oxygen where it is needed
A male has a greater amount of hemoglobin than a female
Anemia—a decrease in number or volume of functional RBCs in a given unit of whole blood
Slide7Formed Elements of Blood
Red blood cells (erythrocytes) (cont.)
Formation of red blood cells
Erythropoiesis—entire process of RBC formation
RBC formation begins in the red bone marrow with hemopoietic stem cells that go through several stages of development to become erythrocytes; entire maturation process requires approximately 4 days
RBCs are created and destroyed at a rate of approximately 100 million per minute in an adult; homeostatic mechanisms operate to balance number of cells formed against number of cells destroyed
Slide8Formed Elements of Blood
Destruction of RBCs
Life span of a circulating RBC averages 105 to 120 days
Macrophage cells phagocytose the aged, abnormal, or fragmented RBCs
Hemoglobin is broken down and amino acids, iron, and bilirubin are released
Slide9Formed Elements of Blood
White blood cells (leukocytes, WBCs)
Granulocytes
Neutrophils —make up approximately 65% of total WBC count in a normal blood sample; highly mobile and very active phagocytic cells; capable of diapedesis; cytoplasmic granules contain lysosomes
Eosinophils —account for 2% to 5% of circulating WBCs; numerous in lining of respiratory and digestive tracts; weak phagocytes; capable of ingesting inflammatory chemicals and proteins associated with antigen-antibody reaction complexes; provide protection against infections caused by parasitic worms and allergic reactions
Basophils —account for only 0.5% to 1% of circulating WBCs; motile and capable of diapedesis; cytoplasmic granules contain histamine and heparin
Slide10Formed Elements of Blood
White blood cells (cont.)
Agranulocytes (Figures 17-12 and 17-13)
Lymphocytes—smallest of the WBCs; second most numerous type of WBC; account for approximately 25% of circulating WBCs; T lymphocytes and B lymphocytes have an important role in immunity—T lymphocytes directly attack an infected or cancerous cell, and B lymphocytes produce antibodies against specific antigens
Monocytes—largest type of leukocyte; mobile and highly phagocytic cells
Slide11Formed Elements of Blood
WBC numbers—a cubic millimeter of normal blood usually contains 5,000 to 9,000 leukocytes, with different percentages for each type; WBC numbers have clinical significance because they change with certain abnormal conditions
Formation of WBCs
Granular and agranular leukocytes mature from the undifferentiated hemopoietic stem cell
Neutrophils, eosinophils, basophils, and a few lymphocytes and monocytes originate in red bone marrow; most lymphocytes and monocytes develop from hemopoietic stem cells in lymphatic tissue
Slide12Formed Elements of Blood
Platelets
Structure
In circulating blood, platelets are small, pale bodies that appear as irregular spindles or oval disks
Three important properties are agglutination, adhesiveness, and aggregation
Platelet counts in adults average 250,000 per mm
3
of blood; normal range is 150,000 to 400,000 per mm
3
Functions of platelets
Important role in hemostasis and blood coagulation
Hemostasis—refers to stoppage of blood flow; however, if injury is extensive, the blood-clotting mechanism is activated to assist
Slide13Blood Types (Blood Groups)
The ABO system
Every person’s blood belongs to one of four ABO blood groups
Named according to antigens present on RBC membranes
Type A—antigen A on RBC
Type B—antigen B on RBC
Type AB—both antigen A and antigen B on RBC; known
as universal recipient
Type O—neither antigen A nor antigen B on RBC; known
as universal donor
Slide14Blood Types (Blood Groups)
The Rh system
Rh-positive blood—Rh antigen is present on
the RBCs
Rh-negative—RBCs have no Rh antigen present
Anti-Rh antibodies are not normally present in blood; anti-Rh antibodies can appear in Rh-negative blood if it has come in contact with Rh-positive RBCs
Slide15Blood Plasma
Plasma—liquid part of blood; clear, straw-colored fluid; made up of 90% water and 10% solutes
Solutes—6% to 8% of plasma solutes are proteins, consisting of three main compounds:
Albumins—helps maintain osmotic balance of the blood
Globulins—essential component of the immunity mechanism
Fibrinogen—key role in blood clotting
Plasma proteins have an essential role in maintaining normal blood circulation
Slide16Blood Plasma
Plasma—liquid part of blood; clear, straw-colored fluid; made up of 90% water and 10% solutes
Solutes—6% to 8% of plasma solutes are proteins, consisting of three main compounds:
Albumins—helps maintain osmotic balance of the blood
Globulins—essential component of the immunity mechanism
Fibrinogen—key role in blood clotting
Plasma proteins have an essential role in maintaining normal blood circulation
Slide17Blood Clotting (Coagulation)
Mechanism of blood clotting—goal of coagulation is to stop bleeding and prevent loss of vital body fluid in a swift and sure method; the “classic theory” is as follows:
“Classic theory” of coagulation advanced in 1905
Identified four components critical to coagulation:
Prothrombin
Thrombin
Fibrinogen
Fibrin
Slide18Blood Clotting (Coagulation)
Mechanism of blood clotting (cont.)
Current explanation of coagulation involves three stages:
Stage I—production of thromboplastin activator by one or the other of the following:
chemicals released from damaged tissues (extrinsic pathway)
chemicals present in the blood (intrinsic pathway)
Stage II—conversion of prothrombin to thrombin
Stage III—conversion of fibrinogen to fibrin and production of fibrin clot
Slide19Blood Clotting (Coagulation)
Conditions that oppose clotting
Clot formation in intact vessels is opposed
Several factors oppose clotting
Perfectly smooth surface of the normal endothelial lining of blood vessels does not allow platelets to adhere
Antithrombins—substances in the blood that oppose or inactivate thrombin; prevent thrombin from converting fibrinogen to fibrin; e.g., heparin
Slide20Blood Clotting (Coagulation)
Conditions that hasten clotting
Rough spot in the endothelium
Abnormally slow blood flow
Clot dissolution
Fibrinolysis—physiological mechanism that dissolves fibrin
Fibrinolysin—enzyme in the blood that catalyzes the hydrolysis of fibrin, causing it to dissolve
Additional factors are presumed to aid clot dissolution; e.g., substances that activate profibrinolysin