lecture 19, blood

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Fundamentals of

Anatomy & PhysiologySIXTH EDITION

Frederic H

. MartiniLecture 19, Blood

Lecturer: Dr. Ebadi

Room P313

Phone: (718) 260-5285

E-Mail: ibarjis@citytech.cuny.edu

Learning Objectives

• List the components of the cardiovascular system and explain the major functions of this system.

• Describe the important components and major functions of the blood

• List the characteristics and functions of red blood cells.

• Describe the structure of hemoglobin and indicate its functions.

• Discuss red blood cell production and maturation.

Learning Objectives

• Explain the importance of blood typing and the basis for ABO and Rh incompatibilities.

• Categorize the various white blood cells on the basis of structure and function.

• Describe the structure, function and production of platelets.

• Describe the reaction sequences responsible for blood clotting.

• Provides a mechanism for rapid transport of nutrients, waste products, respiratory gases and cells

The cardiovascular system

• Fluid connective tissue

• Functions include

• Transporting dissolved gases, nutrients, hormones, and metabolic wastes

• Regulating pH and ion composition of interstitial fluids

• Restricting fluid loss at injury sites

• Defending the body against toxins and pathogens

• Regulating body temperature by absorbing and redistributing heat

Functions and Composition of Blood

Blood Composition

Blood

Plasma 46-63% Formed Elements 37-54%

Plasma Protein 7% Water 92% Other Solutes 1% Platelets RBC 99.9% WBC

Albumin

Fibrinogen

Globulin

Regulatory Proteins

Eg. Electrolytes

Monocytes

Basophils

Eosinophils

Neatrophils

Lymphocytes

The composition of blood

• Plasma and formed elements comprise whole blood.

• Plasma elements include blood cells:

• Red blood cells (RBC)

• White blood cells (WBC)

• Platelets

• Can fractionate whole blood for analytical or clinical purposes

The Composition of Whole Blood

Fresh whole blood for testing in a lab is usually collected from a superficial vein.

When checking the efficiency of gas exchange, it may be necessary to draw a blood sample from an artery

The Composition of Whole Blood

The chief difference between plasma and interstitial fluid involves the concentration of dissolved oxygen and proteins.

The Composition of Whole Blood

• Process of blood cell formation

• Hemocytoblasts are circulating stem cells that divide to form all types of blood cells

• Whole blood from anywhere in the body has roughly the same temperature (38ºC), pH (7.4) and viscosity.

• Bright red color if taken from artery

• Dull red color if taken from vein

Hemopoiesis

• Accounts for 46-63% of blood volume

• 92% of plasma is water

• Higher concentration of dissolved oxygen and dissolved proteins than interstitial fluid

Plasma

• more than 90% are synthesized in the liver

• Albumins are the most abundant plasma proteins

• 60% of plasma proteins

• Responsible for viscosity and osmotic pressure of blood

Plasma proteins

• Globulins

• ~35% of plasma proteins

• Include immunoglobins which attack foreign proteins and pathogens

• Include transport globulins which bind ions, hormones and other compounds

• Fibrinogen

• Converted to fibrin during clotting

• Are necessary for blood clotting

• Removal of fibrinogen leaves serum

Additional Plasma Proteins

• Erythrocytes (RBC) account for slightly less than half the blood volume, and 99.9% of the formed elements.

• Hematocrit measures the percentage of whole blood occupied by formed elements

• Commonly referred to as the volume of packed red cells

Red Blood Cells

Abundance of RBCs

• Biconcave disc, providing a large surface to volume ration

• Shape allows RBCs to stack, bend and flex

• RBCs lack organelles

• Typically degenerate in about 120 days.

Structure of RBCs

The Anatomy of Red Blood Cells

• Molecules of hemoglobin account for 95% of the proteins in RBCs

• Hemoglobin is a globular protein, formed from two pairs of polypeptide subunits

• Each subunit contains a molecule of heme which reversibly binds an oxygen molecule

• Damaged or dead RBCs are recycled by phagocytes

Hemoglobin

The Structure of Hemoglobin

“Sickling” in Red Blood Cells

• Replaced at a rate of approximately 3 million new blood cells entering the circulation per second.

• Replaced before they hemolyze

• Components of hemoglobin individually recycled

• Heme stripped of iron and converted to biliverdin, then bilirubin

• Iron is recycled by being stored in phagocytes, or transported throughout the blood stream bound to transferrin

RBC life span and circulation

Red Blood Cell Turnover

• Erythropoeisis = the formation of new red blood cells

• Occurs in red bone marrow

• Process speeds up with in the presence of EPO (Erythropoeisis stimulating hormone)

• RBCs pass through reticulocyte and erythroblast stages

RBC Production

Stages of RBC Maturation

• Determined by the presence or absence of surface antigens (agglutinogens)

• Antigens A, B and Rh (D)

• Antibodies in the plasma (agglutinins)

• Cross-reactions occur when antigens meet antibodies

Blood types

Blood Typing and Cross-Reactions

Blood Type Testing

Rh Factors and Pregnancy

• Have nuclei and other organelles

• Defend the body against pathogens

• Remove toxins, wastes, and abnormal or damaged cells

• Are capable of amoeboid movement (margination) and positive chemotaxis

• Some are capable of phagocytosis

The White Blood Cells

Leukocytes

Granular and agranular

• Granular leukocytes

• Neutrophils – 50 to 70 % total WBC population

• Eosinophils – phagocytes attracted to foreign compounds that have reacted with antibodies

• Basophils – migrate to damaged tissue and release histamine and heparin

Types of WBC

• Agranular leukocytes

• Agranular leukocytes are formed inred bone marrow.

• Agranular leukocytes include:

• Monocytes - become macrophage

• Lymphocytes – includes T cells, B cells, and NK cells

Types of WBC

White Blood Cells

• Indicates a number of disorders

• Leukemia = inordinate number of leukocytes

Differential count

• Granulocytes and monocytes are produced by bone marrow stem cells

• Divide to create progenitor cells

• Stem cells may originate in bone marrow and migrate to peripheral tissues

• Several colony stimulating factors are involved in regulation and control of production

WBC Production

Figure 19.12

The Origins and Differentiation of Formed Elements

Animation: The origins and differentiation of blood cells (see tutorial)

• Flattened discs

• Circulate for 9-12 days before being removed by phagocytes

Platelets

• Transporting chemicals important to clotting

• Forming temporary patch in walls of damaged blood vessels

• Contracting after a clot has formed

Platelet functions

• Megakaryocytes release platelets into circulating blood

• Rate of platelet formation is stimulated by thrombopoietin, thrombocyte-stimulating factor, interleukin-6, and Multi-CSF

Platelet production (thrombocytopoiesis)

Hemostasis

• Prevents the loss of blood through vessel walls

• Three phases –

• Vascular phase

• Platelet phase

• Coagulation phase

Hemostasis

• Vascular phase

• Local blood vessel constriction (vascular spasm)

• Platelet phase

• Platelets are activated, aggregate at the site, adhere to the damaged surfaces

The Vascular and Platelet Phases of Hemostasis

Coagulation phase

• Factors released by platelets and endothelial cells interact with clotting factors to form a clot

• Extrinsic pathway

• Intrinsic pathway

• Common pathway

• Suspended fibrinogen is converted to large insoluble fibrin fibers

The Coagulation Phase of Hemostasis

The Coagulation Phase of Hemostasis

Clot retraction

• Final phase of healing

• Platelets contract and pull the edges of the vessel together

Fibrinolysis

• Clot gradually dissolves through action of plasmin

• Activated form of plasminogen

• Clotting can be prevented through the use of drugs that depress the clotting response or dissolve existing clots

• Anticoagulants include heparin, coumadin, aspirin, dicumarol, t- PA, streptokinase, and urokinase

You should now be familiar with:

• The components of the cardiovascular system and its major functions.

• The important components and major functions of the blood.

• The characteristics and functions of red blood cells.

• The structure of hemoglobin and its functions.

• Red blood cell production and maturation.

You should now be familiar with:

• The importance of blood typing and the basis for ABO and Rh incompatibilities.

• The various white blood cells.

• The structure, function and production of platelets.

• The reaction sequences responsible for blood clotting.