Blood part 1

7/29/2019 Blood part 1

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The Cardiovascular System:Blood


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The CV System

cardiovascular system

consists of three interrelated components:

Blood

Heart

Blood vessels.


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Blood

Hematology

The study of blood, blood forming tissues, and the

disorders associated with them

Blood contributes to homeostasisby:

Transporting respiratory gasses, nutrients, and

hormones to and from your bodys cells.

Helping to regulate body pH and temperature.

Providing protection through its clotting

mechanisms and immune defenses.


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Characteristics of Blood

Blood is more dense and viscous (thicker) than water.

Has a temperature of 38 deg C

1 deg C higher than oral or rectal body temp

Slightly alkaline

pH ranging from 7.35 7.45

Changes from dark to bright red depending on oxygen content

Plasma volume constitutes roughly 25% of extracellular fluid (ECF)

Other 75% of ECF is interstitial fluid (ISF)

Average blood volume in:

Males = 5 to 6 liters (~1.5 gal)

Females = 4 to 5 liters (~1.2 gal)

Difference mainly due to body size


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Blood

Blood is a type of connective tissue

Composed of:

Plasma

Formed elements

Interstitial fluid (ISF)

Fluid that bathes body tissues

Constantly renewed by blood

Discussed in more detail during blood vessels and

hemodynamics lecture


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Components of Blood

Plasma

A watery liquid extracellular matrix that containsdissolved substances.

~91.5% water and 8.5% solutes The majority of the solutes in plasma are protiens

Specific proteins confined blood are called plasma proteins

Most of the plasma proteins are produce by the liver

These proteins have many functions but a very important

one is a contribution to the maintenance of proper bloodosmotic pressure

Other solututes include electrolytes, nutrients, gasses,regulatory substances, and waste products


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Components of Blood

Formed Elements

3 principal components

Red Blood Cells (RBCs)

White Blood Cells (WBCs)

Platelets


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Formed Elements

Hemopoiesis (hematopoiesis)

Process by which the formed elements of blood develop

From late fetal development to death, red bone marrow isthe primary site of hemopoiesis

All Blood cells arise from pluripotent stem cells found within thered marrow

The pluripotent stem cells give rise to 2 types of stem cells: Myeliod andlymphoid stem cells

Lymphoid cells are named so due to their beginning development inthe red bone marrow and ending in the lymphoid tissue

Some of the myeloid stem cells give rise to progenator cells

The other myeloid stem cells, lymphatic stem cells, and progenitor cellsgive rise to precurser cells (blasts) which then differentiate into the bloodcells


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Regulation of Hemopoiesis

Hemopoietic growth factors

Hormones that regulate the differentiation and proliferation ofparticular progenator cells

Erythropoietin (EPO) increases the # of RBC precursers EPO is primarily produced cells in the kidneys

Renal failure leads to RBC defficiency

Exogenous or synthetic EPO is also a banned substance in most professional sports

Thrombopoetin (TPO) stimulates formation of platelets frommegakaryocytes

TPO is produced by the liver

Cytokines small glycoproteins that regulate the development of differentblood cells

Typically produced by cells such as red bone marrow cells, leukocytes, macrophages,

fibroblasts, and endothelial cells Laboratory made hemopoietic growth factors have shown great

promise in helping reduce some of the side effects of chemotherapyas well as treatment of particular disieases and genetic defficiencies


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Formed Elements


Also called erythrocytes

make up the bulk of the blood cells Hematocrit = the % of RBCs per unit blood volume

Normal Hct is around 45% bi-concave discs

Allows for high surface area which is optimal forgas exchange

Also allows RBCs to deform without rupturing Very important in capillary circulation

Amongst many other membrane proteins, theRBC membrane contains glycolipid surfacemarkers that designate ABO Rh blood type


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Developing RBCs lose their nucleus and many otherorganelles as they mature

When a maturing RBC loses its nucleus, it becomes a reticulocyte

The mature form is highly specialized for oxygen transport Due to the lack of most organelles, the majority of their internal

space is available for oxygen transport

Cytosol of mature RBCs contain a high amount of hemoglobin ~33% of the cells weight

Each RBC contains about 280 million hemoglobin molecules

Hemoglobin (Hgb) is a protein molecule adapted to carry O2 (andCO2 as well)

A Hgb molecule consists of 4 large globin proteins (2 alpha and 2 betachains), each embedding an iron-containing heme center

The iron binds oxygen


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Lack mitochondria

Generate ATP anaerobically so they do not use up the oxygen beingtransported

As previously stated, mature RBCs lack a nucleus or any proteinmaking machinery

This means they cannot synthesize new components to repair damaged ones Thus they are destined to die

Average RBC life is about 120 days.

~1% of RBCs must be destroyed and replaced every day

250 billion cells per day!

Old RBCs a subject to bursting when passing through the narrow channels inthe spleen

Ruptured RBCs are removed from circulation and destroyed by fixed phagocytoticmacrophages in the spleen and liver

Some of the breakdown products are recycled and others are excreted as shown in thefollowing slide

In a sense, mature RBCs are not really cells, but remnants of cells witha very specific purpose to carry O2to the tissues of the body


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Abnormalities of Erythropoiesis

Anemia A condition of insufficient RBCs or hemoglobin (quality or

quantity) It is most often the result of low iron intake, hemolysis,

autoimmune disease, blood loss, or lack of production in the

bone marrow Polycythemia

a condition of excess number of RBCs per unit volume It occurs in response to:

Hypoxia Condition in which the body or a region of the body is deprived of an

adequate oxygen supply

Blood doping - receiving a transfusion of RBCs right before asporting event to increase the bloods oxygen carrying capacity

Natural blood doping is training at high altitude shots of EPO (illegal doping) smoking (COPD) dehydration


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Anemias

Iron deficiency anemia is the most common

anemia in the U.S., and affects primarily

menstruating women In the United States, 20% of all women of

childbearing age have iron deficiency anemia,

compared with only 2% of adult men

Hemorrhagic anemia is the result of

precipitous blood loss, and results in an equal

decrease in Hct, Hgb content, and RBC count


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Anemias

Sickle-cell disease (SCD) also called sickle-cell anemia An autosomal recessive disorder.

A genetic defect in the primary DNA sequence leads toproduction of a faulty Hgb chain, and RBCs that takeon a rigid, sickle-shape

People who only have one sickle-cell gene mayexperience mild symtoms

People who have two copies of the sickle-cell genemay experience severe symptoms

Sickling decreases the cells' flexibility and resultsin a variety of complications;

Decreased oxygen carrying capacity Easily ruptured RBCs Increased risk of stroke

life expectancy is shortened Many others

May confer an advantage in malaria proneenvoronments

People who inherit one copy of the mutated sickle-cellgene show increased resistance to infection and effectsof the plasmodium parisite

http://en.wikipedia.org/wiki/File:Sickle_cell_

01.jpg


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Next Lecture

Lecture 1 part 2: Blood

Documents

Blood part 1