Chapter 19
Cardiovascular
System
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BLOOD
Functions of Blood
Transport – primary ‘highway’ & delivery system of the body
Maintenance – maintains homeostasis
Protection – immune system role
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Blood Function - Transport
Delivery of O2 & nutrients to body cells
Removal of CO2 and other metabolic wastes
Substances needed for maintenance & protection transported
throughout body
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Blood Function - Maintenance
Homeostasis maintained:
Blood buffers help maintain pH in body fluids
excess heat transport to skin by blood
blood clot formed when tissues damaged
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Blood Functions - Protection
Immune cells (white blood cells)
label & attack foreign cells & substances such as microorganisms,
parasites & toxins
Clotting protects against fluid loss
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Components of Blood
Plasma – the fluid portion of blood
(55% of volume)
Formed Elements - cells & cell fragments
(45% of volume)
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Plasma Components
91% water
7% protein
albumin
globulins
fibrinogen
2% other solutes
ions
nutrients
gases
waste
hormones & other regulators
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Formed Elements
Cells & cell fragments
95% = Erythrocytes (red blood cells, RBCs)
5% = Leukocytes (white blood cells, WBCs) & Platelets
WBCs include:
neutrophils
lymphocytes
monocytes
eosinophils
basophils
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Origins of Formed Elements
Blood cell production is called Hemopoesis
All cells & cell fragments come originate from a population of
Stem Cells found in red bone marrow…
Different stem cell lines include:
Proerythroblasts  red blood cells
Myeloblasts  granulocytes
Lymphoblasts  lymphocytes
Monoblasts  monocytes
Megakaryoblasts  platelets
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Potentiality of Stem Cells
Pluripotential – a cell with several possible outcomes
Unipotential – a cell with a single possible outcome
Stem cells are pluripotential and may become either of the previous cell
types (see previous slide).
Once their initial step is taken their ultimate destiny is locked. They
are then unipotential.
See figure 19.xxx on page xxx for possible choices for stem cell
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Erythrocytes - RBCs
NO NUCLEUS
most common blood cell
5.2 million / mm3 in males
4.5 million / mm3 in females
Shape = biconcave disk with thick edge & thin center
imagine a round pillow with all stuffing forced away from center
Filled with hemoglobin – carries O2
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Hemoglobin
Four proteins
two alpha (α)
two beta (β)
Each protein binds a heme molecule containing an iron molecule
heme is the portion of the molecule which attracts & carries O2
When carrying O2 hemoglobin is bright red & called oxyhemoglobin
when O2 absent, darker red, deoxyhemoglobin
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Developmental Changes in Hemoglobin
Children & adults use ‘adult hemoglobin’ which is the least efficient O2
carrier
Fetal hemoglobin is a more efficient O2 carrier & is used by the fetus
WHY?
This ‘stronger’ hemoglobin allows fetus to attract O2 from maternal
blood across the placenta. Otherwise the fetus would not get enough
O2.
Embryonic hemoglobin is MOST EFFICIENT – this is used by very
young embryo before implanting in uterine wall and allows scavenging
of O2 from body fluids – EXTREMELY attractive for O2
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Red Blood Cell Lifespan
Stimulated by low blood levels of O2. Kidneys produce erythropoetin
which causes marrow to produce erythrocytes.
Stem cell – proerythroblast – erythroblast – reticulocyte – erythrocyte
Typical RBC lives about 110 days (♀) - 120 days (♂)
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Removal of Old RBCs
Old or damaged cells are destroyed by macrophages in spleen, liver &
lymphatic tissues.
Enzymes break cells & digest hemoglobin.
Heme broken into biliverdin then to bilirubin
Free bilirubin is taken up by liver & conjugated
Some leaves & is carried to kidney (urine)
Most deposited by liver as part of bile into intestine. In intestine it is
further broken down into pigments which color feces.
Excess bilirubin in circulation colors skin yellow = jaundice
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Leukocytes (White Blood Cells)
Referred to as ‘white’ because they lack hemoglobin
These cells serve as ‘body police’ & ‘garbage disposal’ cells to attack
invaders & dispose of dead or dying cells.
Many of these cells are motile (self-mobile) and move by extending
part of the cell membrane and then flowing into the extension
(amoeboid movement)
In a specialized type of movement, diapedesis some of these cells
become elongated & thin to leave the circulation and travel into tissues
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Neutrophils
Most common WBC
Stain with both acid/base (doesn’t ‘prefer’ either stain)
Nucleus has multiple lobes – “Polymorphonuclear cells”
Short lifespan – about 2 days
Leave bloodstream early in their life (10-12 hours old)
Move into tissues where they are phagocytic (eating invading cells &
‘foreign’ substances)
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Produce lysozymes – digestive enzymes to break down bacteria
Eosinophils
Cytoplasmic granules stain bright red with eosin (an acidic dye)
These cells leave circulation in response to inflammation
Increase in # during allergic response or parasite infection
Mediate inflammation by producing enzymes to break down histamine
Phagocytize antigen/antibody complexes (as do neutrophils)
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Basophil
Cytoplasmic granules stain blue or purple with basic dyes
Least common WBC.
Leave circulation & enter tissues in response to allergic reaction &
inflammation.
Release histamine to INCREASE inflammation
Release heparin, an anticoagulant to inhibit blood clots
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Lymphocytes
Smallest WBCs – barely larger than RBC
very little cytoplasm – sometimes just a thin halo around nucleus
Originate in bone marrow but unlike most other blood cells they can
divide outside bone marrow
Multiple types of lymphocytes:
B- Lymphs respond to bacteria & foreign substances by producing
antibodies (protective proteins)
T- Lymphs attack foreign cells & viruses
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Monocytes
Largest WBCs - leave circulation after about 3 days
enter tissues to become macrophages (“big eaters”) where they engulf
& destroy bacteria, damaged cells, foreign substances & debris
May be increased during prolonged infections
May process foreign substances & “show” these foreign components to
lymphocytes.
This activates lymphocytes which can ‘target’ the invaders.
Much like police handing out photo of suspect
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Platelets
These cell fragments are produced when megakaryocytes (very large
cells) break up.
Lifespan of platelet is short, 5-9 days
Contain actin & myosin which can produce contraction
Membrane contains glycoproteins & proteins which function as
attachment molecules
Play large protective role by forming platelet plug to seal small breaks
or by forming clots to seal larger damage
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Platelet Plug
Sealing small breaks in blood vessel walls
1) Von Willibrand’s Factor a collagen produced by endothelial cells in
damaged vessel wall. Platelets bind to this material
2) Platelets activated to release adenosine diphosphate (ADP),
thromboxanes & other chemicals which activate nearby platelets in
a cascade effect.
3) Platelets produce surface receptors which bind fibrinogen (a plasma
protein found in blood) which cross-links platelets to form a solid
plug.
4) Production of Platelet factor III & Coagulation Factor V
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Vascular Spasm
A short term solution to larger damage – when a platelet plug is not
enough
Small blood vessels can contract smooth muscle in their walls closing
off to prevent fluid loss.
Produced in response to chemicals released during platelet plug
formation (thromboxanes & endothelin) & by nerve reflex
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Coagulation – Plugging Larger Holes
Blood clotting – a meshwork of fibrin (fibrous protein) forms which
traps blood cells & platelets preventing fluid loss.
Mediated by a series of coagulation factors (see table 19.3)
These factors normally circulate in blood but don’t clot unless
activated.
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Intrinsic
Extrinsic
Stage 1
Stage 2
Stage 3
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Clot Control
Anticoagulants produced to prevent uncontrolled clot
growth/production
Antithrombin (from liver) inactivates thrombin (slowly)
Heparin (from basophils & endothelium) together with antithrombin
inactivate thrombin (rapidly)
Prostacyclin (from prostaglandin) stops platelets from releasing
clotting factors & causes vasodilation
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Clot Retraction & Dissolution
Clots condense into a dense form by clot retraction as platelets contract
(using actin & myosin).
As the clot condenses it pulls the damaged edges together to promote
healing and close gaps.
Epithelial cells at wound margin divide and fill damaged space.
Clot dissolves as fibrin is broken down (fibrinolysis) by plasmin (an
enzyme)
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Blood Grouping
Red Blood Cells are ‘labeled’ with many types of cell surface proteins
These proteins are a normal part of cell function - one role is labeling
cells as ‘self’ so your immune system will not attack them.
These label proteins and any other markers recognized by the immune
system are called antigens.
Antigens are markers (often proteins) recognized by the immune
system.
There are 35+ currently recognized antigen groups on RBCs
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Antibodies
Antibodies are immune system (blood serum) proteins which recognize
specific antigens.
Antibodies are VERY specific and will recognize and attach only to
their unique antigens
Once an antibody has recognized and attached to an antigen it can
cause clumping or agglutination.
Hemolysis (rupturing of red cells) is triggered by antigen/antibody
attachment
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ABO & Rh Blood Groups
ABO blood group is the most commonly examined cell surface antigen
when considering blood compatibility
Rh is another cell surface antigen which is also considered – it is a
different protein.
Both of these groups of proteins are commonly examined in simple
blood typing.
Many other groups of blood cell surface markers (proteins) exist:
Lewis, Duffy, Kidd, Lutheran…
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ABO
This family of proteins labels RBC surfaces.
An individual may have the gene which makes protein type A
May have the gene which makes protein type B
May have one copy of each gene A & B
May have a ‘dud’, defective gene which makes neither A nor B
Remember – you get one copy of a gene from Mom and one from Dad
so you have two ‘ABO’ genes
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Genes Determine Blood Proteins
Type A proteins (type A blood) are made if you have an A gene
Type B proteins (type B blood) are made if you have a B gene
Type A & B proteins are made in an individual who has one copy of
each
Type O IS NOT A PROTEIN – it is simply a lack of either A or B and
occurs when you have two ‘dud’ defective genes. This isn’t a bad
thing, it simply means you don’t have these cell markers – there are lots
of others!
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Genotype & Blood Type
If your genes are
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You have Blood Type
A&A
A
A & --
A
B&B
B
B & --
B
A& B
AB
-- & --
O
IMPORTANT INFO
Your blood contains antibodies which will recognize as foreign, and
ATTACK any blood antigen (eg. A or B) which you don’t normally
make.
Remember those A & B proteins label ‘self’ so your immune system
doesn’t attack you…. If you don’t normally have the protein your body
will think it foreign and ATTACK..
RULE OF THUMB – Never give someone a blood protein they don’t
normally make.
You CAN give them blood which has proteins they normally make OR
which lacks proteins they make
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First Patient with Type A blood gets a pint of Type A – a good match
Second Patient with Type B blood gets a pint of Type B – a bad match
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Who can donate to who?
Two climbers – John (A) and Jenna (AB) are climbing
Accident occurs
Jenna needs blood – can John donate?
John needs blood – can Jenna donate?
Should their friend Phil (O) arrive what use might he be?
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Donors & Acceptors
Since you can not give anyone a blood group they don’t already have…
Type O- (no A or B, no Rh) is said to be the ‘Universal Donor”
Type AB+ is called the “Universal Acceptor”
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Paternity with Blood Groups
Since a child inherits ABO blood group genes from each parent they
are useful in addressing question of parentage
Mom type A Baby type AB
Possible father #1 = blood type O
Possible father #2 = Blood type B
Mom could be either AA or A__
Father #1 is __, __ (couldn’t provide the B which we see in baby)
Father #2 could be BB or B__ (might be father)
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Population Distribution
White Americans
O -- 47%
A -- 41%
B – 9%
AB – 3%
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Black Americans
O -- 46%
A -- 27%
B – 20%
AB – 7%
Rh factor
Rh is simply another blood cell surface protein.. Where ABO has two
blood proteins and four possible types (A, B, AB & O) this has only
one protein (Rh) and two possible types (+ and -)
If you have this protein you are said to be Rh positive, if you lack this
protein you are Rh negative
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Male
44-54%
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Female
38-48%
White Blood Cell Count
normal values – 5000 – 10,000 cells per mm3
Leukopenia – fewer than normal WBC count
Leukocytosis – higher than normal WBC count
Leukemia (bone marrow cancer) can be one cause of leukocytosis as
can infection
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Differential Count
Typical values for WBCs
Neutrophil 60-70%
Lymphocytes 20-30%
Monocytes 2-3%
Eosinophils 1-4%
basophils 0.5-1%
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