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Biology 12
Chapter 10 Circulation Class Notes
 The circulatory system is the organ system that is largely responsible
for the transport of materials such as nutrients, gases, and waste
material throughout the body
 It consists of the following components:
A. Blood Vessels
(i)
Arteries & Arterioles

 Arteries larger than arterioles in diameter

 Arterial layers:
-inner endothelium layer (squamous epithelium)
- elastic tissue layer
-outer fibrous connective tissue layer
Figure 1: Walls of artery

 Arteries can regulate blood pressure:
 Constriction of arteries →
 Dilation of arteries →
(ii)
Capillaries

 Made up of a single layer of endothelial cells
(squamous epithelium) and basement membrane
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 Where nutrients, wastes and gases are exchanged
from blood to and from tissues surrounding
capillaries
 Capillary beds (or networks) open and close via precapillary sphincter to shunt blood from one body
system to another→ known as the ____________
________ (or _________ ________)

 Thus, capillary beds can be bypassed in certain areas
to allow blood to move to or concentrate in areas
where it is needed more (e.g. digestion vs. Exercise)
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Figure 2: Diagram of Capillary bed
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(iii) Veins & Venules

 Veins function to return blood from capillary beds to
heart and to act as reservoir for blood as at any time
over 70% of blood is found in veins

 Walls of veins thinner than arteries

 Veins also have valves to prevent back flow of blood
which are not present in arteries
Figure 3: Valves in veins
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 Nervous stimulation of veins can cause t
 in case of injury and bleeding blood moves away
from veins in areas of bleeding to areas where there
is no injury (this is how veins and venules act as
reservoirs)
 the two largest veins in body are the superior vena
cava (drains head and neck) and inferior vena cava
(drains rest of body) which are about 20 mm in
diameter
B. Heart

 A cone shaped muscular organ

 Located behind the sternum (breast bone)

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Figure 4: Anatomy of the Heart
(a)External Structure
 Lies within thin membranous fluid filled sac called pericardium
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 Middle layer is made of ____________ which consists of
cardiac muscle cells branched and connected via gap junctions
 Outer layer called the ____________, ( a.k.a. ________
____________) is made of squamous epithelial cells and
underlying loose connective tissue
(b) Internal Structure

 Two thick walled ___________

 Both atria and ventricles separated by thick walled _________

 Upper atria and lower ventricles separated by __________________
_________
 ______________ valve—a.v. valve separating R.A. and R.V.
 ________ or ________ valve—a.v. valve separating L.A. and L.V.
 ____________ valves separate ventricles from their blood vessels
 ________________________—separates R.V. from pulmonary trunk
 _________________________________—separates L.V. from Aorta
 _______________________—are fibrous strings that are connected
to the valves and papillary muscles in heart to anchor valves and
prevent inversion during contraction of heart
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Figure 5: Internal Anatomy of Heart
C. Path of Blood Through Heart
Superior/Inferior Vena Cava → R.A. → tricuspid valve → R.V. → pulmonary
semilunar valve →Pulmonary Trunk → Pulmonary arteries → Lungs →
Pulmonary Veins → L.A. → bicuspid or mitral valve →L.V. → aortic
semilunar valve → Aorta
Note: heart is double pump with 2 separate paths where oxygenated and
deoxygenated blood never mix
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
D. Heartbeat

 Each heartbeat represents a cardiac cycle
 It consists of the contraction (__________) and relaxation (_______)
of heart muscle

 Each heartbeat lasts about 0.85 seconds
Table 1: Cardiac Cycle:
Cardiac Cycle
Time (sec)
0.15
0.30
0.40
Atria
Systole
Diastole
Diastole
Ventricles
Diastole
Systole
Diastole
E. Heart Sounds
 Typically has a “lub-dup” sound
 “lub” _____________________________________________
 “dup” _____________________________________________
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 ____________________ are slushy sounds that occur after the
lub—often due to damaged or ineffective AV-valves that allow blood
to pass back into atria
 ____________________ results from bacterial infection causing
faulty valves, usually the bicuspid and may require surgery to
correct (replaced with artificial valves)
F. Pulse

 Often measured on radial artery near outer border of palm side of
wrist

 Arterial wall pulse whenever left ventricle contracts
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G. Conduction System: Intrinsic Control of Heartbeat
Figure 6: S.A. and A.V. nodes
(a)
S.A. Node (Sinoatrial)

 Found in upper dorsal wall of right atrium

(b) A.V. (Atrioventricular) Node

 When receives stimulation from SA node, AV node signals
ventricles to contract by way of Purkinje fibers
(c) Artificial Pacemaker

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(d) Electrocardiogram (ECG or EKG)
Figure 7: EKG
 Records ionic changes that occur with contraction of heart
muscle
 P wave
 QRS wave
 T wave show repolarization of ventricles causing
recovery/relaxation of the ventricles
(e) Ventricular Fibrilation
Figure 8: Ventricular Fibrilation

 Can be due to drug overdose but cause mostly unknown
 Can be corrected by defibrillation—
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(f) Nervous Control of Heartbeat: Extrinsic Control
 Autonomic nervous______________________________________

 Autonomic nervous system made of _______________ and
__________________ nervous system
 Sympathetic component promotes speeding up heartbeat

 A variety of factors: increased blood pressure, need for oxygen,
perceived threat or danger or other reasons may activate these
systems
Figure 9: Autonomic Nervous System
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(g) Blood Pressure and Swiftness of Flow

 Systolic blood pressure is the highest blood pressure and results
from blood being pumped out of left ventricle into arteries

 Blood pressure decreases with distance from left ventricle

 Blood pressure highest in aorta, then drops in arterioles and also
again in capillaries due to increase in cross sectional area of blood
vessels (see diagram on page 233)
Figure 10: Diagram of how velocity, surface area and blood pressure are related
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
 As pressure decreases, due to increased cross-sectional area, so does
velocity

 Slow capillary velocity allows more time for exchange of nutrients,
gases, and waste products with tissues
In the veins, blood velocity increases due to:
i)
ii)
Reduction in cross-sectional area as small venules join to form
veins which results in increased velocity
iii)
H. Vascular Pathways
(i)
Pulmonary circuit

 Deoxygenated blood enters via pulmonary arteries

 Oxygenated blood leaves lungs via pulmonary veins to L.A.
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(ii)
Systemic Circuit

 Deoxygenated blood enters R.A. via the inferior and superior
vena cava (largest veins)
(iii) Coronary Arteries

 Are R and L coronary arteries and R & L cardiac veins

 Found on hearts surface

 Are small diameter arteries and can become blocked
(iv) Hepatic Portal System

 Capillaries in villi of small intestine → converge into venules
→ hepatic portal vein → divides into smaller venules in liver
→ sinusoids → central vein → hepatic vein → inferior vena
cava
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I—Blood
(i)
Helps maintain homeostasis

 Guards body against microbial invasion

 Reduces blood loss by clotting
(ii)
Blood Components

(a)Plasma
 Made of suspended or dissolves inorganic & organic
substances in water (see table 10.1 page 301)
 plasma proteins (7-8 %) of plasma function in:
---e.g. bilirubin transported by albumin and
--- maintains blood volume as proteins are too large to
pass through capillary walls→ thus, are hyperosmotic
with respect to their surrounding tissue fluids
-- fibrinogen
--immunoglobulins
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(b)
Red Blood Cells (Erythrocytes)

 4—6 million r.b.c.’s per mm3 of blood

 Iron from broken haemoglobin is reused

 Hgb made of four polypeptide chains (2α and 2β chains) that
form the protein __________
Figure 11: haemoglobin molecule
 Each polypeptide chain has an iron containing ______ group
associated with it—carries oxygen on iron
 When rbc’s destroyed in liver, ________ is degraded and
excreted by liver to become bile pigments

 rbc numbers increase when there is reduced oxygen
concentration in blood
 Kidneys produce _________________ that stimulates rbc
formation in stem cells (erythroblasts) of red bone marrow

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Anemia
 is a disease of the blood whereby not enough r.b.c.’s are produced,
too much blood is lost or too little haemoglobin per r.b.c.→
symptoms are fatigue and weakness
 iron-deficiency anemia—
 pernicious anemia—
 cured through vitamin B12 injections
(c) White Blood Cells (leukocytes)

 Larger than r.b.c.’s
 Have nucleus

 Fewer than r.b.c.’s (5,000 – 11,000/mm3)

 Life span ranges from days to years

Types of W.B.C.’s

 Granules are proteins
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Figure 12: Granular vs Agranular Leukocytes
(a)
Granular leukocytes

 Made of basophils, neutrophils and eosinophils
(i) Neutrophils


known as polymorphonuclear leukocytes

(iii) Basophils

 release chemicals called histamines resulting in increased
blood flow to an area of injury
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(iv) Eosinophils

 act as phagocytes for pathogens and antibody covered
antigens (i.e. foreign bodies)

Both basophils and eosinophils are important in attacking foreign
bodies
(b) Agranular leukocytes

 Spherical or kidney shaped nucleus
 Made of ___________ and ________________
(i) Monocytes
 largest of wbc’s
 Monocytes become _________________ in tissues and
phagocytose bacteria
(ii) lymphocytes

 Produce antibodies and other immune cells
Leukemia

 Result is they crowd out other blood cells such as rbc’s
Infectious mononucleosis
 Viral disease resulting in excess of B-lymphocytes
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AIDS

Platelets (Thrombocytes)
 Originate from fragmentation of _____________ in bone marrow

 150 000 – 300 000 per ml

Note: when blood clots in a test tube, a yellow fluid forms over the clot
which is called _________= plasma without fibrinogen
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Steps in the Blood Clotting Process
Exchange Between Blood And Tissue Fluid

 Interstitial fluid is the fluid (similar in composition to blood plasma) that
exists between a capillary and the cells surrounding it:
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
 Two forces control fluid movement (and therefore substances) across
capillary walls
i.
____________ Pressure causes water to move from tissue fluid
to blood
ii.
_________ pressure causes water to move from blood to tissue
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
 Arterial process is termed filtration because large red blood cells and
plasma proteins stay in blood, water and small molecule nutrients can
leave however
 Substances leaving capillaries contribute to ______ fluid or ________
fluid which exists between cells

 Midway in capillaries, blood pressure and osmotic pressures are about
equal; solutes such as salts and amino acids diffuse along concentration
gradients with nutrients (glucose and oxygen) moving into tissues and
wastes (including carbon dioxide) diffuse into capillary blood

 In venule side of capillaries, osmotic pressure is greater than blood
pressure; water moves into capillary along with other material

 Lymph is returned to venous blood when lymph vessels join _________
________ in shoulder region
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Circulatory Disorders
a) Hypertension

 Women = 160/95

 Diastolic pressure more critical in treatment
 Some people have 2 genes that can result in high b.p—one
gene produces angiotensinogen which is converted into a
vasoconstrictor by enzyme product of second gene – causes
hypertension
b) Hypotension

 Symptoms:
 Can be caused by low blood volume (hemorrhage, excessive
fluid loss from diarrhea or vomiting), excessive vasodilation
(due to increased parasympathetic, or decreased sympathetic
stimulation)

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c) Atherosclerosis

 Can occlude blood vessels and prevent blood from reaching
different tissues and organs resulting in necrosis of affected
tissue
 When attached to blood vessel called a _________
 If becomes dislodged it is called an ___________

 Treatment is proper diet (low in saturated fats and cholesterol)
and exercise
d) Stroke and heart Attack

i) Strokes (also called cardiovascular accident)—caused by part of
brain being starved of oxygen
 Causes of stroke are:
-- Can cause variety of symptoms depending on what part of
brain affected (e.g. speech, motor, sensory, etc.)

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iii.
Heart attack (also called myocardial infarction)

 If coronary artery is only partially blocked, can experience
angina pectoris (left arm pain)
 Tx. =
 If completely block coronary artery, major heart attack
results
e) Dissolving Blood Clots

 ______ (tissue plasminogen activator)
 both above convert plasminogen into plasmin which can
dissolve clots
 _____________ (anticoagulant) can also be used to inhibit
stickiness of platelets
f) Clearing Clogged Arteries
i.
Angioplasty

 Risk of reclosing due to smooth muscle growing in response
to trauma
ii.
Coronary Bypass Surgery

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Angioplasty
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Coronary bypass surgery
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