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Circulatory
and
Respiratory
Systems
Biology
Vertebrate Circulatory
System
• Closed system with a chambered heart that
pumps blood through arteries that lead away
from the heart to capillaries.
• Capillaries—small vessels in tissues where
exchange of materials take place
• Blood is carried back to heart through veins
Human Heart
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Located beneath the sternum
About the size of your fist
Composed mostly of cardiac muscle tissue
2 atria have thin walls and function as
collection chambers for returning blood
• 2 ventricles have thick, powerful walls that
pump blood to the organs
Blood Vessels
• Arteries—carry blood away from the heart
to the tissues
– Branch into smaller arterioles, which supply
blood to tissues via capillaries
– Thick-walled, muscular (smooth muscle), and
elastic, transporting blood at high pressure
– Blood is oxygenated, except the pulmonary
artery that carries deoxygenated blood from
tissues to lungs through the right atrium and
ventricle
• Veins—carry blood to the heart from the capillaries
– Capillaries branch into larger venules, which supply blood to
veins and back to the heart
– Thin-walled, little smooth muscle, transporting blood at low
pressure, and contain many valves to prevent backflow
– Veins have no pulse and carry deoxygenated blood, except
the pulmonary vein which carries oxygenated blood from
the lungs
– Skeletal muscle contraction aids in systemic circulation
• Capillaries—thinwalled vessels (simple
squamous)
• Permit exchange of
materials between
blood and body cells
• Capillaries
• Fluid containing water
with nutrients and
hormones seep from
capillaries into tissues,
driven by pressure
• Cells and proteins are
retained in the
capillaries and draw
water back into the
capillaries by osmosis
• Excess fluid in tissue
can enter lymphatic
system to be filtered
and cycled back to the
circulatory system
Blood Components
Erythrocytes: Red Blood Cells
• Primary function to carry
oxygen
• Produced in red bone marrow
of bones
• Mature cells lack nuclei and
circulate ~4mos.
• Mature cells lack
mitochondria—produce ATP
without oxygen through
glycolysis
• Contain hemoglobin-pigment
that binds oxygen
Erythrocytes: Red Blood Cells
• Red blood cells (rbc)
manufacture 2 antigens,
antigen A (Blood Type A)
and antigen B (Blood
Type B)
– No antigens create the
Blood Type O
• Plasma carries antibodies
for the antigens that are
not present on the rbcs
Leukocytes: White Blood Cells
• Involved in immune
functions in the body
– Phagocytes—engulf
bacteria
– Lymphocytes (B and T
cells)—immune response
• B cells produce antibodies
• Helper T cells kill infected
cells
Leukocytes: White Blood Cells
• Platelets—cell
fragments produced
in marrow
– Involved in blood
clotting mechanism
– Activation of a
protein in the blood,
fibrin, that forms a
net across the
wound, trapping
more cells and
blocking the flow of
blood
Two separate circulatory loops
–Pulmonary circulation
• Pumps oxygen-poor
blood through pulmonary
arteries to the lungs
• Pick up O2/Unload CO2
• Oxygenated blood
returns to left side of
heart through pulmonary
veins
–Systemic circulation
• Pumps oxygen-rich
blood through arteries to
the tissues of the body
• Delivers O2/Picks up
CO2
• Returns deoxygenated
blood to right side of
heart through veins
Four valves function to prevent backflow of blood
–Atrioventricular
valves
• Prevent backflow
when ventricles
contract
–Semilunar valves
• Prevent backflow
when ventricles
relax
Control of Heart Rhythm
• Sinoatrial (SA) node—cells are selfexcitable—generate electrical impulses
• Cardiac muscle cells are electrically
coupled by intercalated discs b/w cells
Control of Heart Rhythm
• Atrioventricular (AV) node—receives signal
from atria, delays 0.1 sec, and then sends
signal throughout walls of ventricle
Cardiovascular Disease
• Heart attack—death of
cardiac muscle tissue
resulting from artery
blockage of one or more
coronary arteries which
supply oxygen to the heart
• Stroke—death of nervous
tissue in the brain resulting
from artery blockage in the
head
Ventilating Lungs: Breathing
Automatic Control of Breathing
• Breathing control center
in brain = medulla
oblongata and pons
• Monitors CO2 levels in
blood by changes in pH
– CO2 + H2O  Carbonic acid
–  pH =  depth and rate of
breathing
• altitude =  O2 levels
• Sensors in aorta and
carotid arteries detect and
signal control center to 
breathing rate
Loading and
Unloading of
Respiratory Gases
Oxygen Transport
• Oxygen carried by respiratory pigments
– Vertebrates utilize hemoglobin—four heme
groups surrounding an Fe atom
• Can carry four oxygen atoms
Carbon Dioxide Transport
• Hemoglobin transports CO2 and assists with
buffering the blood—prevents dramatic
changes in pH
• 7% CO2 released by cells transported as
dissolved CO2 in plasma
• 23% binds to amino group of hemoglobin in
red blood cells
• 70% transported in form of bicarbonate ions
Emphysema
• Alveoli lose their
elasticity
• Makes it difficult to
release air during
exhalation
• Person must use more
and more energy just
to breathe
• Person suffers from
constant fatigue and
breathlessness
Lung Cancer
• Abnormal cell growth
• Affected lung is
usually removed
• Fewer than 10% of
lung cancer victims
live more than 5 years