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Campbell & Reece Chapter 42
Circulatory System
Blood: the "chemical highway" that
connects the many cells of an organism
•Carries nutrients, oxygen to each cell
•Carries wastes away from cells (CO2, urea)
to kidneys, lungs, skin
•Carries enzymes, hormones, water,
antibodies around body for distribution
Components of Blood
•Men, on average, have
about 10-12 pints
•Women, on average, have
about 8-10 pints
•each cc (cubic mL) of blood
contains about 4 million
RBCs and 7,000 WBCs
Plasma
Plasma = 60% of blood; straw-colored fluid
• about 90% of the plasma is water
• carries most CO2, nutrients, plasma proteins,
hormones, etc.
plasma proteins:
• albumin (to maintain high osmotic potential)
• fibrinogen (clotting)
• globulins (immunity, antibodies)
Red Blood Cells
• Called “erythrocytes”
• Transport oxygen; about 30 trillion in
bloodstream
• contain HEMOGLOBIN (red pigment protein)
which acts like an "oxygen magnet"; iron
• non-nucleated (cannot repair themselves)
• short lifespan (120-130 days)
• Replaced from bone marrow stem cells
White Blood Cells
• called “leukocytes”
• 1 or 2 WBC for every 1,000 RBC
• larger than RBC, have nucleus, no hemoglobin,
colorless
• Can migrate outside of vessels (RBC’s cannot) to
directly cleanse tissues (lymph)
• Some act by: phagocytosis of bacteria/viruses/etc.
• Others make antibodies (proteins) that attack
microorganisms
• "Pus"-dead WBC; new WBC form in spleen, bone
marrow
Platelets
• colorless, oval/irregular shaped
• smaller than RBCs
• "little bags of chemicals" that function in
clotting and plugging up breaks in vessels
Blood Clotting- a complex series of chemical reactions, involving platelets and plasma
"clotting factors". Often referred to as the "clotting cascade".
Thromboplastin
(produced in liver)
Prothrombin------------------------------>Thrombin
Fibrinogen---------------------------------------------> Fibrin
15 CF’s involved in this conversation (Hemophiliacs usually
genetically lack Factor VIII)
clotting animation
The Cardiovascular System
Vascular Circuitry
Heart--->Arteries--->Arterioles--->Capillaries--->Venules--->Veins--->Heart (etc)
Arteries
• thick, muscular walls,
• elastic, to allow for high pressure
• made of layers of
endothelium/muscle/connective tissues
• Narrow down into smaller arterioles
Veins
•
•
•
•
•
•
carry blood back toward the heart
thinner walls (than arteries)
less elastic (less pressure to withstand)
have valves to prevent backflow
endothelium, muscle, connective tissue layers
narrow down into smaller diameter venules
Arteries –vs- Veins (anatomy)
Capillaries
Diffusion
• the site of all exchange with cells
• in very close contact with all cells
• Lined with a single layer of epithelium
• smallest diameter of all vessels -only about 5
micrometers in diameter- (RBCs pass in single file)
Atherosclerosis
•…is a disease affecting arterial
blood vessels.
•Main cause: cholesterol buildup
in arteries (plaques)
•It is commonly referred to as
"hardening" of the arteries.
• It is caused by the formation of
multiple plaques within the
arteries
•This often leads not only to
clogs, but also hypertension
(high blood pressure), which
both may result in heart attacks.
The Heart
Evolution of the Heart
• simplest (in earthworms)
are enlarged, muscular
portions of a blood vessel =
"aortic arches"
•Mollusks= tube shaped heart with open
circulation
•Vertebrates= multi-chambered heart with
closed circulation
•multiple chambers serve to separate
oxygenated/ deoxygenated blood
•Atrium (receiving chamber)
•Ventricle (pumping chamber)
The Human Heart
is made of epithelial, nerve, connective tissues and
cardiac muscle (infatiguable)
Four chambers (2 atria,
2 ventricles)
septum- dividing wall
between right and left
side of heart
valves at strategic
locations prevent
backflow
separation into
chambers prevents
mixing oxygenated,
deoxygenated blood
Do right and left seem
backward? That's because
you're looking at an
illustration of somebody
else's heart. To think about
how your own heart works,
imagine wearing this
illustration on your chest.
Did you know that your heart
beats over 100,000 times a
day? Get "heart smart" by
checking out these amazing
heart facts.
The Human Heart
• Superior and Inferior Vena Cava
lead into heart (right atrium)
• Pulmonary artery brings blood
to lungs; pulmonary vein
returns oxygenated blood to the
heart
• Aorta leads out to systemic
circulation
• semilunar valves: prevent
backflow between
vessels/chambers
• atrioventricular valves: (mitral
and tricuspid) between atria &
ventricles; allow one-way flow
between atria and ventricle
Trace the Path of Blood Through the Heart
“How Stuff Works” narrated animation of cardiac parts
& cycle
How your heart works (animation)
Initiation and Regulation of Heartbeat
• Cardiac muscle is able to initiate its own
impulse
• Sinoatrial Node (SA)- "pacemaker" in Right
Atrium; initiates beat through both Atria;
stimulates another area near center of
heart called AV Node
• Atrioventicular Node (AV)...then impulse is
carried to the ventricles by the BH
• Bundle of His (BH) = like the transfer of an
electrical current along a circuit
• Heart Rate (bpm) is modified by the
Autonomic Nervous System (vagus nerve)
– Parasympathetic Nerves- slow down HR
– Sympathetic Nerves- increase HR
1. Oxygen-poor blood (shown in
blue) flows from the body into
the right atrium.
2. Blood flows through the right
atrium into the right ventricle.
3. The right ventricle pumps the
blood to the lungs, where the
blood releases waste gases and
picks up oxygen.
4. The newly oxygen-rich blood
(shown in red) returns to the
heart and enters the left atrium.
5. Blood flows through the left
atrium into the left ventricle.
6. The left ventricle pumps the
oxygen-rich blood to all parts of
the body.
To assess heart rate
(BPM), take your arterial
pulse!
@ rest?
After exercise?
How much blood does the heart
pump?
• The heart pumps the equivalent of 5,000 to 6,000
quarts (about 6800 L) of blood each day!
• Total volume of blood pumped by heart per minute =
“cardiac output”
• Cardiac Output = Heart Rate x Stroke volume
• (L/min) = (BPM) x (L/beat)
• [ex: 72 BPM x 0.07 L/beat = 5 L/min.]
Blood Pressure Regulation
Blood Pressure
• arterial BP >>> venous BP
120 = systole; ventricles contract (empty);arteriole diameter enlarged
80 =diastole; ventricles relax (fill)
Cardiovascular Regulating Center (in medulla)
• controls activity of the nerves regulating the smooth (circular)
muscle contraction of the blood vessel
• also controls strength of heartbeat, HR
• receives and interprets and responds to sensors through the
cardiovascular system (esp. in the walls of the vessels)
baroreceptors, CO2 receptors
The Lymphatic System
• Under arterial pressure, the BP
exceeds the osmotic potential,
thus forcing some plasma and
WBC out into tissues.
• This “lymphatic fluid” is collected
by Lymph vessels which clean the
tissue/ cellular debris (such as
bacteria) out of the body cells.
• Lymph flows thru Lymph Nodes
to be cleaned
• These also make Lymphocytes
(WBC’s)
• Lymph re-enters the circulatory
vessels via the Subclavian Veins in
the neck (back into bloodstream)