Download Circulation and Gas Exchange

Biosc 41 Announcements 11/5
Review: Fishes
§  Review of fish
§  Which group of fishes is a basal craniate, but often
not grouped as a true “vertebrate”?
§  Quiz covering fish
§  Lecture: circulation and gas exchange
§  Lab: video (“Your Inner Reptile”), amphibians &
reptiles (frog dissection)
§  Which groups of fishes are agnathans?
§  Which group of fishes are the most primitive
gnathostomes?
§  Which group of fishes has a heterocercal caudal fin?
§  Next quiz: tetrapods (all), Wed. 11/12
§  Which fishes have a homocercal caudal fin?
§  Type of scales in sharks?
© 2014 Pearson Education, Inc.
© 2014 Pearson Education, Inc.
Review: Fishes
Review: Fishes
§  Oviparous vs ovoviviparous vs viviparous?
§  What organ do chondrichthyans use for buoyancy?
§  What is the class of ray-finned fishes?
§  Most energy-efficient mode of locomotion?
§  Lobe-finned fishes? Differences from above?
§  How do freshwater fish osmoregulate?
§  Examples of lobe-finned fishes?
§  How do seawater fish osmoregulate?
§  Which group of fishes have an operculum?
§  Swim-bladder?
© 2014 Pearson Education, Inc.
Quiz 8
© 2014 Pearson Education, Inc.
Circulation and Gas Exchange
1.  Which groups of fishes are agnathans? (common
names OR scientific names are fine!)
2.  What organ do (a) cartilaginous fishes, and (b) bony
fishes use for buoyancy?
Reference: Chapter 42
3.  List two ways that fish osmoregulate in freshwater.
4.  List two ways that fish osmoregulate in seawater.
5.  List two ways in which lobe-finned fishes differ
physically from ray-finned fishes.
© 2014 Pearson Education, Inc.
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1
Concept 42.1: Circulatory systems link respiratory
surfaces with cells throughout the body
§  O2 and CO2 move between cells and their surroundings by
diffusion
§  Diffusion is only efficient over small distances because the
time it takes to diffuse is proportional to the distance
§  In small or thin animals, cells can exchange materials
directly with the surrounding medium
§  In most animals, cells exchange
materials with the environment via
a fluid-filled circulatory system
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Gastrovascular Cavities
§  Some animals lack a circulatory
system
§  Some cnidarians have elaborate
gastrovascular cavities
§  Functions in both digestion and
distribution of substances throughout
the body
§  Body wall enclosing GVC is only two
cells thick
§  Flatworms have GVC and a flat body
to minimize diffusion distances
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Open and Closed Circulatory Systems
§  A circulatory system has:
§  Circulatory fluid
§  A set of interconnecting vessels
§  A muscular pump, the heart
§  Circulatory system connects body tissues with organs that
exchange gases, absorb nutrients, dispose wastes
§  Circulatory systems can be open or closed and vary in the
number of “circuits”
(a) An open circulatory system
§  In a closed circulatory
system, blood is confined to
vessels and is distinct from
interstitial fluid
Organization of Vertebrate Circulatory Systems
Single Circulation
§  Arteries branch into arterioles and carry blood away from the
heart to capillaries
§  Capillary beds are the sites of exchange between blood and
interstitial fluid
§  Venules converge into veins and return blood from capillaries
to the heart
Tubular heart
(b) A closed circulatory system
Heart
Interstitial fluid
Blood
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§  The three main types of blood vessels are arteries, veins,
and capillaries; each has one-way blood flow
Hemolymph in sinuses
Pores
Small
branch vessels
in each organ
§  Annelids, cephalopods, and
vertebrates have closed
circulation
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§  Humans and other vertebrates have a closed circulatory
system called the cardiovascular system
Heart
§  Arthropods and some molluscs
have circulatory fluid called
hemolymph that bathes
organs directly in open
circulation
Dorsal
vessel
(main
heart)
Auxiliary
hearts
Ventral vessels
(a) Single circulation:
fish
Gill
capillaries
§  Bony fishes, rays, and
sharks have single
circulation with a twochambered heart
Artery
Heart:
§  In single circulation,
blood leaving the heart
passes through two
capillary beds (gills and
body) before returning
Atrium (A)
Ventricle (V)
Vein
Body
capillaries
Key
Oxygen-rich blood
Oxygen-poor blood
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© 2014 Pearson Education, Inc.
2
Double Circulation
(b) Double circulation:
amphibian
Pulmocutaneous circuit
§  Amphibians, reptiles, and
mammals have double
circulation
Lung
and skin
capillaries
§  O2-poor and O2-rich blood
are pumped separately
from the right and left
sides of the heart
§  In amphibians, O2-poor
blood flows through a
pulmocutaneous circuit to
pick up O2 through the
lungs and skin
Atrium
(A)
Atrium
(A)
Systemic
capillaries
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Pulmonary circuit
§  In reptiles and mammals,
O2-poor blood flows
through the pulmonary
circuit to pick up O2
through the lungs
Lung
capillaries
Systemic circuit
Oxygen-rich blood
Oxygen-poor blood
§  Amphibians have a three-chambered heart: two atria
and one ventricle
§  Reptiles have a three-chambered heart: two atria and
one ventricle, partially divided by a septum
V
Systemic circuit
Key
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Oxygen-rich blood
Oxygen-poor blood
Concept 42.2: Coordinated cycles of heart
contraction drive double circulation in mammals
Capillaries of
Upper body
7
Superior vena cava
Pulmonary artery
Right lung
capillaries
Pulmonary artery
Left lung
capillaries
Aorta
9
6
2
3
4
11
Pulmonary vein
1
Right atrium
Pulmonary vein
5
10
Left atrium
Left ventricle
Right ventricle
Aorta
Inferior vena cava
8
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Left
Systemic
capillaries
3
§  Mammals and birds are endotherms and require more
O2 than ectotherms
V
Right
§  Double circulation
maintains higher blood
pressure in organs than
single circulation
§  Mammals and birds have a four-chambered heart with
two atria and two ventricles
§  The left side of the heart pumps and receives only O2rich blood, while the right side receives and pumps
only O2-poor blood
A
A
§  O2-rich blood delivers O2
through the systemic
circuit
Right
Left
Ventricle (V)
Key
(c) Double circulation:
mammals & reptiles
Double Circulation
Capillaries of
Lower body
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The Mammalian Heart: A Closer Look
§  The two atria have
relatively thin walls
and serve to collect
blood returning to
the heart
§  Ventricles have
thicker walls and
contract much more
forcefully
Pulmonary artery
Right
atrium
§  The heart contracts and relaxes in a rhythmic cycle called
the cardiac cycle
Pulmonary
artery
§  The contraction, or pumping, phase is called systole
Left
atrium
§  The relaxation, or filling, phase is called diastole
§  The heart rate (pulse) is the number of beats per minute
Semilunar
valve
Semilunar
valve
Atrioventricular
(AV) valve
Atrioventricular
(AV) valve
Right
ventricle
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Aorta
§  The stroke volume is the amount of blood pumped in a
single contraction
§  The cardiac output is the volume of blood pumped into
the systemic circulation per minute and depends on both
the heart rate and stroke volume
Left
ventricle
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3
Maintaining the Heart s Rhythmic Beat
§  Four valves prevent
backflow of blood in
the heart
§  Atrioventricular
(AV) valves
separate each atrium
and ventricle
§  Semilunar valves
control blood flow to
the aorta and the
pulmonary artery
Aorta
Pulmonary artery
Pulmonary
artery
Right
atrium
Left
atrium
§  The sinoatrial (SA) node (pacemaker) sets the rate and timing
at which cardiac muscle cells contract
§  Impulses that travel during the cardiac cycle can be recorded as
an electrocardiogram (ECG or EKG)
1 Signals (yellow)
from SA node
spread through
atria.
Semilunar
valve
2 Signals are
delayed at AV
node.
3 Bundle branches
pass signals to
heart apex.
4 Signals
spread
throughout
ventricles.
Semilunar
valve
Atrioventricular
(AV) valve
Atrioventricular
(AV) valve
Right
ventricle
SA node
(pacemaker)
Left
ventricle
AV
node
Bundle
branches
Heart
apex
Purkinje
fibers
ECG
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Education, Inc.
© 2014 Pearson Education, Inc.
Concept 42.3: Patterns of blood pressure and flow
reflect structure and arrangement of vessels
§  The pacemaker is regulated by two portions of the nervous
system: the sympathetic and parasympathetic divisions
§  The epithelial layer that lines blood vessels is called the
endothelium; it is smooth to minimize resistance
§  The sympathetic division speeds up the pacemaker
§  Capillaries are barely wider than a red blood cell, and have thin
walls to facilitate exchange
§  The parasympathetic division slows down the pacemaker
§  Also regulated by hormones and temperature
§  Arteries have thicker walls than veins to accommodate high
pressure blood pumped from the heart
§  In the thinner-walled veins, muscle action pushes blood back to
the heart
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Blood Flow Velocity
Changes in Blood Pressure During the
Cardiac Cycle
§  Systolic pressure is the pressure in the arteries during
ventricular systole; it is the highest pressure in the arteries
§  Diastolic pressure is the pressure in the arteries during
diastole; it is lower than systolic pressure
Systolic
pressure
Venae
cavae
Veins
Venules
Capillaries
Diastolic
pressure
Arteries
120
100
80
60
40
20
0
§  The recoil of elastic arterial walls helps maintain pressure
Aorta
50
40
30
20
10
0
Arterioles
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Velocity
(cm/sec)
§  Slow flow in capillaries
facilitates exchange of
materials
§  Blood pressure is the pressure that blood exerts in all
directions, including against the walls of blood vessels
5,000
4,000
3,000
2,000
1,000
0
Pressure
(mm Hg)
§  Blood flow is slowest
in capillary beds, due
to high resistance
Area (cm2)
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§  A pulse is the rhythmic bulging of artery walls with each
heartbeat
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4
Regulation of Blood Pressure
§  Homeostatic mechanisms regulate arterial blood pressure
by altering arteriole diameter
§  Vasoconstriction is the contraction of smooth muscle in
arteriole walls; it increases blood pressure
§  Vasodilation is the relaxation of smooth muscles in the
arterioles; it decreases blood pressure
§  Fainting is caused by inadequate
blood flow to the head
§  Animals with long necks need
very high systolic pressure to
pump blood against gravity!
§  Blood is moved through veins by
smooth and skeletal muscle
contraction, and expansion of the
vena cava with inhalation
§  One-way valves in veins prevent
backflow of blood
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§  Exchange of substances between blood and interstitial
fluid occurs across the thin endothelial walls of capillaries
§  The difference between blood pressure and osmotic
pressure drives fluids across capillary walls
§  Most blood proteins and all blood cells are too large to
pass through the endothelium
INTERSTITIAL FLUID
Net fluid movement out
Body cell
Blood
pressure
Osmotic
pressure
Arterial end
of capillary
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Education, Inc.
Direction of blood flow
Venous end
of capillary
Concept 42.4: Blood components function in
exchange, transport, and defense
§  With open circulation, circulatory fluid is continuous with
the fluid surrounding all body cells
§  Closed circulatory systems of vertebrates have a more
highly specialized fluid called blood
Fluid Return by the Lymphatic System
§  The lymphatic system returns
fluid that leaks from capillary
beds (lymph), and drains into
veins in the neck
Lymph nodes
§  Valves in lymph vessels prevent
backflow (edema is swelling
caused by disruptions in the flow
of lymph)
§  Lymph nodes are organs that
filter lymph and play an important
role in the body s immune
defense
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Blood Composition and Function
§  Blood in vertebrates is connective tissue made of several
kinds of cells suspended in a liquid matrix called plasma
Plasma 55%
Constituent
Water
Major functions
Cellular elements 45%
Solvent
Ions (electrolytes)
Sodium
Potassium
Calcium
Magnesium
Chloride
Bicarbonate
Osmotic balance,
pH buffering,
and regulation
of membrane
permeability
Number per
µL (mm3) of blood
Cell type
Separated
blood
elements
Leukocytes (white blood cells)
5,000–10,000
Functions
Defense and
immunity
Lymphocytes
Basophils
Plasma proteins
Albumin
Osmotic balance,
pH buffering
Immunoglobulins Defense
(antibodies)
Apolipoproteins
Lipid transport
Fibrinogen
Clotting
Eosinophils
Neutrophils
Platelets
Monocytes
250,000–400,000
Blood clotting
Substances transported by blood
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Nutrients (glucose, lipids, vitamins)
Waste products of metabolism
Respiratory gases (O2 and CO2)
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Erythrocytes
(red blood cells)
5,000,000–6,000,000 Transport of O2
and some CO2
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Plasma
§  Plasma contains inorganic salts as dissolved ions,
sometimes called electrolytes
§  Plasma proteins influence blood pH and help maintain
osmotic balance between blood and interstitial fluid
§  Particular plasma proteins function in lipid transport,
immunity, and blood clotting
Cellular Elements
§  Suspended in blood plasma are two types of cells
§  Red blood cells (erythrocytes) transport O2
§  White blood cells (leukocytes) function in defense
§  Platelets are fragments of cells, involved in clotting
§  Plasma is similar in composition to interstitial
fluid, but plasma has a much higher protein concentration
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Erythrocytes
§  Red blood cells, or erythrocytes, are the most numerous
blood cells
§  Contain hemoglobin (Hb), the iron-containing protein that
transports O2
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§  Sickle-cell disease is caused by abnormal hemoglobin
proteins that form aggregates
§  The aggregates can deform an erythrocyte into
a sickle shape
§  Sickled cells can rupture or block blood vessels
§  Each molecule of Hb binds up to four molecules of O2
§  In mammals, mature erythrocytes lack nuclei and
mitochondria
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© 2014 Pearson Education, Inc.
Leukocytes
Stem Cells and the Replacement of Cellular
Elements
§  There are five major types of white blood cells
(leukocytes): basophils, eosinophils, neutrophils,
monocytes and lymphocytes
§  Function in defense either by phagocytizing bacteria and
debris or mounting immune responses against foreign
substances
§  They are found both in and outside the circulatory system
§  Erythrocytes, leukocytes, and platelets all develop
from a common source of stem cells in the red
marrow of bones, especially ribs, vertebrae, sternum,
and pelvis
§  The hormone erythropoietin (EPO) stimulates
erythrocyte production when O2 delivery is low
§  Physicians can use recombinant EPO to treat people
with conditions such as anemia
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6
Cardiovascular Diseases: Atherosclerosis,
Heart Attacks, and Stroke
§  Atherosclerosis, is caused by buildup of fatty deposits
(plaque) within arteries
§  Cholesterol is a key player in the development
of atherosclerosis
§  A heart attack, or myocardial infarction, is damage or
death of cardiac muscle tissue from blockage of one or
more coronary arteries
§  A stroke is death of nervous tissue in the brain, usually
from rupture or blockage of arteries in the head
§  Angina is chest pain caused by partial blockage of the
coronary arteries
§  Low-density lipoprotein (LDL) delivers
cholesterol to cells (bad)
Endothelium
§  High-density lipoprotein (HDL)
scavenges excess cholesterol for return
to the liver (good)
Thrombus
(clot)
§  Risk for heart disease increases with a
high LDL to HDL ratio; inflammation is
also a factor
Plaque
© 2014 Pearson Education, Inc.
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Figure 42.20
Risk Factors and Treatment of Cardiovascular
Disease
1 A stent and a balloon
are inserted into an
obstructed artery.
Artery
Plaque
Stent
around
balloon
2 Inflating the balloon
expands the stent,
widening the artery.
§  High LDL/HDL ratio increases cardiovascular disease risk
§  LDL can be decreased by exercise and avoiding smoking
and trans fats
§  Drugs called statins reduce LDL and heart attack risk
§  Inflammation contributes to atherosclerosis and clots
3 The balloon is removed,
leaving the stent in
place.
Increased
blood
flow
© 2014 Pearson Education, Inc.
Concept 42.5: Gas exchange occurs across
specialized respiratory surfaces
§  Gas exchange supplies O2 for cellular respiration and
disposes of CO2
§  Partial pressure is the pressure exerted by a particular
gas in a mixture of gases in air or liquid
§  Aspirin inhibits inflammation, reduces cardiovascular risk
§  Hypertension (high blood pressure) also contributes to
heart attack and stroke, but can be controlled by dietary
changes, exercise, and/or medication
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Respiratory Media
§  Animals can use air or water as the O2 source
(respiratory medium)
§  In a given volume, less O2 is available in water than air
§  Obtaining O2 from water requires greater efficiency than
air breathing
§  Gases undergo net diffusion from a region of higher
partial pressure to a region of lower partial pressure
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7
Respiratory Surfaces
Gills in Aquatic Animals
§  Animals require large, moist respiratory surfaces for
exchange of gases between their cells and the
respiratory medium, either air or water
§  Gills are outfoldings of the body that create a large
surface area for gas exchange
§  Gas exchange across respiratory surfaces takes place by
diffusion
§  Respiratory surfaces vary by animal and can include the
skin, gills, tracheae, and lungs
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§  Ventilation moves the respiratory medium over the
respiratory surface
§  Aquatic animals move through water or move water
over their gills for ventilation
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Figure 42.21
§  Fish gills use countercurrent exchange, where blood flows
opposite to water passing over gills
§  In fish gills, more than 80% of the O2 dissolved in the water is
removed as water passes over the respiratory surface
O2-poor blood
Gill arch
O2-rich blood
Blood
vessels
Coelom
Gill arch
Gills
Parapodium
(functions as gill)
(a) Marine worm
Gills
Water
flow
Water flow
Tube foot
(b) Crayfish
Lamella
Operculum
Blood flow
Countercurrent exchange
(c) Sea star
PO (mm Hg) in water
2
Gill filaments
150 120
Net diffusion of O2
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Tracheal Systems in Insects
60
30
50
20
PO (mm Hg)
2
in blood
Lungs
§  The tracheal system of insects is a network of branching tubes
§  Tracheal tubes supply O2 directly to body cells
Body
cell
Air
sac
Tracheole
Air sacs
§  Lungs are an infolding of the body surface; the circulatory
system transports gases between lungs and the body
§  Lung size and complexity correlate with metabolic rate
§  Respiratory and circulatory systems are separate
Tracheae
90
140 110 80
§  Air passes through the pharynx, larynx, trachea, bronchi,
and bronchioles to alveoli, where gas exchange occurs
§  O2 diffuses through the moist epithelium into capillaries
(secretions called surfactants coat the surface of alveoli)
§  CO2 diffuses from capillaries across epithelium into alveoli
for exhalation from body
Trachea
Air
§  Alveoli lack cilia and are susceptible to contamination
External opening
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8
Figure 42.24
Concept 42.6: Breathing ventilates the lungs
Branch of
pulmonary artery
(O2-poor blood)
Branch of
pulmonary vein
(O2-rich blood)
Terminal
bronchiole
§  Amphibians ventilate by positive pressure breathing, which
forces air down the trachea
Nasal
cavity
Pharynx
Larynx
Left lung
(Esophagus)
Alveoli
50 µm
Trachea
Right lung
Capillaries
Bronchus
§  The process that ventilates the lungs is breathing, the
alternate inhalation and exhalation of air
§  Ventilation in birds is highly efficient; air passes through the
lungs in one direction only
Anterior
air sacs
Bronchiole
Posterior
air sacs
Diaphragm
Dense capillary bed
enveloping alveoli (SEM)
(Heart)
Lungs
Posterior
air sacs
Lungs
3
2
Anterior
air sacs
4
1
1
2
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How a Mammal Breathes
3
4
Second inhalation
Second exhalation
Control of Breathing in Humans
§  Mammals ventilate lungs by negative pressure breathing,
which pulls air into the lungs
§  Lung volume increases as rib muscles and diaphragm contract
§  After exhalation, a residual volume of air remains in the lungs
Rib cage
expands as
rib muscles
contract
First inhalation
First exhalation
§  In humans, breathing is usually regulated by involuntary
mechanisms
§  The breathing control centers are found in the medulla
oblongata of the brain
§  Regulates the rate and depth of breathing
Rib cage
gets smaller
as rib muscles
relax
§  In response to pH changes in cerebrospinal fluid
Lung
Diaphragm
1
INHALATION: Diaphragm
(moves down)
2
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contracts
EXHALATION: Diaphragm
relaxes (moves up)
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Figure 42.28
Coordination of Circulation and Gas Exchange
NORMAL BLOOD pH
(about 7.4)
Blood CO2 level falls
and pH rises
Medulla detects
decrease in pH of
cerebrospinal fluid
Cerebrospinal
fluid
Signals from
medulla to rib
muscles and
diaphragm
increase rate
and depth of
ventilation
Alveolar
epithelial
cells
Blood pH falls
due to rising levels of
CO2 in tissues (such as
when exercising)
Medulla receives
signals from major
blood vessels
Inhaled air
Alveolar
spaces
CO2
O2
Alveolar
capillaries
Pulmonary
arteries
Carotid
arteries
Aorta
Medulla
oblongata
Exhaled air
Pulmonary
veins
Systemic
veins
Sensors in major
blood vessels
detect decrease
in blood pH
Systemic
arteries
Heart
CO2
O2
Systemic
capillaries
Body tissue
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9
Two video resources posted on Angel:
§  BioFlix- gas exchange in lungs
§  Khan Academy- blood flow through the heart
§  https://www.khanacademy.org/science/health-andmedicine/human-anatomy-and-physiology/heartintroduction/v/flow-through-the-heart
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