Transcript Circulatory System

The
Cardiocascular
System
Chapter 11
The Cardiovascular System
• A closed system of the heart and blood vessels
– The heart pumps blood
– Blood vessels allow blood to circulate to all
parts of the body
• The function of the cardiovascular system is to
deliver oxygen and nutrients and to remove
carbon dioxide and other waste products
The Heart
• Location
– Thorax between the lungs
– Pointed apex directed toward left hip
• About the size of your fist
The Heart
Figure 11.1
The Heart: Coverings
• Pericardium – a double serous membrane
– Visceral pericardium
• Next to heart
– Parietal pericardium
• Outside layer
• Serous fluid fills the space between the layers of
pericardium
The Heart: Heart Wall
• Three layers
– Epicardium
•Outside layer
•This layer is
the parietal
pericardium
•Connective
tissue layer
–Myocardium
•Middle layer
•Mostly
cardiac
muscle
–Endocardium
•Inner layer
•Endothelium
External Heart Anatomy
Figure 11.2a
The Heart: Chambers
• Right and left side act as separate pumps
• Four chambers
– Atria
• Receiving chambers
–Right atrium
–Left atrium
– Ventricles
• Discharging chambers
–Right ventricle
–Left ventricle
Figure 11.2c
Blood Circulation
Figure 11.3
The Heart: Valves
• Allow blood to flow in only one direction
• Four valves
– Atrioventricular valves – between
atria and ventricles
• Bicuspid valve (left)
• Tricuspid valve (right)
– Semilunar valves between ventricle
and artery
• Pulmonary semilunar valve
• Aortic semilunar valve
The Heart: Valves
• Valves open as blood is pumped through
• Held in place by “heart strings”
• Close to prevent backflow
Operation of Heart Valves
Figure 11.4
The Heart: Associated Great Vessels
• Aorta
– Leaves left
ventricle
• Pulmonary arteries
– Leave right
ventricle
• Vena cava
– Enters right
atrium
• Pulmonary veins (four)
– Enter left atrium
Coronary Circulation
• Blood in the heart chambers does not
nourish the myocardium
• The heart has its own nourishing
circulatory system
– Coronary arteries
– Cardiac veins
– Blood empties into the right atrium
via the coronary sinus
The Heart: Conduction System
• Intrinsic conduction system
(nodal system)
– Heart muscle cells contract, without
nerve impulses, in a regular, continuous
way
The Heart: Conduction System
• Special tissue sets the pace
• Sinoatrial node
–Pacemaker of the heart
• Atrioventricular node
• Atrioventricular bundle
• Bundle branches
• Purkinje fibers
Heart Contractions
• Contraction is initiated by the sinoatrial node
• Sequential stimulation occurs at other
autorhythmic cells
Heart Contractions
Figure 11.5
Filling of Heart Chambers – the
Cardiac Cycle
Figure 11.6
The Heart: Cardiac Cycle
• Atria contract simultaneously
• Atria relax, then ventricles contract
• Systole = contraction
• Diastole = relaxation
The Heart: Cardiac Cycle
• Cardiac cycle – events of one complete heart
beat
– Mid-to-late diastole – blood flows into
ventricles
– Ventricular systole – blood pressure builds
before ventricle contracts, pushing out blood
– Early diastole – atria finish re-filling,
ventricular pressure is low
The Heart: Cardiac Output
• Cardiac output (CO)
– Amount of blood pumped by each side
of the heart in one minute
– CO = (heart rate [HR]) x (stroke volume
[SV])
• Stroke volume
– Volume of blood pumped by each
ventricle in one contraction
Cardiac Output Regulation
Figure 11.7
Hear bypass surgery
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• Part II
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• Part III
• http://www.youtube.com/watch?v=Bpy20INIuj
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Cardiac Cath Angiolplasty
• http://www.youtube.com/watch?v=JeH4zPzQg
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The Cardiovascular
System
The Heart: Regulation of Heart Rate
• Stroke volume usually remains
relatively constant
– Starling’s law of the heart – the
more that the cardiac muscle is
stretched, the stronger the
contraction
• Changing heart rate is the most
common way to change cardiac output
The Heart: Regulation of Heart Rate
• Increased heart
rate
– Sympathetic
nervous system
•Crisis
•Low blood
pressure
– Hormones
•Epinephrine
•Thyroxine
– Exercise
– Decreased
blood volume
The Heart: Regulation of Heart Rate
• Decreased heart rate
–Parasympathetic nervous system
–High blood pressure or blood
volume
–Dereased venous return
Blood Vessels: The Vascular System
• Taking blood to the tissues and back
–Arteries
–Arterioles
–Capillaries
–Venules
–Veins
Figure 11.8a
The Vascular System
Figure 11.8b
Blood Vessels: Anatomy
• Three layers (tunics)
– Tunic intima
• Endothelium
– Tunic media
• Smooth muscle
• Controlled by sympathetic
nervous system
– Tunic externa
• Mostly fibrous connective tissue
Differences Between Blood Vessel Types
• Walls of arteries are the thickest
• Lumens of veins are larger
• Skeletal muscle “milks” blood in veins
toward the heart
• Walls of capillaries are only one cell
layer thick to allow for exchanges
between blood and tissue
Movement of Blood Through Vessels
• Most arterial
blood is pumped
by the heart
• Veins use the
milking action of
muscles to help
move blood
Figure 11.9
Capillary Beds
• Capillary beds
consist of two types
of vessels
– Vascular shunt –
directly connects
an arteriole to a
venule
Figure 11.10
Capillary Beds
• True capillaries –
exchange vessels
• Oxygen and
nutrients cross
to cells
• Carbon dioxide
and metabolic
waste products
cross into
blood
Figure 11.10
Diffusion at Capillary Beds
Figure 11.20
Major Arteries of Systemic
Circulation
Figure 11.11
Major Veins of Systemic Circulation
Figure 11.12
Arterial Supply of the Brain
Figure 11.13
Hepatic Portal Circulation
Figure 11.14
Circulation to the Fetus
Figure 11.15
Pulse
• Pulse –
pressure wave
of blood
• Monitored at
“pressure
points” where
pulse is easily
palpated
Figure 11.16
Blood Pressure
• Measurements by health professionals are
made on the pressure in large arteries
– Systolic – pressure at the peak of
ventricular contraction
– Diastolic – pressure when ventricles relax
• Pressure in blood vessels decreases as the
distance away from the heart increases
Measuring Arterial Blood Pressure
Figure 11.18
Comparison of Blood Pressures in
Different Vessels
Figure 11.17
Blood Pressure: Effects of Factors
• Neural factors
– Autonomic nervous system
adjustments (sympathetic division)
• Renal factors
– Regulation by altering blood volume
– Renin – hormonal control
Blood Pressure: Effects of Factors
• Temperature
–Heat has a vasodilation effect
–Cold has a vasoconstricting effect
• Chemicals
–Various substances can cause
increases or decreases
• Diet
Factors Determining Blood Pressure
Figure 11.19
Variations in Blood Pressure
• Human normal range is variable
– Normal
• 140–110 mm Hg systolic
• 80–75 mm Hg diastolic
– Hypotension
• Low systolic (below 110 mm HG)
• Often associated with illness
– Hypertension
• High systolic (above 140 mm HG)
• Can be dangerous if it is chronic
Capillary Exchange
• Substances exchanged due to
concentration gradients
– Oxygen and nutrients leave the blood
– Carbon dioxide and other wastes leave
the cells
Capillary Exchange: Mechanisms
• Direct diffusion across plasma
membranes
• Endocytosis or exocytosis
• Some capillaries have gaps
(intercellular clefts)
– Plasma membrane not joined by tight
junctions
• Fenestrations of some capillaries
– Fenestrations = pores
The Cardiovascular System
•Three Major Elements –
Heart, Blood Vessels, &
Blood
–1. The Heart- cardiac
muscle tissue
–highly interconnected cells
–four chambers
•Right atrium
•Right ventricle
•Left atrium
•Left ventricle
Pathway of the
blood
•Superior Vena Cava
•Right Atrium
•Tricuspid Valve
•Right Ventricle
•Pulmonary Semilunar Valve
•Lungs
•Pulmonary Vein
•Bicuspid Valve
•Left Ventricle
•Aortic Semilunar Valve
•Aorta
•To the bodies organs & cells
Circuits
•Pulmonary circuit
–The blood pathway
between the right side of
the heart, to the lungs, and
back to the left side of the
heart.
•Systemic circuit
–The pathway between
the left and right sides of
the heart.
The Cardiovascular System
2. Blood Vessels -A network of tubes
–Arteriesarterioles move away from the heart
•Elastic Fibers
•Circular Smooth Muscle
–Capillaries – where gas exchange takes place.
•One cell thick
•Serves the Respiratory System
–VeinsVenules moves towards the heart
•Skeletal Muscles contract to force blood back from legs
•One way values
•When they break - varicose veins form
Disorders of the Circulatory System
• Anemia - lack of iron in the blood, low RBC count
• Leukemia - white blood cells proliferate wildly, causing
anemia
• Hemophilia - bleeder’s disease, due to lack of fibrinogen in
thrombocytes
• Heart Murmur - abnormal heart beat, caused by valve
problems
• Heart attack - blood vessels around the heart become
blocked with plaque, also called myocardial infarction
Unit 11B – The Heart
The Heart In Greater Depth
Functions of the Heart
• Generating blood pressure
• Routing blood
– Heart separates pulmonary and
systemic circulations
Functions of the Heart
• Ensuring one-way blood flow
– Heart valves ensure one-way
flow
• Regulating blood supply
– Changes in contraction rate and
force match blood delivery to
changing metabolic needs
Size, Shape, Location
of the Heart
•Size of a closed fist
•Shape
–Apex: Blunt
rounded point of
cone
–Base: Flat part at
opposite of end of
cone
•Located in thoracic
cavity in mediastinum
Heart Cross Section
Pericardium
Heart Wall
• Three layers of tissue
– Epicardium: This serous membrane of
smooth outer surface of heart
– Myocardium: Middle layer composed
of cardiac muscle cell and
responsibility for heart contracting
– Endocardium: Smooth inner surface of
heart chambers
Heart Wall
External Anatomy
•Four chambers
–2 atria
–2 ventricles
•Auricles
•Major veins
–Superior vena
cava
–Pulmonary veins
•Major arteries
–Aorta
–Pulmonary trunk
External Anatomy
Coronary Circulation
Heart Valves
•Atrioventricular
–Tricuspid
–Bicuspid or
mitral
•Semilunar
–Aortic
–Pulmonary
•Prevent blood
from flowing back
Heart Valves
Function of the Heart Valves
Blood Flow Through Heart
Systemic and Pulmonary
Circulation
Heart Skeleton
•Consists of plate
of fibrous
connective tissue
between atria and
ventricles
•Fibrous rings
around valves to
support
Heart Skeleton
•Serves as electrical
insulation between
atria and ventricles
•Provides site for
muscle attachment
Cardiac Muscle
• Elongated,
branching cells
containing 1-2
centrally located
nuclei
• Contains actin and
myosin
myofilaments
Cardiac Muscle
• Intercalated
disks: Specialized
cell-cell contacts
• Desmosomes
hold cells
together and gap
junctions allow
action potentials
Cardiac Muscle
• Electrically,
cardiac muscle
behaves as single
unit
Conducting System of Heart
Electrical Properties
• Resting membrane potential (RMP)
present
• Action potentials
– Rapid depolarization followed by rapid,
partial early repolarization. Prolonged
period of slow repolarization which is
plateau phase and a rapid final
repolarization phase
– Voltage-gated channels
Action Potentials in
Skeletal and Cardiac Muscle
SA Node Action Potential
Refractory Period
• Absolute: Cardiac muscle cell completely
insensitive to further stimulation
• Relative: Cell exhibits reduced sensitivity
to additional stimulation
• Long refractory period prevents tetanic
contractions
Electrocardiogram
• Action potentials
through
myocardium
during cardiac
cycle produces
electric currents
than can be
measured
Electrocardiogram
• Pattern
– P wave
• Atria
depolarization
Electrocardiogram
• Pattern
– QRS complex
• Ventricle
depolarization
• Atria
repolarization
Electrocardiogram
• Pattern
– T wave:
• Ventricle
repolarization
Cardiac Arrhythmias
• Tachycardia: Heart rate in excess of
100bpm
• Bradycardia: Heart rate less than 60
bpm
• Sinus arrhythmia: Heart rate varies
5% during respiratory cycle and up to
30% during deep respiration
• people
Cardiac Arrhythmias
• Premature atrial contractions:
Occasional shortened intervals
between one contraction and
succeeding, frequently occurs in
healthy people
Alterations in
Electrocardiogram
Cardiac Cycle
• Heart is two pumps that work together,
right and left half
• Repetitive contraction (systole) and
relaxation (diastole) of heart chambers
• Blood moves through circulatory system
from areas of higher to lower pressure.
– Contraction of heart produces the
pressure
Cardiac Cycle
Events during Cardiac Cycle
Heart Sounds
• First heart sound or “lubb”
– Atrioventricular valves and
surrounding fluid vibrations as
valves close at beginning of
ventricular systole
Heart Sounds
Second heart sound or “dupp”
– Results from closure of aortic and
pulmonary semilunar valves at
beginning of ventricular diastole,
lasts longer
Heart Sounds
• Third heart sound (occasional)
– Caused by turbulent blood flow
into ventricles and detected near
end of first one-third of diastole
Location of Heart Valves
Regulation of the Heart
• Intrinsic regulation: Results from
normal functional
characteristics, not on neural or
hormonal regulation
– Starling’s law of the heart
• Extrinsic regulation: Involves
neural and hormonal control
Regulation of the Heart
– Parasympathetic stimulation
•Supplied by vagus nerve,
decreases heart rate,
acetylcholine secreted
– Sympathetic stimulation
•Supplied by cardiac nerves,
increases heart rate and
force of contraction,
epinephrine and
Heart Homeostasis
• Effect of blood pressure
– Baroreceptors monitor blood
pressure
• Effect of pH, carbon dioxide, oxygen
– Chemoreceptors monitor
Heart Homeostasis
• Effect of extracellular ion concentration
– Increase or decrease in extracellular
K+ decreases heart rate
• Effect of body temperature
– Heart rate increases when body
temperature increases, heart rate
decreases when body temperature
decreases
Effects of Aging on the Heart
• Gradual changes in heart
function, minor under resting
condition, more significant
during exercise
• Hypertrophy of left ventricle
• Maximum heart rate decreases
Effects of Aging on the Heart
• Increased tendency for valves to
function abnormally and
arrhythmias to occur
• Increased oxygen consumption
required to pump same amount
of blood
Developmental Aspects of the
Cardiovascular System
• A simple “tube heart” develops in the
embryo and pumps by the fourth week
• The heart becomes a four-chambered
organ by the end of seven weeks
• Few structural changes occur after the
seventh week
The Closed Circulatory System
•Humans have a closed circulatory system, typical
of all vertebrates, in which blood is confined to
vessels and is distinct from the interstitial fluid.
–The heart pumps blood into large vessels
that branch into smaller ones leading into the
organs.
–Materials are exchanged by diffusion between the
blood and the interstitial fluid bathing the cells.