Download The Cardiovascular System

The Cardiovascular
System
The Cardiovascular System
 A closed system of the heart and blood
vessels
 The function of the cardiovascular
system is to deliver oxygen and
nutrients and to remove carbon dioxide
and other waste products
 Extensive some 60,000 miles worth.
 Due to diffusion!
The Heart
 Location
 Thorax between the lungs
 Pointed apex directed toward left hip
 lies upon diaphragm
 About the size of your fist
 Average Size of Heart
 14 cm long
 9 cm wide
The Heart
Pericardium
• Superficial fibrous pericardium
• Protects, anchors, and prevents overfilling
• Deep two-layered serous pericardium
– Parietal layer lines the internal surface of the
fibrous pericardium
– Visceral layer (epicardium) on external surface of
the heart
– Separated by fluid-filled pericardial cavity
(decreases friction)
The Heart: Heart Wall
 Three layers
 Epicardium
 Myocardium
 Endocardium
The Heart: Chambers
 Right and left side act as separate pumps
 Four chambers
 Atria- Receiving chambers
 Separated internally by the interatrial septum
 Coronary sulcus (atrioventricular groove)
encircles the junction of the atria and ventricles
 Ventricles- Discharging chambers
 Separated by the interventricular septum
Brachiocephalic trunk
Superior vena cava
Right pulmonary
artery
Ascending aorta
Pulmonary trunk
Right pulmonary
veins
Right atrium
Right coronary artery
(in coronary sulcus)
Anterior cardiac vein
Right ventricle
Right marginal artery
Small cardiac vein
Inferior vena cava
(b) Anterior view
Left common carotid
artery
Left subclavian artery
Aortic arch
Ligamentum arteriosum
Left pulmonary artery
Left pulmonary veins
Auricle of
left atrium
Circumflex artery
Left coronary artery
(in coronary sulcus)
Left ventricle
Great cardiac vein
Anterior interventricular
artery (in anterior
interventricular sulcus)
Apex
Figure 18.4b
Aorta
Superior vena cava
Right pulmonary
artery
Pulmonary trunk
Right atrium
Right pulmonary
veins
Fossa ovalis
Pectinate muscles
Tricuspid valve
Right ventricle
Chordae tendineae
Trabeculae carneae
Inferior vena cava
Left pulmonary
artery
Left atrium
Left pulmonary
veins
Mitral (bicuspid)
valve
Aortic valve
Pulmonary valve
Left ventricle
Papillary muscle
Interventricular
septum
Epicardium
Myocardium
Endocardium
(e) Frontal section
Figure 18.4e
Blood Flow
• The heart is two side-by-side pumps
– Right side is the pump for the pulmonary
circuit
• Vessels that carry blood to and from the
lungs
• Very thin myocardium?
– Left side is the pump for the systemic circuit
• Vessels that carry the blood to and from all
body tissues
• Very thick myocardium
Pulmonary
Circuit
Pulmonary arteries
Venae cavae
Capillary beds
of lungs where
gas exchange
occurs
Pulmonary veins
Aorta and branches
Left atrium
Left ventricle
Right atrium
Right ventricle
Oxygen-rich,
CO2-poor blood
Oxygen-poor,
CO2-rich blood
Heart
Systemic
Circuit
Capillary beds of all
body tissues where
gas exchange occurs
Figure 18.5
Left
ventricle
Right
ventricle
Interventricular
septum
Figure 18.6
Blood Circulation
Path of Blood Flow
Coronary Circulation
• Arteries
– Right and left coronary (in atrioventricular
groove), marginal, circumflex, and anterior
interventricular arteries
• Veins
– Small cardiac, anterior cardiac, and great
cardiac veins
Superior
vena cava
Anastomosis
(junction of
vessels)
Right
atrium
Aorta
Pulmonary
trunk
Left atrium
Left
coronary
artery
Circumflex
artery
Right
coronary
Left
artery
ventricle
Right
ventricle
Anterior
Right
interventricular
marginal Posterior
artery
artery
interventricular
artery
(a) The major coronary arteries
Figure 18.7a
Superior
vena cava
Anterior
cardiac
veins
Great
cardiac
vein
Coronary
sinus
Small cardiac vein
Middle cardiac vein
(b) The major cardiac veins
Figure 18.7b
The Heart: Valves
 Allow blood to flow in only one direction
 Four valves
 Atrioventricular valves –
 Bicuspid valve (left)- mitral valve
 Tricuspid valve (right)
 Chordae tendineae
 Semilunar valves between ventricle and
artery
 Pulmonary semilunar valve- right ventricle
 Aortic semilunar valve- left ventricle
Pulmonary
valve
Aortic
valve
Area of
cutaway
Mitral
valve
Tricuspid
valve
Chordae tendineae
attached to tricuspid valve flap
(c)
Papillary
muscle
Figure 18.8c
Operation of Heart Valves
The Heart: Associated Great
Vessels
 Aorta
 Pulmonary arteries
 Vena cava
 Pulmonary veins (four)
The Heart: Conduction System
 Intrinsic conduction system
(nodal system)
 1% of cardiac cells are self excitable
 Heart muscle cells contract, without nerve impulses,
in a regular, continuous way
 However, these cells are synchronized by the
sinoatrial (SA) node, or pacemaker,
 located in the wall of the right atrium.
The Heart: Conduction System
 Sinoatrial node- Pacemaker
 75 bpm
 Atrioventricular node
 50 bpm
 Atrioventricular bundle
 Bundle branches
 Purkinje fibers
 30 BPM
Superior vena cava
Right atrium
1 The sinoatrial (SA)
node (pacemaker)
generates impulses.
Internodal pathway
2 The impulses
pause (0.1 s) at the
atrioventricular
(AV) node.
3 The atrioventricular
(AV) bundle
connects the atria
to the ventricles.
4 The bundle branches
conduct the impulses
through the
interventricular septum.
5 The Purkinje fibers
Left atrium
Purkinje
fibers
Interventricular
septum
depolarize the contractile
cells of both ventricles.
(a) Anatomy of the intrinsic conduction system showing the
sequence of electrical excitation
Figure 18.14a
Control
• While the SA node sets the tempo for the entire
heart, it is influenced by a variety of
physiological cues.
– Two sets of nerves affect heart rate with one set
speeding up the pacemaker and the other set
slowing it down.
– The pacemaker is also influenced by hormones.
• For example, epinephrine from the adrenal glands
increases heart rate.
– The rate of impulse increases in response to
increases in body temperature and with exercise.
The vagus nerve
(parasympathetic)
decreases heart rate.
Dorsal motor nucleus of vagus
Cardioinhibitory center
Medulla oblongata
Cardioacceleratory
center
Sympathetic trunk ganglion
Thoracic spinal cord
Sympathetic trunk
Sympathetic cardiac
nerves increase heart rate
and force of contraction.
AV node
SA node
Parasympathetic fibers
Sympathetic fibers
Interneurons
Figure 18.15
The Heart: Cardiac Cycle
 Atria contract simultaneously
 Atria relax, then ventricles contract
 Systole = contraction
 Diastole = relaxation
The Heart: Cardiac Output
 Cardiac output (CO)
 CO = (heart rate [HR]) x (stroke volume [SV])
 5.25 L/min up to 35 L/min
 Stroke volume
 The average stroke volume for a human is
about 75 mL
 Heart Rate
 Varies but at rest is 70 bpm
Cardiac Output Regulation
The Heart: Regulation of Heart
Rate
 Starling’s law of the heart – more stretch =
stronger 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
Electrocardiogram
• recording of electrical changes that occur in the
myocardium:
• P wave – atrial depolarizatoin
• QRS wave – ventricular depolarization
• T wave – ventricular repolarization
QRS complex
Sinoatrial
node
Atrial
depolarization
Ventricular
depolarization
Ventricular
repolarization
Atrioventricular
node
P-Q
Interval
S-T
Segment
Q-T
Interval
Figure 18.16
SA node
Depolarization
R
Repolarization
R
T
P
S
1 Atrial depolarization, initiated
by the SA node, causes the
P wave.
R
AV node
T
P
Q
Q
S
4 Ventricular depolarization
is complete.
R
T
P
T
P
Q
S
2 With atrial depolarization
complete, the impulse is
delayed at the AV node.
R
Q
S
5 Ventricular repolarization
begins at apex, causing the
T wave.
R
T
P
T
P
Q
S
3 Ventricular depolarization
begins at apex, causing the
QRS complex. Atrial
repolarization occurs.
Q
S
6 Ventricular repolarization
is complete.
Figure 18.17
(a) Normal sinus rhythm.
(b) Junctional rhythm. The SA
node is nonfunctional, P waves
are absent, and heart is paced by
the AV node at 40 - 60 beats/min.
(c) Second-degree heart block. (d) Ventricular fibrillation. These
chaotic, grossly irregular ECG
Some P waves are not conducted
deflections are seen in acute
through the AV node; hence more
heart attack and electrical shock.
P than QRS waves are seen. In
this tracing, the ratio of P waves
to QRS waves is mostly 2:1.
Figure 18.18
Blood Vessels: The Vascular
System
 Arteries
 Arterioles
 Capillaries
 Venules
 Veins
The Vascular System
Blood Vessels: Anatomy
 Three layers (tunics)
 Tunic interna
 Endothelium
 Tunic media
 Smooth muscle
 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
Capillary Beds
Diffusion at Capillary Beds
Major Arteries of Systemic Circulation
Major Veins of Systemic Circulation
Pulse
 Pulse –
pressure wave
of blood
 Monitored at
“pressure
points” where
pulse is easily
palpated
Blood Pressure
 Systolic –ventricular contraction
 Diastolic –ventricles relax
 Pressure in blood vessels decreases as
the distance away from the heart
increases
Measuring Arterial Blood Pressure
Comparison of Blood Pressures in
Different Vessels
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
Variations in Blood Pressure
 Human normal range is variable
 Normal
 140–110 mm Hg systolic
 80–70 mm Hg diastolic
 Hypotension
 (below 110 mm HG)
 Often associated with illness
 Hypertension
 (above 140 mm HG)
 Can be dangerous if it is chronic
Capillary Exchange: Mechanisms
 Direct diffusion across plasma
membranes
 Endocytosis or exocytosis
 Some capillaries have gaps (intercellular
clefts)
 Fenestrations of some capillaries
 Fenestrations = pores
OLD AGE STINKS
•
•
•
•
deposition of cholesterol in blood vessels
heart enlarges
cardiac muscle cells die
fibrous connective tissue of heart
increases
• adipose tissue of heart increases
• blood pressure increases
• resting heart rate decreases