Download Right coronary artery

Ch. 11
THE CARDIOVASCULAR
SYSTEM
Copyright © 2010 Pearson Education, Inc.
Heart Anatomy
• Approximately the size of a fist
• Location
• In the mediastinum; superior to diaphragm
• Leans to the left
• Enclosed in pericardium, a double-walled sac
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Midsternal line
2nd rib
Sternum
Diaphragm
(a)
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Point of
maximal
intensity
(PMI)
Figure 18.1a
Superior
vena cava
Aorta
Parietal
pleura (cut)
Pulmonary
trunk
Left lung
Pericardium
(cut)
Diaphragm
Apex of
heart
(c)
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Figure 18.1c
Pericardium
• Superficial fibrous pericardium
• Protects, anchors, and prevents overfilling
• Deep two-layered serous pericardium
• Parietal layer lines internal surface of fibrous
pericardium
• Visceral layer on external surface of heart
• Separated by fluid-filled pericardial cavity
(decreases friction)
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Pulmonary
trunk
Pericardium
Myocardium
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Fibrous pericardium
Parietal layer of
serous pericardium
Pericardial cavity
Epicardium
(visceral layer Heart
of serous
wall
pericardium)
Myocardium
Endocardium
Heart chamber
Layers of the Heart Wall
1. Epicardium=visceral
layer of serous
pericardium
2. Myocardium
• Cardiac Muscle Tissue
3. Endocardium
• Is continuous
endothelium of blood
vessels
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Chambers
• Four chambers
• Two atria
• Top of heart; receiving
chambers
• Separated by the interatrial
septum
• Two ventricles
• Bottom of heart;
discharging chambers
• Separated by the
interventricular septum
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Major Blood Vessels of the Heart
• Vessels entering right atrium
• Superior vena cava
• Inferior vena cava
• Coronary sinus
• Vessels entering left atrium
• Right and left pulmonary
veins
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Ventricles: The Discharging Chambers
• Vessel leaving the right
ventricle
• Pulmonary trunk
• Vessel leaving the left
ventricle
• Aorta
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Pathway of Blood Through the Heart
• 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
• Left side is the pump for the systemic circuit
• Vessels that carry the blood to and from all
body tissues
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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
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Heart
Systemic
Circuit
Capillary beds of all
body tissues where
gas exchange occurs
Figure 18.5
Pathway of Blood Through the Heart
• Right atrium  tricuspid valve  right
ventricle
• Right ventricle  pulmonary semilunar valve
 pulmonary trunk  pulmonary arteries 
lungs
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Pathway of Blood Through the Heart
• Lungs  pulmonary veins  left atrium
• Left atrium  bicuspid valve  left ventricle
• Left ventricle  aortic semilunar valve 
aorta
• Aorta  systemic circulation
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Coronary Circulation
• Blood supply to the heart muscle itself
• Arteries
• Right and left coronary arteries
• Branch from base of aorta
• Veins
• Cardiac veins empty into coronary sinus
right atrium
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Homeostatic Imbalances
• Angina pectoris
• Thoracic pain caused by a deficiency in blood
delivery to the heart
• Myocardial infarction (heart attack)
• Prolonged coronary blockage
• Areas of cell death are repaired with
noncontractile scar tissue
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Heart Valves
• Ensure unidirectional blood flow through the heart
• Atrioventricular (AV) valves
• Prevent backflow into the atria when ventricles
contract
• Tricuspid valve (right)
• Bicuspid valve/Mitral valve (left)
• Chordae tendineae anchor AV valve cusps to
papillary muscles
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Pulmonary
valve
Aortic
valve
Area of
cutaway
Mitral
valve
Tricuspid
valve
Chordae tendineae
attached to tricuspid valve flap
(c)
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Papillary
muscle
Figure 18.8c
Heart Valves
• Semilunar (SL) valves
• Prevent backflow into the ventricles when
ventricles relax
• Aortic semilunar valve
• Pulmonary semilunar valve
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Opening of inferior
vena cava
Tricuspid valve
Mitral valve
Chordae
tendineae
Myocardium
of right
ventricle
Myocardium
of left ventricle
Papillary
muscles
(d)
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Interventricular
septum
Pulmonary
valve
Aortic valve
Area of
cutaway
Mitral valve
Tricuspid
valve
Figure 18.8d
Microscopic Anatomy of Cardiac Muscle
• Cardiac muscle cells are striated, short,
branched
• Endomysium connects to the fibrous skeleton
• T tubules are wide but less numerous; SR is
simpler than in skeletal muscle
• Numerous large mitochondria
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Nucleus
Intercalated discs
Gap junctions
Cardiac muscle cell
Desmosomes
(a)
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Figure 18.11a
Microscopic Anatomy of Cardiac Muscle
• Intercalated discs: junctions between cells
anchor cardiac cells
• Desmosomes prevent cells from separating
during contraction
• Gap junctions allow ions to pass; electrically
couple adjacent cells
• Heart muscle behaves as a functional
syncytium
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Cardiac
muscle cell
Mitochondrion
Intercalated
disc
Nucleus
T tubule
Mitochondrion
Sarcoplasmic
reticulum
Z disc
Nucleus
Sarcolemma
(b)
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I band
A band
I band
Figure 18.11b
Heart Physiology: Electrical Events
• Intrinsic cardiac conduction system
• Defined: A network of noncontractile
(autorhythmic) cells that initiate and distribute
impulses to coordinate the depolarization and
contraction of the heart
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Autorhythmic Cells
• Spontaneously depolarize
• Do not require neural stimulation
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Heart Physiology: Sequence of Excitation
1. Sinoatrial (SA) node (pacemaker)
• Generates impulses about 75 times/minute
(sinus rhythm)
• Depolarizes faster than any other part of the
myocardium
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Heart Physiology: Sequence of Excitation
2. Atrioventricular (AV) node
•
Delays impulses ~ 0.1 second
•
Depolarizes 50 times/min. in absence of
SA node input
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Heart Physiology: Sequence of Excitation
3. Atrioventricular (AV) bundle (bundle of His)
• Only electrical connection between the atria
and ventricles
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Heart Physiology: Sequence of Excitation
4. Right and left bundle branches
•
Two pathways in the interventricular septum
that carry the impulses toward the apex of
the heart
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Heart Physiology: Sequence of Excitation
5. Purkinje fibers
•
Complete the pathway into the apex and
ventricular walls
•
AV bundle and Purkinje fibers depolarize
only 30 times per minute in absence of AV
node input
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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
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Homeostatic Imbalances
•
Defects in the intrinsic conduction system
may result in
1. Arrhythmias: irregular heart rhythms
2. Fibrillation: rapid, irregular contractions;
useless for pumping blood
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Homeostatic Imbalances
• Defective AV node may result in
• Partial or total heart block
• Few or no impulses from SA node reach the
ventricles
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Extrinsic Innervation of the Heart
• Heartbeat is modified by the ANS
• Cardiac centers are located in the medulla
oblongata
• Cardioacceleratory center innervates: SA and
AV nodes, heart muscle, and coronary arteries
• Cardioinhibitory center inhibits: SA and AV
nodes
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The vagus nerve
(parasympathetic)
decreases heart rate.
Cardioinhibitory center
Medulla oblongata
Cardioacceleratory
center
Sympathetic trunk ganglion
Sympathetic cardiac
nerves increase heart rate
and force of contraction.
AV node
SA node
Parasympathetic fibers
Sympathetic fibers
Interneurons
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Electrocardiography
•
Electrocardiogram (ECG or EKG): a
composite of all the action potentials
generated by nodal and contractile cells at a
given time
•
Three waves
1. P wave: depolarization of SA node
2. QRS complex: ventricular depolarization
3. T wave: ventricular repolarization
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QRS complex
Sinoatrial
node
Atrial
depolarization
Ventricular
depolarization
Ventricular
repolarization
Atrioventricular
node
P-Q
Interval
S-T
Segment
Q-T
Interval
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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.
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Q
S
6 Ventricular repolarization
is complete.
(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.
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Figure 18.18
Mechanical Events: The Cardiac Cycle
• Cardiac cycle: all events associated with
blood flow through the heart during one
complete heartbeat
• Systole—contraction
• Diastole—relaxation
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Cardiac Output (CO)
• Volume of blood pumped by each ventricle in
one minute
• CO = heart rate (HR) x stroke volume (SV)
• HR = number of beats per minute
• SV = volume of blood pumped out by a
ventricle with each beat
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Cardiac Output (CO)
• At rest
• CO (ml/min) = HR (75 beats/min)  SV (70 ml/beat)
= 5.25 L/min
• Maximal CO is 4–5 times resting CO in nonathletic
people
• Maximal CO may reach 35 L/min in trained athletes
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Regulation of Stroke Volume
• SV = EDV – ESV
• Three main factors affect SV
• Preload
• Contractility
• Afterload
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Homeostatic Imbalances
• Tachycardia: abnormally fast heart rate
(>100 bpm)
• If persistent, may lead to fibrillation
• Bradycardia: heart rate slower than 60 bpm
• May result in grossly inadequate blood
circulation
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Congestive Heart Failure (CHF)
• Progressive condition where the CO is so low
that blood circulation is inadequate to meet
tissue needs
• Caused by
• Coronary atherosclerosis
• Persistent high blood pressure
• Multiple myocardial infarcts
• Dilated cardiomyopathy (DCM)
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Developmental Aspects of the Heart
• Fetal heart structures that bypass pulmonary
circulation
• Foramen ovale connects the two atria
• Ductus arteriosus connects the pulmonary
trunk and the aorta
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BLOOD VESSEL PHYSIOLOGY
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Blood Vessels
• Arteries: carry blood away from the heart;
oxygenated except for pulmonary arteries
• Capillaries: contact tissue cells and directly
serve cellular needs
• Veins: carry blood toward the heart
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Venous system
Large veins
(capacitance
vessels)
Small veins
(capacitance
vessels)
Postcapillary
venule
Thoroughfare
channel
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Arterial system
Heart
Large
lymphatic
vessels
Lymph
node
Lymphatic
system
Arteriovenous
anastomosis
Elastic arteries
(conducting
vessels)
Muscular arteries
(distributing
vessels)
Lymphatic
Sinusoid
capillary
Arterioles
(resistance vessels)
Terminal arteriole
Metarteriole
Precapillary sphincter
Capillaries
(exchange vessels)
Structure of Blood Vessel Walls
• Arteries and veins
• Tunica intima – Endothelium that lines the lumen of all vessels
• Tunica media - Smooth muscle and sheets of elastin
• Sympathetic vasomotor nerve fibers control vasoconstriction
and vasodilation of vessels
• Tunica externa - Collagen fibers protect and reinforce
• Lumen
• Central blood-containing space
• Capillaries
• Endothelium with sparse basal lamina; Size allows only a single
RBC to pass at a time
• Functions: exchange of gases, nutrients, wastes, hormones, etc.
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Tunica intima
• Endothelium
Valve
Internal elastic lamina
Tunica media
(smooth muscle and
elastic fibers)
External elastic lamina
Tunica externa
(collagen fibers)
Lumen
Artery
(b)
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Capillary
network
Capillary
Lumen
Vein
Basement membrane
Endothelial cells
Pinocytotic vesicles
Red blood
cell in lumen
Endothelial cell
Endothelial cell nucleus
Basement membrane
Tight junction
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Fenestration
(pore)
Intercellular cleft
Figure 19.16 (1 of 2)
Capillary Exchange of Respiratory Gases
and Nutrients
• Diffusion of
• O2 and nutrients from the blood to tissues
• CO2 and metabolic wastes from tissues to the blood
• Lipid-soluble molecules diffuse directly through
endothelial membranes
• Water-soluble solutes pass through clefts and
fenestrations
• Larger molecules are actively transported in
pinocytotic vesicles etc.
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Lumen
Intercellular
cleft
Caveolae
Pinocytotic
vesicles
Endothelial
fenestration
(pore)
4 Transport
via vesicles or
caveolae (large
substances)
3 Movement
Basement through
membrane fenestrations
1 Diffusion
through
membrane
(lipid-soluble
substances)
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2 Movement
through intercellular
clefts (water-soluble
substances)
(water-soluble
substances)
Hydrostatic Pressures
• Capillary hydrostatic pressure (HPc) (capillary
blood pressure)
• Tends to force fluids through (out of) capillary
walls
• Is greater at arterial end (35 mm Hg) than
venous end (17 mm Hg)
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Colloid Osmotic Pressures
• Capillary oncotic pressure (OPc)
• Created by nondiffusible plasma proteins,
which draw water toward themselves
• ~26 mm Hg
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Net Filtration Pressure (NFP)
• NFP = (HPc—Opc)
• At arterial end = hydrostatic forces dominate
• At venous end =osmotic forces dominate
• Excess fluid is returned to blood (lymphatic
system)
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Arteriole
Venule
Interstitial fluid
Capillary
Net HP—Net OP
(35
– 25 = 10
Net
HP
35
mm
Net
OP
25
mm
NFP (net filtration pressure)
is 10 mm Hg; fluid moves out
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HP = hydrostatic pressure
• Due to fluid pressing against a wall
• “Pushes”
• In capillary (HPc)
• Pushes fluid out of capillary
• 35 mm Hg at arterial end and
17 mm Hg at venous end of
capillary in this example
Net HP—Net OP
(17 -25 = -8)
Net
HP
17
mm
Net
OP
25
mm
NFP is ~8 mm Hg;
fluid moves in
OP = osmotic pressure
• Due to presence of nondiffusible
solutes (e.g., plasma proteins)
• “Sucks”
• In capillary (OPc)
• Pulls fluid into capillary
• 26 mm Hg in this example
BLOOD VESSEL PHYSIOLOGY
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Arteries of the head and trunk
Common carotid arteries
Subclavian artery
Brachiocephalic trunk
Aortic arch
Ascending aorta
Thoracic aorta (above
diaphragm)
Celiac trunk
Abdominal aorta
Superior mesenteric artery
Renal artery
Gonadal artery
Common iliac artery
Inferior mesenteric artery
Internal iliac artery
(b) Illustration, anterior
view
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Arteries that supply
the upper limb
Subclavian artery
Axillary artery
Brachial artery
Radial artery
Ulnar artery
Deep palmar arch
Superficial palmar arch
Digital arteries
Arteries that supply
the lower limb
External iliac artery
Femoral artery
Popliteal artery
Anterior tibial artery
Posterior tibial artery
Figure 19.21b
Anterior
Cerebral arterial
circle
(circle of Willis)
• Anterior
communicating
artery
• Anterior
cerebral artery
• Posterior
communicating
artery
• Posterior
cerebral artery
Basilar artery
Middle
cerebral
artery
Internal
carotid
artery
Vertebral artery
Posterior
(d) Major arteries serving the brain (inferior view, right side
of cerebellum and part of right temporal lobe removed)
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Vertebral artery
Common carotid
arteries
Left subclavian artery
Right subclavian artery
Brachiocephalic trunk
Axillary artery
Descending aorta
Brachial artery
Radial artery
Ulnar artery
Deep palmar arch
Superficial palmar arch
Digital arteries
Anterior view
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Liver (cut)
Inferior vena cava
Diaphragm
Esophagus
Celiac trunk
Common hepatic
artery
Hepatic artery
proper
Gastroduodenal
artery
Right gastric artery
Gallbladder
Left gastric
artery
Stomach
Splenic artery
Pancreas
(major portion lies
posterior to stomach)
Right
gastroepiploic
artery
Superior
mesenteric
mesenteric
Duodenum
Abdominal aorta
Left
gastroepiploic
artery
Spleen
(b) The celiac trunk and its major branches. The left half of the liver has been removed.
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Figure 19.24b
Diaphragm
Inferior
phrenic artery
Adrenal
(suprarenal)
gland
Renal artery
Kidney
Superior
mesenteric
artery
Celiac trunk
Abdominal aorta
Lumbar arteries
Gonadal
(testicular or
ovarian) artery
Inferior
mesenteric
artery
Common
iliac artery
(c) Major branches of the abdominal aorta.
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Figure 19.24c
Common iliac artery
Internal iliac artery
External iliac artery
Femoral artery
Popliteal artery
Anterior tibial artery
Posterior tibial artery
Fibular artery
(b) Anterior view
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Figure 19.25b
Popliteal artery
Anterior tibial artery
Posterior tibial
artery
Lateral plantar
artery
Medial plantar
artery
(c) Posterior view
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Fibular artery
Plantar arch
Veins of the head and trunk
Veins that drain
the upper limb
External jugular vein
Subclavian vein
Axillary vein
Internal jugular vein
Right and left
brachiocephalic veins
Superior vena cava
Brachial vein
Ulnar vein
Radial vein
Digital veins
Veins that drain
the lower limb
External iliac vein
Inferior vena cava
Femoral vein
Common iliac vein
Popliteal vein
Internal iliac vein
Posterior tibial vein
Anterior tibial vein
(b) Illustration, anterior
view. The vessels of the
pulmonary circulation
are not shown.
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Inferior vena cava
(not part of hepatic
portal system)
Hepatic veins
Liver
Hepatic portal
vein
Small intestine
Gastric veins
Spleen
Inferior vena cava
Splenic vein
Inferior
mesenteric vein
Superior
mesenteric vein
Large intestine
Rectum
(c) The hepatic portal circulation.
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Cystic vein
Hepatic
portal
system
Inferior
vena cava
Inferior phrenic veins
Hepatic veins
Hepatic portal vein
Superior mesenteric vein
Splenic vein
Suprarenal
veins
Renal veins
Inferior
mesenteric
vein
Gonadal veins
Lumbar veins
R. ascending
lumbar vein
L. ascending
lumbar vein
Common iliac veins
External iliac vein
(a) Schematic flowchart.
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Internal iliac veins
Figure 19.29a
Common iliac vein
Internal iliac vein
External iliac vein
Inguinal ligament
Femoral vein
Great saphenous
vein (superficial)
Popliteal vein
Small saphenous
vein
Fibular vein
Anterior tibial vein
Dorsalis pedis vein
Dorsal venous arch
Dorsal metatarsal
veins
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(b) Anterior view
Figure 19.30b
Great saphenous
vein
Popliteal vein
Anterior tibial vein
Fibular vein
Small saphenous
vein (superficial)
Posterior tibial vein
Plantar veins
Deep plantar arch
(c) Posterior view
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Digital veins
Figure 19.30c
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
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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