chapter 15
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Anatomy ∙ Physiology II
Chapter 15, Section 1
The Cardiovascular System
FUNCTIONS OF THE HEART
It pumps 7000L (1800 gallons) of blood through our body every day.
The heart contracts 2.5 billion times in a lifetime.
The heart is composed of two pumps
The pulmonary circuit carries
blood to the lungs
The systemic circuit carries
blood to the body
The heart is located within the mediastinum
1/3 2/3
It is about the size of a fist (14cm x 9cm)
2/3 of the heart is left of the midline
The heart is posterior to the sternum
Base
attachment of major vessels
2nd intercostal space
Apex
Pointed inferior margin
5th intercostal space
The heart is surrounded by a pericardial membrane.
The fibrous pericardium forms a thick outer layer
of connective tissue.
The parietal pericardium is a serous membrane
attached directly to the fibrous layer.
A visceral pericardium is a serous membrane that
forms the outer layer of the heart wall.
The pericardial cavity contains serous fluid.
The wall of the heart contains 3 layers
The epicardium is also called the visceral pericardium
The myocardium contains a thick layer of cardiac muscle,
with blood vessels and nerves
The endocardium is a smooth layer of squamous epithelium
that lines the heart chambers and valves
The heart contains 4 chambers
The left atrium receives
blood from the lungsThe right atrium receives
blood from the body
The left ventricle pumps
blood towards the body
The right ventricle pumps
blood towards the lungs
Interventricular septum
A pocket, called the auricle
increases the capacity of the atria.
blood enters the heart through the great veins
The superior vena cava
returns blood from the
upper body to the heart
The inferior vena cava
returns blood from the
lower body to the heart
The coronary sinus
returns blood from the
myocardium to the heart
Four pulmonary veins
return blood from the
lungs to the heart
Great arteries carry blood away from the heart
The aorta delivers oxygenated
blood to the systemic circulation
The pulmonary trunk* delivers
deoxygenated blood to the lungs
* The pulmonary trunk immediately divides
into a left and right pulmonary artery.
AV valves prevent backflow into the atria.
The tricuspid valve
guards the right AV
orifice
The bicuspid (mitral)
valve guards the left
AV orifice
*AV = atrioventricular
Chordae tendineae anchored to the
cusps papillary muscles
Papillary muscles contract to pull the
valves tightly shut
AV valves are anchored to the ventricles by chordae tendineae
Mitral Valve Prolapse – cusp of the mitral valve protrudes into atrium.
Symptoms include: chest pain, heart palpitations, and fatigue.
An aortic valve (not shown) is
located at the base of the aorta
Semilunar valves prevent backflow of blood into the ventricles
A pulmonary valve is located at
the base of the pulmonary trunk
Each cusp of a semilunar valve is
shaped like a crescent moon
path of blood through the right heart
1. Blood enters right atrium through the
SVC, IVC, and coronary sinus
2. It passes through the tricuspid valve
into the right ventricle
3. Blood is pumped from the right
ventricle, through the pulmonary valve,
and into the pulmonary trunk.
4. Blood passes into the pulmonary
arteries towards the lungs
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path of blood through the left heart
5. Oxygenated blood is returned to
the heart through 4 pulmonary veins.
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9. Blood enters systemic circulation to
the tissues throughout the body.
6. Blood enters the left atrium.
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7. Blood passes through the bicuspid
valve into the left ventricle.
8. The left ventricle pumps blood
through the aortic valve into the aorta.
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Section 2, Chapter 15
Cardiac Cycle & Cardiac Conduction
Systole – contraction
Diastole – relaxation
Ventricular Diastole
• Ventricles are relaxed, filling with blood
• Ventricles are 70% full before atria contract
• Atrial systole pushes the remaining 30% of blood into ventricles
• AV valves are opened while semilunar valves are closed
Ventricular Systole
• Ventricles contract to expel blood
• Atria are in diastole during ventricular systole, filling with blood
• Semilunar valves are opened, while AV valves are closed
The left and right sides of the heart contract
together in a coordinated fashion
The cardiac cycle
Heart Sounds
The heart valves produce a distinct sound as they close, which
can be heard through a stethoscope.
Lubb-DuppLubb (S1) = sound of AV valves closing
occurs during ventricular systole
Dupp (S2) = sound of semilunar valve closingoccurs during ventricular diastole
murmur = abnormal sound from the cusps not closing completely
Heart Sounds - Ausculation
Image from Grant’s Atlas of Anatomy. Each heart valve is indicated by a colored oval and the area of auscultation of the valve is indicated as a circle of the same color containing the first letter of the valve name.
aortic valve (A)
heard at 2nd intercostal space,
right of the sternum
pulmonary valve (P)
heard at 2nd intercostal space,
left of the sternum
tricuspid valve (T)
heard at 5th intercostal space,
either right or left of the sternum
mitral valve (M)
heard at 5th intercostal space,
below left nipple
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Cardiac Conduction of the Heart
The heart is autorhythmic:Specialized cardiac tissue initiate and distribute electrical impulses that generate heart contractions.
Syncytium – intercalated discs contain gap junctions that transmit action potentials from cell-to-cell. Cardiac muscles contract as a functional unit (syncytium)
Atrial Syncytium – left and right atria contract together
Ventricular Syncytium – left and right ventricles contract together
Cardiac Conduction of the Heart
Pacemaker of heart
Initiates atrial syncytium
Fires 80 impulses per minute
Parasympathetic inhibition keeps heart rate at about 72 beats per minute
conduct impulses towards towards AV node
Figure 15.18 Illustrates the cardiac conduction system.
sinoatrial (SA) node
junctional fibers
Cardiac Conduction of the Heart
Located within inferior wall of interatrial septum
Provides a junction between atrial and ventricular syncytia
Only known conduction pathway between atria and ventricles
divides into left and right bundle branches
Figure 15.18 Illustrates the cardiac conduction system.
atrioventricular (AV) node
AV Bundle (Bundle of His)
Cardiac Conduction of the Heart
Conduction pathways along the
interventricular septum
Gives rise to Purkinje Fibers
Transmits action potentials to
ventricular myocardium and papillary
muscles
Initiates ventricular syncytium at apex
of heart
bundle branches (left and right)
purkinje fibers
Figure 15.19 Summarizes the cardiac conduction system
Figure 15.20 Muscle fibers of the ventricles are
whorled shape, which increases the blood output
during ventricular systole.
End of Section 2, Chapter 15
An electrocardiogram, or ECG (or EKG) is a recording of the
electrical changes in the myocardium during the cardiac cycle.
Electrocardiogram
section 3, chapter 15
atrial depolarization that initiates atrial contraction
conduction of electrical impulse across atria from right to left and downward
Ventricular depolarization that initiates contraction of the ventricles
This massive wave hides the atria repolarization
Electrocardiogram
P Wave
QRS Complex
T Waverepresents repolarization of ventricles
Electrocardiogram
Normal ECG pattern
ECG of a regular heart rhythm at 75 beats per minute
Atrial Flutter. Atria fire 250-350 times per minute. For every QRS complex there may be 4 or more P waves.
Heart Arrhythmias:
normal
Bradycardia – cardiac rhythm less than 60 beats per minute.
Tachycardia– cardiac rhythm greater than 100 beats per minute.
Examples of Heart Arrhythmias. Arrows indicate p Wave.
Atrial fibrillation. Instead of contracting, the atria become quivering chambers. The ventricles respond only to impulses that make it to the AV node.
Ventricular fibrillation = Life threatening arrhythmia. Ventricles quiver, and are unable to pump blood properly. Requires immediate defibrillation.
Examples of Heart Arrhythmias, fibrillation
The heart rate is controlled intrinsically by the SA node, but
sympathetic and parasympathetic fibers alter the rate at which
the pacemaker fires.
regulation of cardiac cycle
Cardiac Control Center
Located within Medulla Oblongata
Receives sensory impulses from throughout the cardiovascular system and relays motor impulses to heart in response.
The cardiac control centers include a Cardioinhibitor & cardioaccelerator reflex center
Cardioinhibitor reflex center
Parasympathetic fibers from vagus nerves innervate SA &
AV nodes.
Vagus nerves release Acetylcholine (ACh) that decreases
the firing rates of SA & AV nodes.
Heart rate decreases
Cardioaccelerator reflex center
Sympathetic fibers from accelerator nerves innervate SA & AV nodes.
Norepinephrine released from fibers increases the firing rates of SA &
AV nodes.
Heart rate and force of contraction increases
Cardioinhibitor & cardioaccelerator reflex centers alter the heart rate in response to sensory impulses from receptors
Baroreceptors – monitor blood pressure•Located within aortic arch and carotid sinuses
•Rising blood pressure stimulates cardioinhibitor center
`
Figure 15.24b Illustration of the baroreflex arc
End of Section 3, Chapter 15
Section 4, Chapter 15
Blood Vessels
Arteries
• Convey blood away from the heart
Arterioles
• Thinner vessels that convey blood towards capillaries
Capillaries
• Site of exchange between blood and body tissues
Venules
• Receives blood from capillaries
Veins
• Returns blood towards the heart
Endothelium
•A layer of smooth simple squamous
epithelium
•Secretes biochemicals with a wide
variety of functions.
Basement membrane
•Bed of connective tissue with elastic &
collagenous fibers
Tunica Interna (inner)
Walls of the blood vessels consists of 3 Layers
Tunica Media (middle)
Smooth Muscles
•Vasoconstriction – muscles contract,
decreasing diameter of vessel
•Vasodilation – muscles relax, allowing vessel
diameter to increase
Elastic Connective tissue
•Recoil of elastic fibers helps propel
blood through vessels
3 Layers of the blood vessel wall
Tunica Externa (outer)
Fibrous Connective Tissue
Elastic and collagenous fibers
Attaches blood vessel to organs
Vasa Vasorum “vessels of the vessels”
Provide blood supply to walls of thicker arteries
3 Layers of the blood vessel wall
Figure 15.27An arteriovenous shunt
provided by a metarteriole.
Arterioles are smaller divisions of arteries.
metarterioles – small arterioles that join capillaries
Arteriovenous shunt – connects an arteriole directly to a venule
Shunt allows blood to bypass a capillary bed.
Arterioles
Figure 15.28 Substances are exchanged through openings (slits) separating endothelial cells.
Capillaries
smallest diameter blood vessels that
consists of a single layer of endothelial cells
Site of gas, nutrient, and waste exchange
Capillaries
Slits
Spaces between endothelia
that facilitate diffusion across
vessel wall
Figure 15.26 A precapillary sphincter at the base of a capillary.
Capillaries
Precapillary sphincters
Smooth muscles that regulate the flow
of blood through a capillary
Closes a capillary bed when oxygen
demand to an organ is low
Artificially colored electron micrograph depicts sinusoids throughout the liver.
Capillaries
large cavities within discontinuous capillaries
Sinusoids allow a rapid exchange of nutrients,
debris, proteins, and even cells.
located throughout the liver and spleen.
Sinusoids
Venules
Continue from capillaries and merge to form veins
Veins
Convey blood from body back to the atria of heart
Veins follow a pathway roughly parallel to arteries
Vessel wall of veins has 3 layers (tunics) similar to arteries
Figure 15.31. Venous valves (a) open as blood moves towards the heart, but (b) close to prevent blood from moving backward away from the
heart.
Veins have poorly developed tunica mediaThinner walls, and a larger lumen than arteries
Tunica Interna of veins contain valvesValves prevent blood from flowing backwards towards capillaries.
Veins act as blood reservoirsMost blood (60-70%) is in the veins and venules.
Differences between veins and arteries
Figure 15.25 Blood vessels (a) the wall of an artery. (b) The wall of a vein. (c) cross section
of an arteriole (bottom) and a venule (top).
Differences between
veins and arteries
End of Section 4, Chapter 15
Blood Pressure
Section 5, Chapter 15
Blood Pressure
Blood pressure is the force the blood exerts against
the inner walls of the blood vessels
Usually refers to pressure in systemic arteries
Arterial blood pressure:
Rises with ventricular contractions and falls as
ventricles relax
Systolic pressure is the maximum pressure during
ventricular contraction
Diastolic pressure is the minimum pressure when
the ventricles relax
.1Cardiac Output- volume of blood ejected from one ventricle per minute
Volume of blood expelled from ventricle with each contraction
Average = 70 milliliters per beat (mL/beat) for adult male
Average = 72 beats per minute
Stroke Volume
70 mL/beat X
Heart Rate
70 beats/minute =
Cardiac Output
5040mL/minuteexample:
Factors that influence blood pressure
cardiac output = stroke volume (mL) X heart rate (beats/minute)
Stroke Volume
Heart Rate
Cardiac output (and blood pressure) increases with an increase in stroke volume or heart rate.
Factors that influence blood pressure
blood pressure increases
heart rate increases stroke volume increasesor
Blood Volume
Average blood volume in adults = 5 Liters (1.3 gallons)
As blood volume increases, blood pressure initially increases
Peripheral Resistance
Peripheral resistance = friction between blood and blood vessels
Vasoconstriction increases resistance and increases blood pressure
Vasodilation decreases blood pressure
Viscosity of blood
Viscosity = resistance of a fluid to flow (thickness of a fluid).
Blood cells and some plasma proteins increase the viscosity of blood.
Anemia (deficiency of red blood cells) reduces viscosity & lowers blood
pressure
Factors that influence blood pressure
Some of the factors that influence arterial blood pressure
Factors that influence blood pressure
blood volume increases heart rate increases stroke volume increases
blood viscosity increasesperipheral resistance
increases
blood pressure increases
blood pressure is maintained
Increased blood pressure
heart rate decreases stroke volume decreases
cardiac output decreases peripheral resistance decreases
cardiac output increasesperipheral resistance increases
heart rate increases stroke volume increases
decreased blood pressure
Control of Blood Pressure
Factors that affect stroke volume
End-diastolic volume (EDV)
Volume of blood in ventricles at the end of ventricular diastole
Ventricles are filled with blood
End-systolic volume (ESV)
Volume of blood in ventricles at the end of ventricular systole
Only 60% of blood is expelled from heart during a normal
contraction
Increasing the force of ventricular contractions decreases ESV
Stroke volume = EDV– ESV
Increase stroke volume by increasing EDV or decreasing ESV
stroke volume
Stroke Volume is directly related to the force of ventricular contraction.
Two events that occur in the ventricles coincide with stroke volume:
1. End-diastolic volume (EDV)
Volume of blood in ventricles at the end of ventricular diastole
As ventricles fill with blood, muscle fibers are mechanically
stretched - preload
2. End-systolic volume (ESV)
Volume of blood in ventricles at the end of ventricular systole
A normal health heart expels 60% of blood present in ventricle.
stroke volume
Stroke Volume is the difference between end diastolic
volume (EDV) and end systolic volume (ESV): Stroke Volume = EDV - ESV
Frank-Starling Principle:
The ability of a heart muscle to generate force depends
on the original stretch of a muscle prior to contraction
(similar to stretching a rubber band)
The degree of stretch (preload) of the myocardial fibers
before contraction determines the stroke volume
A greater end diastolic volume results in a greater force of
contraction, leading to a greater stroke volume.
Figure 15HBlood pressure decreases as blood moves away from the heart.
Blood pressure rapidly decreases as the blood moves through the
arterial system and into the capillary network.
Little pressure remains in the veins, therefore heart actions contribute
very little to venous return.
Venous Return
Venous return depends on:
Skeletal muscle contractions – massaging actions push blood towards heart
Respiratory movements – generates pressure in abdominal and thoracic cavities
Changes in pressure pushes blood along veins
Vasoconstriction – contraction of smooth muscles in tunica media
Sympathetic reflexes vasoconstrict the smooth muscles in veins, which can
propel additional blood from venous reservoir towards the heart.
Venous Return
AortaMain trunk of the systemic circulation
Divisions of the aortaAortic root = attachment to heartAscending AortaAortic archThoracic aorta Abdominal aorta
Arterial System
Aortic Valve
Aortic Sinus
Swelling at aortic root
Right and left coronary arteries
Supply blood to myocardium of the heart
Myocardial infarction = blocked coronary artery
Aortic Bodies
Chemoreceptors - monitor CO2 & O2 levels in blood
Components of the aortic root
Brachiocephalic Artery Brachiocephalic artery divides into:
Right common carotid artery Supplies blood to right
side of face and head
Right subclavian artery - Supplies blood to right arm
Left common carotid arterysupplies blood to left side of face and head
Left subclavian artery
supplies blood to left arm
Branches of the aortic arch
Figure 15.42 The major branches of the aortic arch are highlighted in yellow.
End of Section 5, Chapter 15
Section 6, Chapter 15
•Aorta - Main trunk of the systemic circulation.
•Divisions of the aorta•Aortic root = attachment to heart
•Ascending Aorta
•Aortic arch
•Thoracic aorta
•Abdominal aorta
Arterial Divisions
Section 6, Chapter 15
Systemic arteries and veins
Aorta - Main trunk of the systemic circulation.
Divisions of the aortaAortic root = attachment to heart
Ascending Aorta
Aortic arch
Thoracic aorta
Abdominal aorta
Arterial Divisions
Aortic Valve
Aortic Sinus - Swelling at aortic root
Aortic Bodies
Chemoreceptors - monitor CO2 & O2 levels in blood
4. Right and left coronary arteries
Structures at the aortic root
Right Coronary Artery branchesPosterior interventricular artery: supplies walls of both ventricles
Marginal artery:supplies right atrium and right ventricle
Coronary Arteries
Left Coronary Artery branchesAnterior interventricular artery:supplies walls of both ventricles
Circumflex Artery:supplies left atrium and left ventricle
Blocked coronary artery = myocardial infarction
Brachiocephalic artery Right common carotid artery: supplies
right neck and head
Right subclavian artery:supplies right arm
2. Left common carotid artery supplies left neck and head
3. Left subclavian artery Supplies left arm
Branches of Aortic Arch
Branches of Thoracic Aorta
Grant’s Anatomy. Branches of the thoracic aorta
Bronchial Arteries – supplies bronchi
Pericardial artery – supplies pericardium
Esophageal arteries – supplies esophagus
Branches of Abdominal Aorta
Phrenic arteriessupply diaphragm
Celiac Trunk Gastric a. - supply stomachSplenic a. – supply spleen & pancreasHepatic a. – supplies liver with O2 blood
Superior Mesenteric a. Supplies small intestine
Suprarenal a.Supplies adrenal glands
Branches of Abdominal Aorta
Gonadal arteries. Male = testicular arteriesFemale = Ovarian arteries
Renal arteriesSupplies kidneys
Lumbar arteriesSupplies skin and muscles of lower back
Inferior mesenteric arterySupplies most of large intestine
Divisions of Common Carotid Arteries
External Carotid ArteriesSupplies blood to face, neck, and scalp
Internal Carotid ArteriesSupplies blood to brain
Provides 75% of blood to brain
Carotid Sinus - point of bifurcationCarotid bodies – chemoreceptorsCarotid baroreceptorsCommon site of stenosis (narrowing)
Arteries to the Brain, Head, and Neck
Branches of Internal Carotid Artery
1. Ophthalmic arterysupplies eyes
2. Anterior cerebral artery supplies medial surface of brain
3. Middle cerebral artery Supplies lateral surface of brain
Internal carotid arteries
Arteries to the Brain, Head, and Neck
Vertebral ArteriesProvides 25% of blood supply to
brain
Branch from subclavian arteries
Pass through transverse foramen of cervical vertebrae
Enter skull through foramen magnum
Arteries to the Brain, Head, and Neck
Basilar ArteryBoth vertebral arteries merge to form a basilar artery at the base of the brain.
Supplies blood to brainstem
Branch: Posterior cerebral arterySupplies occipital and temporal lobes
Arteries to the Brain, Head, and Neck
Cerebral Arterial Circle (Circle of Willis)Joins the internal carotid arteries with basilar artery at base of brain
Provides anastomoses (alternate routes) for blood flow
Arteries to the Brain, Head, and Neck
Arteries to the Shoulder and Upper Limb
Axillary Artery Arises from subclavian artery
Brachial Artery Continuation of axillary arteryUsed for measuring blood pressure
Ulnar ArteryContinues along medial arm to wrist
Radial Artery Continues along lateral arm to wrist
Convenient vessel for taking your pulse
Veins that drain the head and neck
Dural Venous SinusesLocated between 2 layers of dura materMajor CSF draining pathway from brain
Internal Jugular VeinsDrains blood from brain and
deep faceArise from dural sinuses
External Jugular VeinsDrains blood from face, scalp, and neck
Veins that drain the arm
Ulnar & Radial Veinsdrain forearm and handsMerge for form brachial veins
Basilic VeinLocated on medial aspect of armJoins the brachial vein near the axilla
Cephalic VeinCourses upward on the lateral armJoins axillary vein to form subclavian vein
Axillary VeinFormed from the merging of basilic and brachial veins
Median Cubital VeinJoins basilic and cephalic veins at elbowOften the site of venipuncture
Hepatic Portal System
Portal System – drains blood from one capillary bed into a second capillary bed.
Hepatic Portal Vein (HPV)•Carries nutrient rich blood
from abdominal viscera to the liver for processing
Hepatic Portal SystemTributaries of Hepatic Portal VeinGastric vein – blood from stomach
Splenic vein – blood from spleen & pancreas
Superior mesenteric vein – blood from small intestine
Inferior mesenteric vein – blood from large intestine
Pathway of Hepatic Portal System
End of Chapter 15
heart aorta abdominal viscera HPV liver hepatic vein IVC heart