Chapter 20 The Heart

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Chapter 20 The Heart

• BIO 211 Lab
• Instructor Dr. Gollwitzer

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• Today in class we will
• Identify the cardiovascular organs
• Describe the location of the heart and its
  functional organization
• Systemic circuit
• Pulmonary circuit
• Describe and identify the structures of the
  pericardium
• Begin identification of anatomical structures of
  the heart

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Cardiovascular System (CVS)

• Includes
• Heart
• Arteries
• Veins
• Capillaries
• Network of blood vessels between heart and
  peripheral tissues
• Has 2 circuits that begin and end at heart
• Pulmonary circuit
• Systemic circuit
• Blood alternates between the two circuits

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Organization of the Cardiovascular System

• Pulmonary circuit
• To/from lungs for gas exchange
• Shorter network so less resistance to blood flow
• Systemic circuit
• To/from rest of body for nutrient, waste and gas
  exchange
• Longer network so much greater resistance to
  blood flow

Figure 20-1 An Overview of the Cardiovascular
System
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3 Types of Blood Vessels

• Arteries
• Carry blood away from heart
• Veins
• Carry blood to heart
• Capillaries (exchange vessels)
• Networks between arteries and veins
• Exchange nutrients, waste products, dissolved
  gases

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Fun Facts about the Heart

• Bodys most incredible muscle
• NEVER rests
• Beats 100,000 times/day
• Pumps 8000 Liters of blood/day
• Enough to fill 40 55-gallon drums
• Size of clenched fist

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Location of the Heart

• At an angle to longitudinal axis, rotated to L
  side
• In anterior portion of mediastinum
• Between two pleural cavities, also contains
  thymus, esophagus, trachea
• Surrounded by pericardial cavity

• Directly behind sternum
• Slightly left of midline

Figure 202a
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Relation to Thoracic Cavity
Figure 202b
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Pericardial Sac

• aka Fibrous pericardium
• Surrounds heart
• Consists of collagen fibers
• Stabilizes position of heart and associated
  vessels within mediastinum
• Inner surface lined by pericardium
• 2-layers of serous membrane
• Separated by pericardial cavity

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Heart and Pericardium
Fig. 20-2c p. 671
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Pericardium Double-membrane Structure that
Lines Pericardial Cavity

• Visceral pericardium (epicardium)
• Covers and adheres to outer surface of heart
• Parietal pericardium
• Lines inner surface of pericardial cavity
• Pericardial cavity
• Space between parietal and visceral pericardia
• Contains pericardial fluid (lubricant)

Fig. 20-2c, p. 671
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Pericarditis

• Infection of pericardium ? inflammation
• Causes
• Pericardial surfaces to rub against each other
• ? Severe pain
• Scratching sound heard with stethoscope
• Increased production of pericardial fluid
• Restricts heart movement
• ? Cardiac tamponade
• Also caused by injuries that produce bleeding in
  the pericardial cavity

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Heart Wall

• Epicardium
• Visceral pericardium
• Covers outside of heart
• Attached to myocardium
• Myocardium
• Muscular wall of heart
• Forms atria and ventricles
• Contains cardiac muscle tissue, blood vessels,
  nerves
• Endocardium
• Covers inner surface of heart, including heart
  valves

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Heart Wall
Figure 204
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Heart Wall Connective Tissues

• Many collagen and elastic fibers
• Provide physical support for cardiac muscle
  fibers, blood vessels and nerves
• Help distribute forces of contraction
• Add strength and prevent overexpansion of heart
• Provide elasticity helps heart return to
  original size and shape after contracting

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Cardiac Muscle Cells

• Predominant cell in heart
• Small cells
• Single, central nucleus
• Interconnected by intercalated discs
• Same proteins/arrangement as skeletal muscle,
  i.e., actin, myosin
• Striated
• Involuntary

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Cardiac Muscle Cells
Figure 205
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4 Chambers of the Heart

• Right atrium
• Collects blood from systemic circuit
• Right ventricle
• Pumps blood to pulmonary circuit
• Left atrium
• Collects blood from pulmonary circuit
• Left ventricle
• Pumps blood to systemic circuit

Figure 20-1 An Overview of the Cardiovascular
System
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Superficial Anatomy

• Atria
• Superior regions
• Form base of heart
• Thin, muscular walls, highly expandable
• When not filled with blood, outer portion
  deflates and becomes a lumpy wrinkled flap
  (auricle ear)
• Ventricles
• Inferior regions
• Form apex of heart
• Thick, muscular walls
• Larger than atria

Figure 20-3a The Superficial Anatomy of the Heart
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Right Atrium (RA)

• Receives blood from
• Systemic circuit
• Superior vena cava
• From head, neck, upper limbs and chest
• Opens into superior and posterior portion of RA
• Inferior vena cava
• From rest of trunk, viscera, lower limbs
• Opens into inferior and posterior portion of RA
• Cardiac circulation
• Coronary sinus
• Pumps blood into RV

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Right Ventricle (RV)

• Receives blood from RA
• Pumps blood into pulmonary circuit
• Pulmonary trunk ? pulmonary arteries (LtRt) ? ?
  pulmonary arterioles ? capillaries around
  pulmonary alveoli ? pulmonary venules ? pulmonary
  veins (Lt Rt) ? LA

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Left Atrium (LA)

• Receives blood from pulmonary circuit via
  pulmonary veins
• Pumps blood into LV

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Left Ventricle

• Receives blood from LA
• Pumps blood into systemic circuit
• Ascending aorta ? aortic arch ? descending aorta
  ? etc.

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Superficial Anatomy
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Other Structures

• Ligamentum arteriosum
• Fibrous remnant of fetal vessel (ductus
  arteriosum) between aorta and pulmonary trunk
• Atrioventricular (AV) (or coronary) sulcus
  (groove)
• Deep groove between As and Vs
• Anterior interventricular (IV) sulcus
• Front groove between R L Vs
• Posterior interventricular (IV) sulcus
• Rear groove between R L Vs

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• Today in class we will
• Continue identification of anatomical structures
  of the heart
• Identify some major systemic blood vessels
• Identify the major coronary blood vessels
• Trace blood flow through the heart and pulmonary
  circuit

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Internal Anatomy
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Internal Anatomy

• Septa
• Interatrial (IA) septum
• Muscular partition between atria
• Fossa ovalis shallow depression left from
  closing of foramen ovale (opening between atria
  before birth, closes in 3 months)
• Interventricular (IV) septum
• Partition between ventricles
• Much thicker than IA septum

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Internal Anatomy

• Atrial structures
• Entrance for coronary sinus (RA only)
• Pectinate muscles prominent muscular ridges
  that run along the inner surface of atrial wall
• Sinoatrial (SA) node located in wall of RA near
  base of SVC natural pacemaker of heart
• Atrioventricular (AV) node located between RA
  and RV specialized cardiocytes that relay
  contractile stimulus to remainder of conducting
  system (bundle of His, bundle branches, Purkinje
  fibers, ventricular myocardium)

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Internal Anatomy

• Ventricular structures
• Trabeculae carneae muscular ridges on internal
  surface of RV that make up conducting system
• LV larger and has thicker walls than RV
• Must be able to develop enough pressure to push
  blood through systemic circuit
• Nevertheless, LV contains same amount of blood as
  RV

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Left and Right Ventricles

• Have significant structural differences
• R is pouch-shaped L is round
• LV
• Larger thicker muscle and more powerful
• Develops more pressure
• Similar internally to right ventricle

Figure 207
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Heart Valves

• Heart has two major types of valves
• Atrioventricular (AV) valves R and L
• Semilunar (half moon) valves
• Pulmonary valve
• Aortic valve

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Heart Valves

• Atrioventricular (AV) valves
• Folds of fibrous tissue (cusps)
• Extend into openings between As Vs
• ? 1-way blood flow from As to Vs
• AV valves close when Vs contract
• Prevent backflow into As
• Chordae tendineae (tendinous cords)
• Attach to free edge of each cusp and to
• Papillary muscles
• Relax/contract and open/close valves

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Heart Valves

• R AV valve
• aka tricuspid valve
• Has 3 fibrous flaps
• Controls blood flow from RA to RV
• L AV valve
• aka bicuspid valve and mitral valve
• Has 2 fibrous flaps
• Controls blood flow from LA to LV

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Heart Valves

• Semilunar (half-moon) valves
• Have 3 semilunar cusps
• ? 1-way blood flow from Vs to pulmonary trunk and
  aorta
• Valves open after Vs contract
• Control blood flow leaving heart
• Pulmonary (semilunar) valve
• Controls blood flow into pulmonary trunk from RV
• Aortic (semilunar) valve
• Controls blood flow into ascending aorta from LV

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Heart Valves
Fig. 20-8a, p. 679
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Heart Valves
Fig. 20-8b, p. 679
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Fig. 20-8c, p. 679
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Relaxed and Contracting Ventricles

• When heart beats
• Both atria contract first
• Followed by both ventricles
• Ventricles pump equal volumes of blood out of
  heart

Figure 207
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Fibrous Skeleton

• 4 dense bands of tough elastic tissue
• Encircle bases of
• Pulmonary trunk, aorta, heart valves
• Stabilize positions of
• Valves and ventricular muscle cells
• Physically isolate ventricular cells from atrial
  cells

Figure 20-8b Valves of the Heart (Part 1 of 2)
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Blood Supply to the HeartCoronary Arterial
Circulation

• Coronary arteries originate at base of ascending
  aorta
• Highest systemic pressure
• Greatest O2 levels
• R coronary artery
• Runs lateral and posterior in AV (coronary)
  sulcus under RA
• Forms posterior interventricular artery (in
  posterior IV sulcus)
• Supplies blood to RA, LV, RV, portion of
  conducting system)
• L coronary artery
• Passes lateral and posterior in AV
  (coronary)sulcus under LA
• Branches and forms
• Anterior interventricular artery (in anterior IV
  sulcus)
• Circumflex artery
• Supplies LA, LV, IV septum

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Blood Supply to the HeartCoronary Venous
Circulation

• Cardiac (coronary) veins ? drain (carry) blood
  back to interior of heart
• 80 returns to R atrium via
• Great cardiac vein originates in anterior IV
  sulcus and proceeds posteriorly
• Middle cardiac vein originates in posterior IV
  sulcus and proceeds superiorly
• ? Coronary sinus collects blood, empties into R
  atrium at opening of coronary sinus
• 20 empties directly into R ventricle

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Fig. 20-9a, p. 681
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Fig. 20-9b, p. 681
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Coronary Artery Disease (CAD)

• Occurs when have partial/complete blockage of
  coronary arterial circulation
• ? Reduced blood supply (coronary ischemia)
• Treatment procedures
• Balloon angioplasty, stents
• CABG (coronary artery bypass graft)

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CABG

• Small section of a small blood vessel is removed
  from another part of body, e.g.,
• Internal thoracic artery
• Peripheral vein (e.g., great saphenous vein)
• Used to create detour around obstructed portion
  of coronary artery
• May have 3-5 arteries replaced (triple, quintuple
  bypass)

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Carditis

• Inflammation of the heart
• Can result in valvular heart disease (VHD)
• e.g., rheumatic fever

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Blood Flow Through the Heart

• Superior and inferior vena cavae ?
• RA ?
• R AV valve/tricuspid ?
• RV ?
• Pulmonary valve ?
• Pulmonary trunk ?
• Pulmonary arteries ?
• Arterioles ?

• Capillaries (around alveoli) ?
• Venules ?
• Pulmonary veins ?
• LA ?
• L AV valve/bicuspid ?
• LV ?
• Aortic valve ?
• Ascending aorta

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Figure 20-6a The Sectional Anatomy of the Heart
6 Pulmonary trunk
1 Superior vena cava
5 Pulmonary valve
7 Left pulmonary arteries
7 Right pulmonary arteries
2 Right atrium
3 Right AV/tricuspid valve
4 Right Ventricle
1 Inferior vena cava
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8 Arterioles
9 Capillaries (around aveloli)
10 Venules
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Figure 20-6a The Sectional Anatomy of the Heart
16 Ascending aorta
6 Pulmonary trunk
1 Superior vena cava
5 Pulmonary valve
7 Left pulmonary arteries
7 Right pulmonary arteries
11 Left pulmonary veins
2 Right atrium
12 Left Atrium
13 Left AV/mitral valve
3 Right AV/tricuspid valve
14 Left Ventricle
4 Right Ventricle
1 Inferior vena cava
15 Aortic valve
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Circulation Patterns
Figure 21-19