Heart Anatomy

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Heart Anatomy

• Approximately the size of your fist
• Wt. 250-300 grams
• Location
• In the mediastinum between the lungs
• Superior surface of diaphragm
• ?s of it lies to the left of the midsternal line
• Anterior to the vertebral column, posterior to
  the sternum

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Heart Anatomy
Figure 18.1
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Coverings of the Heart

• Pericardium a double-walled sac around the
  heart
• Composed of
• A superficial fibrous pericardium
• A deep two-layer serous pericardium
• The parietal layer lines the internal surface of
  the fibrous pericardium
• The visceral layer or epicardium lines the
  surface of the heart
• They are separated by the fluid-filled
  pericardial cavity called the pericardial cavity
• Protects and anchors the heart
• Prevents overfilling of the heart with blood
• Allows for the heart to work in a relatively
  friction-free environment

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Pericardial Layers of the Heart
Figure 18.2
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Layers of the Heart Wall

• Epicardium visceral pericardium
• Myocardium cardiac muscle layer forming the
  bulk of the heart
• Endocardium endothelial layer of the inner
  myocardial surface

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Heart Anatomy

• External markings
• Apex - pointed inferior region
• Base - upper region
• Coronary sulcus
• Indentation that separates atria from ventricles
• Anterior and posterior interventricular sulcus
• Separates right and left ventricles
• Internal divisions
• Atria (superior) and ventricles (inferior)
• Interventricular and interatrial septa

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Atria of the Heart

• Atria - receiving chambers of the heart
• Receive venous blood returning to heart
• Separated by an interatrial septum (wall)
• Foramen ovale - opening in interatrial septum in
  fetus
• Fossa ovalis - remnant of foramen ovale
• Each atrium has a protruding auricle
• Pectinate muscles mark atrial walls
• Pump blood into ventricles
• Blood enters right atria from superior and
  inferior venae cavae and coronary sinus
• Blood enters left atria from pulmonary veins

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Gross Anatomy of Heart Frontal Section
Figure 18.4e
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Ventricles of the Heart

• Ventricles are the discharging chambers of the
  heart
• Papillary muscles and trabeculae carneae muscles
  mark ventricular walls
• Separated by an interventricular septum
• Contains components of the conduction system
• Right ventricle pumps blood into the pulmonary
  trunk
• Left ventricle pumps blood into the aorta
• Thicker myocardium due to greater work load
• Pulmonary circulation supplied by right ventricle
  is a much low pressure system requiring less
  energy output by ventricle
• Systemic circulation supplied by left ventricle
  is a higher pressure system and thus requires
  more forceful contractions

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External Heart Anterior View
Figure 18.4b
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Structure of Heart Wall

• Left ventricle three times thicker than right
• Exerts more pumping force
• Flattens right ventricle into a crescent shape

Figure 18.7
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Heart Valves

• Heart valves ensure unidirectional blood flow
  through the heart
• Composed of an endocardium with a connective
  tissue core
• Two major types
• Atrioventricular valves
• Semilunar valves
• Atrioventricular (AV) valves lie between the
  atria and the ventricles
• R-AV valve tricuspid valve
• L-AV valve bicuspid or mitral valve
• AV valves prevent backflow of blood into the
  atria when ventricles contract
• Chordae tendineae anchor AV valves to papillary
  muscles of ventricle wall
• Prevent prolapse of valve back into atrium

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Semilunar Heart Valves

• Semilunar valves prevent backflow of blood into
  the ventricles
• Have no chordae tendinae attachments
• Aortic semilunar valve lies between the left
  ventricle and the aorta
• Pulmonary semilunar valve lies between the right
  ventricle and pulmonary trunk
• Heart sounds (lub-dup) due to valves closing
• Lub - closing of atrioventricular valves
• Dub- closing of semilunar valves

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Fibrous Skeleton

• Surrounds all four valves
• Composed of dense connective tissue
• Functions
• Anchors valve cusps
• Prevents overdilation of valve openings
• Main point of insertion for cardiac muscle
• Blocks direct spread of electrical impulses

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Heart Valves
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Conducting System

• Cardiac muscle tissue has intrinsic ability to
• Generate and conduct impulses
• Signal these cells to contract rhythmically
• Conducting system
• A series of specialized cardiac muscle cells
• Sinoatrial (SA) node sets the inherent rate of
  contraction

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Conducting System
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Innervation

• Heart rate is altered by external controls
• Nerves to the heart include
• Visceral sensory fibers
• Parasympathetic branches of the vagus nerve
• Sympathetic fibers from cervical and upper
  thoracic chain ganglia

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External Heart Posterior View
Figure 18.4d
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Major Vessels of the Heart

• Vessels returning blood to the heart include
• Superior and inferior venae cavae
• Open into the right atrium
• Return deoxygenated blood from body cells
• Coronary sinus
• Opens into the right atrium
• Returns deoxygenated blood from heart muscle
  (coronary veins)
• Right and left pulmonary veins
• Open into the left atrium
• Return oxygenated blood from lungs

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Major Vessels of the Heart

• Vessels conveying blood away from the heart
  include
• Pulmonary trunk
• Carries deoxygenated blood from right ventricle
  to lungs
• Splits into right and left pulmonary arteries
• Ascending aorta
• Carries oxygenated blood away from left atrium to
  body organs
• Three major branches
• Brachiocephalic
• Left common carotid,
• Left subclavian artery

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Blood Flow Through the Heart
Figure 18.6
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Pathway of Blood Through the Heart and Lungs
Figure 18.5
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Coronary Circulation

• Coronary circulation
• The functional blood supply to the heart muscle
  itself
• R and L Coronary arteries are 1st branches off
  the ascending aorta
• Coronary sinus (vein) empties into R. atrium
• Collateral routes ensure blood delivery to heart
  even if major vessels are occluded

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Coronary Circulation - Arteries

• Right Coronary Artery
• Supplies blood to
• Right atrium and posterior surface of both
  ventricles
• Branches into the
• Marginal artery - extends across surface of R.
  ventricle
• Posterior interventricular artery
• Found in posterior interventricular sulcus
• Left Coronary Artery
• Supplies blood to
• Left atrium and left ventricle
• Branches into
• Circumflex artery
• Anterior interventricular artery
• Found in anterior interventricular sulcus
• Connected with posterior interventricular artery
  via arterial anastomoses

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Coronary Circulation Arterial Supply
Figure 18.7a
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Coronary Circulation - Veins

• Coronary sinus -
• Vein that empties into right atrium
• Receives deoxygenated blood from
• Great cardiac vein - on anterior surface
• Posterior cardiac vein
• Drains area served by circumflex
• Middle cardiac vein
• Drains area served by posterior interventricular
  artery
• Small cardiac vein
• Drains blood from posterior surfaces of right
  atrium and ventricle

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Coronary Circulation Venous Supply
Figure 18.7b
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Microscopic Anatomy of Heart Muscle

• Cardiac muscle cells
• Short, striated, branched, and interconnected
• The connective tissue endomysium acts as both
  tendon and insertion
• Intercalated discs anchor cardiac cells together
  and allow free passage of ions
• Heart muscle behaves as a functional syncytium
• Many mitochondria (25 of total volume)

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Microscopic Anatomy of Heart Muscle
Figure 18.11
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Disorders of the Heart

• Coronary artery disease
• Atherosclerosis fatty deposits
• Arteriosclerosis - hardening of the arteries
• Angina pectoris chest pain
• Myocardial infarction blocked coronary artery
• Silent ischemia no pain or warning
• Fibrillation - irregular heart beat may occur in
  either atria or ventricles