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Closed System
The blood remains in blood vessels and heart.
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Double System
- 4 chambers separated between oxygenated and deoxygenated blood.
- Double Organ: Right side pumps to lungs; Left side pumps to body tissues
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Arteries
- Blood Vessel
- Carry blood away from the heart
- Usually carry blood high in oxygen
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Veins
- Blood Vessel
- Carry blood back toward the heart
- Usually carry blood low in oxygen
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Pulmonary Circuit
- Pathways of flow between heart & lungs
- Includes: Chambers on right side of heart; Pulmonary arteries & veins
- Transports oxygen-poor blood from the heart to lungs (Pulmonary arteries)
- Transports oxygen-rich blood from lungs to heart (Pulmonary veins)
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Pulmonary Arteries
- Transport oxygen poor blood from heart to lungs
- Reduces carbon dioxide and and replenishes oxygen in blood
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Pulmonary veins
Transport oxygen rich blood from lungs to heart
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Systemic Circuit
- Pathway flow between heart & body tissues
- Includes: Chambers on left side of heart; Systemic arteries & veins
- Transport oxygen-rich blood from heart to body tissues (Systemic arteries)
- Transports oxygen-poor blood from body tissues to heart (Systemic veins)
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Systemic Arteries
Transport oxygen rich blood from heart to body tissues
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Systemic Veins
Transport oxygen-poor blood from body tissues to heart
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Location of the heart
- Mediastinum, 2/3 to Left of midline
- Deep to sternum
- Medial to lungs
- Superior to Diaphragm
- Anterior to Esophagus
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Right border of Heart
- Formed by the right atrium and right ventricle
- Located more anteriorly
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Left Border of Heart
- Formed by Left atrium & left ventricle
- Located more posteriorly
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Superior Border of Heart
Formed from the ascending aorta, pulmonary trunk, superior vena cava
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Inferior Border of Heart
- Formed by the Right ventricle
- Rests on diaphragm
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Base of the Heart
- Posterior surface
- Most made up of Left atrium
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Pericardium
- Encloses Heart & bases of Great Vessels
- Surrounds, protects & confines heart
- Composed of two main parts: Fibrous Pericardium & Serous Pericardium
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Fibrous Pericardium
- Tough, inelastic, dense irregular C.T.
- Rests on & attaches to diaphragm; Attaches to Great Vessels
- Prevents overstretching of heart
- Anchors heart in mediastinum
- Superficial layer
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Serous Pericardium
- Thin, double-layered serous membrane
- Outer Parietal Layer
- Inner Visceral Layer
- Contains a Pericardial Cavity
- Inner Pericardium
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Parietal Layer
- Outer layer of Serous Pericardium
- Its fused to fibrous pericardium
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Visceral Layer
- Inner layer of Serous Pericardium
- Covers external heart surface
- Also known as Epicardium
- Areolar
Connective tissue- Outer
layer of heart wall
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Pericardial Cavity
- Space between the parietal and visceral layers
- Contains pericardial fluid
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Layers of Heart Wall
- Epicardium (Visceral Pericardium)
- Myocardium
- Endocardium
(Superficial to Deep)
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Myocardium
- Thickest Layer (esp in L Ventricle)
- Cardiac Muscle Tissue
- Middle Layer
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Endocardium
- Inner most layer of the heart
- Made of Endothelium & Areolar CT
- Lines all chambers, valves, and septa
- Extends into blood vessels as "Tunica Intima"
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Atria (2)
- Two superior chambers
- Receive blood from veinsPumps blood to ventricles
- Contain Auricles (ear like flaps)
- Singular known as Atrium
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Right Atrium
- Carries oxygen poor blood from systemic veins
- (Sup & inf Venae Cavae & Coronary sinus)
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Left Atrium
Carries oxygen rich blood from Pulmonary Veins of lungs
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Septa
- Internal walls of the heart
- Separate chambers
- 2 septa: Interatrial septum & Interventricular Septum
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Interatrial Septum
- Between the Atria
- Depression "Fossa ovalis"
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Interventricular Septum
Between the ventricles
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Sulci
Grooves, indicates boundaries of Chambers
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Coronary Sulci
- Between atria & ventricles
- Around circumference of heart
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Interventricular Sulci
Between Ventricles
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Heart Valves
- One-Way, direct blood flow
- Passive; blood pushes them open and closed
- 2 pairs of Atrioventricular Valves (Cuspid): Tricuspid and Bicuspid
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Atrioventricular Valves
- Cuspid Valves
- Tricuspid- Right side
- Bicuspid- Left side
- Between the atria and ventricles
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Chordae Tendineae
- Strong, fibrous strings
- Prevent cusp eversion
- Anchor Atrioventricular valves
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Papillary Muscles
- Conical extensions of Myocardium in ventricles
- Contract and pull on chordae tendineae
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Semilunar Valves
- Between the Ventricles and Arteries
- Prevents back flow into ventricles
- 2 types: Pulmonary Semilunar Valve (right) & Aortic Semilunar Valve (left)
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Pulmonary Semilunar valve
- In the right ventricle
- Prevent blood flow back
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Aortic Semilunar Valve
- In the left ventricle
- Prevents back flow of blood
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Pectinate Muscle
- Muscular ridges
- Auricles & anterior wall of atria
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Trabeculae Carnae
Muscular ridges of ventricular walls
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Septomarginal Trabecula (Moderator Band)
- Band of muscle in R ventricle
- Between interventricular septum and papillary muscle
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Fibrous Skeleton
- Between atria & ventricles
- Dense regular C.T.
- Encircle valves & great arteries
- Attachment for cardiac muscle
- Electrical insulation between atria & ventricles
- Stabilizes valves
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Histology of Cardiac Muscle Tissue
- Myocardium - Cardiac muscle tissue
- Short, branched, muscle fibers
- Striated; 1-2 central nuclei
- Intercalated discs - thickenings of sarcolemma at the ends of cells
- Muscle fibers arranged in spiral bundles
- Desmosomes & Gap Junctions
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Gap Junctions
Allow the entire atrial or ventricular myocardium to contract as a single coordinated unit
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Demosomes
Hold the fibers together
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Autorhythmic
Heart is inherent & rhythmical electrical activity
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Specialized cardiac muscle fibers..
- Are self excitable
- Capable of generating & conducting action potentials
- Acts as a pacemaker - Sets rhythm of electrical excitation stimulating contractions
- Froms conduction system - Provides path for excitation to progress through the heart
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Sinoatrial Node
- Initiates impulse at 100 times/minute
- "Pacemaker"
- Posterior wall of R Atrium
- Each impulse propagates through both atria via gap junctions
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Atrioventricular Node
- Floor of R atrium, near interatrial septum
- AV node delays signal, allows for ventricular filling
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Atrioventricular Bundle
- Receives from AV node & conducts into interventricular septum
- Only site where action potentials can conduct from atria to ventricles
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L & R Bundle branches
Branches of AV bundle within interventricular spetum; conduct to Purkinje Fibers
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Purkinje Fibers
- Within myocardium of ventricles
- Extended up from apex
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Heart Innovation
- Involuntary control by Autonomic Nervous System (ANS)
- Innervated by Coronary Plexus
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Coronary Plexus
- Innervates heart
- 2 Parts:
- Sympathetic pathway increases rate & force of contraction
- Parasympathetic pathway slows heart rate (without effecting force of contraction)
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Cardiac Cycle
- Events of one heartbeat to the next
- Systole
- Diastole
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Systole
- The contraction phase of heart chamber
- Blood forced out of chamber
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Diastole
- Relaxation phase of the chamber
- Chamber fills with blood
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Steps in Cardiac Cycle
- Atrial Systole
- Ventricular Systole & Atrial Diastole
- Ventricular Diastole & Atrial Diastole
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Atrial Systole
- First step in Cardiac Cycle
- Atria contract; ventricles finish filling
- AV valve are open; semilunar valves closed
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Ventricular Systole & Atrial Diastole
- 2nd step in cardiac cycle
- Atria relaxed
- Ventricles contract
- AV valves close; semilunar valves open
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Ventricular Diastole & Atrial Diastole
- Last step in Cardiac Cycle
- Atria & Ventricles relax
- Atria Passively fills with blood
- Semilunar valves close; AV valves open
- Ventricles start passively filling
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