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Questions and Answers
What is the outermost layer of the heart wall called?
What is the outermost layer of the heart wall called?
- Epicardium
- Pericardium (correct)
- Myocardium
- Endothelium
The epicardium consists of multiple layers of complex tissue with muscle fibers.
The epicardium consists of multiple layers of complex tissue with muscle fibers.
False (B)
What is released into the blood within 3 to 12 hours after a myocardial infarction?
What is released into the blood within 3 to 12 hours after a myocardial infarction?
Troponin
The cardiac valves are primarily composed of a core of __________ fibers.
The cardiac valves are primarily composed of a core of __________ fibers.
Match the following components with their functions:
Match the following components with their functions:
Which layer of the heart wall is the thickest?
Which layer of the heart wall is the thickest?
The pericardium is composed of three layers.
The pericardium is composed of three layers.
What type of epithelium is found in the endocardium?
What type of epithelium is found in the endocardium?
The _____ is the innermost layer of the heart wall.
The _____ is the innermost layer of the heart wall.
Match the layers of the pericardium with their descriptions:
Match the layers of the pericardium with their descriptions:
Which component provides a low electrical resistance area between cardiac muscle cells?
Which component provides a low electrical resistance area between cardiac muscle cells?
The atrial natriuretic factor (ANF) is produced by granules found in the ventricular muscle fibers.
The atrial natriuretic factor (ANF) is produced by granules found in the ventricular muscle fibers.
What do the sinoatrial (S.A.) node and atrioventricular (A.V.) node have in common?
What do the sinoatrial (S.A.) node and atrioventricular (A.V.) node have in common?
The cytoplasm of cardiac muscle fiber is composed of parallel myofibrils made of __________ and __________ filaments.
The cytoplasm of cardiac muscle fiber is composed of parallel myofibrils made of __________ and __________ filaments.
Match the following components of the heart's conducting system with their respective locations:
Match the following components of the heart's conducting system with their respective locations:
What is the primary function of the atrial natriuretic hormone (ANP)?
What is the primary function of the atrial natriuretic hormone (ANP)?
The Atrioventricular node (A.V. node) initiates electrical impulses in the heart.
The Atrioventricular node (A.V. node) initiates electrical impulses in the heart.
Where is the Sinoatrial node located?
Where is the Sinoatrial node located?
Purkinje muscle fibers contain high amounts of ______ and have ______ nuclei.
Purkinje muscle fibers contain high amounts of ______ and have ______ nuclei.
Match the following components of the heart's conducting system with their respective characteristics:
Match the following components of the heart's conducting system with their respective characteristics:
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Study Notes
Cardiovascular System
- Distributes blood throughout the body
- Composed of the heart and blood vessels
The Heart
- Formed of three layers: endocardium, myocardium, and pericardium
Endocardium
- Innermost layer of the heart wall
- Composed of:
- Simple squamous epithelium
- Supporting connective tissue containing smooth muscle and elastic fibers
- Subendothelial loose connective tissue which merges with the myocardium and contains the heart's conducting system
Myocardium
- Middle layer of the heart wall
- Thickest layer of the heart wall
- Primarily composed of cardiac muscle fibers
Pericardium
- Outermost layer of the heart wall
- Divided into two layers:
- Visceral pericardium
- Parietal pericardium:
- Serous pericardium
- Fibrous pericardium
Epicardium
- Simple squamous mesothelium supported by a layer of connective tissue containing blood vessels and nerves
- Reflected back to form the parietal layer of the pericardium
- Reflects back to form the parietal layer of the pericardium
Valves of the Heart
- Composed of:
- Connective tissue core primarily composed of collagen fibers
- Covered by fibroelastic tissue on both sides
- Simple squamous epithelium (endothelium) covering layer
Clinical Application: Cardiac Muscle Injury
- Cardiac muscle is rich in blood supply
- Ischemia (lack of blood flow) is damaging to cardiac muscle, leading to cell death
- Cell death releases specific markers in the blood, including troponin
- Troponin is a complex of three globular protein subunits found in relation to actin filaments
- Troponin is released into the blood within 3 to 12 hours after a myocardial infarction (MI)
Cardiac Muscle Regeneration
- Localized injury to cardiac muscle (MI) is repaired by replacement with fibrous connective tissue
Structure of Cardiac Muscle Fiber
- Mitochondria:
- Most numerous in all types of muscular tissue
- Occupies 40% of the cytoplasmic volume
- Myofibril:
- Cardiac fibers are full of parallel myofibrils
- Composed of thick (myosin) and thin (actin) myofilaments
- Arrangement of actin and myosin filaments gives muscle the striation pattern
- Cardiac Diad:
- Composed of a T tubule and one terminal cisterna of the sarcoplasmic reticulum
- Intercalated Disc:
- Junction between cardiac muscle fibers
- Includes:
- Gap junctions: provide low electrical resistance between cells
- Desmosomes: connect adjacent cells
- Fascia adherens: anchor actin fibers to each end of the cell
- Atrial Natriuretic Granules (ANG/ANP):
- Located in atrial muscle fiber and secrete atrial natriuretic factor (ANF)
- ANF regulates blood pressure
Conducting System of the Heart
- Composed of muscle fibers that act as transducers rather than contractile cells
- Components:
- Sinoatrial node (S.A. node): located in the right atrial wall
- Atrioventricular node (A.V. node): located in the floor of the right atrium
- Atrioventricular bundle (A.V. bundle)
- Purkinje muscle fibers:
- Located in ventricular wall
- Responsible for impulse conduction
- Larger and paler than cardiac muscle fibers due to high glycogen content and contain fewer myofibrils
Purkinje Muscle Fibers
- Located in the ventricular wall
- Responsible for impulse conduction
- Larger and paler than cardiac muscle fibers due to high glycogen content, with eccentric nuclei
- Contain few myofibrils
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