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Questions and Answers
What is the primary function of the cardiac skeleton?
What is the primary function of the cardiac skeleton?
- To provide structure and support for the heart (correct)
- To enhance cardiac muscle contraction speed
- To produce electrical signals in the heart
- To facilitate blood flow through the heart
Which types of junctions are found in an intercalated disc?
Which types of junctions are found in an intercalated disc?
- Fascia adherens, tight junctions, and gap junctions
- Fascia adherens, desmosomes, and gap junctions (correct)
- Desmosomes, adherens junctions, and plasmodesmata
- Desmosomes, tight junctions, and gap junctions
What do desmosomes do in cardiac muscle cells?
What do desmosomes do in cardiac muscle cells?
- Anchor actin to the sarcomere
- Facilitate ion movement between cells
- Prevent separation during contraction (correct)
- Enhance energy production in cells
What is a defining characteristic of all cardiac valves?
What is a defining characteristic of all cardiac valves?
Which statement is true regarding atrioventricular (A-V) valves?
Which statement is true regarding atrioventricular (A-V) valves?
What connects the chordae tendinae to the heart wall?
What connects the chordae tendinae to the heart wall?
How do Purkinje fibers differ from regular cardiac muscle fibers?
How do Purkinje fibers differ from regular cardiac muscle fibers?
Which heart valve type has a thinner central core than the A-V valves?
Which heart valve type has a thinner central core than the A-V valves?
Which layer of the heart is the innermost and in direct contact with blood?
Which layer of the heart is the innermost and in direct contact with blood?
What is the primary component of the myocardium?
What is the primary component of the myocardium?
Which layer of the pericardium is responsible for reducing friction between the heart and its covering?
Which layer of the pericardium is responsible for reducing friction between the heart and its covering?
What corresponds to the tunica adventitia of blood vessels?
What corresponds to the tunica adventitia of blood vessels?
Which of the following is NOT a layer of the cardiac wall?
Which of the following is NOT a layer of the cardiac wall?
What structural feature is a characteristic of cardiac muscle fibers?
What structural feature is a characteristic of cardiac muscle fibers?
The outermost layer of the heart wall is known as the:
The outermost layer of the heart wall is known as the:
Which part of the pericardium sticks to the fibrous pericardium?
Which part of the pericardium sticks to the fibrous pericardium?
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Study Notes
Heart Wall Layers
- The heart wall is made of three layers:
- Epicardium: Outer layer, also known as visceral pericardium, contains coronary blood vessels and nerves.
- Myocardium: Middle layer, composed of cardiac muscle, responsible for the heart's pumping action.
- Endocardium: Inner layer, lines the heart chambers and is continuous with the inner lining of blood vessels.
Pericardium
- The pericardium is the sac that surrounds the heart and consists of three layers:
- Fibrous pericardium: Outermost layer, made of dense connective tissue, helps hold the heart in place and prevents overfilling.
- Parietal layer: Middle layer, lines the fibrous pericardium.
- Visceral layer: Innermost layer, also known as the epicardium, is the outermost layer of the heart wall.
- Between the parietal and visceral layers is the pericardial cavity, filled with serous fluid that reduces friction during heart contractions.
Cardiac skeleton
- Provides structure and support for the heart.
- Composed of dense connective tissue, which helps isolate the atria from the ventricles.
- Fibrous rings attach to the heart valves and act as anchor points for cardiac muscle fibers.
Intercalated discs
- Specialized junctions between cardiac muscle cells.
- Composed of three types of cell junctions:
- Fascia adherens: Anchor sites for actin filaments, connecting to the nearest sarcomere.
- Desmosomes: Prevent cell separation during contraction by binding filaments together.
- Gap junctions: Allow rapid conduction of electrical impulses between heart cells, enabling synchronized contraction.
Cardiac valves
- Endocardial folds that prevent backflow of blood.
- Supported by internal plates of dense connective tissue, continuous with the fibrous rings of the cardiac skeleton.
- Atrioventricular (AV) valves: Tricuspid and mitral valves have a core of dense irregular connective tissue lined by endothelium.
- Connected to the fibrous skeleton by chordae tendinae, which attach to papillary muscles.
- Semilunar valves: Aortic and pulmonary valves have a thinner central core than AV valves.
- All cardiac valves are avascular.
Purkinje fibers
- Modified cardiac muscle cells specialized for conducting electrical impulses.
- Located beneath the endocardium.
- Distal branches of the atrioventricular node bundles.
- Larger than typical cardiac muscle fibers, with one or two peripheral nuclei and abundant glycogen.
- Have a clear, empty appearance in most preparations.
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