Histology of the Cardiac System Flashcards
What are the three layers of the heart?
- Endocardium
- Myocardium
- Epicardium
What is the innermost layer of the heart?
Endocardium
What is the endocardium composed of?
- Simple squamous epithelium known as endothelium
- Connective tissue
- Subendocardium (comes in contact with cardiac muscle, contains small vessels, nerves, and Purkinje fibers)
What are Purkinje fibers?
Impulse conducting fibers in large modified muscle cells that cluster together in groups (1-2 nuclei, stain pale due to fewer myofibrils)
What is the thickest layer of the heart wall?
Myocardium
Where are the terminal branches of the AV bundle branches?
Subendocardial connective tissue
Where is the myocardium most thick and why?
Left ventricle; pumps the hardest to overcome the highest pressure of the systemic circulation
Where is the myocardium thinnest and why?
Right atrium because of the low resistance to back flow
What is the myocardium composed of?
Myocytes (cardiac muscle cells)
How are cardiac muscle cells different from smooth or skeletal muscle cells?
Placement of nuclei (central), presence of fibers with cross striations, intercalated discs, branching myocytes
What are intercalated disks?
Junctional complexes that contain fascia adherens, desmosomes, and gap junctions to provide connection and communication
What is the function of intercalated disks?
Bind myocytes and allow ion exchange to facilitate electrical impulses
Describe smooth muscle cells.
Long, slender central nuclei lying within narrow, fusiform cells; no cross striations
Describe skeletal muscles.
Fibers with cross-striations and peripheral nuclei
What is the outermost layer of the heart?
Epicardium
