Cardiac Histo Flashcards
Smooth Muscle
Occur in bundles or sheets of elongated fusiform cells with finely tapered ends
No striations
Interconnected by gap junctions
Produces continuous contraction of low force
Rhythmic contraction that is inherent, but responsive to ANS
Smooth muscle contraction
Possess a contractile apparatus of thin and thick filaments
Anchor to cytoplasmic densities/dense bodies
Dense bodies comprised of demin and vimentin intermediate filaments
Tension transmitted via densities to the membrane
cells contract as one unit and assume a globular shape
Cardiac Muscle
Cells are short, branched, and y-shaped
Extensive capillaries
Intercalated discs
In cardiac muscle
Transverse junction at the ends of cells that allow passage of electrical current
Coincide with the z line
Bind cells, transmit forces of contraction and allow the spread of excitation
Purkinje cells
Modified cardiac muscle cells that act as the pacemaker for the heart
Fibrous Pericardium
Outer covering of dense connective tissue
Parietal layer of serous pericardium
Lines the inner surface of the fibrous pericardium
Visceral layer of serous pericardium
Covers the outer surface of the heart
Pericadial cavity
Space between the parietal and visceral layers
Epicardium
Outermost layer of the heart wall
Synonymous with visceral pericardium
Dense fibrocollagenous CT with elastic fibers, lined wit mesothelium
Branches of coronary arteries are embedded in adipose tissue
Myocardium
Thickest layer of the heart: Cardiomyocytes, nodal cardiomyocytes, myoendocrine cardiomyocytes
Characterized by: Striations, intercalated discs, dyad T-tubles system, mitochondria, lipofuscin granules, atrial granules
Fascia adherens
Transverse region, membrane to membrane contact
Actin filaments at the ends of terminal sarcomeres insert into junction
Transmit contractile forces between cells
Most predominant
Desmosomes
Transveres region, membrane to membrane contact
Provide anchorage for the intermediate filaments of cytoskeleton
Gap junctions
Longitudinal region, membrane to membrane contacts
Sites of low electrical resistance
allows excitation to pass between cells
Dyad T-tubules
dyad=1 t-tuble + 1 SR cisterna
Fingerlike invaginations of sarcolemma
Found at z lines
Permits uniform contraction of myofibrils within a single cardiomyocte
Lipofuscin granules
Small bodies that accumulate with age in stable non-dividing cells (ie cardiomyocytes)
Contain material derived from residual bodies after lysosomal digestion
Atrial Granules
Myoendocrine cells
Atrial cardiomyocytes that contain membrane bound granules
Smaller quantities are found in the left atrium and the ventricles
Contain precursor of atrial natriuretic factor ANF
ANF targets kidneys to decrease Na+ and H20 retention
Endocardium
Endothelium plus thin layer of loose CT
Thickness differs in ventricles vs atria:
Ventricular endocardium has a subendocardial layer that contains thin layer of CT with smooth muscle and purkinje fibers
In the atria, purkinje fibers are often closer to the endothelium and intermixed with the myocardium
Conducting System
Nodal cardiomyocytes are modified cells with in the SA and AV nodes that initiate/ relay electrical signals
Parasympathetic and sympathetic fibers terminate in the nodes
Only modify rate of intrinsic cardiac muscle contraction
Purkinje Fibers
Highly specialized conduction fibers that generate and transmit impulse
Larger and typically seen at periphery of myocardium
Mostly lack t tubules
Cardiac Skeleton
Contributes to interventricular and interatrial septa
Extends into the valve cusps and chordae tendineae
Insertion of cardiac muscle
Electrical insulator between atria and ventricles
Dense irrecgular CT located in the endocardium
Anchors valves and surrounds AV canals to maintain shape
Heart Valves
Core of fibroelastic CT covered by endothelium
Continuous with the cardiac skeleton
Fibroelastic layer of endocardium condenses to form a valve ring
Creates central portion of the valve
