CVS histology (till the end of smooth muscles)

What are the components of the Cardiovascular System?

"Heart, Arteries, Capillaries & Sinusoids, Veins"

What is the main function of the CVS?

"Transport O2/nutrients to tissues, remove CO2/waste, temperature regulation, hormone distribution, immune function"

What are the layers of the Heart Wall (Outermost to Innermost)?

"Epicardium, Myocardium, Endocardium"

What is the composition of the Cardiac Skeleton?

"Four bands of dense white fibrous C.T. encircling valve bases and trunks"

What is the function of the Cardiac Skeleton?

"Support, muscle attachment, electrical isolation (except AV node)"

What is the composition of the Endocardium?

"Simple squamous epithelium (endothelium) + Subendocardial tissue"

What does the Subendocardial Tissue contain?

"Loose highly vascular C.T., Purkinje fibers"

What is the Epicardium?

"Outermost layer, visceral layer of pericardium"

What is the composition of the Epicardium?

"Mesothelium derivative, adipocytes, neurovascular tissue"

What is the Myocardium?

"Middle and thickest layer, contains cardiac muscle cells"

What are the two types of Cardiomyocytes?

"Contractile and Conductive"

What is the shape of a Contractile Cardiomyocyte?

"Short cylindrical, branching, end-to-end connected"

What does the cytoplasm of a Contractile Cardiomyocyte look like under LM?

"Acidophilic, transverse striations, intercalated discs"

What are the nuclear characteristics of a Contractile Cardiomyocyte?

"Usually single (sometimes bi-), large, oval, vesicular, central"

What EM feature provides energy in Contractile Cardiomyocytes?

"Numerous mitochondria"

What EM feature relates to calcium handling in Contractile Cardiomyocytes?

"Sarcoplasmic reticulum forms diad system with T-tubules"

What constitutes the Diad System in Cardiac Muscle?

"One T-tubule + One terminal cisterna of SR"

What storage molecule is abundant in Contractile Cardiomyocytes (EM)?

"Numerous glycogen granules"

What pigment granule might be seen in aging Contractile Cardiomyocytes (EM)?

"Lipofuscin granules"

What special granules are found in atrial Contractile Cardiomyocytes (EM)?

"Atrial granules (contain ANP - atrial natriuretic peptide)"

What is the function of Intercalated Discs?

"Junctional complexes fixing cardiac muscle cells together"

What junctions make up the Transverse Component of an Intercalated Disc?

"Desmosomes, Adherens junctions (anchoring)"

What junctions make up the Lateral Component of an Intercalated Disc?

"Gap junctions (facilitate fast depolarization spread)"

What forms the core of a Cardiac Valve?

"Core of dense white fibrous C.T. (collagen, elastic fibers, macrophages)"

What covers the surface of a Cardiac Valve?

"Simple squamous epithelium (endothelium)"

What is a common effect of Rheumatic Fever on heart valves?

"Mitral valve commonly affected

What property allows Conductive Cardiomyocytes easier depolarization?

"Inherently leaky ion channels -> easier depolarization, less resistance to AP flow"

Where are Conductive Cardiomyocytes located?

"Sinoatrial (SA) node, Atrioventricular (AV) node, Purkinje fibers"

What is the LM appearance of Purkinje Fibers?

"Formed of few Purkinje cells surrounded by C.T. sheath"

How does Purkinje Fiber cell size compare to contractile cardiomyocytes?

"Larger diameter"

What does the cytoplasm of a Purkinje Fiber look like under LM?

"Pale, vacuolated (glycogen), acidophilic, NO transverse striations, NO intercalated discs"

Where are the myofibrils located in Purkinje Fibers?

"Fewer, peripherally situated"

What are the nuclear characteristics of a Purkinje Fiber?

"Usually single, eccentric"

How does injured Cardiac Muscle heal?

"Heals by fibrous tissue formation (scar)

Why can't Cardiac Muscle regenerate?

"Lack of satellite cells"

What is the prenatal origin of Smooth Muscle?

"Undifferentiated Mesenchymal Cells (UMCs)"

What is the postnatal origin of Smooth Muscle?

"Pericytes"

What is the shape of a Smooth Muscle Cell?

"Non-branched, spindle-shaped (fusiform)"

How are Smooth Muscle Cells typically arranged?

"Bundles or sheaths"

What membrane feature replaces T-tubules in Smooth Muscle?

"Caveolae (invaginations)"

How are Smooth Muscle Cells electrically connected?

"Gap junctions"

What does the sarcoplasm of a Smooth Muscle Cell look like?

"Acidophilic, organelles in perinuclear region"

What are the nuclear characteristics of a Smooth Muscle Cell?

"Single, central, oval ('cigar-shaped' in contraction)"

Does Smooth Muscle have striations? Why?

"No, due to irregular actin/myosin arrangement"

Where do actin filaments attach within the Smooth Muscle Cell cytoplasm?

"Dense bodies (equivalent to Z-lines)"

Where do actin filaments attach at the Smooth Muscle Cell membrane?

"Attachment plaques (dense plaques)"

What type of intermediate filaments are found in Smooth Muscle?

"Desmin (inserts into dense bodies and plaques)"

Can Smooth Muscle regenerate? How?

"Yes, possible via division of healthy cells or differentiation of pericytes"

What are the main functions of Smooth Muscle?

"Involuntary contraction (viscera, vessels), Synthesis of C.T. fibers/matrix"

What is Desmin Immunohistochemistry used for clinically?

"Identification of muscular origin of undifferentiated tumors (e.g., sarcomas)"

What is the role of Smooth Muscle in Bronchial Asthma?

"Over-activity causes narrowing of small respiratory passages"

How do Beta-Agonist Drugs work in Asthma?

"Relax respiratory smooth muscles, improving symptoms"

What surrounds each Smooth Muscle cell externally?

"Basal lamina (contains thin reticular fibers)"