6. Heart and Vascular System I Flashcards
What is the main difference between skeletal muscle, cardiac muscle and smooth muscle?
Skeletal: striated and volunatry
Smooth: nonstriated and involuntary
CARDIAC: STRIATED AND INVOLUNTARY
Smooth muscle occurs as sheets/bundles of elongated fusiform cells, with centrally located nuclei. There are no visible striations (looks like collagen). How are they interconnected and what do they produce?
Interconnected by gap junctions to help spread electrical current
Produces continuous contraction of low force: Rhythmic contraction that is inherent but responsive to ANS
As skeletal muscle, smooth muscle contains contractile apparatus of thin and thick filaments. What are they anchored to and what are those made of?
Filaments anchor to cytoplasmic densities/dense bodies which are comprised of desmin and vimentin intermediate filaments
How does contraction work and what shape does the smooth muscle assume?
Tension is trasmitted via densities to the membrane and the cells contract as one unit and assume globular shape
What are caveolae?
Indents on the smooth muscles whicha are equal to T tubules in skeletal M
Cardiac Muscle is short, branched and Y-shaped with more centrally located nuclei. They have extensive capillaries because the heart needs alot of O2. What are the two main hallmarks of cardiac muscle?
Intercalated discs and purkinje cells
What are intercalated discs?
Transverse junctions at the ends of cells that allow passage of electrical currents & communication
What are purkinje cells?
Modified cardiac muscle cells that act as the pacemaker for the heart
Fibrous pericardium is the outer covering of dense connective tissue. What are the 3 components of serous pericardium?
- parietal serous pericardium : inner surface of fibrous
- Visceral serous pericardium: covers outer surface heart (EPICARDIUM)
- pericardial cavity is space between parietal and visceral
What are the three layers of the heart wall?
Epicardium
Myocardium
Endocardium
Epicardium is ther outermost layer of the heart, and can also be called visceral serous pericardium. What is in this layer?
Simple squamous epithelium - Mesothelium
and dense fibrocollagenous CT with elastic fibers
**coronary artery branches embedded in adipose tissue
The thickest layer of the heart is the myocardium. What are the three different things that compose it?
Cardiomyocytes which are contractile Nodal cardiomyocytes (purkinje) in SA/AV node Myoendocrine cardiomyocytes
What is the difference between skeletal and cardiac muscles regarding T tubules?
Cardiac have Dyad (diad) T tubules which skeletal have triad
What are the main characterizations of myocardium? (6)
Striations intercalated discs Dyad T tubule system LOTS of mitochondria Lipofuscin granules atrial granules (myoendocrine cells)
Intercalating discs connect cardiomyocytes where and for what function?
Connect always at Z lines, where cells meet end to end
They bind cells, transmit forces of contraction and spread excitation/electrical signaling
What are the three types of membrane to membrane contacts of intercalating junctions?
Transverse region (perpendicular to cell striations): 1. fascia adherens and 2. desmosomes Longitudinal region (parallel to cell striations): 3. gap (Nexus) junctions
What are actin filaments at the ends of terminal sarcomeres that insert into the junction and transmit contractile forces between cells? **most predominant kind of intercalating disc
Fascia adherins
What provide anchorage for the intermediate filaments of the cytoskeleton?
Desmosomes
What are sites of low electrical resistance that allow excitation to pass between cells?
Gap/Nexus junctions
Dyad T-tubules consist of 1 T tubules and 1 SR cisterna (Ca2+), and can be found where and do what?
Found at Z lines, in fewer quantity that Triad
Permits uniform contraction of myofibrils within a single cardiomyocyte
Lipofuscin granules are small bodies that accumulate with age in non-dividing cells… What do they contain?
material derived from residual bodies after lysosomal disgestion
Myoendocrine cells are atrial cardiomyocytes that contain membran bound granules (small amount found in left atrium and ventricles) which contain what to do what?
Contain precursor of atrial natriuretic factor (ANF) and brain factor BNF which targets kidney to decrease H+ and H20 retention
The endocardium is NOT thick walled and contains simple squamous endothelium and a thin layer of loose CT. Why does thickness differ in ventricles vs atria?
Ventricular endocardium has a subendocardial layer with a thin layer of CT with smooth muscle and contains purkinje fibers
What is different about endocardium in the atria?
Purkinje fibers are often closer to the endothelium and intermixed with myocardium
