Histo lecture 1 Flashcards
What are the qualities of cardiac muscle cells?
Smooth?
Striated and Involuntary
Non-striated and Involuntary
What do the smooth muscle occur as?
What about the nucleus?
Occur as bundles or sheets of elongated fusiform cells with finely tapered ends
centrally located nucleus but only 1 (skeletal had peripheral nuclei). it’s typically elongated and can’t be flatted down really. they keep their volume
Where is smooth muscle found?
What connects the smooth muscle to one another?
visceral organs, pelvic organs, abdominal organs, vasculature
gap junctions so they can contract uniformly.
What is unique to smooth muscle?
what is it controlled by?
It can sustain very long contractions… intestines or the GI during labor or something like that.
ANS and enteric nervous system
What is the mechanism to smooth muscle contraction?
what isn’t there as compared to smooth muscle?
contraction is identical in that they have actin and myosin, it’s just that there is a different orientation.
There is actin, myosin, and these things called dense bodies
What do the contractile proteins anchor to?
dense bodies, which are found all throughout the cytoplasm. these anchor to other cytoskeleton elements (design and vimentin). this is how we anchor contractile elements to the actual boundary of the cell
What happens to the dense bodies during contraction?
when the contractile proteins contract down, they pull on the dense bodies and pull in unison. this allows the cell that was originally fusiform to contract down all across its length
What are the little indentations found all along the edges of smooth muscle?
Calveolae
these are the T tubules that you would have in skeletal muscle.
this is a way for calcium signaling to get down into the smooth muscle.
What does cardiac muscle look like generally?
Cells are short, branch, and Y shaped. There are a lot of capillaries
centralized nucleus
What is the hallmark of cardiac muscle tissue?
Intercalated discs = transverse junctions that run parallel to the sarcomere. These allow passage of electrical current
Purkinje fibers: modified cardiac cells that act as the “pacemaker” for the heart
What do you see around the nucleus in a cardiac cell?
different structures, like collagen or elastic fibers.. whatever it is bend around the nucleus. so there’s a free zone so the nucleus isn’t impeded by the contractile forces
What are the different layers of the pericardium?
what creates the pericardial cavity?
Fibrous Pericardium = outer covering of dense connective tissue
Parietal Serous Pericardium
Visceral Serous Pericardium (covers the heart)
the visceral comes up and folds onto itself.. forming the parietal layer. the space between is the cavity.
Why does the epicardium have a layer of simple squamous epithelium?
what’s under it?
mesothelium.
fat and loose areolar tissue.
What’s deep to the epicardium?
myocardium –> where we see cardiac muscle
What’s deep to the myocardium?
endocardium.. this is loose areolar CT lined with endothelium
What’s endothelium?
why do we have this on the heart?
Inner lining of the blood vessels.
we want a smooth way for the blood to move, we don’t want turbulence.
What are the different component layers of the epicardium?
It’s also visceral pericardium
It has dense fibrocollagenous CT with elastic fibers, and is lined with mesothelium
What is there to know about the myocardium?
It’s the thickest layer of the heart.. full of cardiac muscle tissue.
You’ll see it in different orientations because of the movement of blood.
what are cardiomyocytes?
nodal cardiomyocytes
Along with the above 2, what do these 2 + myoendocrine cardiomyocytes a part of?
contractile cells of the heart
also called purkinje cells –> these are in the SA and AV nodes
myocardium
What is the myocardium characterized by?
Striations, Intercalated discs, Dyad T-Tubule system, mitochondria, lipofuscin granules, atrial granules
What’s different about the T tubule system in the skeletal muscle vs. the cardiac muscle?
cardiac = dyad
skeletal = triad
Where are T tubules positioned in cardiac muscle?
specifically on Z discs. that’s why there are fewer and why dyads are formed and not triads.
What element do intercalated discs always coincide with?
What is their function?
Z lines
Bind cells + transmit forces of contraction + allow the spread of excitation
What are the 3 different membrane-to-membrane contacts with interdigitating junctions?
Transverse regions
- Fascia Adherens
(anchors for actin filaments) Actin filaments at the ends of terminal sarcomeres that insert into junction –> this helps to transmit contractile forces b/w cells so we don’t damage cardiac muscle, bundles, and fibers
- Desmosomes - provide anchorage for intermediate filaments and help give structural support
Longitudinal region
- Gap junctions - sites of low electrical resistance. allow for excitation to pass b/w cells for uniform contraction
What is the dyad T tubule?
where are they found?
what do they permit?
Dyad = 1 T-tubule + 1 SR cisterna
these are found at the Z-lines
permit uniform contraction of a single cardiomyocyte
What’s the best way to find junctions?
find the direction of the sarcomere
What are lipofuscin granules?
small bodies that accumulate with age in stable non-dividing cells
they contain material derived from residual bodies after lysosomal digestion
What are Myoendocrine Cells?
atrial cardiomyocytes that contain membrane bound granules specifically releasing Atrial natriuretic factor (ANF)
this targets the kidney to decrease Na+ and H2O retention
Endocardium?
Endothelium + thin layer of loose CT
How do you know if its the endocardium or the epicardium?
look at the thickness. you don’t want a thick wall of the endocardium.
What’s the difference between atrial and ventricular endocardium?
Ventricular has a subendocardial layer that has thin layer of CT w/smooth muscle and contains PURKINJE fibers!
What are nodal cardiomyocytes?
what do they lack?
cells w/in the SA/AV nodes that initiate/relay electrical signals
modified by PNS + SNS, only modify rate of intrinsic cardiac muscle contraction
they lack intercalated disc
What is the conducting system?
SA –> AV –> AV bundle –> R/L bundle branches –> Purkinje fibers
What are purkinje fibers?
What do they do?
What is their hallmarks?
What do they lack?
have some intercalated disc but fewer than their cardiomyocyte neighbors.
they generate and transmit impulse
the cells are much larger and the nucleus is much larger.
they’re more rounded and not y shaped and branched.
they lack a t tubule system
What is the fibrous skeleton?
what is a weird one of this?
4 rings, one around each valve.
dense regular connective tissue. acting like a ligament that anchors the valves in place, provide structural support and extends into heart valves to give structural support.
also insulates the spread of electrical current.
The membranous portion of the inter ventricular septum.
What are the heart valves?
what are they lined with?
extension of the endocardium
they extend off of that and have components of the fibrous rings and they have a core of fibroelastic CT –> we need flexibility
they are lined with endothelium on both sides because we don’t want blood to flow in the lumen.
