Histo lecture 1

Question 1

What are the qualities of cardiac muscle cells?

Smooth?

Answer 1

Striated and Involuntary

Non-striated and Involuntary

Question 2

What do the smooth muscle occur as?

What about the nucleus?

Answer 2

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

Question 3

Where is smooth muscle found?

What connects the smooth muscle to one another?

Answer 3

visceral organs, pelvic organs, abdominal organs, vasculature

gap junctions so they can contract uniformly.

Question 4

What is unique to smooth muscle?

what is it controlled by?

Answer 4

It can sustain very long contractions… intestines or the GI during labor or something like that.

ANS and enteric nervous system

Question 5

What is the mechanism to smooth muscle contraction?

what isn’t there as compared to smooth muscle?

Answer 5

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

Question 6

What do the contractile proteins anchor to?

Answer 6

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

Question 7

What happens to the dense bodies during contraction?

Answer 7

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

Question 8

What are the little indentations found all along the edges of smooth muscle?

Answer 8

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.

Question 9

What does cardiac muscle look like generally?

Answer 9

Cells are short, branch, and Y shaped. There are a lot of capillaries

centralized nucleus

Question 10

What is the hallmark of cardiac muscle tissue?

Answer 10

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

Question 11

What do you see around the nucleus in a cardiac cell?

Answer 11

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

Question 12

What are the different layers of the pericardium?

what creates the pericardial cavity?

Answer 12

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.

Question 13

Why does the epicardium have a layer of simple squamous epithelium?

what’s under it?

Answer 13

mesothelium.

fat and loose areolar tissue.

Question 14

What’s deep to the epicardium?

Answer 14

myocardium –> where we see cardiac muscle

Question 15

What’s deep to the myocardium?

Answer 15

endocardium.. this is loose areolar CT lined with endothelium

Question 16

What’s endothelium?

why do we have this on the heart?

Answer 16

Inner lining of the blood vessels.

we want a smooth way for the blood to move, we don’t want turbulence.

Question 17

What are the different component layers of the epicardium?

Answer 17

It’s also visceral pericardium

It has dense fibrocollagenous CT with elastic fibers, and is lined with mesothelium

Question 18

What is there to know about the myocardium?

Answer 18

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.

Question 19

what are cardiomyocytes?

nodal cardiomyocytes

Along with the above 2, what do these 2 + myoendocrine cardiomyocytes a part of?

Answer 19

contractile cells of the heart

also called purkinje cells –> these are in the SA and AV nodes

myocardium

Question 20

What is the myocardium characterized by?

Answer 20

Striations, Intercalated discs, Dyad T-Tubule system, mitochondria, lipofuscin granules, atrial granules

Question 21

What’s different about the T tubule system in the skeletal muscle vs. the cardiac muscle?

Answer 21

cardiac = dyad

skeletal = triad

Question 22

Where are T tubules positioned in cardiac muscle?

Answer 22

specifically on Z discs. that’s why there are fewer and why dyads are formed and not triads.

Question 23

What element do intercalated discs always coincide with?

What is their function?

Answer 23

Z lines

Bind cells + transmit forces of contraction + allow the spread of excitation

Question 24

What are the 3 different membrane-to-membrane contacts with interdigitating junctions?

Answer 24

Transverse regions

1. 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

2. Desmosomes - provide anchorage for intermediate filaments and help give structural support

Longitudinal region

1. Gap junctions - sites of low electrical resistance. allow for excitation to pass b/w cells for uniform contraction

Question 25

What is the dyad T tubule?

where are they found?

what do they permit?

Answer 25

Dyad = 1 T-tubule + 1 SR cisterna

these are found at the Z-lines

permit uniform contraction of a single cardiomyocyte

Question 26

What’s the best way to find junctions?

Answer 26

find the direction of the sarcomere

Question 27

What are lipofuscin granules?

Answer 27

small bodies that accumulate with age in stable non-dividing cells

they contain material derived from residual bodies after lysosomal digestion

Question 28

What are Myoendocrine Cells?

Answer 28

atrial cardiomyocytes that contain membrane bound granules specifically releasing Atrial natriuretic factor (ANF)

this targets the kidney to decrease Na+ and H2O retention

Question 29

Endocardium?

Answer 29

Endothelium + thin layer of loose CT

Question 30

How do you know if its the endocardium or the epicardium?

Answer 30

look at the thickness. you don’t want a thick wall of the endocardium.

Question 31

What’s the difference between atrial and ventricular endocardium?

Answer 31

Ventricular has a subendocardial layer that has thin layer of CT w/smooth muscle and contains PURKINJE fibers!

Question 32

What are nodal cardiomyocytes?

what do they lack?

Answer 32

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

Question 33

What is the conducting system?

Answer 33

SA –> AV –> AV bundle –> R/L bundle branches –> Purkinje fibers

Question 34

What are purkinje fibers?

What do they do?

What is their hallmarks?

What do they lack?

Answer 34

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

Question 35

What is the fibrous skeleton?

what is a weird one of this?

Answer 35

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.

Question 36

What are the heart valves?

what are they lined with?

Answer 36

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.