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CP Exam 2 > Lecture 4: Cardiac Histology > Flashcards

Lecture 4: Cardiac Histology Flashcards

1
Q

What are some characteristics of smooth muscle?

  • Type of cell
  • Nucleus
  • Striated or not?
A
  • Elongated fusiform cells with tapered ends
  • One elongated, nucleus that is located centrally
  • Not striated
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2
Q

How are cells in smooth muscle connected?

What does this permit?

A

They are connected by gap junctions, which allows them to contract at the same time with a low force.

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3
Q

What controls the contractions of smooth muscle? (2)

A

1. Autonomic NS

2. Enteric NS

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4
Q

How are the contractile filaments in smooth muscle organized?

A

Smooth muscle has thick and thin filaments (actin and myosin) that is anchored to cytoplasmic densities/dense bodies.

Tension is then transmitted from the densities–> membrane, allowing uniform contraction.

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5
Q

Contractile elements (thick and thin filaments) in smooth muscle are connected to dense bodies/cytoplasmic bodies in smooth muscle. What are the dense bodies made up of?

A
  1. Desmin
  2. Vimentin intermediate filaments
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6
Q

When the thin and thick filaments contract, it causes the fusiform cells to change shapes. Describe the change in shape.

A

Cells go from a thick body with tapered ends–> globular (ball like).

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7
Q

What are some characteristics of cardiac muscle?

  • What does it look like?
  • Nucleus?
  • What else can you find in the muscle? (3)
A
  • Short, branched, Y shaped
  • 1 or more nucleus that are more round
  • Many capillaries, intercalated discs, purkinje cells
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8
Q

What allows the passage of electrical currents in cardiac muscle?

A

Intercalated discs–> transverse junctions at the end of cells that allow currents to be passed from cell–> cell.

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9
Q

Cardiac muscle consists of purkinje cells. What are they?

A

Purkinje cells are

modified cardiac muscle that act as the “pacemaker for the heart”.

They prevent cardiac muscle from tearing.

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10
Q

What are the layers of pericardium of the heart?

A

Outermost–> innermost

1. Fibrous pericardium

2. Parietal serous pericardium

3. Visceral serous pericardium.

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11
Q

What kind of tissue is the fibrous pericardium?

A

dense connective tissue.

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12
Q

Visceral layer of the serous pericardium is also called what?

A

Epicardium.

It is the outer surface of the heart.

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13
Q

What are the 3 layers of the heart wall?

A
  1. Epicardium
  2. Myocardium
  3. Endocardium
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14
Q

What are the characteristics of epicardium (visceral serous pericardium)?

A
  • Outermost layer of the heart
  • Dense CT with elastic fibers, lined with simple squamous epithelium (mesothelium).

+ Adipose tissue ( with coronary arteries embedded in it)

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15
Q

What is mesothelium?

A

Simple squamous epithelium thiat is located in pericardium, pleura, peritoneum

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16
Q

What cells are located in myocardium, the thiccest layer of the heart?

A
  1. Cardiomyocytes (which are contractile)
  2. Nodal cardomyocytes (these are purkinje cells, located in the SA and AV node)
  3. Myoendocrine cardiomyocytes
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17
Q

Myocardium is characterized by (6):

A

1. Striated

2. Intercalated discs

3. DYAD t-tubule system

4. mT

5. Lipofuscin granules

6. Atrial granules (myoendrocrine granules)

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18
Q

Where are intercalated discs located?

A

In between 2 cardiomyocytes; always coincide with the Z-disk.

They always coincide with the Z disc.

19
Q

What are the components of the intercalated discs, interdigitating junctions located between cardiomyocytes?

A

The components of intercalated discs are organized into a transverse region and a longitudinal region.

Transverse region (percendicular to the length of the cell)

1. Fascia adherens

2. Desmosomes

Longitudinal region (parallel to the length of the cell)

3. Gap (nexus ) junctions

20
Q

Interacalated discs are made up of fascia adherens located in the transverse region of the cardiomyocyte. What are they?

A

Fascia adherens are most predominant contact, made up of actin filaments junctions, located at the end of the terminal sarcomere that help cells contract.

They transmit contractile forces between cells.

21
Q

Interacalated discs are made up of desmosomes located in the transverse region of the cardiomyocyte. What are they?

A

Desmosomes are where intermediate filaments anchor to the cytoskeleton

22
Q

Interacalated discs are made up of gap (nexus) junctions located in the longitudinal region of the cardiomyocyte. What are they?

A

Allows excitation to pass between cells.

They are sites of low electrical resistance.

23
Q

The mycardium is made up of dyad T-tubules. Describe these?

A

Dyad T-tubules= 1 T-tubule and 1 SR cisterna.

invaginations of the sarcolemma that are found at the Z-line. Thus, they allow uniform contraction within one cardiomyocyte

24
Q

Because the dyad T-tubules in myocardium located at the Z-line. What does this allow?

A

It allows the uniform contraction of myofibrils within one cardiomyocyte.

25
Q

Lipofuscin granules are located in the myocardium. What is their role?

A

Lipofuscin granules are small bodies that consist of material from residual bodies after they are ingested by lyosomes.

They accumulate with age in stable, non-dividing cells.

26
Q

Myocardium contains atrial granules. What are atrial granules?

A

Atrial granules (myoendocrine cardiomyocytes) are atrial cardiomyocytes that contain membrane-bound granules that contains the PRECURSOR to ANF (atrial natriuretic factor).

27
Q

What is atrial natriuretic factor (ANF)?

A

ANF is released from atrial granules.

It goes to the kidneys decreases retention of H20 and Na+.

28
Q

What is endocardium made up of?

A

1. Endothelium

2. Thin layer of loose CT

29
Q

How does endocardium differ in the ventricles and atria?

A

Endocardium differs in thickness in the ventricles and atria.

In the ventricles, it contains a subendocardial layer.

30
Q

The endocardium located in the _________, has a subendcardial layer.

A

ventricles.

31
Q

What is the subendocardial layer of endocardium in the ventricles look like?

A
  • Thin layer of CT with smooth muscle,

that has purkinje fibers.

32
Q

What does the endocardium in the atria look like?

A

Purkinje fibers are closer to the endothelium and intermixed with the myocardium.

33
Q

Describe the conducting system of the heart.

Are intercalated discs present?

A

The conducting system is made up of nodal cardiomyocytes, innervated by the the parasympathetic and sympathetic NS.

Does not have intercalated discs!

34
Q

What are nodal cardiomyocytes?

A

Modified cells located in the SA/AV node that initate and relay electrical signals.

35
Q

T/F: The parasympathetic NS and sympathetic NS only MODIFIES the intrisic cardiac muscle contraction.

A

T

36
Q

Conduction pathway of the heart:

A

SA node –> AV node–> AV bundle (bundle of his)–> LR bundle branches–> purkinje fibers

37
Q

Describe purkinje fibers.

Where are they typically found?

A
  • Fibers that conduct impulses
  • typically adjacent to endocardium and at the periphery of the myocardium.
  • do not have t-tubules.
38
Q

How can we distinguish purkinje fibers from myocardium?

A
  • Cell is larger with LOOKS like it lacks nuclei.
  • less intercalated discs that myocardium
  • more rounded
  • located at the periphery of myocardium
39
Q

What is the cardiac skeleton

A

A fibrous skeleton with

  • 4 rings, one around each valve
  • 2 trigons, which connects the valves.
  • membranous portion of the septum
40
Q

What is the function of the cardiac skeleton?

A
  1. Anchors the valves
  2. Surrounds the AV canals to maintain shape
  3. Makes the interventricular and interatrial septa, creating the electrical insulator between the atria and ventricle
  4. Insertion point for cardiac muscle
41
Q

What kind of tissue is the cardiac skeleton and where is it located?

A

-Dense irregular CT located in the endocardium

42
Q

Describe the structure of heart valves.

A

Extensions of endocardium (endothelium located on both sides) with a core of fibroelastic CT (lamina fibrosa) that condenses –> valve ring

43
Q

Heart valves are continous with the ___________________.

A

Cardiac skeleton.

44
Q
A

CP Exam 2 (27 decks)

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