Cardiac Histology

Question 1

What structures can be seen near the nuclei of cardiac muscle cells?

Answer 1

lipofuscin granules

• “gold splotches”
• lysosomal residue

Question 2

What are some hallmark characteristics of cardiac muscle tissue?

Answer 2

• striated
• intercalated discs
• lipofuscin granules

Question 3

What is the characteristic shape of smooth muscle nuclei in a longitudinal cut?

Answer 3

-elongated

Question 4

What types of cells are the endocardium epithelium?

Answer 4

-simple squamous epithelium

Question 5

What makes up the endocardium?

Answer 5

-endothelium + thin layer of loose connective tissue

Question 6

What is the main layering difference between the endocardium of the ventricles vs. the atria?

Answer 6

ventricular endocardium has a subendocardial layer

Question 7

What is the subendocardial layer?

Answer 7

• layer in the endocardium of the ventricles

- thin layer of connective tissue + smooth muscle

Question 8

What is the thickest middle layer of the heart?

Answer 8

myocardium

Question 9

How are the cardiac myocytes bundled in the atria?

Answer 9

-bundled in a way that narrows the heart upon ctx

Question 10

How are the cardiac myocytes bundled in the ventricles?

Answer 10

-bundled in a way to shorten the heart upon ctx

Question 11

Where are nodal cardiocytes?

Answer 11

• sinuatrial node

- atrioventricular node

Question 12

What is the function of myoendocrine cardiocytes?

Answer 12

-secrete hormonal peptides

Question 13

What types of cardiocytes are found in the myocardium?

Answer 13

• contractile cardiocytes
• nodal cardiocytes
• myoendocrine cardiocytes

Question 14

Why do intercalated discs hold cardiocytes together so well?

Answer 14

-interdigitating junctions make stronger connections b/w cells than smooth surfaces

Question 15

What are the three membrane-to-membrane connections of intercalated discs?

Answer 15

• fascia adherens (perpendicular)
• desmosomes (perpendicular)
• gap junctions (parallel)

Question 16

What is fascia adherens?

Answer 16

• actin filaments at the ends of sarcomeres that insert into the junction
• most predominant membrane-membrane connection

Question 17

What is the role of fascia adherens?

Answer 17

-transmit contractile force

Question 18

What is the role of desmosomes?

Answer 18

-provide anchorage for the intermediate filaments of the cytoskeleton

Question 19

What are gap junctions?

Answer 19

-sites of low electrical resistance

Question 20

What is the role of gap junctions?

Answer 20

-allows excitation to pass b/w cells

Question 21

What is a T-tubule?

Answer 21

-fingerlike invaginations of the sarcolemma

Question 22

What is a diad T-tubule that are found in the myocardium?

Answer 22

one T-tubule plus one cisterna of the sarcoplasmic reticulum

Question 23

Where, along the cardiocytes, are diad T-tubules found?

Answer 23

-at the Z lines

Question 24

What is the function of the diad T-tubules?

Answer 24

permit uniform contraction of myofibrils within a single cardiocyte

Question 25

Where are myoendocrine cardiocytes mostly found?

Answer 25

right atrium

Question 26

What structures are contained within myoendocrine cardiocytes?

Answer 26

atrial granules

Question 27

What is contained within the atrial granules of myoendocrine cardiocytes?

Answer 27

precursor to atrial natriuretic factor (ANF)

Question 28

What is the function of atrial natriuretic factor (ANF)?

Answer 28

- target the kidneys to decrease sodium and water retention | - increase glomerular filtration rate (GFR)

Question 29

Delineate the electrical conduction system of the heart.

Answer 29

sinuatrial node ... atrioventricular node ... atrioventricular bundle, right/left bundle branches, subendocardial branches

Question 30

What tissue makes up the fibrous skeleton of the heart?

Answer 30

-dense irregular connective tissue

Question 31

In what layer of the heart is the fibrous skeleton?

Answer 31

endocardium

Question 32

What is the role of the fibrous skeleton?

Answer 32

- anchors valves (insertion of muscle) - electrical insulator b/w atria and ventricles - maintains shape of atrioventricular canals - contributes to the septa

Question 33

What tissue lines the heart valves and why is it beneficial?

Answer 33

- endothelium (simple squamous) | - provides a smooth surface for blood to flow

Question 34

With what framework structure are the heart valves continuous?

Answer 34

continuous with the fibrous skeleton

Question 35

What tissue forms the core of the heart valves?

Answer 35

fibroelastic connective tissue

Question 36

What is a valve ring?

Answer 36

-component of the fibrous skeleton comprised of condensed layer of fibroelastic endocardium