Cardiac Histology

Question 1

How are smooth muscle cells different in appearance from cardiac muscle cells?

Answer 1

• Smooth muscle cells are not striated
• Smooth muscle cells occur as sheets/bundles of elongated fusiform cells

Question 2

How are smooth muscle cells interconnected?

Answer 2

Gap junctions

Question 3

What types of contractions do smooth muscle produce?

Answer 3

• Continuous contractions of low force
• Rhythmic contraction responsive to ANS stimulation

Question 4

What are some of the key histological features of cardiac muscle?

Answer 4

• Cells short, branched, Y shaped
• Extensive capillaries
• Intercalated discs/transverse junctions
• Purkinje cells (may or may not be able to see depending on magnification)

Question 5

What is present in cardiac cells that allows the passage of electrical current?

Answer 5

Intercalated discs/transverse junctions

Question 6

What type of cells are present in cardiac muscle that act as the “pacemaker” cells?

Answer 6

Purkinje Cells

Question 7

What are the key features of the epicardium/visceral pericardium?

Answer 7

• Outermost layer of the heart wall
• Dense fibrocollagenous CT w/ elastic fibers, lined with mesothelium
• Branches of coronary arteries are embedded in adipose tissue

Question 8

What are some key features of the myocardium?

Answer 8

• Thickest layer of the heart
• Contains
  
  • Striation
  • Intercalated discs
  • Dyad T tubule system
  • Mitochondria (lots-since the heart is always pumping blood)
  • Lipofuscin granules
  • Atrial granules (myoendocrine cells)

Question 9

Where are intercalated discs located?

Answer 9

• At sites where cells meet end to end
• Always coincide with Z lines

Question 10

What are the three types of membrane-membrane contact in cardiac muscle cells?

Answer 10

• Fascia adherens (Transverse region)
• Desmosomes (Transverse region)
• Gap junctions (Longitudinal region)

Question 11

What are the features of the fascia adherens?

Answer 11

• Actin filaments @ end of terminal sarcomeres
• Transmit contractile forces between cells

Question 12

What is the most prominent of the three types of membrane-membrane contacts?

Answer 12

Fascia adherens

Question 13

What are the features of desmosomes?

Answer 13

• Provide anchorage for intermediate filaments of the cytoskeleton
• Prevent tearing depending on the force of contraction

Question 14

What are the features of gap junctions?

Answer 14

• Sites of low electrical resistance
• Allow excitation to pass between cells

Question 15

What makes up a Dyad T tubule?

Answer 15

1 T tubule + 1 SR cisterna

Question 16

Where are dyad t tubules found? What is there function?

Answer 16

Z lines, Permits uniform contraction of myofibrils within a single cardiomyocyte

Question 17

Define lipofuscin granules

Answer 17

• small bodies that accumulate with age in stable non-dividing cells
• contain material from residual bodies after lysosomal digestion
• Pretty close to the nucleus on histology slide (if staining permits you to see them)

Question 18

Define atrial granules

Answer 18

• Atrial cardiomyocytes with membrane bound granules
• Contain ANF
  
  • ​Increases GFR
  • Decrease Na+ and H20 retention in kidneys

Question 19

What are some key features of the endocardium?

Answer 19

• Endothelium + loose aereolar CT
• Thickness differs in ventricles v atria
  
  • ​Ventricles have subendocardial layer which contains Purkinje Fibers
  • In the atria, Purkinje Fibers are closer to endothelium and intermixed with myocardium
    *

Question 20

What are nodal cardiomyocytes?

Answer 20

• Modified cells in SA/AV node that initiate and relay electrical signals
• LACK INTERCALATED DISCS
• Only MODIFY rate of intrinsic cardiac muscle contraction

Question 21

What are Purkinje fibers? What are some of their histological features?

Answer 21

• Conducting fibers that generate and transmit impulse
• Located at periphery of myocardium/ adjacent to to endocardium
• Lack T tubules
• Cells larger and have larger nucleus
• Few intercalated discs
• Nuclei are more round in appearance

Question 22

What are the histological features of the cardiac skeleton?

Answer 22

• Dense irregular CT located in endocardium
• Anchors valves and surrounds AV valves to maintain shape

Question 23

What is the overall function of the cardiac skeleton?

Answer 23

Electrical insulator between atria and ventricles

Question 24

What are the histological features of heart valves?

Answer 24

• Continuous with cardiac skeleton
• Core of fibroelastic CT (lamina fibrosa) covered by endothelium
• Fibroelastic layer condenses to form valve ring (makes central portion of valve)

Question 25

Answer 25

Skeletal muscle

Cardiac muscle

Smooth muscle

Question 26

Identify the tissue type.

Answer 26

Smooth muscle

Question 27

Identify the tissue types.

Answer 27

Top= longitudinal section of smooth muscle

Bottom= cross section of smooth muscle

Question 28

Identify the tissue type

Answer 28

Cardiac muscle

Question 29

Identify the three arrows.

Answer 29

Top arrow= endocardium

Middle arrow=myocardium

Bottom arrow= epicardium

Question 30

Identify the tissue type shown.

Answer 30

Epicardium

Question 31

Identify the arrows.

Answer 31

Intercalated discs.

Question 32

Answer 32

Top to bottom:

• Desmosome
• Desmosome
• Fascia adherens
• Gap junction
• Fascia adherens

Question 33

Answer 33

Left (top to bottom)

• Intercalated disc
• Gap junction

Right

-Terminal cisterna of SR

Question 34

Identify the tissue feature.

Answer 34

Lipofuscin granules

Question 35

Identify the circled structure

Answer 35

Atrial granules

Question 36

Identify the features on the histological slides

Answer 36

• Ventricular endocardium (with subendocardium)
• Atrial endocardium
• M=myocardium
• P= Purkinje Fibers

Question 37

Identify the cell type.

Answer 37

Purkinje Fibers

Question 38

Identify.

Answer 38

Left to right top to bottom

• Left atrium
• Endocardium
• Endothelium
• Valve ring
• Left ventricle
• Endocardium
• Endothelium
• Lamina fibrosa