7. Cardiac Histology

Question 1

smooth m contains:

Answer 1

bundles of fusiform cells

centrally located nuclei

no visible striations

Question 2

what is the fxn of smooth m

Answer 2

interconnected by gap jxns - rhythmic contractions inherent (but can be changed by ANS)

continous contraction w low force

Question 3

how can you differentiate btn smooth M & dense regular CT

Answer 3

smooth m = no waves

dense regular CT = wavy

Question 4

Answer 4

smooth m

cross section (centrally located nuclei w unstained region)

longitudinal (elongated nuclei w rounded ends)

Question 5

what are the components that help smooth m contraction occur?

Answer 5

contractile apparatus of think & thick filaments

calveolae - allow movement of Ca2+

dense bodies/cytoplasmic densities - anchor filaments

contract as one unit (globular shape)

Question 6

what are the dense bodies made of

Answer 6

desmin vimentin intermediate filaments

tension transmitted via these densities

Question 7

what does cardiac M contain

Answer 7

short, branched, y-shaped cells w/ 1-2 nuclei

extensive capillaries

intercalated discs

purkinje cells

Question 8

what are intercalated discs

Answer 8

transverse jxns at ends of cells that allow passage of electical current

interdigiting jxns btn cardiocytes

coincide w/ z line

= bind cell, transmit force of contract & spread excitation

Question 9

what is the fxn of purkinje cells

Answer 9

modifies cardiac M cells that act as a pacemaker for the heart

conduct electrical impulses that allow coordinated contraction

-less myofibrils, lack T-tubules & more glycogen

Question 10

Answer 10

cardiac M

cross-section: cells vary in diameter w/ central nuclei

longitudinal: striations, intercalated discs

also contain lipofuscin granules - lysosomal residues

Question 11

what is the difference btn fibrous & serous pericardium

Answer 11

fibrous: outer covering of dense CT
serous: produce serous fluid to prevent friction; line the fibrous pericardium (parietal) & outer surface of heart (visceral)

Question 12

Answer 12

epicardium aka visceral serous pericardium

= outer layer of heart

= dense fibrocollagenous . CT w/ elastic fibers

-lined w/ mesotheium

contain branches of coronary As embedded in fat tissue

Question 13

what are the cells that make up the myocardium

Answer 13

cardiocytes - contractile

nodal cardiocytes - in SA & AV node

myoendocrine cardiocytes - secrete hormonal peptides

Question 14

what is the difference btn the cardiac M bundles in the atria vs the ventricles

Answer 14

atria = more circular to help push down blood

ventricles = figure 8 to help push blood up against gravity

Question 15

what is the myocardium characterized by

Answer 15

striations

intercalated discs

lipofuscin granules

diad T tubule

mitochondria

atrial granules (myoendocrine cardiocytes)

Question 16

what is the fxn of the part being pointed to

Answer 16

= intercalated discs

bind cells, transmit force of contraction & spread excitation

Question 17

what are the 3 types of membrane to membrane contacts of the interdigiting jxns

Answer 17

transverse region

1. fascia adherens
2. desmosomes

longitudinal region

1. gap (nexus) jxns

Question 18

what are the fascia adherens & what is its fxn

Answer 18

actin filaments at the ends of terminal sarcomeres that insert into the interdigiting jxn

= transmit contractile force btn cells

Question 19

what is the fxn of desmosomes

Answer 19

provide anshorage for the intermediate filaments of cytoskeleton

Question 20

what are gap jxns

Answer 20

sites of low electical resistance

-allow excitation to pass btn cells

Question 21

what are diad t-tubles

Answer 21

1 T tuble + 1 SR cisterna

fingerlike invaginations of sarcolemma @ Z line

• allows uniform contraction of myofibrils w/i a single cardiocyte

Question 22

what are nodal cardiocytes

Answer 22

modified cells w/i SA & AV nodes that initiate & relay singals =inherent pacemakers

parasym & sym dibers terminate in the nodes & ONLY modify rate of intrisic cardiac m contraction

Question 23

what are these & what are the fxns

Answer 23

atrial granules (myoendocrine cardiocytes)

contain precursor of ANF –> (increase GFR -> kidneys filter more, decrease Na & h2o retention -> pee more)

Question 24

how is the endocardium different in the atria vs ventricles

Answer 24

atria: no subendocardial layer w purkinje fibers close to endothelium, intermixed with myocardium
ventricle: contain subendocardial layer - thin layer of CT w smooth m; merge w/ myocardium & contain purkinje fiber branches

Question 25

Answer 25

ventricular endocardium

Question 26

Answer 26

atrial endocardium

Question 27

what is the fibrous (cardiac) skeleton made of & what is its fxn

Answer 27

dense irregular CT in endocardium

• = anchor valves & surround AV canals to maintain shape
• = contribupe to intercentricular & interatrial septa
• =insertion of cardiac M
• = electrical insulater btn atria & ventricles

Question 28

Answer 28

cardiac skeleton

(CT = chordae tendineae & C = CT)

Question 29

what are heart valves made of

Answer 29

core of fibroelastic CT covered by endothelium

-fibroelastic layer condense to form valve ring (create central portion of the valve)