Cardiac Histo

Question 1

What are the characteristics of smooth muscle?

Answer 1

• bundles of elongated fusiform cells
• centrally located nuclei
• GAP JUNCTIONS
• NO STRIATIONS
• continuous low force contraction (respond to ANS)
• NOT WAVY UPON STAINING

Question 2

How do smooth muscle contract?

Answer 2

• thick & thin filaments anchored to cytoplasmic densities
• dense bodies contain design and vitmentin
• tension transmitted via densities to membrane

Question 3

What is special about smooth muscle contraction?

Answer 3

Lacks T-tubules (unlike cardiac and skeletal)

Question 4

What are characteristic of cardiac muscle?

Answer 4

• Y - shaped
• branched ; extensive capillaries
• intercalated discs
• purkinje cells
• lipofuscin granules (lysosomal residue)

Question 5

What are intercalated discs?

Answer 5

transverse junctions at ends of cardiac cells the allow passage of electrical current

Question 6

What are Purkinje cells?

Answer 6

modified cardiac m. cells that act as the pacemaker for the heart

Question 7

What is the epicardium made of?

Answer 7

dense fibrocollagenous CT w/ elastic fibers, lined with mesothelium

Question 8

What is the Pericardium made of

Answer 8

serous membrane = mesothelial lined tissue (simple squamous)

Question 9

What 3 cell types make up the myocardium?

Answer 9

1) cardiocytes
2) nodal cardiocytes (SA & AV nodes)
3) myoendocrine cardiocytes (hormone)

Question 10

What are characteristics of the myocardium?

Answer 10

striations ; IC discs ; DIAD t-tubule ; lipofuscin granules ; mito ; serial granules (myoendo)

Question 11

What are the characteristics of IC discs?

Answer 11

-interdigitated junctions b/w cariocytes ; always line up with Z lines

Question 12

What are the functions of IC discs?

Answer 12

1) bind cells
2) help transmit the force of contraction
3) transmission of electrical pulse

Question 13

What are the 3 membrane to membrane contact the IC discs makes and their function?

Answer 13

Transverse (perpendicular)

1) fascia adherent -> actin filaments at end of sarcomere = transmit force of contraction **
2) desmosomes = anchor for intermediate filaments of the cytoskeleton

Longitudinal (parallel)
3) gap junctions - transmit electrical impulse (low resistance)

Question 14

What is special about the t - tubule system of the myocardium?

Answer 14

its DIAD = 1 T-TUBULE & 1 CISTERNA

-permits uniform contraction of a myofibril w/in a single cardiocyte

Question 15

What are nodal cardiocytes?

Answer 15

modified cardiocytes w/in SA & AV nodes that initiates and relay electrical signals

-parasympathetic sna sympathetic fibers end here

Question 16

What is the ONLY change nodal cardiocytes can make?

Answer 16

on the intrinsic HR

Question 17

What are Purkinje fibers?

Answer 17

specialized cells that conduct electrical impulses for coordinated contraction

• • ^ ^ ^ glycogen
• lack t-tubules (mostly)

appear “puffy and round”

Question 18

What are myoendocrine cardiocytes?

Answer 18

atrial cells that contain membrane bound granules

ie = precursor for atrial natriuretic factos (ANF) = decrease Na and H20 retention

Question 19

What is the endocardium made of?

Answer 19

endoderm + thin layer of loose CT

Question 20

How are the ventricular and atrial endocardium different?

Answer 20

the ventricle = sub endothelial cells (Purkinje)

Question 21

What makes up the Fibrous/Cardiac Skeleton and where is it located?

Answer 21

-dense irregular CT located in endocardium

Question 22

What are the roles of the fibrous skeleton?

Answer 22

1) anchors valves & sure. AV canals to maintain shape
2) contribute to IV & IA septa
3) extends into valve cusps & chordae tendonae (insertion of cardiac m. and electrical insulator)

Question 23

What are the heart valves composed of?

Answer 23

core of fibroelastic CT (lamina fibrosa) covered by endothelium

• continuous with cardiac skeleton
• fibroelastic layer= condense to form valve ring to form central portion of valve