Cardiac Histo

Question 1

Smooth Muscle

Answer 1

Occur in bundles or sheets of elongated fusiform cells with finely tapered ends

No striations

Interconnected by gap junctions

Produces continuous contraction of low force

Rhythmic contraction that is inherent, but responsive to ANS

Question 2

Smooth muscle contraction

Answer 2

Possess a contractile apparatus of thin and thick filaments

Anchor to cytoplasmic densities/dense bodies

Dense bodies comprised of demin and vimentin intermediate filaments

Tension transmitted via densities to the membrane

cells contract as one unit and assume a globular shape

Question 3

Cardiac Muscle

Answer 3

Cells are short, branched, and y-shaped

Extensive capillaries

Question 4

Intercalated discs

Answer 4

In cardiac muscle

Transverse junction at the ends of cells that allow passage of electrical current

Coincide with the z line

Bind cells, transmit forces of contraction and allow the spread of excitation

Question 5

Purkinje cells

Answer 5

Modified cardiac muscle cells that act as the pacemaker for the heart

Question 6

Fibrous Pericardium

Answer 6

Outer covering of dense connective tissue

Question 7

Parietal layer of serous pericardium

Answer 7

Lines the inner surface of the fibrous pericardium

Question 8

Visceral layer of serous pericardium

Answer 8

Covers the outer surface of the heart

Question 9

Pericadial cavity

Answer 9

Space between the parietal and visceral layers

Question 10

Epicardium

Answer 10

Outermost layer of the heart wall
Synonymous with visceral pericardium

Dense fibrocollagenous CT with elastic fibers, lined wit mesothelium

Branches of coronary arteries are embedded in adipose tissue

Question 11

Myocardium

Answer 11

Thickest layer of the heart: Cardiomyocytes, nodal cardiomyocytes, myoendocrine cardiomyocytes

Characterized by: Striations, intercalated discs, dyad T-tubles system, mitochondria, lipofuscin granules, atrial granules

Question 12

Fascia adherens

Answer 12

Transverse region, membrane to membrane contact

Actin filaments at the ends of terminal sarcomeres insert into junction
Transmit contractile forces between cells

Most predominant

Question 13

Desmosomes

Answer 13

Transveres region, membrane to membrane contact

Provide anchorage for the intermediate filaments of cytoskeleton

Question 14

Gap junctions

Answer 14

Longitudinal region, membrane to membrane contacts

Sites of low electrical resistance

allows excitation to pass between cells

Question 15

Dyad T-tubules

Answer 15

dyad=1 t-tuble + 1 SR cisterna

Fingerlike invaginations of sarcolemma

Found at z lines

Permits uniform contraction of myofibrils within a single cardiomyocte

Question 16

Lipofuscin granules

Answer 16

Small bodies that accumulate with age in stable non-dividing cells (ie cardiomyocytes)

Contain material derived from residual bodies after lysosomal digestion

Question 17

Atrial Granules

Answer 17

Myoendocrine cells

Atrial cardiomyocytes that contain membrane bound granules

Smaller quantities are found in the left atrium and the ventricles

Contain precursor of atrial natriuretic factor ANF

ANF targets kidneys to decrease Na+ and H20 retention

Question 18

Endocardium

Answer 18

Endothelium plus thin layer of loose CT

Thickness differs in ventricles vs atria:
Ventricular endocardium has a subendocardial layer that contains thin layer of CT with smooth muscle and purkinje fibers

In the atria, purkinje fibers are often closer to the endothelium and intermixed with the myocardium

Question 19

Conducting System

Answer 19

Nodal cardiomyocytes are modified cells with in the SA and AV nodes that initiate/ relay electrical signals

Parasympathetic and sympathetic fibers terminate in the nodes

Only modify rate of intrinsic cardiac muscle contraction

Question 20

Purkinje Fibers

Answer 20

Highly specialized conduction fibers that generate and transmit impulse

Larger and typically seen at periphery of myocardium

Mostly lack t tubules

Question 21

Cardiac Skeleton

Answer 21

Contributes to interventricular and interatrial septa

Extends into the valve cusps and chordae tendineae

Insertion of cardiac muscle

Electrical insulator between atria and ventricles

Dense irrecgular CT located in the endocardium

Anchors valves and surrounds AV canals to maintain shape

Question 22

Heart Valves

Answer 22

Core of fibroelastic CT covered by endothelium

Continuous with the cardiac skeleton

Fibroelastic layer of endocardium condenses to form a valve ring

Creates central portion of the valve