Cardio Lecture 3--Cardio Histology And Ultrastructure

Front 1

How many nuclei are found in myocytes? Are they located at the center or at the periphery?

Back 1

1 or at most 2 in cases of hypertrophy--centrally located

Front 2

Do myocytes form a syncytium?

Back 2

No--they split into smaller branches at each longitudinal end that lie adjacent to each other

Front 3

What percent of the cells in the heart are myocytes? What percent of the mass of the heart do they represent?

Back 3

1/3--75%

Front 4

What must be inferred from finding a carcinoid tumor on the heart?

Back 4

The heart has no epithelium, so an epitheloid tumor there must be a metastisis

Front 5

True/False: The left and right ventricles have three layers of myocardial fibers.

Back 5

FALSE--the left has THREE layers: the subendocardium, the middle layer, and the superficial layer--the right layer has only a subendocardial and a subepicardial layer

Front 6

What is the function of the three layers of the LEFT VENTRICLE?

Back 6

The subendocardium is where contraction starts and moves from the apex to the base; the middle layer is thickest and constricts the ventricle; the superficial layer squeezes the ventricle to provide the final contribution to systole

Front 7

What is the epicardium composed of?

Back 7

It is a sheet of fibrous tissue containing elastic fibers

Front 8

What secretes pericardial fluid?

Back 8

The mesothelial cells on the outer surface secrete lubricating pericardial fluid

Front 9

True/False: Endocardium is completely different from endothelium.

Back 9

FALSE--they are analogs because the heart is modified blood vessels in the early embryological stage

Front 10

Where are purkinje fibers found? How do they relate to regular myocytes?

Back 10

They are found in the endocardium only and they are less eosinophilic and larger than regular myocytes

Front 11

What separates the purkinje layer from normal myocardium?

Back 11

Sometimes a layer of fibroelastic tissue separates the bundled branches from the underlying myocardium

Front 12

The interstitium is composed primarily of what? What is one of the main functions of this substance?

Back 12

Collagen--it keeps the cell to cell alignment preventing overdistention that might result in hypertrophy during cardiac relaxation(diastole)

Front 13

What can cause collagen to increase and what can cause it to decrease?

Back 13

Increases with age or pathological condition due to deposition and degradation OR pressure overload situations like hypertrophy and aortic stenosis--it can decrease in cases of VOLUME overload such as mitral or aortic regurgitation

Front 14

What organ possesses the highest density of mitochondria?

Back 14

The heart

Front 15

See Sarcomere Diagram

Back 15

Slide 14

Front 16

What organelles are most important in the heart?

Back 16

The mitochondria and the sarcoplasmic reticulum

Front 17

What is the unit of contraction in the heart?

Back 17

The sarcomere

Front 18

True/False: Myosin attaches indirectly to the Z lines through titin

Back 18

FALSE

Front 19

True/False: Due to the action of the intercalated discs, there is no need for an advanced T tubule system in heart muscle.

Back 19

FALSE--T tubules extend deep into the myocyte to connect the membrane of the cell to the SR

Front 20

True/False: Purkinje fibers are modified muscle cells that have nexus, desmosomes, and intercalated discs, as well as more glycogen than regular myocytes.

Back 20

FALSE--they do have more glycogen as well as nexus and desmosomes, but THEY DON'T HAVE INTERCALATED DISCS

Front 21

What is the ultimate effect of T tubules?

Back 21

Calcium is released from storage in the terminal cisternae and binds to contractile proteins to cause sarcomere contraction

Front 22

What is calcium induced calcium release?

Back 22

Stimulus from the cellular membrane continues on to the next myocyte while depolarizing the current myocyte

Front 23

What are the two components of the intercalated discs? What are their functions?

Back 23

Desmosomes and nexuses; desmosomes are where the cytoskeletal proteins desmin and vimentin anchor--nexuses are the specialized structures responsible for ionic continuity and contraction

Front 24

What proteins are found in the nexus?

Back 24

Connexin 43(important in ventricular muscle) and Connexin 40(important in purkinje fibers)

Front 25

Which band changes in size...the A band or the I band?

Back 25

I band

Front 26

The heart gains energy through glycogen and what other means?

Back 26

Lipids through fatty acid oxidation

Front 27

What are the three components of the intercalated disc and what do they do?

Back 27

Fascia adherens(actin filament attachment points), desmosomes(anchorage for IM filaments), and nexuses(transmit ions)

Front 28

What are the three layers of the aortic valve?

Back 28

Ventricularis, Spongiosa, and Fibrosa

Front 29

What is the ventricularis and what is it composed of? Does it have any action?

Back 29

The layer of the aortic valve that is closest to the ventricle--it is composed of elastin and collagen--its function is to extend in diastole and contract in systole

Front 30

What is the spongiosa and what is it primarily composed of? Does it have a function or action?

Back 30

The middle layer of the aortic valve that contains glycosaminoglycans and functions to absorb shear forces and cushion shick between ventricular and fibrous layer during valve movements

Front 31

What is the fibrosa and what is it composed of? What is its function?

Back 31

The outer layer of the aortic valve that is composed of collagen that provides STRUCTURAL INTEGRITY and strength during systole

Front 32

How do the heart valves last so long?

Back 32

The spongiosa and the fibrous layers in all levels transmit stress to the annulus

Front 33

True/False: Cusps contain a rich supply of blood vessels that keeps them functioning throughout a person's lifetime.

Back 33

FALSE--they are avascular except for the proximal 1/3. Vascularization implies diseased valves

Front 34

What are the two types of valve cells?

Back 34

Interstitial cells and endothelial cells--interstitials replenish connective tissue and respond to vasoactives(they are the first cells to calcify)--endothelial cells coat valve surfaces and differentiate eventually into interstitials(no immune response)

Front 35

Are the pulmonary arteries considered to be elastic?

Back 35

Yes--they have a thick media with elastin and collagen and a thin intima of endothelial cells

Front 36

What happens to the elastic arteries with aging?

Back 36

They lose their elasticity and so systolic blood pressure increases and diastolic blood pressure decreases

Front 37

What are the muscular arteries?What is a main anatomical feature of these arteries?

Back 37

CORONARY ARTERIES, cerebrals arteries, radial and femoral arteries--Internal elastic lamina and external elastic lamina separate media from adventitia

Front 38

See artery diagram on slide 36

Back 38

Slide 36

Front 39

Coronary arteries have what feature that protects them during treatment?

Back 39

Thick adventitia with collagen

Front 40

True/False: arterioles possess both an IEL and an EEL

Back 40

False--they lack an IEL

Front 41

Can you insert a catheter into an arteriole?

Back 41

No because the adventitia is thin

Front 42

Capillary walls are composed of what? What are found around the capillaries?

Back 42

Single endothelial cells without media or adventitia--pericytes surround the capillaries and have contractile function

Front 43

What layers are found in venules?

Back 43

Intima and media without elastic fibers--poorly defined IEL, muscular media and adventitia--large veins have collagen and elastic fibers