Virtual Microscope: Cardiac Muscle and Blood Vessels

Question 1

Cardiac Muscle Like Skeletal Muscle is ______

Answer 1

Striated

Question 2

Do cardiomyocytes normally branch

Answer 2

Yes

Question 3

How many nuclei are associate with each cardiomyocyte?

Answer 3

One or two

Question 4

Cardiomyocyte nuclei are located ________ within the fibers.

Answer 4

Centrally

Question 5

Identify the intercalated disks between cardiomyocytes

Answer 5

Question 6

If you were to examine intercalated disks ultrastructurally, what two major cell/cell junctions would you find?

Answer 6

1. Fascia adherens - in the transverse part
2. Gap Junctions - in the lateral part

Question 7

What is the functional significance of intercalated disks?

Answer 7

The components of intercalated disks enable cell adhesion and electrical coupling of adjacent cardiomyocytes.

Question 8

The cross sectional diameter of cardiomyocytes is ______. Why?

Answer 8

The cross sectional diameter of cardiomyocytes is variable, because cardiomyocytes branch.

Question 9

What morphological features would you look for as evidence of a previous myocardial infarction (MI)?

Answer 9

You would see an accumulation of collagen indicative of scar formation.

Question 10

What does the circulatory system include?

Answer 10

The cardiovascular system and the lymphatic system.

Question 11

What do tissues do blood vessels contain?

Answer 11

1) epithelium, which in blood vessels is termed endothelium
2) connective tissue, which is found in all 3 blood vessels tunicas. (intima, media and adventitia)
3) muscle, specifically smooth muscle

Question 12

What are some of the fucntions of the circulatory system?

Answer 12

1) Transportation of O₂, nutrients, waste products, body fluid, solutes, and immune system components.
2) Facilitate body heat homeostasis

Question 13

Tunica intima

Answer 13

Boaders the Lumen

Consist of endothelium (simple squamous epithelium) and subendothelial connective tissue.

Question 14

What can sometimes be found inbetween the tunica intima and tunica media?

Answer 14

Internal elastic lamina

Question 15

Tunica Media

Answer 15

Consists of vascular smooth muscle arranged in concentric layers along with fenestrated elastic laminae.

Question 16

What seperates the tunica media from the tunica adventitia in large arteries?

Answer 16

External elastic lamina

Question 17

Tunica Adventitia

Answer 17

The outermost layer of the vessel wall.

Question 18

The fenestrated elastic laminae

Answer 18

fenestra - means window

they are sheets of elastic fibers wrapped around the vessel lumen. Within these elastic sheets are fenestra/windows.

Question 19

In the light microscope what does elastic fibers look like?

Answer 19

They appear shiny or refractile, which is most evident when the sub-stage (iris) diaphragm is partially closed.

Question 20

What is the functional significance of the fenestrated elastic laminae in the elastic artery?

Answer 20

The elastic tissue in elastic arteries helps maintain constant arterial pressure by stretching during ventricular contraction (systole) and recoiiling during ventricular relaxation (diastole).

Question 21

The nuclei within the tunica media belong to what cell type?

Answer 21

Smooth muscle cells

Question 22

In a muscular artery

Answer 22

The sub-endothelia CT of the intima is relatively thick.

The tunica media is quite thick in this type of cessel.

Fenestrated elastic laminae are less prominent than when present in the elastic artery.

Question 23

What is the function of the vasa vasorum?

Answer 23

Provide O₂ and nutrients to cells within the tunica media of large vessels, particularly veins which obtain less O₂ by diffusion from the blood due to the O₂ poor quality of the blood they transport.

Question 24

What does A refer to?

What does B refer to?

Answer 24

A = Internal Elastic Lamina

B = External Elastic Lamina

Question 25

The number of coronary artery bypass procedures has declined recently. Which procedure involving coronary artery lumen enlargement is used by cardiologists?

Answer 25

angioplasty (percutaneous transluminal coronary angioplasty (PTCA))

Question 26

What are some possible interventions to promote endothelialization?

Answer 26

1) Local administration of endothelial cell growth factors (e.g. VEGF)
2) Endothelial cell seeding
3) Estrogen-loaded stents - promote healing and reduce SMC migration and proliferation- stes which attract circulating endothelial cells.

Question 27

What is an arteriole characterized by?

Answer 27

• an external diameter less than 100 micrometers (~15 RBCs in diameter from adventitia to adventitia)
• wall thickness that is approximately equal to lumen diameter
• little or no dubendothelial connective tissue
• 2 to 5 smooth muscle layers in the tunica media
• no external elastic lamina
• very thin tunica adventitia

Question 28

What do metarterioles do?

Answer 28

Regulate blood flow from arterioles into capillary beds due to its precapillary sphincters.

Question 29

Capilaries

Answer 29

7 micrometers in diameter

Which allows only a single RBC to pass.

consist of only endothelial cells.

(Nucleus is not always in the same plane of the section)

Question 30

Continuous capillaries

Answer 30

Cardiac and Skeletal Muscle, brain and peripheral nerves

The endothelial cells are tightly attached to each other by junctional complexes

Question 31

Fenesstrated capillaries

Answer 31

Found in the kidneys, intestine and some endocrine glands where rapid exchange occurs between the blood and other tissues.

Have pores (fenestrae/fenestrations) within the endothelial cell cytoplasm.

Question 32

Sinusoidal Capillaries

Answer 32

Found in bone marrow, liver, lymphoid organs and some endocrine glands.

Have unusually wide lumens (30-40 micrometers), fenestrations, gaps between the endothelial cells of their walls and a discontinuous basal lamina outside of the endothelial cells.

Shape is tortuous because it conforms to the channel created by the parenchymal cells of the surrounding tissue.