Histology

Question 1

What are the five layers of the heart wall?

Answer 1

1) Endocardium
2) Myocardium
3) Epicardium
4) Pericardial Cavity
5) Fibrous Pericardium

Question 2

What are the three sublayers of the endocardium and their components?

Answer 2

1) Endothelium–simple squamous epithelium
2) Subendothelium–mostly areolar CT with elastin and smooth muscle
3) Subendocardium–areolar CT, contains Purkinje fibers

Question 3

What are the components of the epicardium?

Answer 3

Epicardium is essentially the visceral pericardium; it has a dense adipose layer and some areolar CT. Coronary vessels are found here. On the surface is the serous pericardium (mesothelium) that secretes pericardial fluid

Question 4

What is the role of the pericardial cavity?

Answer 4

Reduces friction between the pumping heart and the fibrous pericardial sac

Question 5

What are the two main components of the fibrous pericardium?

Answer 5

A serous pericardial layer that also creates pericardial fluid
A fibrous pericardium made of dense irregular CT that forms the bulk of the gross pericardial sac

Question 6

With what is the endothelium of the heart continuous?

Answer 6

Endothelium of the vasculature

Question 7

With what is the fibrous pericardium of the heart continuous?

Answer 7

The tunica adventitia of the great vessels

Question 8

Of what is the fibrous skeleton made and what are its three main components in the heart?

Answer 8

Dense irregular CT

1) Rings around the valve
2) Trigones that anchor the rings to each other
3) Membranous septa that contains branches of the conducting system

Question 9

What are the three main jobs of the fibrous skeleton?

Answer 9

1) Anchors the heart valves
2) Serves as attachment site for the myocardium
3) Insulates electrical impulses

Question 10

What are the three layers of a heart valve?

Answer 10

1) Fibrosa
2) Ventricularis
3) Spongiosa (arterial or auricular [for atria])

Question 11

Of what are the three layers made?

Answer 11

Fibrosa–dense irregular CT
Ventricularis–HIGH dense irregular connective tissue
Spongiosa–more loose areolar with elastin

Question 12

What are the external regulators of the heart?

Answer 12

Parasympathetic = vagus nerve
Sympathetic = cardiac splanchnics

Question 13

What are the intrinsic regulators of heart rhythm and what types of cells are they?

Answer 13

SA node cells (pacemaker)
AV node cells
Bundle of His
Purkinje cells
All are specialized cardiac cells with high conductivity. Most are thin, small, and wavy except the Purkinje cells which are large

Question 14

What are the three layers of a blood vessel and their components?

Answer 14

Tunica intima–endothelium, subendothelium, internal elastic lamina
Tunica media–smooth muscle, external elastic lamina
Tunica adventitia—mostly CT, but may have vessels in it

Question 15

What are the roles of the endothelium?

Answer 15

1) Inhibit coagulation by secreting heparin
2) Promote clotting
3) Change vascular diameter (and resistance) by secreting NO or ACE
4) affect angiogenesis by secreting TNF-beta
5) affect immune response by secreting ILs
6) secreting matrix proteins

Question 16

How do the layers of major elastic arteries appear?

Answer 16

• Tunica intima does not have much of an internal elastic lamina
• The tunic media is VERY thick with numerous elastin layers
• the tunica adventitia is comparatively thin but does have blood vessels and nerves

Question 17

How do the layers of muscular arteries appear?

Answer 17

• there is a small or absent subendothelium
• the internal elastic lamina is VERY obvious
• tends to have spiraling smooth muscle
• the external elastic lamina is obvious
• there may be arterioles and venules in the tunica adventitia

Question 18

How do the layers of arterioles appear?

Answer 18

The elastic lamina appears less obvious as the diameter decreases
tunica media is typically between 1 and 4 cell layers thick
-there is no external elastic lamina
-the tunica adventitia blends with surrounding tissues

Question 19

How do the layers of a venule appear?

Answer 19

There is no subendothelium nor internal elastic lamina
there is a very thin tunica media and no external elastic lamina
-the tunica adventitia blends in with the surrounding tissue

Question 20

How do the layers of a medium vein appear?

Answer 20

there is a thin subendothelium and valves may be microscopically present

• the tunica media is thin
• the tunica adventitia is thicker than the other layers

Question 21

How do the layers of a large vein appear?

Answer 21

• there is a thin subendothelium
• there is a thin circular arrangement of smooth muscle in the tunica media
• the tunica adventitia is very thick and contains longitudinal smooth muscle

Question 22

What are the three types of capillaries and where can they be found?

Answer 22

1) Continuous-has occluding layers between cells so only small molecules pass; found in muscle, lungs, and central nervous system
2) Fenestrated–has small gaps in the cells but not the basal lamina; found in the glomerulus of the kidney
3) Discontinuous–rather open fenestrations in cells and basal lamina; found in the liver, spleen, and bone marrow

Question 23

What is a pericyte?

Answer 23

A specialized smooth muscle cell that can occlude a capillary and is proliferative in angiogenesis