Histology Lecture 9 - Cardiovascular System

Question 1

Name the three layers (tunics) of the heart.

Answer 1

Endocardium, myocardium, epicardium

Question 2

Describe the three layers of the endocardium.

Answer 2

Inner layer: composed of endothelium and some CT.
Middle layer: “don’t worry about it”
Outer layer: AKA subendocardium consists of loose CT. Also contains Purkinje fibers

Question 3

Which heart layer is continuous with the tunica intima of vessels entering the heart?

Answer 3

The endocardium

Question 4

In which heart layer are branching myocytes found?

Answer 4

Myocardium

Question 5

What distinguishes the myocardium?

Answer 5

1. Branching myocytes w/ central nuclei

2. Intercalated discs!

Question 6

What is the visceral pericardium? What does it consist of?

Answer 6

It is the outer layer of the epicardium of the heart that is defined as an outer simple squamous epithelium continuous with the lining of the pericardial cavity.

Question 7

What function does the visceral pericardium serve?

Answer 7

Secretes fluid for lubrication of the heart.

Question 8

Do conductile myocytes need nervous stimulation for contraction? How are these cells connected?

Answer 8

Nope. Connected via gap junctions

Question 9

Are Purkinje fibers wide or narrow? Describe them histologically.

Answer 9

Wide!

They have large amounts of glycogen, which gives them a washed-out appearance (this is diagnostic)

Question 10

What are the three tunics of arteries?

Answer 10

Intima, media, adventitia

Question 11

Describe the composition of the tunica intima.

Answer 11

Composed of endothelial cells, loose CT, and arteries also have internal elastic lamina.

Question 12

Describe the composition of the tunica media.

Answer 12

The tunica media has smooth muscle (concentrically arranged), elastic fibers and lamella, reticular fibers, and arteries will have external elastic lamina.

Question 13

Describe the composition of the tunica adventitia.

Answer 13

Composed of Fibroblasts, collagen type I, and elastic fibers.

Question 14

What is characteristic of the tunica media of the large elastic arteries? What is the function of these arteries?

Answer 14

Concentrically arranged and preforated/fenestrated elastic lamina. Function is to smooth out pulsatile flow.

Question 15

How many layers of smooth muscle are found in the tunica media of muscular arteries?

Answer 15

4 to 40 layers.

Question 16

What distinguishes arterioles histologically?

Answer 16

Only 1 to 5 smooth muscle layers, poorly developed adventitia, small lumen.

Question 17

What are pericytes?

Answer 17

Cells that glomb on to the outside of capillaries and venules.

Question 18

What do capillaries/venules consist of?

Answer 18

A tube of endothelium and a basal lamina.

Question 19

How is blood flow to capillaries controlled?

Answer 19

Contraction/relaxation of precapillary sphincters.

Question 20

A sphincter says what?

Answer 20

What?

Exactly.

Question 21

Name the three types of capillaries.

Answer 21

1. Continuous
2. Fenestrated
3. Sinusoidal

Question 22

Describe the composition of a continuous capillary. Where are they found?

Answer 22

Consists of a single uninterrupted layer of endothelial cells. Found in skeletal muscle, lungs, skin, and form part of the blood-brain barrier.

Question 23

Describe the composition of a fenestrated capillary. Where are they found?

Answer 23

These have endothelial pores. Found in tissues where rapid exchange is needed (endocrine glands, intestinal wall, kidneys)

Question 24

Describe the composition of a sinusoidal capillary. Where are they found?

Answer 24

Has a discontinuous endothelium and basal lamina. Found where free exchange of blood components is necessary (liver, bone marrow), and where blood cells need to pass (spleen)

Question 25

What are the three microvascular pathways?

Answer 25

Simple, arteriovenous shunt, and portal system

Question 26

In a capillary, when can free exchange of nutrients occur?

Answer 26

When hydrostatic pressure at the capillary end = oncotic pressure at the venule end.

Question 27

How are veins identified histologically?

Answer 27

Have a lumen that looks collapsed, less smooth muscle, and more collagenous CT.

Question 28

How are muscular veins differentiated from arteries?

Answer 28

In muscular veins, CT and smooth muscle are arranged irregularly in the media, and the media is overall thinner. The adventitia is very thick (thickest layer)

Question 29

Describe the composition of the large veins.

Answer 29

Intima is well developed. Media has more than 5 smooth muscle layers. Adventitia is the thickest layer and contains elastic fibers and bundles of collagen.

Question 30

Can some veins have smooth muscle in the adventitia?

Answer 30

Yes! The largest veins have this (e.g. vena cava)

Question 31

How is a lymphatic vessel identified histologically?

Answer 31

They have an endothelial layer and lack a basal lamina.

Question 32

What is vasa vasorum and where are they found?

Answer 32

Very small blood vessels in the tunica media and adventitia of large arteries or veins that supply oxygen to cells in the arteries.

Question 33

How can you tell the difference between a large elastic artery and a large muscular artery?

Answer 33

Elastic arteries have many elastic fibers in the media, and muscular is predominantly smooth muscle in the media

Question 34

How can you tell the difference between a lymph vessel and venule?

Answer 34

Lymph vessels will have no RBCs (only WBCs) and will also have chylomicrons (fat) that appear as unstained spherical structures.