Vascular Histology

Question 1

What are the three layers of blood vessels walls from outside to inside?

Answer 1

tunica adventitia
tunica media
tunica intima

Question 2

What part(s) of the blood vessel walls give recoil ability?

Answer 2

• internal elastic membrane in the subendothelial layer of the tunica intima
• external elastic membrane in the tunica media

Question 3

What structures are present on the tunica intima of veins, but not arteries?

Answer 3

valves

Question 4

What are the three layers of the tunica intima?

Answer 4

• endothelium (single layer of squamous epithelium)
• basal lamina (collagen, proteoglycans, glycoproteins)
• subendothelial layer (loose connective tissue)

Question 5

What is the composition of the tunica media?

Answer 5

-circumferentially arranged layers of smooth muscles

Question 6

What is the purpose of the tunica media?

Answer 6

-ctx to briefly close off lumen and continually pump blood through the vasculature

Question 7

Is the tunica media thick or thin in the arteries?

Answer 7

thick

Question 8

Is the tunica media thick or thin in the veins?

Answer 8

thin

Question 9

What is the composition of the tunica adventitia (externa)?

Answer 9

longitudinally-arranged collagenous tissue

Question 10

True or False: the tunica adventitia merges with the surrounding connective tissue of a neurovascular bundle

Answer 10

True

Question 11

Is the tunica adventitia thick or thin in the arteries?

Answer 11

thin

Question 12

Is the tunica adventitia thick or thin in the veins?

Answer 12

thick

Question 13

What is the purpose of the tunica adventitia?

Answer 13

prevents overexpansion of the vessels

Question 14

How do the tissues of the blood vessels themselves get nutrients?

Answer 14

vasa vasorum located in the tunica adventitia

Question 15

In which vessels are the vasa vasorum most numerous and why?

Answer 15

large veins d/t lack of diffusion properties

Question 16

In which vessels do vasa vasorum not exist and why?

Answer 16

arterioles and capillaries because they can get their nutrients by diffusion

Question 17

What provides innervation to the vasculature and in what layer of the vessel wall is it located?

Answer 17

nervi vasorum in the tunica adventitia = ANS input that controls ctx of vascular smooth muscle

Question 18

What are two main histological characteristics of large (elastic) arteries?

Answer 18

• elastin forms concentric lamellae b/w muscle layers

- majority of the vessel wall is tunica media

Question 19

What are three main histological characteristics of medium (muscular) arteries?

Answer 19

• more smooth muscle, less elastin
• prominent internal elastic membrane
• tunica media equal in size to tunica adventitia

Question 20

How many layers of smooth muscle do small arteries have and how does that differ from arterioles?

Answer 20

small arteries have up to 8, while arterioles have only 1-2

-arterioles also may not have an internal elastic membrane present

Question 21

In which type of vessel does the ANS do most of its regulation (constriction and dilation)?

Answer 21

-arterioles

Question 22

Which vessels is the site of metabolic exchange?

Answer 22

capillaries

Question 23

What is the diameter of the capillaries?

Answer 23

big enough for one RBC to flow through

Question 24

What types of cells are present in the endothelial layer of capillaries?

Answer 24

pericytes

Question 25

What is the function of pericytes?

Answer 25

contractile cells controlled by nitric oxide that surround capillaries and promote stability

Question 26

What are the three types of capillaries?

Answer 26

continuous (most common)
fenestrated
discontinuous

Question 27

What are characteristics of continuous capillaries?

Answer 27

• restrict passage of molecules

- locations: muscle, brain, peripheral nerves

Question 28

What are characteristics of fenestrated capillaries?

Answer 28

• allow things to seep through

- locations: kidneys, gallbladder

Question 29

What are characteristics of discontinuous capillaries?

Answer 29

• massively leaky, not selective
• discontinuous basal lamina
• locations: bone marrow, liver, spleen

Question 30

How is blood flow regulated through capillary beds?

Answer 30

pre-capillary sphincters

Question 31

What connects arterioles to capillaries?

Answer 31

metarterioles

Question 32

What connects metarterioles to poscapillary venules to bypass the capillary bed if necessary?

Answer 32

thoroughfare channels

• contain no smooth muscle
• still have a small amt of metabolic exchange

Question 33

What are the two types of venules and what distinguishes them from each other?

Answer 33

postcapillary venules
–have no tunica media

muscular venules

Question 34

Most named veins are in which category?

Answer 34

medium veins

Question 35

What are the histological characteristics of medium veins?

Answer 35

thicker tunics

obvious valves

Question 36

What is a histological characteristics of large veins?

Answer 36

tunica adventitia is the thickest layer

Question 37

What are histological characteristics of veins overall?

Answer 37

• tunics not as distinct
• thinner walls
• larger lumen

Question 38

What is the purpose of the lymphatic vessels?

Answer 38

-return fluid to the venous system

Question 39

Where does the lymphatic system originate?

Answer 39

-within the capillary beds as closed-ended tubes

Question 40

What keeps lymph flowing unidirectionally?

Answer 40

overlapping endothelial cells acting as valves

Question 41

What gives lymph vessels their high permeability?

Answer 41

incomplete basal lamina

Question 42

Are lymph vessels moveable or stationary and why?

Answer 42

stationary d/t anchoring filaments

Question 43

Delineate the progession of lymph vessels?

Answer 43

lymphatic capillaries
collecting lymphatic vessels
lymphatic trunks
lymphatic ducts
brachiocephalic vv.

Question 44

What prevents fluid from leaking back out of the lymphatic vessels?

Answer 44

tight junctions

Question 45

What is a major histological characteristic of lymphatic vessels?

Answer 45

NO RBC