Vascular Histology

Question 1

What are the 3 layers within the tunica intima?

Answer 1

endothelium = single layer of squamous epithelial cells
basal lamina = thin EC layer
subendothelial layer = loose areolar CT; interal elastic membrane

Question 2

What makes up the tunica media?

How does it compare btw arteries and veins?

Answer 2

circumferentially arranged layers of smooth muscle; from internal elastic membrane to external elastic membrane; elastin reticular fibers, and proteoglycans

much thicker in arteries

Question 3

What makes up the tunica adventitia?

How does it compare btw arteries and veins?

Answer 3

longitudinally arranged collagenous tissue w/ few elastic fibers; merges w/ loose CT surrounding vessels

thin in arteries; very thick in veins

Question 4

What is the vasa vasorum?

Answer 4

vessels of tunica adventitia that supply blood to vascular walls themselves of large arteries and veins

Question 5

What is the nervi vasorum?

Answer 5

ANS input that controls contraction of vascular smooth muscle

Question 6

What distinguishes large arteries?

Answer 6

a ton of elastin in tunica media that forms lamellae btw muscle layers
No fibroblasts! (smooth muscle makes ECM)

Question 7

What distinguishes medium arteries?

Answer 7

more smooth muscle and less elastin in tunica media than elastic arteries
*prominent internal elastic membrane seen and external elastic membrane is recognizable
tunica adventitia abt same thickness as tunica media

Question 8

What distinguishes small arteries and arterioles?

Answer 8

number of smooth muscle layers
small = up to 8 layers w/ internal elastic membrane
arterioles = 1-2 layers, internal elastic mem may or may not be present

Question 9

What is the site of metabolic exchange?

Answer 9

capillary beds

Question 10

what are pericytes?

Answer 10

perivascular contractile cells in capillaries (instead of smooth muscle)
enclosed w/in BL continuous w/ endothelium

Question 11

What controls perivascular contractile contraction?

Answer 11

Nitric Oxide

Question 12

What controls the permeability of blood vessels?

Answer 12

number of cell-cell junctions btw endothelial cells in the tunica intima

Question 13

What characterizes a continuous capillary?

Answer 13

complete basal lamina; a lot of junctions btw endothelial cells
no fenestrations

Question 14

What characterizes a fenestrated capillary?

Answer 14

fenestrations w/in endothelial cells and in btw them –> allow things through
Basal lamina is still complete

Question 15

What characterizes a discontinuous capillary?

Answer 15

discontinuous basal lamina

fenestrations in endocthelium

Question 16

Where are fenestrated capillaries located?

Answer 16

endocrine glands and sites of fluid/metabolite absorption

Question 17

Where are discontinuous capillaries located?

Answer 17

bone marrow, liver spleen

fenestrations are large enough to let an entire cell through!

Question 18

What is a thoroughfare channel?

Answer 18

distal end of metarteriole
lacks smooth muscle
connects capillary to a postcapillary venule

Question 19

What is a metarteriole?

Answer 19

first branch off of arteriole supplying tissues

Question 20

What happens if precapillary sphincters contract?

Answer 20

bloodflow will shunt so it goes straight from metarteriole –> thoroughfare channel –> venule
skips capillary bed

Question 21

What structures do capillaries lack?

Answer 21

tunica media and tunica adventitia

Question 22

What distinguishes a small vein?

Answer 22

diameter less than 1 mm in diameter; continuous w/ muscular venules
all 3 tunics
media is 2-3 layers thick

Question 23

What distinguishes a medium vein?

Answer 23

have a diameter of as much as 10 mm

these are most of named veins

Question 24

What is the order into a small vein from a capillary?

Answer 24

postcapillary venule –> muscular venules –> small vein

Question 25

What characterizes a postcapillary venule?

Answer 25

drain capillaries

no true tunica media

Question 26

What characterizes a muscular venule?

Answer 26

1-2 layers smooth muscle in media

thin tunica adventitia

Question 27

What characterizes medium veins?

Answer 27

always travel w/ muscular As
thicker tunica media and adventitia
valves
wall often folded

Question 28

What is the thickest layer of a large vein?

Answer 28

tunica adventitia - contains longitudinal smooth muscle!

also has collagen, elastic fibers, and fibroblasts

Question 29

How do you distinguish a large vein from a medium vein?

Answer 29

tunica adventitia on a large vein will be thicker and has longitudinal smooth muscles

Question 30

What holds openings in lymphatic capillaries in place?

Answer 30

anchoring filaments btw endothelial cells

Question 31

What characterizes lymphatic capillaries?

Answer 31

closed-ended tubes among capillary beds
one-way valves formed by endothelial cells overlapping
incomplete BL for more permeability

Question 32

What characterizes lymphatic vessels?

Answer 32

have all vascular tunics and have valves

continuous tight jxns to prevent leakage

Question 33

What is the order of lymph flow?

Answer 33

lymphatic capillaries –> lymphatic vessels –> trunks –> R lymphatic duct –> thoracic duct –> drain into brachiocephalic V.