Vascular Histology

Question 1

Lymph flow throughout the body

Answer 1

lymphatic capillaries

to

lymphatic vessels

to

lymphatic trunks

to

right lymphatic duct

to

thoracic duct

to

brachiocephalic v.

Question 2

Lymphatic capillaries/vessels all have what features?

Answer 2

vascular tunics and posses valves

walls increase in thickness as vessels increase in size

tight junctions prevent leaks

there are afferents and efferents

Question 3

What are close ended tubes found among capillary beds?

Answer 3

• overlapping endothelial cells form 1-way valves for collecting lymph
• incomplete basal lamina increases permeability
• endothelial cells held in place by anchoring filaments
• form lymphatic vessels

Question 4

What is the function of lymphatic vessels?

Answer 4

• circulate lymph through most of the body
• unidirectional, convey fluid only from tissues
• collect lymph and return it to the venous supply

Question 5

Large Veins: Tunica Adventitia

Answer 5

thickest layer of the vessel wall

contains collagen and elastic fibers and fibroblasts

contains longitudinal smooth muscle cells

Question 6

Large Veins: Tunica media

Answer 6

thin, circumferentially arranged smooth muscle cells, collagen and fibroblasts

Question 7

Large Veins: Tunica Intima

Answer 7

thin and blends with tunica media

Question 8

Medium Veins

Answer 8

travel with muscular arteries

thicker tunica media and adventitia

wall is often folded around large lumen

contains valves

Question 9

Postcapillary venules

muscular venules

small veins

Answer 9

drain capillaries, no true tunica media

1-2 layers of smooth muscle in tunica media, thin tunica adventitia

3 tunics, 2-3 layers in tunica media, tunica adventitia thicker

Question 10

Venules

Answer 10

receive blood from capillaries and have a diameter as small as 0.1mm

subclassified as postcapillary and muscular venules

Question 11

Small Veins

Answer 11

Less than 1mm in diameter, are continuous with muscular venules

Question 12

Medium veins

Answer 12

a diameter of as much as 10mm, represent most of the named veins

Question 13

Large Veins

Answer 13

usually have a diameter >10 mm

superior and inferior vena cava, hepatic portal vein

Question 14

Tunics are not as distinct or well defined in veins, but large and medium veins have ____

Tunica intima may contain ____

Answer 14

all three tunics

valve (thin CT core covered in endothelial cells)

Question 15

Veins have thinner walls than ____

____ have larger lumens than ____

lumen in ____ often collapse

Answer 15

arteries!

Veins; arteries!

Veins!

Question 16

How does blood bypass a capillary bed?

Answer 16

Contracted precapillary sphincters will “shunt” blood flow

this prevents exchange within true capillaries and forces blood to enter venous return more quickly

differentially occurs based on metabolic demand

Question 17

Describe blood flow through the well-perfused capillary bed

Answer 17

Metarterioles first branch off of the arteriole supplying tissues

precapillary sphincters regulate blood through the capillaries

then true capillaries branch from the metarteriole, lacking SM and may have pericytes

the thoroughfare channel is the distal end of the metarteriole and connects to a postcapillary venule

Question 18

Compare and contrast continuous, fenestrated and discontinous capillaries

Answer 18

Continuous: only certain, small (size, charge, etc) things can get through

Fenestrated: “holey”, larger things can get through, important for filtering urine

Discontinuous: very leaky, discontinuous basal lamina

Question 19

What forms the innermost layer of the tunica intima?

What is the function of this layer?

Answer 19

single layer of endothelial cells connected via cell-cell junctions

support the basement membrane and produce collagen

involved in blood coagulation and vasodilation/constriction

Question 20

What is the function of the pericytes?

Answer 20

perivascular contractile cells with branching cytoplasmic processes

they are enclosed within the basal lamina, continuous with that of the endothelium

controlled by NO

promote stability of capillaries and venules

Question 21

What is special about small arteries?

Answer 21

up to 8 layers and will have an internal elastic membrane

Question 22

What is special about arterioles?

Answer 22

1-2 layers, internal elastic membrane may/may not be present

FLOW REGULATORS of capillary beds

SNS: tunica media causes vasoconstriction

PNS: tunica media causes vasodilation

Question 23

Where does a prominent internal elastic membrane become apparant as well as a recognizeable external elastic membrane?

Answer 23

Medium (Muscular) arteries

(thicker tinuca adventitia, about the same as the tunica media)

Question 24

What are the hallmark features of the large (elastic) arteries?

Answer 24

elastin forms sheets between muscle cell layers

NO fibroblasts

lumen size reduces pressure and allows strong blood flow to continue during diastole

Question 25

The tunica adventitia contains the vasa vasorum and nervi vasorum which are what?

Answer 25

VV: vessels of the tunica adventitia that supply blood to the vascular tunics themselves (found in large arteries and veins) NV: ANS input that controls contraction of vascular smooth muscle

Question 26

what are the hallmark features of the tunica adventitia/externa

Answer 26

long. arranged collagen tissue with some elastic fibers merges with loose CT around vessels thin in arteries, thick in veins

Question 27

What are some hallmark features of the tunica media?

Answer 27

layers of smooth muscle thick in arteries spans from the internal elastic membrane to the external elastic membrane

Question 28

What are the hallmark features of the tunica intima?

Answer 28

endothelium basal lamina (thin EC layer with collagen, PTG, GP) subendothelial layer (loose CT, internal elastic membrane)

Question 29

Everything we need to know about continuous vessels

Answer 29

* most common * tight, occluding junctions that seal off intercellular clefts * molecular exchange happens via diffusion or transcytosis * continuous basement membrane * **muscle, brain, peripheral nerves, exocrine glands** * cells meet end-to-end

Question 30

Everything we need to know about Fenestrated vessels

Answer 30

* located in organs where molecular exchange with blood is important * tight junctions with fenestrations * greater exchange across the endothelium, limited to size of macromolecule * continuous basement membrane * endocrine, fluid/metabolite absorption, gallbladder, kidney

Question 31

Everything we need to know about discontinuous/sinusoidal vessels

Answer 31

* located where exchange of macromoleucles and cells must openly occur * large fenestrations (the largest) * open exchange occurs, large cell movements allowed * partial discontinuous basement membrane * bone marrow, liver, spleen

Question 32

Everything we need to know about large arteries (elastic)

Answer 32

\>10mm tunica intima: endothelium, CT, Sm. M tunic MEDIA: Sm. M., elastic lamellae tunica adventitia: thinner, CT, elastic fibers

Question 33

Everything we need to know about medium arteries (muscular)

Answer 33

2-10mm tunica intima: endothelium, CT, Sm. M, BIG internal elastic membrane tunica media: Sm.M, collagen fibers, relatively little elastic tissues tunica adventitia: thinner than tunica media, CT, some elastic

Question 34

Everything we need to know about small arteries

Answer 34

0.1-2mm tunica intima: endothelium, CT, Sm. M, internal elastic membrane tunica media: Sm. M (8-10layers), collagen tunica advenitia: thinner, CT, some elastic

Question 35

Everything we need to know about arterioles

Answer 35

10-100um tunica intima: endothelium, CT, Sm.M tunica media: Sm. M (1-2 cell layers) tunica adventitia: thin, CT (poorly defined)

Question 36

Everything we need to know about capillaries

Answer 36

4-10um tunica intima: endothelium tunica media and adventitia: NONE

Question 37

Everything we need to know about postcapillary venules

Answer 37

10-50um tunica intima: endothelium and pericytes tunica media and adventitia: NONE

Question 38

Everything we need to know about muscular venules

Answer 38

50-100 um tunica intima: endothelium tunica media: Sm. M (1-2 cell layers) tunica adventitia: thicker than tunica media, CT, some elastic

Question 39

Everything we need to know about small veins:

Answer 39

0.1-1mm tunica intima: endothelium, CT, Sm. M (2-3 layers) tunica media: Sm. M (2-3 layers with tunica intima) tunica adventitia: thicker, CT, some elastic

Question 40

Everything we need to know about medium veins

Answer 40

1-10mm tunica intima: endothelium, CT, Sm. M, internal elastic membrane sometimes tunica media: Sm. M, collagen tunica adventitia: thicker, CT, some elastic

Question 41

Everything we need to know about large veins

Answer 41

\>10mm tunica intima: endothelium, Ct, Sm. M tunica media: Sm. M, collagen fibers tunica adventitia: Much thicker, Ct, some elastic, long. Sm. M, cardiac muscle extensions into great veins near heart (myocardial sleeves)