20. Vascular Histology

Question 1

whats the commonality btn As & Vs when it comes to histo

Answer 1

both have tunics

(3 layers)

Question 2

what are the 3 tunics

Answer 2

tunica intima

tunica media

tunica adventitia

Question 3

what layers are found w/i the tunica intima & what are their fxns

Answer 3

1. endothelium: 1 layer of squamous epithelial cells - reduce friction
2. basal lamina: endothelial cells- thin layer w/collagen, proteoglycan, glycoproteins
3. subendotheial layer (loose CT) - contain internal elastic mem =fenestrated elastic material w/i As & arterioles (allow recoil)

Question 4

what are the characterisitcs of tunica media & what are the fxns of each

Answer 4

-circumferential Sm. M (allow continous pumping of blood)

-external elastic mem- extends from internal elastic mem & is a layer of elastin that seperates tunica media from adventitia

-varying amount of elastic, reticular fibers & proteoglycans

*A’s have thicker tunica media

Question 5

what are the characteristics of tunica adventitia

Answer 5

-longitudinally arranged collagenous tissue w/ few elastic fibers - prevent overexpansion

As- thin & Vs thick

merge with loose CT of neighboring vasculature

contain vaso vasorum & nervi vasorum

Question 6

what is represented in the solid circles? & what is its fxn

Answer 6

vasa vasorum

-in tunica adventitia- supply blood to vascular tunics themselves

found in large As & esp large Vs (bc carrying deoxy blood)

Question 7

what is represented w/i the dashed circle & what is its fxn

Answer 7

nervi vasorum

ANS input that control contraction of vascular Sm. M

Question 8

what is this and what are its components

Answer 8

Large As (elastic)

• majority = tunica media
• elastin makes concentric layers btn Ms cells (stretch/recoil)

NO FIBROBLAST

Sm M makes collagen, elastin, ground substance of ECM

Question 9

what is this & what are its components

Answer 9

Medium As (muscular)

more Sm M, less elastin

Sm M in spiral - produce ECM components

thick tunica adventitia & media

internal elastic mem & external elastic mem present

Question 10

Answer 10

large As (elastic)

Question 11

Answer 11

medium As (muscular)

Question 12

what are the differences btn small arterioles & arterioles

Answer 12

small arterioles - up to 8 layers of sm. m in tunica media w/ internal elastic mem present

arterioles - 1-2 layers of sm. M - internal elastic mem may/may not be present - contain sym/parasym innervation for flow regulation for cap beds

Question 13

Answer 13

arterioles

Question 14

Answer 14

small arterioles

Question 15

what is this & what are its components

Answer 15

capillaries (=caps)

metabolic exchange & diameter same size or smaller than RBC

single endothelial cell layer

contain pericytes: perivascular contractile cells w/ branching cytoplasmic processes - controlled by NO - & provide stability of capillaries and postcap venules

Question 16

when are pericytes enclosed by basal lamina

Answer 16

when basal lamina is continous with that of the endothelium

Question 17

what is the fxn of the single layer of endothelial cells in capillaries

Answer 17

form inner tunica intima

connected via cell-cell jxn (# of jxns alter permeability)

support basal mem & collagen

metabolically involved in blood coagulation & thrombosis, local vasodilation/constriction

(highlights = weibal palate bodies & arrow = storage granulaes)

Question 18

what are the ways capillaries can be organized?

how do these differ in fxn

Answer 18

1. continous cap - most common - very selective about what can go in/out
2. fenestrated cap- porous - allow large items to go in/out - make filtrate in urine production
3. discontinous (sinusoidal) cap- leaky, not selective - found in spleen, liver, bone marrow

Question 19

explain the relationship of :

metarterioles,

thoroughfare channels,

precap sphincters,

true caps

& postcap venules

Answer 19

metarterioles - first branch of arteriole supplying tissue –> distal end forms the thoroughfare channel –> entry towards cap beds –> precap sphincters regulate the flow thru true cap –> true cap has no sm. m, contain pericytes and allow gas exchange –> out thru thoroughfare channels into postcap venules

Question 20

what happens if the precap sphincter is closed

Answer 20

prevent gas exchange (dont let blood into true caps)

-shunt blood to venous return

Question 21

what is the difference btn postcap venules, muscular venules & small Vs

Answer 21

postcap venules: drain caps, no true tunica media

muscular venules: 1-2 layer sm. m in tunica media w/ thin tunica adventitia

small Vs: all 3 layers present, tunica media = 2-3 layers & tunica adventitia = thick

Question 22

what is this & what are its components

Answer 22

medium Vs

travel w/ muscular Ss

tunica media & adventitia thicker than small Vs

contain valves

Question 23

what is this & what are its components

Answer 23

Large Vs

thickest wall = tunica adventitia (contain longitudinal Sm M cells, collagen, elastic fibers & fibroblasts)

tunica media - thin circumferential Sm M, collagen fibers and some fibroblasts

tunica intima - thin & blends w/ media

Question 24

Answer 24

Medium Vs

Question 25

Answer 25

Large Vs

Question 26

what is the fxn of lymphatic vessels

Answer 26

circulate lymph thru body

unidirectional, convey fluid only from tissues (contain valves & continous tight jxns)

collect lymph & return to venous supply (after cleaning in LN)

all vascular tunica present

Question 27

what are lymphatic capillaries

Answer 27

closed end tubes among cap beds

contain overlapping endothelial cells that form 1 way valves for collecting lymph (openings btn endothelial cells held in place by anchoring filaments)

incomplete basal lamina - increase permeability

Question 28

what is the path for lymph

Answer 28

lympathic caps –>

lymphatic vessels (afferent lymphatic Vs –> LN –> efferent lymphatic Vs) –>

lymphatic trunk –>

right lympatic duct (R side of head, neck UE, thorax) OR thoracic duct (rest of body) –>

branchiocephalic V –>

sup. vena cava