Vascular Histology

Question 1

what are the three layers of a vessel

Answer 1

Trunca intima
Trunca media
Trunca adventitia

Question 2

what are the three aspects of the Tunica intima

Answer 2

Endothelium: single layer of squamous epithelial cells

Basal lamina: thin extra cellular layer of collagen proteoglycans and glycoproteins

Subendotheliallayer: loose CT
-internal elastic membrane (sheet like layer fenestrated elastic material with in arteries and arterioles

Intima in veins contains valves

Question 3

Characteristics of Tunica media

Answer 3

circumferentially arranged layers of smooth muscle

thick in arteries

external elastic membrane: layer of elastin that separates the tunica media and adventitia

varying elastin, reticular fibers, and proteoglycans

Question 4

Characteristics of Tunica adventitia

Answer 4

Longitudinally arranged collagenous tissue with fewer elastin

merges with loose CT around vessels

thin in arterial system
thick in vein system

Question 5

what two vessels are found in the tunica adventitia

Answer 5

Vasa vasorum: vessels that supply the tunica adventitia with blood
-found in large arteries and veins

Nervi vasorum: ANS input that controls contraction of vascular smooth muscle

Question 6

Characteristics of large Arteries

Answer 6

has elastin that forms concentric sheets between the muscle cell layers

has no fibroblasts

strong pressure from systole will expand the arterial wall

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

Question 7

Characteristics of Medium arteries

Answer 7

More smooth muscle and less elastin than elastic arteries

has a prominent internal elastic membrane

a recognizable external elastic membrane

smooth muscle arranged in spiral fashion

relatively thick tunica adventitia

Question 8

Characteristics of small arteries

Answer 8

have up to eight layers, will also have an internal elastic membrane

Question 9

characteristics of arterioles

Answer 9

have 1-2 layers and internal elastic membrane may or may not be present

flow regulators for capillaries

sympathetic innervation to tunica media causes vasoconstriction

parasympathetic innervation to tunica media causes vasodilation

Question 10

Characteristics of capillaries

Answer 10

smallest of all blood vessesl

• site of metabolic exchange
• diameter often smaller than an RBC

contain pericytes (perivascular contractile cells with branching cytoplasmic processes)

Question 11

what is the function of the pericytes

Answer 11

promote stabillity of capillaries and postcapillary venules

controlled by NO via endothelial cells

Question 12

Function of the endothelial cells of the vasculature

Answer 12

connected via cell to cell junctions to help alter permeabillity

support the basement membrane and prodce collagen

metabollically involoved in blood coagulation and thrombosis, local vasodilation and constriction

Question 13

what are the three different capillaries

Answer 13

Continuous
Fenestrated
Discontinuous/sinusoidal

Question 14

characteristics of Continuous capillaries

Answer 14

Most common

have tight occluding junctions sealing off the intercellular clefts

all molecular exchange must occur via diffusion or transcytosis

continuous basement membrane

located throughout the body (muscle, brain, peripheral nerves, exocrine glands)

Question 15

characteristics of Fenestrated Capillaries

Answer 15

Located in organs where molecular exchange with the blood is important

have tight junctions, with fenestrations among the endothelial cells

allows greater exchange across the endothelium, but limited to size of macromolecule

continuous basement membrane

endocrine gland and sites of fluid/metabolite absorption (gallbladder, kidney)

Question 16

characteristics of discontinuous/sinusodial capillaries

Answer 16

located where exchanges of macromolecules and cells (b/w tissue and blood) must openly occur

large fenestrations among endothelial cells

open exchange occurs and large cell movements allowed

partial discontinuous basal membrane

bone marrow, liver, spleen

Question 17

what is the first branch off the arteriole to supply the capillary

Answer 17

Metarterioles

Question 18

function of the precapillary sphincter

Answer 18

regulate blood through true capillaries

Question 19

what is considered the true capillaries

Answer 19

branch from metarteriole that lack smooth muscle , may have pericytes

Question 20

what is the thoroughfare channel

Answer 20

distal end of the metarteriole (lacks the smooth muscle )

will connect with the postcapillary venule

Question 21

if precapillary sphincters are relaxed what is the status of the capillary bed? what about contracted

Answer 21

the capillary bed is well perfused for relaxed sphincftor

if they are contracted: the blood will shunt and move quickly through the thoroughfare channel

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

Question 22

Diameter, charcteristics of Tunica intima, media, and adventitia for: Large artery

Answer 22

> 10mm

Intima: Endothelium, connective tissue, smooth muscle

media: smooth muscle, elastic lamellae

Adventitia: thinner than media, connective tissue and elastic fibers

Question 23

Diameter, charcteristics of Tunica intima, media, and adventitia for: Medium artery

Answer 23

2-10mm

intima: Endothelium, connective tissue, smooth muscle, prominent internal elastic membrane
media: smooth muscle, collagen fibers, relatively little elastic tissues
adventitia: thinner than media, connective tissue, some elastic fibers

Question 24

Diameter, charcteristics of Tunica intima, media, and adventitia for: small artery

Answer 24

0. 1-2mm
   intima: endothelium, connective tissue, smooth muscle, internal elastic membrane
   media: smooth muscle (8 to 10 cell layers), collagen fibers
   adventitia: thinner than media, connective tissue, some elastic fibers

Question 25

Diameter, charcteristics of Tunica intima, media, and adventitia for: arterioles

Answer 25

10-100 um

intima: endothelium, connective tissue, smooth muscle
media: smooth muscle (one or two cell layers)
adventitia: thin, ill defined sheath of connective tissue

Question 26

Diameter, charcteristics of Tunica intima, media, and adventitia for: capillaries

Answer 26

4-10um

intima: endothelium
media: none
adventitia: none

Question 27

characteristics of Venules and small veins and the various types

Answer 27

Postcapillary venules will dran capillaries, no true tunica media

muscular venules: have 1-2 layers of smooth muscle in tunica media
-thin tunica adventitia

small veins: have all three tunicas

• media is 2-3 layers
• has thicker tunica adventitia

Question 28

Characteristics of medium veins

Answer 28

Travel with muscular arteries

thicker tunica media and adventitia

wall is often folded around large lumen

contains valves (tunica intima)

Question 29

characteristics of large veins

Answer 29

Tunica adventitia: thickest layer of the vessel wall

• contains collagen and elastic fibers and fibroblasts
• contain longitudinal smooth muscle cells

media: thisn with circumferentially afrranged smooth muscle cells, collagen fibers and some fibroblasts
intima: is thin and blends with tunica media

Question 30

Diameter, characteristics of Tunica intima, media, and adventitia for: Postcapillary venule

Answer 30

10-50 um

intima: endothelium, pericytes
media: none
adventitia: none

Question 31

Diameter, characteristics of Tunica intima, media, and adventitia for: muscular venule

Answer 31

50-100 um

intima: endothelium
media: smooth muscle (one or two cell layers)
adventita: thicker than media, connective tissue, some elastic fibers

Question 32

Diameter, characteristics of Tunica intima, media, and adventitia for: small vein

Answer 32

0. 1 - 1mm
   intima: endothelium, connective tissue, smooth muscle (two or three layers)
   media: smooth muscle (two or three layers continuous with tunica intima)
   adventitia: thicker than tunica media, connective tissue, some elastic fibers

Question 33

Diameter, characteristics of Tunica intima, media, and adventitia for: medium vein

Answer 33

1-10 mm
most named veins

intima: endothelium, CT, smooth muscle, internal elastic membrane in some cases
media: smooth muscle, collagen fibers
adventitia: thicker than tunica media, connective tissue, some elastic fibers

Question 34

Diameter, characteristics of Tunica intima, media, and adventitia for: Large vein

Answer 34

> 10mm
superior and inferior vena cava

intima: endothelium, CT, smooth muscle
media: smooth muscle (2-15 layers), collagen fibers
adventitia: much thicker than tunica media, CT, some elastic fibers, longitudinal smooth muscles, cardiac muscle extensions (myocardial sleeves) into great veins near the heart

Question 35

characteristics of lymphatic vessels

Answer 35

circulate lymph through most parts of the body

serve as adjuncts to the blood vessels

unidirectional, conveying fluid only from tissues

lymphatic vessels collect lymph and return it to venous supply

contain all vascular tunics and poses valves

continuous tight junctions to prevent leakage

Question 36

characteristics of lymphatic capillaries

Answer 36

closed ended tubes found among capillary beds

overlapping endothelial cells form 1-way valves for collecting lymph

incomplete basal lamina increases its permeabillity

these openings between the endothelial cells are held together by anchoring filaments

Question 37

Flow of lymphatics

Answer 37

Lymphatic capillaries

lymphatic vessels

lymphatic trunks

Right lymphatic duct, thoracic duct (depending on location)

all drain into the brachiocephalic Veins