Page 506 - Clinical Hematology_ Theory _ Procedures ( PDFDrive )

490 PART 7 ■ Principles and Disorders of Hemostasis and Thrombosis

consists o f brous connective tissue th t cont ins utono ic
OVERVIEW OF HEMOSTASIS

AND THROMBOSIS nerve en ings n the v s v soru , s ll networks o
bloo vessels th t supply nutrients to the tissues o the w ll.

T e inten nce o circul tory he ost sis is chieve Veins re l rger n h ve ore irregul r lu en th n

through the process o b l ncing blee ing (he orrh ge) n rteries. In co p rison with rteries, veins re rel tively thin

clotting (thro bosis). He ost sis, the rresting o blee ing, w lle with we ker i le co t. El stin f bers re usu lly

epen s on sever l co ponents. T e our jor co ponents oun only in l rger veins, n there re ewer nerves istrib-

re the v scul r syste , pl telets (thro bocytes), bloo ute to the veins th n to the rteries.

co gul tion ctors, n f brinolysis n ulti te tissue

rep ir. T ree other, less i port nt, co ponents re the co - Arterioles and Venules

ple ent n kinin syste s s well s serine prote se inhibi- Arteries br nch extensively to or tree o ever-s ller

tors. Function lly, sever l nor l processes re involve in vessels. Arterioles re the icroscopic continu tion o rter-

he ost sis ollowing injury to s ll bloo vessel: ies th t give o br nches c lle et rterioles, which in turn

1. Bloo vessel sp s join the c pill ries. T e w lls beco e thinner s the rteri-

2. For tion o platelet plug oles ppro ch the c pill ries, with the w ll o very s ll

3. Cont ct ong ge bloo vessel, bloo pl telet, n rteriole consisting only o n en otheli l lining n so e

co gul tion proteins s ooth uscle surroun e by s ll ount o connective

4. Develop ent o bloo clot roun the injury tissue.

5. Fibrinolytic re ov l o excess he ost tic teri l to rees- T e icroscopic lly size veins re re erre to s venules.

t blish v scul r integrity Venules connect the c pill ries to the veins.

Capillaries

BLOOD VASCULATURE: STRUCTURE T e c pill ries, rterioles, n venules constitute the jor

AND FUNCTION vessels o the icrocircul tion. As unit, the icrocircul -

Arteries and Veins tion unctions s the link between the rteri l n venous
circul tion. Bloo p sses ro the rteri l to the venous sys-

Arteries re the istributing vessels th t le ve the he rt, te vi the c pill ries. C pill ries re the thinnest w lle n

n veins re the collecting vessels th t return to the he rt. ost nu erous o the bloo vessels. Sinusoi s, which re

Arteries h ve the thickest w lls o the v scul r syste . speci lize types o c pill ries, re oun in loc tions such s

Although v ri tions in the size (Fig. 25.1A) n type o ves- the bone rrow, spleen, n liver.

sel exist, the tissue (Fig. 25.1B) in vessel w ll is ivi e C pill ries re s ll structures consisting o supportive

into three co ts or tunics. T ese co ts re the tunic inti , b se ent e br ne to which single l yer o en otheliu

tunic e i , n tunic ventiti . T e tunic inti or s is tightly nchore . T e b se ent e br ne, i e i tely

the s ooth glistening sur ce o endothelium th t lines the j cent to the en otheliu , is co pose o i use net-

lu en (inner tubul r c vity) o ll bloo n ly ph tic ves- work o s ll f bers th t support the en otheliu n ct

sels n the he rt. T e si ple squ ous epitheliu th t s b rrier g inst p rticul te teri l th t y g in ccess

lines these vessels is re erre to s en otheliu . T e tunic to the extr v scul r sp ce. Coll gen b n s lso o er struc-

inti consists o single l yer o en otheli l cells thickene tur l support to the icrov scul r unit. Unlike the vessels

by suben otheli l connective tissue l yer cont ining el s- o the rteri l n venous syste s, c pill ries re co pose

tic f bers. T e tunic e i , the thickest co t, is co pose o only one cell l yer o si ple squ ous epitheliu , which

o s ooth uscle n el stic f bers. T e tunic ventiti per its ore r pi r te o tr nsport o teri ls between

FIGURE 25.1 Bloo v scul ture. A. Size

o vessels. B. issue zones.

A

B