Page 544 - Clinical Hematology_ Theory _ Procedures ( PDFDrive )

528 PART 7 ■ Principles and Disorders of Hemostasis and Thrombosis

TABLE 27.2 Characteristics of Coagulation Factors

Group

Characteristic I * II † III ‡

Molecular weight High Low ?

Plasma Present Present Present

Serum Absent Present, except II Present

Absorption (BaSO) No Yes None or partial
4
Destruction Thrombin, plasmin

Stability Factors V VIII unstable Heat stable Stable
,

Increase In ammation, pregnancy, stress and fear, oral Pregnancy, oral contraceptives

contraceptives

Decrease Oral anticoagulants

* Group I: brinogen group (factors I, V VIII, XIII).
,
† Group II: prothrombin group (factors II, VII, IX, X).

‡ Group III: contact group (factor XI, XII, Fletcher factor, Fitzgerald factor).

regnancy, in the resence o con itions o inf a ation, Factor II (Prothrom bin)

an subsequent to the use o ora contrace tive rugs. Prothro bin is a stab e rotein ( o ecu ar weight, 63,000).

Te prothrombin group consists o actors II, VII, IX, an In the resence o ionize ca ciu , rothro bin is converte

X. A these actors are e en ent on vita in K uring their to thro bin by the enzy atic action o thro bo astin ro

synthesis. Vita in K is avai ab e to the bo y through ietary both extrinsic an intrinsic sources. Prothro bin has a ha -

sources an intestina bacteria ro uction. T is grou is i e o a ost 3 ays with 70% consu tion uring c otting.

inhibite by war arin. T is grou is consi ere to be stab e

2+
+
an re ains we reserve in store as a. Prothro bin Ca extrinsic or intrinsic
Te contact group consists o actors XI, XII, reka ikrein thro bo astin → thro binn

(F etcher actor), an HMWK (Fitzgera actor). T ese

actors are invo ve in the intrinsic coagu ation athway. Factor IIa (Throm bin)

T ey are o erate y stab e an are not consu e uring

coagu ation. T ro bin ( o ecu ar weight, 40,000) is the activate or o
rothro bin, which is nor a y oun as an inert recursor

in the circu ation. T is roteo ytic enzy e, which interacts

with brinogen, is a so a otent ate et-aggregating sub-
NOTE: This is a good time to review the de nitions of the stance. A arge quantity o thro bin is consu e uring the

Key Terms in the Glossary and . It is also a good rocess o converting brinogen to brin. A unit o thro -
time to complete Review Questions related to the preceding bin wi coagu ate 1 L o a stan ar brinogen so ution in

content.
15 secon s at 28°C.

Fibrinogenthro bin → ibrin ono er e ti es
+
Characteristics of Individual Factors

Each o the in ivi ua coagu ation actors has so e unique Tissue Throm boplastin (Form erly Factor III)

characteristics. T ese characteristics inc u e the o owing: issue thro bo astin is the ter given to any non as a

substance containing i o rotein co ex ro tissues.

Factor I (Fibrinogen) T ese tissues can be ro the brain, ung, vascu ar en othe-
iu , iver, acenta, or ki neys; these tissue ty es are ca a-
Fibrinogen is a arge, stab e g obu in rotein ( o ecu ar b e o converting rothro bin to thro bin.

weight, 341,000). It is the recursor o brin, which or s

the resu ting c ot. When brinogen is ex ose to thro bin, Ionized Calcium (Form erly Factor IV)

two e ti es s it ro the brinogen o ecu e, eaving a

brin ono er. T ese ono ers aggregate together to Te ter ionized calcium has re ace the ter actor IV.

or the na o y erize brin c ot ro uct. Ionize ca ciu is necessary or the activation o thro bo-
astin an or the conversion o rothro bin to thro bin.
Fibrinogenthro bin → ibrin ono ers → ibrin c ot Ionize ca ciu is the hysio ogica y active or o ca ciu