Unformatted text preview: materials. There are ﬁve major w of leukocytes, each with a particular role in immunityﬂeamophﬂs engulf
microorganisms, abnormal cells, and foreign particles by phagocytosis. Eosinophil — secrete enzymes that kill parasites;
contribute to tissue damage in allergic reactions; Basophil — secretes chemical mediators of inﬂammation and allergic
reactions; Wes —- secrete cytokines; engulf microorganisms by phagocytosis. Manocytes migrate into tissues where
they become macrophages (big eaters); L h tes — play various roles in the immune system. Click the Home Menu Button WWWW‘M‘W'MW “mm Click the Platelets and hemostasis Button: Blood
, Blood mm: on W immunity. loading to Int-ml vessels get damaged frequently, lending to internal and/or
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"g external bleeding. Without some mechanism to stop bleeding
even a superﬁcial cut would cause death due to blood loss.
g::" m d M, m. _ G0 to the next screen: When a blood vessel is damaged,
McMillan to m' i intrinsic mechanisms trigger a constriction called vascular
m m 3 spasm which increases resistance to blood flow. Damage also
cutmuld com a 9 tends to activate the sympathetic nervous system, which
, "M" ‘° W '° W causes further vasoeonsmction. This minimizes blood loss‘
' other mechanisms also play a role to stop the loss of blood
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"~me (WHEL, mm a " throm es, are non-nucleated fragments of
M m H w ”I w. Platelets possess granules containing a
and. Rim 1.. an. ”'23,... Wigm variety of substances that can be secreted into plasma,
W— "m“ _, . including ADP, serotonin, epinephrine, and a variety of
Em... / "deﬁne” "W“ ' ‘ l chemicals that participate in the formation of a blood clot.
m grmuznmoz'nwn M M m Platelets are also sticky under certain conditions, allowing
warm!” on muﬁ—myf them to adhere to surfaces, especially those of damaged
67' 9‘ blood vessels.
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platelet plugs and the subsequent blood ciot require the
Eti 0 presence of platelets and a fairly large set of speciﬁc plasma proteins. The ﬁrst step in plgsgnaﬂugiomlation is platelgt
adhesion. which occurs when bIOOdJﬁﬁl 9911133“ exmses tissue underlying the endothelium. A key protein released is von Willebrand factor thO that accumulates at the site of vessel damage. m‘mw MM Go to the next screen: When blood contacts this
W Wm M - mu M m "- subendothelial tissue VW in the
“m "W “W P“ subendothelium, triggering the WW
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w—u—u . . activates plateletsz changing their metabolism and surface
a..— properties makingjhemsﬁcky. G0 to the next screen: The production of thromboxane
A2 (TXAZ) further supports platelet ggregation. - 2 ‘ formed from a pho ' ' hidonic W in the
m latelets. ’l'XAz has many roles in homeostasis, including stimulation of platelet aggregation providing
positive feedback for platelet plug formation and
vasoconstriction. Platelet formation is limited to the area of Dun-A < AFR t “\L 6’“ 96’6“ ...
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- Spring '07