ABSTRACT
Mini glossary Anaphylaxis: allergic reaction with widespread histamine release; can be ■ fatal unless treated. Aneurism: balloon-like swelling in the arterial wall. ■ Atherosclerosis: build-up of fatty deposits on endothelial walls of blood ■ vessels. Canaliculi: small canals or channels. ■ Haemostasis: physiological processes, namely coagulation and constriction ■ of damaged blood vessels which arrest bleeding. Hapten: a small molecule that can combine with a body protein to form ■ an antigen. Infarction: e.g. myocardial infarction (Ml); death of local area of tissue ■ due to interrupted blood supply. Ischaemic: having an inadequate blood fl ow to a tissue or organ caused by ■ blood vessel blockage. Platelets: disc-shaped bodies in blood, 1.5-3 µm diameter, produced in ■ bone marrow, involved in haemostasis. Reye’s syndrome: relatively rare childhood syndrome of liver failure with ■ symptoms of encephalitis linked to use of aspirin; aspirin should not be used in children under sixteen years. Thrombocytopaenia: blood platelet reduction. ■
Platelets Are disk-shaped, anuclear structures, 1.5-3 µm in diameter, in the blood ■ of all mammals (see Figure 21.2). Are produced mainly in the bone marrow. ■ Contain an outer membrane, contractile protein, RNA, a system ■ of canaliculi, mitochondria and bodies containing several chemical mediators. Play a major role in the coagulation of blood. ■ Are activated by: ■
epinephrine ❚ adhesion to collagen, which is exposed when the blood vessel ❚ endothelium is damaged contact with ADP, fi brinogen, thrombin and glass. ❚
Are activated through their surface receptors, which trigger: ■ thromboxane (Tx) production, e.g.TxA ❚ 2, which activates platelet GPlIb/IlIa receptor, which ❚ facilitates fi brinogen binding to platelets, which ❚ results in platelet aggregation. ❚
When activated release infl ammatory and other mediators, including: ■ platelet activator-4, which mediates arrest of monocytes on ❚ endothelium nitric oxide ❚ thrombospondin, which is involved in the process of platelet ❚ aggregation and atherosclerosis.
