Complex sentence: They then release chemical messengers such as adenosine diphosphate (ADP), serotonin and thromboxane A2, causing more platelets to stick to the area, release their contents, and enhance vascular spasms.
Split into simpler sentences: They then release chemical messengers such as adenosine diphosphate (ADP), serotonin and thromboxane A2. These chemicals are released to cause more platelets to stick to the area and release their contents and enhance vascular spasms.