Classification of Chemical Messengers
→ Endocrine messengers are classical hormones
→ Synthesized by- Endocrine glands
→ Transported by- blood to the target organs or tissues
→ E.g. growth hormone and insulin.
→ They diffuse from control cells to target cells through
interstitial fluid
→ E.g. prostaglandins and histamine
→ Chemical messengers also known as intracellular chemical
mediators
→ They control the source cells which secrete them. E.g.
leukotrienes