Hormones
Hormones are chemical messengers made by the endocrine glands. The glands have no ducts: they release hormones straight into the blood.
What hormones have in common
- Made in small amounts.
- Carried in the blood.
- Act on particular target organs, often far from the gland.
- Act slowly, but their effects last longer.
- Too much or too little causes disorders.
Endocrine glands
No ducts; secrete into the blood.
Thyroid, pituitary, adrenal glands.
Exocrine glands
Secrete through ducts.
Salivary glands, sweat glands.