Endocrine gland:
- no ducts
- secrete what is called hormone
- hormone: released in the blood stream and circulated in the blood where it finds a particular organ, called target organ
Exocrine gland:
- has duct
- the conduit for the release of products produced by it
- product is discharged in a place where the product of the gland shows its action

• Unicellular- are mucous and goblet cells; inn epithelial linings of the intestinal and respiratorytracts amid columnar cells with other functions

• Multicellular- more complex; composed of a duct and a secretory unit; Classifiedaccording to:
- Duct type (simple: unbranched duct or compound: branched duct)
- Structure of their secretory units (tubular: tubelike , alveolar: small flasklike sacs

Gland: consists of one or two cells that make and secret product