How do we classify exocrine glands based on secretory portions?

Acinous glands: acinus is a spherical or viral like structure, the wall is made of glandular cells in the form of a pyramide; the lumen of the secretory protion and the execretory duct are reduced (simple or compound) Tubular glands: elongated tube appearance with a wall made of cuboidal or columnar cells (striaght simple tubular, branched coiled compound...) Alveolar glands: in the form of a bag with a wide lumen relative to the acinous lumen of secretory portion are greater in size than acinous.