It consist of many cells and are generally located in unerlying connective tissue. e.g.,gastric and intestinal glands.
(B) On the basis of presence or absence of ducts:
(i) Exocrine gland:
These are those glands which discharge their secretory products into ducts.It is also called ducted glands or glands of external secretion. e.g.,Salivary glands,Mammary glands and Tear glands.
They are often called ductless gland,because they discharge their secretory products(Hormone) directly into the blood.e.g.,Pituitary gland,thyroid ,parathyroid and adrenal glands.
These are those glands which are partly endocrine and partly exocrine in function. e.g.,Pancreas.
Structural classification of exocrine glands:
Multicellular exocrine glands are classified by structure ,using the shape of their ducts and the complexity(branching) of their ducts system as distinguishing characteristics. Shape include tubular and aveolar(Sac like).Simple exocrine glands e.g.,intestinal gland, mammalian sweat glands,cutaneous glands of frog etc.have only one duct leading to surface .Compound exocrine glands have two or more ducts e.g.,liver,salivary glands etc.
|Simple tubular||Intestinal glands,crypts of Lieberkuhn in ileum.|
|Simple coiled tubular||Sweat glands in man.|
|Simple branched tubular.||Gastric (stomach) gland,and Uterine gland.|
|Simple alveolar||Mucous gland in skin of frog,Poison gland of toad and seminal vesicle.|
|Compound tubular||Brunner's gland ,bulbourethral gland and liver.|
|Compound alveolar.||Sublingual and submandibular salivary gland.|
|Compound tubulo alveolar.||Parotid salivary glands,Mammary gland and Pancreas.|