Exocrine gland

Exocrine gland
Exocrine gland
	An acinus is a round cluster of exocrine cells connected to a duct .
Details
Identifiers
Latin	glandula exocrina
MeSH	D005088
TH	H2.00.02.0.03014
FMA	9596
	Anatomical terminology [ edit on Wikidata ]

Exocrine glands are glands that secrete substances onto an epithelial surface by way of a duct . ^[1] Examples of exocrine glands include sweat , salivary , mammary , ceruminous , lacrimal , sebaceous , prostate and mucous . Exocrine glands are one of two types of glands in the human body, the other being endocrine glands , which secrete their products directly into the bloodstream . The liver and pancreas are both exocrine and endocrine glands; they are exocrine glands because they secrete products? bile and pancreatic juice ?into the gastrointestinal tract through a series of ducts, and endocrine because they secrete other substances directly into the bloodstream. Exocrine sweat glands are part of the integumentary system; they have eccrine and apocrine types.

Classification [ edit ]

Structure [ edit ]

Exocrine glands contain a glandular portion and a duct portion, the structures of which can be used to classify the gland. ^[1]

The duct portion may be branched (called compound) or unbranched (called simple).
The glandular portion may be tubular or acinar , or may be a mix of the two (called tubuloacinar). If the glandular portion branches, then the gland is called a branched gland.

Method of secretion [ edit ]

Depending on how their products are secreted, exocrine glands are categorized as merocrine , apocrine , or holocrine . ^[1]

Merocrine ? the cells of the gland excrete their substances by exocytosis into a duct; for example, pancreatic acinar cells, eccrine sweat glands ^{[
dubious
–
discuss
]}, salivary glands , goblet cells , intestinal glands , tear glands , etc.
Apocrine ? the apical portion of the cytoplasm in the cell membrane , which contains the excretion, buds off . Examples are sweat glands of arm pits, pubic region, skin around anus, lips and nipples; mammary glands , etc.
Holocrine ? the entire cell disintegrates to excrete its substance; for example, sebaceous glands of the skin and nose, meibomian gland , zeis gland , etc.

Merocrine secretion
Apocrine secretion
Holocrine secretion

Product secreted [ edit ]

Serous cells secrete proteins , often enzymes . Examples include gastric chief cells and Paneth cells
Mucous cells secrete mucus . Examples include Brunner's glands , esophageal glands , and pyloric glands
Seromucous glands (mixed) secrete both protein and mucus. Examples include the salivary glands : although the parotid gland (saliva secretion 25%) is predominantly serous, the sublingual gland (saliva secretion 5%) mainly mucous gland, and the submandibular gland (saliva secretion 70%) is a mixed, mainly serous gland.
Sebaceous glands secrete sebum , a lipid product. These glands are also known as oil glands, e.g. Fordyce spots and Meibomian glands .

Additional images [ edit ]

Section of the human esophagus .
Dissection of a lactating breast.

References [ edit ]

^ ^a ^b ^c Young, Barbara; O'Dowd, Geraldine; Woodford, Phillip (2013). Wheater's Functional Histology: A Text and Colour Atlas (Sixth ed.). Elsevier. p. 95. ISBN 978-0702047473 . LCCN 2013036824 .

External links [ edit ]

Diagram at mhhe.com

[wheater-1] Young, Barbara; O'Dowd, Geraldine; Woodford, Phillip (2013). Wheater's Functional Histology: A Text and Colour Atlas (Sixth ed.). Elsevier. p. 95. ISBN 978-0702047473 . LCCN 2013036824 .

[1]