Gland

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This article is about the gland in animals. Gland_sentence_0

For for information specific to plants, see Gland (botany). Gland_sentence_1

For other uses, see Gland (disambiguation). Gland_sentence_2

Gland_table_infobox_0

GlandGland_header_cell_0_0_0
DetailsGland_header_cell_0_1_0
IdentifiersGland_header_cell_0_2_0
LatinGland_header_cell_0_3_0 glandulaGland_cell_0_3_1
THGland_header_cell_0_4_0 Gland_cell_0_4_1

A gland is a group of cells in an animal's body that synthesizes substances (such as hormones) for release into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland). Gland_sentence_3

Structure Gland_section_0

Main article: List of glands of the human body Gland_sentence_4

Development Gland_section_1

Every gland is formed by an ingrowth from an epithelial surface. Gland_sentence_5

This ingrowth may in the beginning possess a tubular structure, but in other instances glands may start as a solid column of cells which subsequently becomes tubulated. Gland_sentence_6

As growth proceeds, the column of cells may split or give off offshoots, in which case a compound gland is formed. Gland_sentence_7

In many glands, the number of branches is limited, in others (salivary, pancreas) a very large structure is finally formed by repeated growth and sub-division. Gland_sentence_8

As a rule, the branches do not unite with one another, but in one instance, the liver, this does occur when a reticulated compound gland is produced. Gland_sentence_9

In compound glands the more typical or secretory epithelium is found forming the terminal portion of each branch, and the uniting portions form ducts and are lined with a less modified type of epithelial cell. Gland_sentence_10

Glands are classified according to their shape. Gland_sentence_11

Gland_unordered_list_0

  • If the gland retains its shape as a tube throughout it is termed a tubular gland.Gland_item_0_0
  • In the second main variety of gland the secretory portion is enlarged and the lumen variously increased in size. These are termed alveolar or saccular glands.Gland_item_0_1

Function Gland_section_2

Glands are divided based on their function into two groups: Gland_sentence_12

Endocrine glands Gland_section_3

Main article: Endocrine gland Gland_sentence_13

Endocrine glands secrete substances that circulate through the blood stream. Gland_sentence_14

The glands secrete their products through basal lamina into the blood stream. Gland_sentence_15

Basal lamina typically can be seen as a layer around the glands to which a million, maybe more, tiny blood vessels are attached. Gland_sentence_16

These glands often secrete hormones which play an important role in maintaining homeostasis. Gland_sentence_17

The pineal gland, thymus gland, pituitary gland, thyroid gland, and the two adrenal glands are all endocrine glands. Gland_sentence_18

Exocrine glands Gland_section_4

Main article: Exocrine gland Gland_sentence_19

Exocrine glands secrete their products through a duct onto an outer or inner surface of the body, such as the skin or the gastrointestinal tract. Gland_sentence_20

Secretion is directly onto the apical surface. Gland_sentence_21

The glands in this group can be divided into three groups: Gland_sentence_22

Gland_unordered_list_1

  • Apocrine glands – a portion of the secreting cell's body is lost during secretion. 'Apocrine glands' is often used to refer to the apocrine sweat glands, however it is thought that apocrine sweat glands may not be true apocrine glands as they may not use the apocrine method of secretion, e.g. mammary gland, sweat gland of arm pit, pubic region, skin around anus, lips and nipples.Gland_item_1_2
  • Holocrine glands – the entire cell disintegrates to secrete its substances, e.g. sebaceous glands: meibomian and zeis glands.Gland_item_1_3
  • Merocrine glands – cells secrete their substances by exocytosis, e.g. mucous and serous glands; also called "eccrine", e.g. max sweat gland of humans, goblet cells, salivary gland, tear gland and intestinal glands.Gland_item_1_4

The type of secretory product of exocrine glands may also be one of three categories: Gland_sentence_23

Gland_unordered_list_2

Clinical significance Gland_section_5

Adenosis is any disease of a gland. Gland_sentence_24

The diseased gland has abnormal formation or development of glandular tissue which is sometimes tumorous. Gland_sentence_25

Additional images Gland_section_6

Gland_unordered_list_3

  • Gland_item_3_8
  • Gland_item_3_9
  • Gland_item_3_10
  • Gland_item_3_11
  • Gland_item_3_12
  • Gland_item_3_13
  • Gland_item_3_14
  • Gland_item_3_15


Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Gland.