MAIN COMPONENTS OF EXOCRINE GLANDS
Most exocrine glands are made up of two parts: a secretory portion and a conducting portion, formed by one or more excretory ducts.
The internal lining of the intestines (the intestinal mucosa) has a large amount of small tubular exocrine glands. The tubules of each of these glands execute both the secretory and excretory functions. In most exocrine glands, however, these portions are distinct, separate structures, although the excretory portion is often partially or entirely embedded within the secretory one.
Secretory portion
It may be formed by one or more cell types whose characteristics and arrangements are specific to the various types of glands.
The cells that form this portions often gather around a small, or sometimes large, central space (the lumen of the secretory portion). The secretory product of each cell is released into this lumen, which continues with the lumen of the excretory ducts.
Excretory portion
The wall of the excretory ducts is formed by a lining epithelium, wich is arranged to form a hollow tube with a central lumen.
The epithelium that forms the wall of the initial part of the duct is often a simple cuboidal epithelium. If the gland is small and the duct is short, this structure is maintained throughout its entire course.
In longer ducts of more complex glands, the duct may enlarge, fuse with other ducts and form even larger and wider ducts. The epithelial wall that forms these larger ducts may become simple columnar and in even larger ducts the epithelium may become stratified (click to view an excretory duct whose wall is a stratified epithelium).
Look at the figure. This is an image of a section containing an entire small gland. Its secretory portion is formed by several groups of secretory cells and is seen in light blue color after placing the mouse over the image or clicking on the image.
The excretory duct (highligted in dark blue after using the mouse) is lined by a layer of a simple cuboidal epitlelium. However this can not easily be seen here due to the small magnification of the image.
The gland and its duct are embedded in a connective tissue that is an important component of the wall of the esophagus. Small areas of smooth muscle are also present in the connective tissue.
The cavity (lumen) of this organ, where this excretory duct opens, is lined by a stratified squamous epithelium (highlighted in red).
The internal lining of the intestines (the intestinal mucosa) has a large amount of small tubular exocrine glands. The tubules of each of these glands execute both the secretory and excretory functions. In most exocrine glands, however, these portions are distinct, separate structures, although the excretory portion is often partially or entirely embedded within the secretory one.
Secretory portion
It may be formed by one or more cell types whose characteristics and arrangements are specific to the various types of glands.
The cells that form this portions often gather around a small, or sometimes large, central space (the lumen of the secretory portion). The secretory product of each cell is released into this lumen, which continues with the lumen of the excretory ducts.
Excretory portion
The wall of the excretory ducts is formed by a lining epithelium, wich is arranged to form a hollow tube with a central lumen.
The epithelium that forms the wall of the initial part of the duct is often a simple cuboidal epithelium. If the gland is small and the duct is short, this structure is maintained throughout its entire course.
In longer ducts of more complex glands, the duct may enlarge, fuse with other ducts and form even larger and wider ducts. The epithelial wall that forms these larger ducts may become simple columnar and in even larger ducts the epithelium may become stratified (click to view an excretory duct whose wall is a stratified epithelium).
Look at the figure. This is an image of a section containing an entire small gland. Its secretory portion is formed by several groups of secretory cells and is seen in light blue color after placing the mouse over the image or clicking on the image.
The excretory duct (highligted in dark blue after using the mouse) is lined by a layer of a simple cuboidal epitlelium. However this can not easily be seen here due to the small magnification of the image.
The gland and its duct are embedded in a connective tissue that is an important component of the wall of the esophagus. Small areas of smooth muscle are also present in the connective tissue.
The cavity (lumen) of this organ, where this excretory duct opens, is lined by a stratified squamous epithelium (highlighted in red).
