Glandular Epithelium
Glandular epithelial cells are specialized epithelial cells that secrete bodily products, sometimes called simply glands. Glands include two types: endocrine and exocrine.
A Comparison of Endocrine and Exocrine Glands:
Endocrine Glands | Exocrine Glands |
No duct system | Ducts to release products |
Secretions directed into the extracellular fluid (basal side), move into vascular system | Secretions released to the apical cell surface, move out of ducts to outside environment |
Exocrine glands are often the only glands associated with the term "glandular epithelium." These glands are classified by the following morphological characteristics.
Number of Cells
Unicellular Glands | Multicellular Glands |
Made of only one glandular epithelium cell; called intraepithelial cells | Multiple cells make up one gland; called extraepithelial cells |
Goblet cells are the only human example (Figure 1) | Many examples, including secretory sheets in the human stomach |
Figure 1. A goblet cell, in the villi of the intestine, secreting mucus.
Source: http://www.kumc.edu/instruction/medicine/anatomy/histoweb/glands/glands.htm
Type of Secretion
Serous | Mucous | Mixed Serous-Mucous |
Thin, watery protein-rich secretion | Viscous secretion with lubricating or protective function | Serous demilunes (cells) secrete into space between mucous cells |
Where are glandular epithelial cells found? What do they do?
Glandular epithelial cells make up any glands within the body. Examples include sebaceous glands of the skin and glands in the intestinal lining (exocrine glands), and many endocrine glands releasing hormones, such as the thyroid follicle as seen below in Figure 2. The function of glandular epithelial cells is directly related to their location. Exocrine glands hold secretions for linings and coverings of the body until the secretions are needed, at which time the cells follow the above secretion mechanisms. Endocrine glands control hormone production processes, enclosing the formed hormones until they are needed in the body.
Figure 2. Representation of a thyroid follicle, which is surrounded by glandular epithelium. The follicle holds necessary components of thyoid hormones (T3 and T4) until they can be assembled and secreted from the cell as shown above.
Source: Reprinted with permission from Health Implications of Perchlorate Ingestion ©2005 by the National Academy of Sciences, Courtesy of the National Academies Press, Washington, D.C.
Mechanism of Secretion
Merocrine | Apocrine | Holocrine |
Expelled by exocytosis | Uses membrane vesicles | Entire secretory cell lost, as plasma membrane breaks to release product |
Only secretory product is lost | Secretory product and some membrane lost | Sebaceous glands use this method |
Shape and Arrangement
Shapes include tubular, coiled tubular, acinar or alveolar, or a combination of these. The arrangement could be simple, branched, or compound (Figure 3). |
Figure 3. A hand-drawn representation of various shapes and arrangements of glands. Glandular epithelial cells are shown by rectangular shapes, which line the exterior of the glands.
Adenocarcinoma, a malignant tumor of the glandular epithelium, accounts for 40% of all lung cancer, making it the most common type. A histological example of adenocarcinoma is shown in Figure 4.
Figure 4. Adenocarcinoma of the Lung. Glandular epithelial cells create the lining of the duct, while the cancerous cells shown in the center of the duct are malignant glandular epithelial cells.
Source: http://peir2.path.uab.edu/scripts/acdis.dll?cmd=see&fp=/dbif/PEIR/00003022.tif&fmt=jpg&q=100&h=512
References:
Adenocarcinoma - definition and more from the free merriam-webster dictionary. Retrieved 9/6/2010, 2010, from http://www.merriam-webster.com/dictionary/adenocarcinoma
Anderson, P.PEIR digital library: Search results. Retrieved 9/11, 2010, from http://peir2.path.uab.edu/pdl/dbr.cgi?db=images&uid=default&Collection=*&Collection2={*}&Type=*&Type2=[*]&Description=adenocarcinoma+&syn=off&mh=20&hits=`20!&File=&view_records=View+Records&view_records=Search
Balaban Naomi E. (c2008). In Bobick James E, &ebrary Inc(Eds.), The handy anatomy answer book. Detroit: Visible Ink Press.
Cooper, D. (1998). LIVER, SALIVARY GLANDS, AND PANCREAS. Retrieved 9/6/2010, 2010, from http://www.sacs.ucsf.edu/home/cooper/Anat118/GI-Glands/lvrpancsaliv.htm
EPXTHELXUX C &. Retrieved 9/6/2010, 2010, from http://www.mc.vanderbilt.edu/histology/labmanual2002/labsection1/GlandularEpithelium03.htm
Exercise 4: Epithelium. Retrieved 9/6/2010, 2010, from http://education.vetmed.vt.edu/Curriculum/VM8054/Labs/Lab4/Notes/glndstruc.htm
National Research Council of the National Academies. (2005). Health implications of perchlorate ingestion. Washington, DC: National Academies Press.
What is lung cancer? - WebMD. (2010). Retrieved 9/12/2010, 2010, from http://www.webmd.com/lung-cancer/guide/understanding-lung-cancer-basics
Wolf, M., & Scarbrough, M. (2010). Glands. Retrieved 9/10, 2010, from http://www.kumc.edu/instruction/medicine/anatomy/histoweb/glands/glands.htm