anatomy Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having it ...

and

physiology Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical ...

, a duct is a circumscribed channel leading from an

exocrine gland Exocrine glands are glands that secrete substances on to an epithelial surface by way of a duct. Examples of exocrine glands include sweat, salivary, mammary, ceruminous, lacrimal, sebaceous, prostate and mucous. Exocrine glands are one of ...

or organ.

Types of ducts

Examples include:

Duct system

As ducts travel from the acinus which generates the fluid to the target, the ducts become larger and the epithelium becomes thicker. The parts of the system are classified as follows: Some sources consider "lobar" ducts to be the same as "interlobar ducts", while others consider lobar ducts to be larger and more distal from the acinus. For sources that make the distinction, the interlobar ducts are more likely to classified with simple columnar epithelium (or

pseudostratified epithelium A pseudostratified epithelium is a type of epithelium that, though comprising only a single layer of cells, has its cell nuclei positioned in a manner suggestive of stratified epithelia. As it rarely occurs as squamous or cuboidal epithelia ...

), reserving the stratified columnar for the lobar ducts. File:Gray1025.png, Section of

submaxillary gland The paired submandibular glands (historically known as submaxillary glands) are major salivary glands located beneath the floor of the mouth. They each weigh about 15 grams and contribute some 60–67% of unstimulated saliva secretion; on stimula ...

of kitten. Duct semidiagrammatic. X 200. File:Gray1173.png, Section of portion of mamma.

Intercalated duct

The intercalated duct, also called intercalary duct (ducts of Boll), is the portion of an

leading directly from the acinus to a striated duct. The intercalated duct forms part of the

intralobular duct In anatomy and physiology, a duct is a circumscribed channel leading from an exocrine gland or organ. Types of ducts Examples include: Duct system As ducts travel from the acinus which generates the fluid to the target, the ducts become larger ...

. This duct has the thinnest epithelium of any part of the duct system, and the epithelium is usually classified as "low" simple cuboidal. They are found in both the

pancreas The pancreas is an organ of the digestive system and endocrine system of vertebrates. In humans, it is located in the abdomen behind the stomach and functions as a gland. The pancreas is a mixed or heterocrine gland, i.e. it has both an en ...

and in

salivary gland The salivary glands in mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands ( parotid, submandibular, and sublingual), as well as hundreds of minor salivary glands. Salivary ...

Striated duct

A striated duct (Pflüger's ducts ) is a gland duct which connects an

intercalated duct In anatomy and physiology, a duct is a circumscribed channel leading from an exocrine gland or Organ (anatomy), organ. Types of ducts Examples include: Duct system As ducts travel from the acinus which generates the fluid to the target, the du ...

to an interlobular duct. It is characterized by the basal infoldings of its plasma membrane, characteristic of ion-pumping activity by the numerous mitochondria. Along with the intercalated ducts, they function to modify salivary fluid by secreting HCO₃⁻ and K⁺ and reabsorbing Na⁺ and Cl⁻ using the Na-K pump and the Cl-HCO₃ pump, making the saliva hypotonic. Their epithelium can be simple cuboidal or simple columnar. Striated ducts are part of the

s. They are found in the submandibular gland, sublingual duct, and the

parotid gland The parotid gland is a major salivary gland in many animals. In humans, the two parotid glands are present on either side of the mouth and in front of both ears. They are the largest of the salivary glands. Each parotid is wrapped around the ma ...

, but are more developed in the parotid gland. They are not present in

Intralobular duct

An intralobular duct is the portion of an

inside a lobule, leading directly from acinus to an interlobular duct (between lobules). It is composed of two subdivisions, the

and the striated duct. In the human mammary gland, the intralobular duct is a part of the glandular system that resides within the lobules. Lobules contain clusters of ducts whose secretory alveolies are drained by the intralobular duct. The intralobular ducts are usually lined with simple cuboidal epithelial cells that are lined by myoepithelial cells as well. The intralobular ducts of the lobules drain into the interlobular ducts between lobules. They can be seen in: *

salivary glands The salivary glands in mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands ( parotid, submandibular, and sublingual), as well as hundreds of minor salivary glands. Salivary gl ...

References

External links

Overview at uwa.edu.au

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