20 julio, 2024

What are the accessory glands of the digestive system? (And which are they)

We explain what the annexed glands of the digestive system are, their functions and location

What are the accessory glands?

The glands attached to the digestive system, also called accessory or auxiliary glands, are the salivary glands, the liver, the pancreas, and the gallbladder. These, without properly belonging to the digestive system, actively participate in its functions, contributing significantly to digestive activity.

The digestive system is the organ system of the human body that is in charge, as its name suggests, of digestion.

Digestion is the process by which the body converts ingested food into energy and nutrients for the cells that compose it, thus allowing events such as cell multiplication, tissue repair, respiration and metabolism, among many other things.

Digestive system

The human digestive system is composed mainly of what is known as the gastrointestinal tract, which consists of a channel that internally connects the mouth with the anus, and a set of accessory organs or glands.

The gastrointestinal tract begins with the oral cavity, where food enters and is processed with the teeth. The salivary glands are the first accessory organs of the digestive system and participate in the breakdown of some carbohydrates and fats during chewing.

It continues with the pharynx, which is the part of the throat immediately after the mouth – it also participates in the respiratory system – and continues with the esophagus, which connects the pharynx with the stomach.

The stomach is located in the upper part of the abdomen and is a hollow muscular organ in the shape of a «J» that receives chewed food that travels from the mouth to the esophagus. The stomach allows some breakdown of the food it receives and the formation of a paste called chyme.

Next are the small and large intestines, where the processes of digestion, absorption of nutrients and water and «discard» of undigested material take place, respectively.

The small intestine is associated with accessory organs – pancreas, liver and gallbladder – which are primarily responsible for the production of digestive enzymes.

These enzymes facilitate the breakdown of proteins, fats, and carbohydrates contained in food, so that the molecules that make them up can be absorbed by cells in the intestinal epithelium.

What are the accessory glands?

The glands considered annexed to the human digestive system are:

salivary glands

They are glands located in the region of the head and neck, and whose function has to do with the production of saliva.

They are exocrine glands, which means that their products are released onto a surface of the body, in this case, onto the surface of the gastrointestinal tract.

The human body possesses two types of salivary glands known as major salivary glands and minor salivary glands.

The largest are the parotid, submandibular, and sublingual glands, and the smallest are the anterior lingual, posterior mucous, and von Ebner glands.

Gallbladder

This gland is responsible for storing bile, one of the products secreted by the liver. It is a greenish gland, pear-shaped and approximately 10 cm long. Its job is to release bile into the small intestine when needed.

The pancreas

The pancreas is a very special organ, as it has functions as an exocrine gland and as an endocrine gland. It has a spongy appearance and looks like a flattened pear, varying in length between 16 and 25 cm.

From an endocrine point of view, the pancreas works on the synthesis and release of the hormones insulin and glucagon into the blood, which have important homeostatic and metabolic functions.

From the exocrine point of view, on the other hand, their functions are related to the digestive system, since they are responsible for the production and release of very important digestive enzymes into the lumen of the small intestine.

The liver

It is the largest gland in the human body. It weighs about 1.3 kg, is reddish-brown in color and has a fleshy appearance and rubbery texture. It has two pairs of lobes, one larger and the other smaller.

Its main function as a gland attached to the digestive system in the production of bile, but it also works in the «cleaning» of the blood, in the metabolism of some drugs and in the production of some important proteins for blood coagulation.

Functions of the accessory glands

The annexed glands have different functions:

Of the salivary glands and their products

The salivary glands are responsible for the production of saliva, on which their functions depend.

Saliva is an extremely important fluid from the digestive point of view, as well as for the health of the organs contained in the oral cavity. Here are some of its main functions:

Lubricates the oral mucosa
Produces antibacterial and electrolytic compounds
Contains protective and useful enzymes for the predigestion of some food molecules such as certain lipids and carbohydrates
Participate in the taste sensation
Promotes hydration of what is chewed
Provides a vehicle for the movement of chewed food through the throat during swallowing (when swallowed)

From the liver, bile and gallbladder

The liver functions as a gland attached to the digestive system by producing and releasing bile, the fluid that is stored in the gallbladder when it is not immediately needed.

The gallbladder functions essentially in the storage of bile produced by the liver. Bile is a yellowish fluid composed of water, bile salts, bile pigments, and cholesterol.

The bile salts contained in this fluid work as emulsifying agents, favoring the digestion and absorption of fats.

In addition, through bile the body gets rid of cholesterol and pigments derived from the degradation of hemoglobin contained in erythrocytes (red blood cells), excreting them into the digestive system and with it, out of the body with feces.

Of the pancreas and its products

The exocrine function of the pancreas is the one that has to do with the digestive system. This gland is responsible for the synthesis and production of enzymes such as:

youripsin and chymotrypsin, for breakdown of dietary proteins
TOmilase, for the breakdown of carbohydrates such as starch, for example
Lipasa, for the breakdown of fats

Pancreatic juices -the fluid produced by the pancreas where all these enzymes are mixed with water, bicarbonate and other electrolytes- are released into the first portion of the small intestine, the duodenum.

There, they facilitate the digestion of fats, carbohydrates and proteins, as well as the neutralization of stomach acids.

References

de Paula, F., Teshima, THN, Hsieh, R., Souza, MM, Nico, MMS, & Lourenco, SV (2017). Overview of human salivary glands: highlights of morphology and developing processes. The Anatomical Record, 300(7), 1180-1188.
Fox, S.I. (2009). Fundamentals of human physiology (Vol. 749). McGraw-Hill.
Gartner, L.P., & Hiatt, J.L. (2006). Color textbook of histology e-book. Elsevier Health Sciences.
Netter, FH (1990). Atlas of Human Anatomy/Frank H. Netter. East Hanover, New Jersey, 592.
SEER Training Modules, Module Name. US National Institutes of Health, National Cancer Institute. training.seer.cancer.gov
Stanfield, CL, Germann, WJ, Niles, MJ, & Cannon, JG (2011). Principles of human physiology. Benjamin Cummings.

Deja una respuesta

Tu dirección de correo electrónico no será publicada. Los campos obligatorios están marcados con *