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Digestive system organs

The easiest way to understand the digestive system is to divide its organs into two main categories. The first group is the organs that make up the alimentary canal. Accessory digestive organs comprise the second group and are critical for orchestrating the breakdown of food and the assimilation of its nutrients into the body. Accessory digestive organs, despite their name, are critical to the function of the digestive system.

Alimentary canal organs

Also called the gastrointestinal (GI) tract or gut, the alimentary canal    (aliment- = “to nourish”) is a one-way tube about 7.62 meters (25 feet) in length during life and closer to 10.67 meters (35 feet) in length when measured after death, once smooth muscle tone is lost. The main function of the organs of the alimentary canal is to nourish the body. This tube begins at the mouth and terminates at the anus. Between those two points, the canal is modified as the pharynx, esophagus, stomach, and small and large intestines to fit the functional needs of the body. Both the mouth and anus are open to the external environment; thus, food and wastes within the alimentary canal are technically considered to be outside the body. Only through the process of absorption do the nutrients in food enter into and nourish the body’s “inner space.”

Accessory structures

Each accessory digestive organ    aids in the breakdown of food ( [link] ). Within the mouth, the teeth and tongue begin mechanical digestion, whereas the salivary glands begin chemical digestion. Once food products enter the small intestine, the gallbladder, liver, and pancreas release secretions—such as bile and enzymes—essential for digestion to continue. Together, these are called accessory organs because they sprout from the lining cells of the developing gut (mucosa) and augment its function; indeed, you could not live without their vital contributions, and many significant diseases result from their malfunction. Even after development is complete, they maintain a connection to the gut by way of ducts.

Histology of the alimentary canal

Throughout its length, the alimentary tract is composed of the same four tissue layers; the details of their structural arrangements vary to fit their specific functions. Starting from the lumen and moving outwards, these layers are the mucosa, submucosa, muscularis, and serosa, which is continuous with the mesentery (see [link] ).

Layers of the alimentary canal

This image shows the cross section of the alimentary canal. The different layers of the alimentary canal are shown as concentric cylinders with major muscles and veins labeled.
The wall of the alimentary canal has four basic tissue layers: the mucosa, submucosa, muscularis, and serosa.

The mucosa    is referred to as a mucous membrane, because mucus production is a characteristic feature of gut epithelium. The membrane consists of epithelium, which is in direct contact with ingested food, and the lamina propria, a layer of connective tissue analogous to the dermis. In addition, the mucosa has a thin, smooth muscle layer, called the muscularis mucosa (not to be confused with the muscularis layer, described below).

Epithelium —In the mouth, pharynx, esophagus, and anal canal, the epithelium is primarily a non-keratinized, stratified squamous epithelium. In the stomach and intestines, it is a simple columnar epithelium. Notice that the epithelium is in direct contact with the lumen, the space inside the alimentary canal. Interspersed among its epithelial cells are goblet cells, which secrete mucus and fluid into the lumen, and enteroendocrine cells, which secrete hormones into the interstitial spaces between cells. Epithelial cells have a very brief lifespan, averaging from only a couple of days (in the mouth) to about a week (in the gut). This process of rapid renewal helps preserve the health of the alimentary canal, despite the wear and tear resulting from continued contact with foodstuffs.

Questions & Answers

knuckle of the middle finger
James Reply
because of the gases (nitrogen, oxygen)
Nejat
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Joshua Reply
To prevent collision with the lungs, lubricates the heart, protects the heart from infection in the event a peripheral organ is effected, and stabilizes the heart within the mediastinum.
Jeremiah
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aman Reply
adenohypophysis is made up of what type of cells and what is the name of those cells?
Mannu Reply
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armstrong Reply
motor root of the trigeminal nerve
Vandana
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Joshua
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Amina Reply
muscular system
Vandana
nucleus ribosome Golgi body call membrane cytoplasm
Sabina
these are the cellular components that functions to provide energy,remove waste and cell division
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Organelles of the cell are: Mitochondria,Ribosome,golgi apparatus, nucleus, secretory granules, nuclear e t c
Khadijah
what are local hormones
Richard
Local hormones are hormones that effect the cell that released them or cells near the releasing cell and they do not circulate within the blood stream.
Jeremiah
the trachea bifurcated into how many branches on the right lung
barbie
three lobes
Richard
Explain the normal flow of blood.
Shikha
how can we maintain the internal living things
Choolwe Reply
how many seconds does a human will stop if you sneeze
Kharl Reply
idk
Erika
1 sec not specific
Jane
1_3seconds
Mannu
physiology of vision
Sudipta Reply
Can pure water become gel like?
ovie Reply
No
Abdulazeez
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Laura Reply
It is the ability of an organism to co ordinate it's internal environment so as to achieve balance in all areas
ovie
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Sandra Reply
what is physiology
Sandra
The study of how the body works
Joseph
the branch of biology dealing with the functions and activities of leaving organisms and their parts including all physical and chemical processes
Maria
the study of human body . phicically and chemically it's called anotomy physiology
Raj
the branch of biology dealing with the functions and activities of living organisms
Salman
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it is the scientific study of the body structure
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What Choolwe Muselitata said is the definition of anatomy
KWAKU
Physiology can also be described as the way in which a living organism or bodily part functions
KWAKU
Anotomy is the science which we humen body of structure and function know as the anotomy
Aman
study of the body funtion and structure
Kaoum
functional study of the body
Mosele
it is the study about the functions of body organs
Mannu
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jeniffer Reply
You start the TPR then BP after explaining the procedure to the patient and your requirements ready.
Dauda
which type of vein to you inject to give infusions?
Belinda
*do
Belinda
how long do u take radial pulse
Flavian Reply
1 minute
Mannu
You can take it for 15 seconds , the number you got you multiply wth 2
Likius
but in the aspect of the multiplying that isn't right
Sabina
radial pulse kya hai?
OM
?
OM
for more accurate values you must do the 1 minute
Jane
1 minute.
Andrew
60 seconds
Richard
1 minute
Kaoum
yes @sabina
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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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