The digestive system consists of 1)mouth 2) pharynx 3)esophagus 4)stomach 5)small intestine 6)large intestine.it is one of the most important systems of our body, that helps to digest food.it is very important to know how the digestive system work.so let’s study the digestive system.
DIGESTION- Food must be broken down into mole that is small enough to enter body cells, a process known as digestion.
DIGESTIVE SYSTEM- The organ involved in the breakdown of food collectively called the digestive system.
GASTROENTEROLOGY- The medical specialty that deals with the structures, function, diagnosis, and treatment of disease of stomach and intestine is called gastroenterology.
OVERVIEW OF DIGESTIVE SYSTEM
Two groups of organs compose the digestive system.
1. The gastrointestinal tract
2.accessory digestive organ.
1.GASTROINTESTINAL TRACT ALSO CALLED ALIMENTARY CANAL
GI is the continuous tube that extends from mouth to anus. through the thoracic and abdominopelvic activities.
ORGANS OF TH GASTROINTESTINAL TRACT
2)Most of pharynx
-The length of the gi tract is about 5-7 m in a living person.
THE ACCESSORY DIGESTIVE ORGAN.
The accessory digestive organ include,
THE DIGESTIVE SYSTEM PERFORMS SIX BASIC PROCESSES.
1.INGESTION; This process involves taking foods and liquids into the mouth.
2.SECRETION; Each day, cells within the walls GI tract total of about 7 lit of water, acid, buffers, and enzymes into the lumen (interior space) of the tract.
3.MIXING AND PROPULSION; Alternating contraction and relaxation of smooth muscle in the wall of GI tract, mix food and secretions. and propel them towards the anus.
[This capability of the GI tract to mix and move material along its length is called MOTILITY]
4.DIGESTION- Mechanical and chemical processes break down ingested food into a small mole.
There are two types of digestion.
IN MECHANICAL DIGESTION;
- The teeth cut the food before it swallowed.
- Then smooth muscles of the stomach and small intestine churn the food.
- As a result food mole dissolved. and thoroughly mix with the digestive system.
IN CHEMICAL DIGESTION;
- Large carbohydrate, lipid, protein, and a nucleic acid mole in food are split into smaller molecules by hydrolysis.
- Digestive enzymes produced by the salivary gland, tongue, stomach,pancrea,s and small intestine.
- Few substances in food can be absorbed without chemical digestion. eg; vitamin, cholesterol, water.
FUNCTION OF DIGESTIVE SYSTEM
- INGESTION; Taking food into the mouth.
- SECRETION; Release of water, acid, buffer, and enzyme into the lumen of the GI tract.
- MIXING AND PROPULSION; Churning and propulsion of food through the GI tract.
- DIGESTION; Mechanical and chemical breakdown of food.
- ABSORPTION; Passage of digested product from GI tract into the blood and lymphatic vessel and then circulate into cells.the entrance of ingested and secreted fluid, ions, and products of digestion into epithelial cell lining. the lumen of the GI tract is called absorption
- DEFECTION; Elimination of feces from the GI tract. waste, indigested sub, bacterial cells remove from epithelial cells and leave the body through anus process called defection.
LAYERS OF GI TRACT
The wall of the GI tract from the lower esophagus to the anal canal has some basic. four-layer arrangement of tissue.
The 4 layers of tract from deep to superficial are;
- mucosa ; or mucus membrane
- Inner laye of GI tract.
- It is composed of 1) epithelial 2) connective tissue 3) smooth muscle.
- EPITHELIAL ;
- 1) A layer of the epithelium in direct contact with contents of the GI tract
. 2) Location-in mouth, pharynx, esophagus, and anal canal.
3) These are mainly non keratinized stratified squamous epithelium that serves protection.
4)Simple columnar epithelium-which functions in secretion and absorption lines the stomach and intestine.
5) Epithelial cells are exocrine cells that secret mucus and fluid into the lumen tract and endocrines cells; collectively called enteroendocrine cells, which secrete hormones.
2.LAYER OF CONNECTIVE TISSUE /LAMINA PROPRIA.
- Is areolar connective tissue, containing many blood vessel and lymphatic vessel.
- Blood vessels and lymphatic vessels carry nutrients absorbed in the GI tract to reach the outer tissue of the body.
- Lamina propria also contains the majority of cells of mucosa-associated lymphatic tissue(MALT)
- MALT contain immune system cell protect against the cell.
- MALT mainly present in the tonsils, small intestine, appendix, large intestine.
3.THIN LAYER OF SMOOTH MUSCLE.
- A thin layer of smooth muscle called muscular mucosae.
- Muscularis mucosae through the mucus membrane of the stomach, small intestine into many small folds which increase the area of absorption and digestion.
- The submucosa consists of areolar connective tissue that binds mucosa to the muscular.
- This layer consists of many types of blood and lymphatic vessel that receive absorbed food molecules.
- the submucosa contains a network of neurons called SUBMUCOSAL PLEXUS.
- The submucosa may also contain gland and lymphatic tissue.
- The muscular mouth, pharynx, and superior and middle part of the esophagus contain skeletal muscle that produces voluntary swallowing.
- muscular also contain smooth muscle that generally found in 2 sheets
- INNER SHEET-of circular fiber and
- OUTER SHEET-longitudinal fiber.
- Involuntary contraction of smooth muscle help break down food, mix it with digestive secretion and propel it along the tract.
- Those portions of the GI tract suspended in the abdominopelvic cavity have a superficial layer called serosa.
- This layer composed of areolar connective tissue and simple squamous epithelium.
- serosa also called visceral peritoneum.
- it forms a portion of the peritoneum.
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