Layers of Gastrointestinal Track (GI Track)
The wall of Gastrointestinal (GI) tube consist of four layerslayer. Each GI layer has different tissues and functions. Layers of GI track are from the outside in, they are -
1. Serosa /serous; Outer layer
2. Muscularis externa
3. Submucosa
4. Mucosa /mucous; Innermost layer
1. Serosa/ Serous
Serous is the outermost layer of GI track. Peritoneum is the largest serous membrane or serosa of the body. Serous consist of areolar connective tissue and squamous epithelium (mesothelium).
Serous membranes have two layers-
1. Parietal peritoneum
2. Visceral peritoneum
Between the parietal and visceral layers is a very thin fluid-filled serous sac or space or cavity. In which peritoneal fluid/ serous fluid are present.
Adventitia/ Tunica/ Tunica Externa/ Tunica Adventitia
Where epithelium is lacking (as in esophagus), outer most lamina is called Adventia.
Adventist consist only single layer of alveolar connective tissue.
Function of Serosa/ Serous Membrane
1. Reduce friction
2. Lubrication
3. Muscle movement
4. Injury protection
5. Slippery
6. Provide protection from injury
7. Shock absorbing
8. Provide support
2. Muscularis Externa
Muscular externa layer of GI adjacent to submucosa. It made up of smooth muscle in two layer-
1. Inner layer; circular muscular layer
2. Outer layer; longitudinal muscular layer
Muscularis of mouth, pharynx and upper esophagus contains skeletal muscle that produce voluntary swallowing.
Sphincter; circular muscle maintains constriction of natural body passage.
Skeletal muscle form; External anal sphincter; Permit voluntary control of defecation.
Between these two layers contain blood vessels, lymph vessels and a plexus of sympathetic and parasympathetic nerves.
Function of Muscularis Externa
1. Muscle joints
2. Involuntary muscle contraction; contraction of smooth muscles help break down of food.
3. Gut movement; peristalsis movement
4. Lymph supply
5. Mix food with digestive secretion
6. Break down of food physically
7. Maintain constriction
8. Uniform direction
9. Peristalsis; propel the content; onwards movement
10. Forms sphincter, situated various point on tract.
3. Submucosa
Submucosa layer of GI tract consist areolar connective tissues. It present between mucosa and muscle layer.
This layer have inside empty space and have outside empty space.
This layer contains plexuses of blood vessels and lymphatic vessels, lymphatic nodule.
Submucosal gland present in oesophagus and duodenum.
Function of Submucosa
1. Help to lubricate
2. Controlling secretion by GI track
3. Receive absorbed food molecules
4. Contains extensive network of neurons
5. Support mucosa
6. Joint muscle mucosa to smooth muscle
7. Nerve plexus is submucosal plexus contains sympathetic and parasympathetic nerve.
4. Mucus Membrane/Mucosa
Mucus membrane is innermost layer of GI tract. Mucus membrane lines internal passageway and orifices of body that open outside of the body.
Mucosa consists of three layer-
1. Epithelial Layer
2. Lamina propria
3. Muscularis Mucosa
1. Epithelial Layer
1. Innner layer of mucosa
2. Direct contact with contents of GI track
3. Epithelial layer
a. Non-keratinized stratified squamous epithelium
b. Mouth, esophagus, anal anal canal
4. Simple columnar epithelium; where food is soft and moist
Function of Epithelial Layer
1. Protection
2. Lubricate
3. Absorption; absorbed food nutrient, assimilation in food
4. Food easily propel
5. No injury
2. Lamina Propria
Underlying layer of -
1. Areolar connective tissue
2. Support epithelium tissue
3. Bind muscularis mucosa
4. Provide blood and lymph supply
5. Contains blood and lymphatic vessels and lymphatic nodule
6. Contains mucosa associated lymphatic tissue (MALT)
7. Help in nutrient in the track reach other tissue of the body.
3. Muscularis Mucosa
1. Outer thin smooth muscle layer
2. Smooth muscle fibre arranged into inner circular layer and outer longitudinal layer
Function of Muscularis Mucosa
1. Lubrication
2. Secretive
3. Protective layer
4. Lubricate solid content
5. Contains absorptive cells and secretory cells that secrete mucus, enzyme and ions.
0 Comments