Anatomy and Cell Biology 3309 Lecture Notes - Lecture 38: Muscular Layer, Muscularis Mucosae, Stratified Squamous Epithelium
2 May 2018
School
Department
Professor
Histology Lecture 5 – Semester 2
Esophagus and Stomach
- Esophagus
- Stomach: Cardiac Region, Body Region, Pyloric Region
- Small Intestine: Duodenum, Jejunum, Ileum
- Large Intestine
- Liver
- Pancreas
- Gall Bladder
Learning Objectives
1. Explain the general organization of the GI tract
2. Name the different layers and their main functions
3. Distinguish upper, intermediate and lower sections of the esophagus according to muscle type in the
muscularis externa.
4. Differentiate between esophagus and stomach according to surface epithelium.
5. Characterize the stomach mucosa as having pits and glands
6. Describe 6 different cell types in the lining epithelium of the stomach and name their functions
7. Describe the location and function of Auerbach’s and Meissner’s nerve plexus.
Layers and functions of the GI tract
- GI tract is along muscular tube from oral cavity to the anus
o Includes associated lands (liver, pancreas)
o Functions in digesting food and absorbing nutrients
- 4 main concentric layers:
o 1. Mucosa
▪ Epithelium
• Interacts with food that comes in
• Located on the lamina propria
• Protective or absorptive-secretory
▪ Lamina Propria Loose CT
▪ Inner lining of the tubular GI tract
o 2. Submucosa
▪ DICT with elastic fibers
▪ Carries in to the mucosa, nerves, blood vessels
▪ If looking at absorption in the small intestine, it will carry all the nutrients and carry
those out of the GI tract
▪ Blood vessels and nerve plexus – Meissner’s plexus
o 3. Muscularis Externa
▪ 2 thick layers of smooth muscle
• INNER CIRCULAR
• OUTER LONGUTIDINAL
▪ NOTE: DOUBLE LAYER
• Running in directions right angles to one another
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▪ Innervated
▪ Allows the gut to move the food along so it does not get stuck
o 4. Adventitia or Serosa
▪ DICT or mesothelium covering
▪ In certain parts of the GI tract that are suspended or hanging in the body cavity
where it is hanging, instead of having adventitia there is a layer of mesothelium
(lining of body cavity – simple epithelium) / Serosa
▪ depending on the location we have either an adventitia or serosa
- Barrier to the outside world
o Immune system (gut associated lymphoid tissue – GALT) lives in the mucosa and submucosa
- Absorption / Digestion
o Specific parts of the mucosa are differentiated to perform this function
o To facilitate this, there are glands (Mostly in the submucosa that provide lubrication to move
things and liquefy the food content)
- Secretion: endocrine and exocrine
- All the different functions are specifically organized in the concentric layers
- Glands:
o Location = lamina propia, submucosa
o Some lie outside GI tract, but connected to it (salivary glands, liver, pancreas)
The General Organization ** KNOW THIS SLIDE **
- Different regions the food passes through in order to nourish us
- Note: submucosa and muscularis externa is very similar along the length of the GI tract (there are
specification such as thickenings, sphincters)
- Mucosa – has many changes along the GI tract, helping you identify the different parts
- Lumen is ALWAYS lined by epithelium
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Esophagus
- Designed to deliver the food into the stomach – convey food to stomach from the pharynx
o Numerous longitudinal folds in lumen
- Straight epithelial lined tubed with mucosa, submucosa
- NOTE: in the muscularis externa, the type of muscle changes and it depends on LOCATION
o Upper third of esophagus = muscularis externa composed of striated muscle (voluntary
muscle)
▪ Once we have taken food in, we are able to active regurgitate it
▪ There are species, where their life depends on it birds feed their young by
regurgitating food
o Toward the stomach = predominantly smooth muscle
o Both types of muscle start mixing in the middle of the esophagus
o * Can look at the nature of the muscularis externa to determine which section of the
esophagus it was taken from*
- Mucous membrane
o Epithelium = stratified squamous, non-keratinized (wear and tear)
o Lamina propia = loose CT with lymphocytes, papillae, cardiac glands
o Muscularis mucosae = longitudinal smooth muscle
- Submucosa
o Dense CT with lymphocytes and esophageal glands
- Muscularis externa
o 2 concentric layers
o Upper third skeletal, middle third mixed, lower third smooth muscle
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Gi tract is along muscular tube from oral cavity to the anus. Includes associated lands (liver, pancreas: functions in digesting food and absorbing nutrients. Interacts with food that comes in: located on the lamina propria, protective or absorptive-secretory, lamina propria loose ct. Inner lining of the tubular gi tract: 2. Muscularis externa: 2 thick layers of smooth muscle. Inner circular: outer longutidinal, note: double layer, running in directions right angles to one another. Innervated: allows the gut to move the food along so it does not get stuck, 4. Adventitia or serosa: dict or mesothelium covering. Barrier to the outside world: depending on the location we have either an adventitia or serosa. Absorption / digestion things and liquefy the food content) All the different functions are specifically organized in the concentric layers. Glands: location = lamina propia, submucosa, some lie outside gi tract, but connected to it (salivary glands, liver, pancreas) The general organization ** know this slide **
