Lecture 20: Basic structure of the GI Flashcards
What is the role of the Gl system?
Bring nutrients/water into internal environment to be used by the body
MSDA (My Sausage Dog Ate)
* Motility: transport food into & through the body,
mixing luminal contents, and transport waste out
- Secretion: synthesise and release enzymes,
mucus & serous fluid into the lumen - Digestion: break nutrients into smaller pieces
(mechanically and chemically) - Absorption: bring nutrients/water from the lumen to
internal environment
What are the majors organs of the digestive tract?
Oral cavity (mouth)
Pharynx
Esophagus
Stomach
Small intestine
Large intestine
What are the accessory organs of the organs of the digestive system?
Teeth/tongue
Salivary glands
Liver
Gall bladder
Pancreas
What structure separates parts of the digestive system and allows for unique environments in each organ?
Sphincters close off ends, and separate sections of tube. This allows for unique environments to be achieved within the digestive tract.
What is the epithelia found in the mouth and esophagus?
Stratified squamous epithelium - allows protection from rough foods etc.
What type of epithelia is found in the stomach, small intestine and large intestine?
Simple columnar epithelium - Good for secretion and absorption of nutrients/water etc.
What are unicellular glands in the GI system?
Goblet cells: (mucus secreting)
* Columnar
* Goblet shape
* Apical mucous granules
* Basal nucleus
What type of epithelium is found at the anus?
Stratified squamous epithelium - provides protection from abrasion
What are the two types of multicellular glands in the GI system?
Epithelium can invaginate to form glands:
- Simple: gland with single duct (e.g. stomach and small
intestine) - Compound: gland with 2 or more ducts (e.g. salivary
glands) = more surface area for greater secretion
What are the four gut tube layers (in order from in to out)?
- Mucosa
- Submucosa
- Muscularis (externa/proper)
- Adventitia
What does the mucosa layer consist of?
- Epithelium
- Basement membrane
- Lamina propria (FCT)
- Muscularis mucosae
Plus, sometimes, glands
What does the submucosa consist of?
- FCT
- Glands
- Blood vessels
How is secretion regulated in the submucosa?
Secretion is regulated by the submucosal nerve plexus, part of the enteric nervous system (ENS)
What does the muscularis consist of? What are the two main layers and what regulates the muscular motility?
The muscularis (externa/proper) consists of smooth muscle
Two main layers:
* Inner circular
* Outer longitudinal
The Myenteric plexus (Part of ENS), Located between muscle layers regulates motility of the muscles
What does the adventitia consist of?
It is the Outermost layer of the gut tube and consists of FCT
What is the role of the mouth and oral cavity?
It is where digestion begins, both Mechanical and Chemical– requires enzymes. Lubrication is needed
Food moves through fauces, into oropharynx &
laryngopharynx then into esophagus
What and where are the three salivary glands and what do they secrete?
- Parotid glands (back of throat) - Serous fluid with amylase
- Sublingual glands (under tongue) – secrete Mucus only
- Submandibular glands (by the jaw) – secrete Mixed
What is the structure of salivary glands and what can the respective cells produce?
Salivary glands are compound secretory glands
The Acinar cells can secrete serous fluid & enzymes
(amylase) and mucus. These are the clusters of cells at the bottom of the gland
The duct cells secrete bicarbonate (pH buffering). These are the cells by the entrance of the gland and line the main tube sort of (easiest to look at slide 20 for a better look)
What is the function of the esophagus? Where is it located?
Located posterior to the trachea, extends from pharynx to
stomach
Basic tube modified to allow passage of food
Highly folded submucosa and mucosa allowing Capacity to expand for passage of bolus (food)
What type of muscle is found in the esophagus?
- First 1/3: skeletal muscle
- Middle 1/3: a mixture
- Last 1/3: smooth muscle
Allows food to be pushed down into the stomach
Does the esophagus have goblet cells?
NO
Need mucus for lubrication and protection but have NO GOBLET CELLS.
Instead have glands with ducts to the surface
* In submucosa
* Plus in mucosa close to stomach
Which salivary gland(s) can produce amylase?
Primarily the Parotid glands
You need mucus to coat the lining of the esophagus. Where in the esophagus could this be made, and how would it be moved to the surface of the epithelium?
Made in the multicellular glands in submucosa, reaches surface via ducts
The four basic layers of the GI tract beginning with the most luminal layer are;
(a) epithelium, submucosa, muscularis externa, serosa
(b) mucosa, lamina propria, muscularis externa, adventitia
(c) mucosa, submucosa, muscularis mucosae, adventitia
(d) mucosa, submucosa, muscularis externa, adventitia
D
Be careful, C is incorrect as the muscularis mucosae is apart of the mucosa layer.
