Lecture 20 GI system Flashcards
whats the Primary function of the GI system?
Bring nutrients into the internal environment so that they can be used
The Gastrointestinal System Specialized for function: what are the 4?
- Motility
- Secretion
- Digestion
- Absorption
what are the Key Structures in the Gastrointestinal System?
- Long tube with outgrowths
- Lined by epithelium (interface with outside world)
Major organs and accessory organs
what are the major organs of digestive tract?
oral cavity pharynx esophagus stomach small intestine large intestine
what are the accessory organs of digestive system?
teeth tongue salivary glands liver gallbladder pancreas
what type of epithelium is found in Mouth/Oral Cavity and Esophagus? and why?
Stratified Squamous
Protection from abrasion
what type of epithelium is found in the Stomach, Small Intestine and Large Intestine? and why?
Simple Columnar
Secretion and absorption
what type of epithelium is found in the Anal canal? and why?
Stratified Squamous
Protection from abrasion
what are Unicellular Glands?
Goblet cells:
- Columnar
- Goblet shape
- Apical mucous granules
- Basal nucleus
what are goblet cells?
Unicellular Glands
- Columnar
- Goblet shape
- Apical mucous granules
- Basal nucleus
in between columnar epithelium of the small intestine
what are Multicellular Glands?
simple and compound
Epithelium can invaginate to form glands: what are the 2?
simple and compound
whats a simple gland?
single duct (e.g. stomach and small intestine)
whats a compound gland?
2 or more ducts (e.g. salivary glands)
what are The Four Layers of the Gut Tube?
- Mucosa
- Submucosa
- Muscularis (externa/proper)
- Adventitia
what does the mucosa consists of?
- Epithelium
- Lamina propria (FCT)
- Muscularis Mucosae
what does the submucosa contains?
- Glands
- Blood vessels
- Connective tissue
- Glands
whats the submucosal nerve
plexus?
regulates secretion
part of enteric nervous system (ENS)
what does the muscularis (externa/proper) consists of?
- Smooth muscle
- Inner circular
- Outer longitudinal
what are the 2 main layers of muscularis (externa / proper)?
Inner circular
Outer longitudinal
whats the Myenteric plexus?
- Part of ENS
- In between smooth muscle layers of muscularis
- Regulates motility
whats the adventitia?
outermost layer of the gut tube
Adventitia
When organs are in the peritoneal cavity what is there?
additional outer covering, the serosa (not one of the four layers)
what are the Four layers of the gut tube (from innermost to outermost)?
- Mucosa
- Submucosa
- Muscularis
- Adventitia
what does the adventitia consist of?
FCT
what are the four basic layers of the GI tract beginning with the most luminal layer?
mucosa, submucosa, muscularis externa, adventitia
whats the Peritoneum?
- Serous membrane
- Parietal (lines body)
- Visceral (lines organ)
- Fluid filled space
what layers consist of the peritoneum?
- Parietal layer: lines the body wall
* Visceral layer: lines the organs
whats between the parietal and visceral layer of the peritoneum?
fluid filled space
whats retroperitoneal?
posterior to peritoneum
whats the Mesentery?
Double layer of visceral peritoneum
Connects organ to body wall
whats the omenta?
Double layer of visceral peritoneum
connects organ to another organ
what epithelium found in oral cavity and mouth?
stratified squamous protect against abrasion
what occurs in Mouth and Oral Cavity?
Food ingested:
where digestion begins (needs enzymes)
lubrication
where does the ingested food go in mouth and oral cavity?
Through fauces, into oropharynx, then into esophagus
what are the salivary glands 3 pairs that are connected to the oral cavity via ducts?
- Parotid - Serous fluid with amylase
- Sublingual – Mucous only
- Submandibular – Mixed
whats the parotid duct?
Close to ear
Serous fluid with amylase (enzyme) for carb digestion
whats the sublingual duct?
Mucous only
Under tongue
whats the submandibular duct?
Mixed (mucous and serous fluid with amylase)
Under mandible
whats the Total volume of salivary secretions?
1L per day
what are salivary glands?
Epithelial layer invaginates to form compound secretory glands
acinus acinar cells (secrete amylase) duct cells (secrete bicarbonate)
what are acinus?
cells in clusters
what do acinar cells secrete?
amylase enzyme
what do duct cells secrete?
bicarbonate for buffering
whats the esophagus?
Long tube (~25cm) Basic tube modified to pass food
wheres the esophagus located?
posterior to the Trachea, extends from pharynx to stomach
what does the epiglottis ensure?
food enters the esophagus, and not the trachea
what does the esophagus consist of?
submucosa and mucosa (highly folded, able to expand)
Mucosa
Muscularis externa
glands with ducts on surface
what epithelium makes up the esophagus mucosa?
stratified squamous
what does the esophagus muscularis externa do?
move food bolus
what kind of muscle makes up the esophagus?
Changes as you go down:
• First 1/3: skeletal muscle
• Middle 1/3: a mixture
• Last 1/3: smooth muscle
the esophagus Need mucous for lubrication and protection but it has no goblet cells. what does it have instead?
glands with ducts to surface
What type of epithelium lines the esophagus?
stratified squamous
Give one reason this epithelium is used in the esophagus.
protection from abrasion
You need mucous 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?
submucosal glands - connected to lumen via ducts
