The GI Tract Flashcards
Alimentary canal is composed of
1.) esophagus
2.) stomach
3.) small intestine
4.) large intestine
(direct contact with food)
The digestive accessory organs are:
1.) liver
2.) gallbladder
3.) pancreas
All accessory digestive organs are derived embryologically as what?
“outgrowths” of the early alimentary canal
5 functions of alimentary canal
1.) propulsion
2.) secretion (2 types = hormonal and fluid/mucous)
3.) digestion (2 types = chemical (enzymes/acisd) mechanical (movement)
4.) absorption (lumen –> bloodstream)
5.) immune function (microbe protection)
Layers of the alimentary canal
1.) mucosa
2.) submucosa
3.) muscularis
4.) outer
3 layers of the mucosa
Epithelium: A layer of cells that can absorb nutrients and provide a protective barrier.
Lamina propria: Connective tissue that supports the epithelium and contains blood vessels and lymphatic vessels.
Muscularis mucosae: A thin layer of smooth muscle that helps move the mucosa and aids in the absorption of nutrients.
Where can large glands, large vessels, very large lymphs be found?
submucosa layer
What is the plexus of neurons existing in the submucosa called? And what does it do?
Meissner’s plexus- regulates secretions and convey sensory info about what’s in the lumen
What are the 2 layers of the muscularis layer?
1.) inner: circular surrounding lumen (squeezes lumen shut)
2.) outer: “longitudinal layer” – smooth muscle fibres run along the length of the canal (shortens the canal)
Sarah (serosa) goes on adventures (adventitia) outside (outer layer).
What is the plexus that regulates the movements of the muscularis layer? Where is it found?
Auerbach’s (myenteric plexus), found between the two layers
What are the 2 parts of the outer layer?
adventitia- anchors esophagus in the chest cavity
Serosa- LCT covered by simple squamous mesothelium
What part of the outer layer of the alimentary canal secretes fluid that collects in the abdominal (peritoneal cavity)?
mesothelium of the serosa layer
What is a source of peritoneal fluid?
mesothelium
What part of the outer layer is continuous with the visceral perritoneal?
serosa
What is the fluid filled gap between the wall of the abdomen and the organs contained within the abdomen
peritoneal cavity
What are the 2 parts of the peritoneal cavity?
visceral : formed by the serosa and liver
parietal: inner lining of the ab. wall. (extremely sensitive to inflammation and other chemical irritants
What does the esophagus connect? What are the 2 muscles?
pharynx –> stomach
upper esoph. sphinchter- pushes food
lower esoph. sphincter- limits stomach acid into esophagus. Relaxes to receive swallowed food
What kind of lining?
stratified squamous epithelium (adventitia NOT serosa)
What kind of cells does the stomach have? What do they do?
low columnar cells
Parietal cells – secrete acid and intrinsic factor
(IF is needed for absorption of B12)
Other cells secrete mucous to protect the lining or digestive enzymes specialized for digesting proteins
What is the sphincter of the stomach?
pyloric- regulates amount of acid chyme that enters duodenum
What’s the innermost muscularis layer of the 3 of the stomach?
oblique
3 components of small intestine
Duodenum- receives chyme from stomach (That duo love to chum (chyme)
Jejunum- Immunity (Immunity is good in June, due to vitamin patches from the payers)
Ileum-longest, reabsorption of bile salts, micronutrients/ vitamins and water (If you are ill, you must reabsorb nutrients)
Don’t Judge Intestines
Which part of the digestive system has highly folded epithelium (microvilli), mucosa (villi) and submucosal layers (circular folds) meant to optimize surface area?
Small intestine
(Columnar epithelium with many microvilli
interspersed with goblet cells and cells that secrete chemical messengers into the blood.
Messengers help regulate propulsion, overall metabolic function, secretions from the pancreas or liver)
Main function of the large intestine?
absorb water from stool, store stool and housing microbes
Does the LI have goblet cells? Microvili?
Yes plenty
Fewer than SI
What’s unique about the muscular layer of the LI?
Continuous circular muscle layer
Longitudinal muscle layer is separated into bands that do not completely surround the canal
How do accessory organs convey their secretions? Where to?
ducts, to the lumen and duodenum
Liver rolesher
Roles of the liver:
Carbohydrate metabolism
Protein synthesis and degradation
Most proteins secreted into the bloodstream are from the liver
Lipid metabolism
Detoxification of molecules so that they can be secreted into the bile and defecated
Making hydrophobic molecules water soluble so that they can be eliminated by the kidney
Storage of vitamins and minerals
Synthesis of bile – essential for lipid digestion
Endocrine – secretion of IGF-1, important hormone regulating growth
Where does the gall bladder release bile to upon contraction?
dupdenum
What do pancreatic hormones and digestive enzymes impact?
glucose, protein and lipid metabolism (insulin, glucagon, somatostatin
Diarrhea, gastroenteritis, inflammatory bowel disease, laxative use, gastrointestinal bleed
Or early bowel obstruction (often described as a high-pitched “tinkling” sound
Increased or decreased bowel sounds?
increased (hyperactive)
Bowel obstruction, peritonitis, intestinal ischemia
Increased or decreased bowel sounds?
decreased
Is hyper or hypoactive bowel more emergent?
hypo
Abdominal pain in the six regions on the “sides” are often due to irritation of the ______ ______.
Parietal peritoneum
Abdominal pain in the three areas in the “centre” can be visceral pain from the ____ or _____.
alimentary tract or accessory organs
Large liver with firm, nontender edge?
Large liver that is firm and an irregular edge. May or may not be tender?
Hepatocellular carcinoma
Liver cirrhosis
