Flashcards in GI Deck (169)
What are the layers of the wall of the GI tract, starting with innermost:
A networks of nerve is between each of the layers
What does the mucosal layer of the esophagus specialized function?
Stratified squamous epithelium that enables gliding of masticated food
What specialized function does the stomach mucosal layer have:
Thick glandular mucosa that provides mucus, acid, and proteolytic enzymes for digestion
What specialized function does the small intestine mucosal layer have:
Villious structure to provide large surface area for absorption
What specialized function does the large intestine mucosal layer have:
Lined with abundant mucus secreting cells that facilitate storage and evacuation of residue
What is the gut nervous system called and what does it innervate?
Enteric nervous system
Stomach muscle, secretory cells, endocrine cells, blood vessels
What is absorbed in the mouth?
Certain drugs that come in contact with the mucosa of the mouth are absorbed into the blood stream
What is absorbed in the stomach?
Water, simple sugars, alcohol
(Water, alcohol, copper, iodide fluoride, molybdenum)
What is absorbed in the small intestine?
The final steps of digestion; glucose, fructose, fatty acids, glycerol, amino acids are absorbed into the blood stream
Duodenum- Ca, Phos, Mag, Fe, vit A, D, E, K, etc
Jejunum- Lipids, monosaccharides, AA, small peptides, vit A, D, E, K, zinc, etc
Ileum- Bile salts/acids, vit C, vit B12, folate, vit D and K, Mag, etc
What is absorbed in the large intestine?
No chemical digestion, only by bacteria
Absorption of water, some minerals, and drugs
Water, vit K, biotin, Na, Cl, K, short chain fatty acid
What are the parts of the small intestine?
Duodenum to jejunum to ileum
A person unable to absorb bile salts may have had their __________ removed?
What hormones stimulate gastric emptying?
Gastrin and motilin
What hormones delay gastric emptying?
Secretin and CCK
What are the 4 main general functions of the GI tract?
1. Movement of nutrients-propulsion/mixing
2. Secretion of digestive juices
3. Digestion of nutrients
4. Absorption of nutrients
What does salivary amylase in the mouth do?
Initiates carbohydrate digestion by breaking down polysaccharides into dextrin and maltose
What facilitates muscular movement through the esophagus?
Gravity (not necessary)
Why is it important for the lower esophageal sphincter to remain tonically constricted?
To prevent the acidic gastric contents from moving into the esophagus. (GERD)
What is the muscular sphincter between the stomach and the duodenum and what does it do?
Controls gastric emptying and limits reflux of bile from small intestine
Where are Chief cells located and what do they do?
Located in the stomach
They produce pepsinogen (the inactive form of pepsin)
Where are Parietal cells located and what do they do?
Located in the stomach
Produce HCl and intrinsic factor which is needed for vit B12 absorption
What do the mucous cells of the stomach do?
Produce an alkaline mucus that shields the stomach wall and neutralize acids close to wall
What is the longest portion of the GI tract?
Describe the lining of the small intestine:
The intestinal wall is marked by circular folds lines with intestinal villi to increase surface area for absorption and digestion. Each villi has microvilli which are covered by a brush border containing digestive enzymes
Where is the ileocecal valve and when does it open?
Located between the small and large intestine
Opened via peristaltic contractions
What are the 2 layers of the enteric nervous system and where are they located?
1. Myenteric plexus; lies between the longitudinal and circular muscular layers (GI movement)
2. Submucosal plexus; like in the submucosa (secretions and sensory functions)
What does gastrin do and where is it secreted?
Secreted in the stomach by G cells in response to food entry. It mediates gastric acid secretion and increases stomach motility. Promotes constriction of LES.
What does CCK do and where is it secreted?
Secreted by I cells in the duodenum in response to fat. Stimulate release of pancreatic enzyme (lipase) and causes contraction of gallbladder and relaxation of sphincter of Oddi=bile released to duodenum.
What does secretin do and where is it secreted?
Secreted by the mucosa of the duodenum in response to acid from stomach. Stimulates pancreatic fluid and bicarb rich solution release = neutralize acidity in intestine