GI Flashcards
Myenteric Plexus
aka Auerbach plexus
Controls contractions and tonicity
Meissner’s Plexus
aka submucosal plexus
Controls local blood flow and wall unfolding
Cecum
Beginning of the large intestine
What is the path of food from the oropharynx to the anus?
Oropharynx –> esophagus (UES and LES) –> stomach (fundus, body, pylorus, pyloric sphincter) –> duodenum –> jejunum –> ileum –> cecum –> ascending colon –> transverse colon –> descending colon –> sigmoid colon –> rectum –> anal canal –> anus
What are the types of salivary glands and their secretions?
Sublingual - serous and mucus Submandibular - serous and mucus
Parotid - serous
Ptyalin
Main component of serous fluid
Digests starches
Salivary contents and salivary pH
H20 Mucus Bicarb K+ Salivary amylase (carb digestion) Linguil lipase (inactive until stomach) pH = 6-7
Actions of swallowing
Tongue pushes bolus back
Soft palate rises to protect nasopharynx
Epiglottis drops back and down to protect airway
Esophagus opens wide
What stimulates salivation?
Sour Smooth Sweet Smell Sight Nausea Insulin secretion Aggression Mostly parasympathetic
Apthous ulcer
Break in mucosal layer, causes erosion of epithelial layer
Can occur anywhere in GI tract
Causes - friction, stress, problem w/ mucus secretion
Tx - artificial barrier, antisthetic rinse
Layers of the GI tract
Mucosa (contains glands)
Submucosa (connective tissue)
Muscularis (longitudinal, circular and oblique)
Serosa (adventitia, continuous with mesentery)
What makes up the enteric nervous system?
Submucosal (Meissner) plexus - in submucosa, controls local blood flow
Myenteric (Auerbach) plexus - in muscularis, controls contractions and tonicity
What are primary and secondary peristalsis?
Primary is when you first swallow. If a bolus gets stuck in the esophagus, secondary peristalsis is triggered to try and move it the rest of the way.
Where are the swallowing center in the CNS?
Pons and medulla
What is splanchic flow?
Blood from GI tract runs through liver for processing and filtering.
Upper and lower esophageal sphincters
UES - prevents air going into stomach
LES - prevents stomach contents from backing up into esophagus
Esophageal stricture and rings
Stricture - scar tissue builds up and narrows esophagus
Rings - bands of muscle form in lower esophagus
Both associated with GERD
Achalasia
Failure of the LES to relax; food becomes stuck in esophagus.
Can lead to swelling, infection and ulcers
Primary functions of the oropharynx
Chewing
Mixing food and saliva
Begin carb and starch digestion
Move food into esophagus (swallow)
Primary functions of the esophagus
Transport food to the stomach
Primary function of the stomach
Store food
Secrete digestive juices and mix with food
Begin protein digestion
Move chyme into duodenum
Anatomical boundaries of the stomach
Cardia, fundus, greater curvature, pyloric sphincter, lesser curvature
Rugae
Folds in the stomach wall
Oxyntic glands
Found in the stomach
Contain parietal cells, chief cells, ECL cells, D cells, G cells and Mucous neck cells (Goblet cells)
Pyloric glands
Found in stomach
Contain G cells, D cells and Mucous neck cells (Goblet cells)
Parietal cells
Secrete gastric acid (HCl) and Intrinsic factor
Intrinsic factor
Needed for vitamin B absorption
Produced by parietal cells
Chief cells
Produce pepsinogen
Pepsinogen
Converted to pepsin w/ HCl
Breaks down proteins
ECL cells
Secrete histamine that binds at H2 receptors and stimulates gastric acid secretion
D cells
Inhibits gastric acid production
G cells
Secrete gastrin to stimulate gastric acid secretion
Mucous neck/Goblet cells
Secrete protective mucus
Peritoneum
Serous membrane that covers abdominal organs
Esophageal spasms
Bolus overstretches esophagus and causes contractions and spasms
Mesentery
Part of the peritoneum that attaches organs to the posterior abdominal wall
What stimulates stomach secretions?
Aggression/hostility Cephalic phase stimulation Gastric secretions PNS More secretion in afternoon/evening than morning
What inhibits stomach secretions?
SNS Bad tastes Rage Fear Pain
What secretions digest what types of food?
Salivary amylase - carbohydrates
Pepsin - proteins
Lingual lipase - fats
Gastroileal reflex
When food hits the stomach, ileal motility increases to make room for more chyme
Gastroenteric/gastrocholic reflex
When the stomach stretches peristalsis is triggered (similar reflex found throughout GI tract)
Function of the small intestine
Absortion
Propulsion
Continued digestion
Brunner’s gland
Found in duodenum
Secrete alkaline mucus for proection
Crypts of Leiberkuhn
Investigation in mucousal layer
Secrete digestive juices
Hold replacements for epithelial cells
I-cells
In duodenum and jejunum
Secrete cholecystokinin
Cholecystokinin
Secreted in small intestine when food enters
Inhibits gastric emptying
Stimulates pancreatic enzyme and bicarb secretion
Stimulates gallbladder to release bile
Inhibits chief and parietal cells and peristalsis
Peyer’s patches
In ileum
Small lymph nodes
What stimulates small intestine activity?
Stretching, gastrin, CCK, insulin, motilin and serotonin trigger peristalsis
Presence of acid, fat, protein byproducts, osomotic imbalance or irritation stimulate CCK and GIP
What inhibits small intestine activity?
Distention, irritation, acidity, CCK, GIP, secretin inhibit emptying
What is GIP?
Gastric inhibitory polypeptide
Stimulates insulin release
Inhibits chief and parietal cells and peristalsis
Pancreatic enzymes
Inactive - trypsin, chymotrypsin, carboxypeptidase
Breakdown proteins into amino acids
Trypsinogen is activated first, helps activate other enzymes
Active - alpha amylase, pancreatic lipase
What helps with carbohydrate digestion in the small intestine?
Sucrase, maltase, lactase (all from small intestine) and pancreatic amylase
What helps with fat digestion in the small intestine?
Liver bile salts and pacreatic lipase
Enterogastric reflex
Presence of lipids, proteins and change in pH in duodenum inhibit gastric secretion
Ileogastric reflex
Stretching of ileum inhibits gastric motility
Cholecystokinin (CCK)
Released in duodeenum when fats and proteins are present
Inhibits gastric secretions
Stimulates bile and pancreatic enzyme release
Relaxes Sphincter of Oddi
Vitamin B12
Needs intrinsic factor from parietal cells to be absorbed.
Important for RBC maturation.
Iron
Found in heme from animal proteins and some fruits/veggies/grains
Low Fe = faster absorption
Needs Vit C for absorption
Intestinointestinal relfex
Over-distention of an intestinal segment inhibits intestinal motility
Peritonitis
Inflammation of peritoneum
Assumes yellowish color and can adhere bowel loops together, leading to colonic obstruction
Haustra
Pockets of large intestine
Formed by the circular and longitudinal (Taenia) coli
Diverticulosis and diverticulitis
Diverticulosis is minimal, non-problematic inflammation in colon caused by feces becoming trapper
Diverticulitis is symptomatic and requires attention
Steps in defecation
Feces enter and stretch rectum
Urge to defecate
Voluntary contraction of external sphincter
Retrograde movement of feces into sigmoidal colon
Falciform ligament
Divides liver into L and R lobes
Secretin
Released in duodenum w/ presence of acid
Inhibits gastric secretions and motility
Stimulates release of pancreatic enzymes and bile
