MODULE 7.1 PRINCIPLES OF GI FUNCTION Flashcards
DEFINE GI-TRACT: GASTROINTESTINAL TRACT
- a hollow, convoluted tube that runs through the body.
- food enters the mouth and is processed in a number of ways in order to extract the necessary nutrients, electrolytes, fluids, vitamins and minerals to sustain life.
DEFINE THE 6 SPINCTERS OF THE DIGESTIVE SYSTEM?
- Upper Esophageal Sphincter. Between pharynx and esophagus.
2- Lower Esophageal/ Cardiac. Between esophagus and stomach.
3- Pyloric. Between stomach and duodenum.
4- Ileocecal. Between small intestine and cecum.
5- Internal anal.
6- External anal
WHAT ARE THE 2 MOST IMPORTANT ACCESSORY ORGANS FOR PROPER FUNCTIONING OF THE GI TRACT?
PANCREAS: secretes digestive enzymes and a bicarbonate-rich solution into the proximal region of the small intestine.
LIVER: secretes bile into the proximal region of the small intestine
SEROSA
(wall of the duodenum)
the outermost connective tissue of the GI tract and is covered with thin flat epithelial cells called squamous epithelium
MUSCULARIS EXTERNA
(wall of the duodenum)
contains two layers of smooth muscle: the inner circular layer and the outer longitudinal layer. Enteric neurons lie between these two muscle layers.
SUBMUCOSA
(wall of the duodenum)
inward into the GI wall: made up of loose connective tissue and large blood vessels and may contain glands for secretion of contents in the GI lumen
MUCOSA
(wall of the duodenum)
surrounded by the muscularis mucosae. Its made up of an epithelial cell layer and the underlying loose connective tissue called the lamina propria (which contains capillaries, enteric neurons, and immune cells like mast cells, plus a thin layer of smooth muscle called lamina muscularis mucosae. Mucosal surface area is very large. In the small intestine, villi, crypt glands, and apical microvilli drastically increase the surface area to increase the efficacy of absorption.
MESENTERY
(cross-section of the gut)
surrounds the intestine and is made up of membranous tissue containing blood vessels that exchange oxygen and nutrients for carbon dioxide and waste from the intestine.
“gut” /”bowel” refers to the?
INTESTINES
both terms are used for the small and large intestine.
( the gut or bowl of the gastrointestinal tract begins after pyloric sphincter and ends at the anus)
Sort the layers of the gut from deep to superficial (i.e., from the inside out).
- Lumen
- Enterocytes
- Mucosa
- Mucosal Muscle
- Submucosa
- Circular Muscle
- Longitudinal Muscle
- Serosa
Mechanical disruption?
-in the form of chewing and churning helps to break apart out food into manageable sizes.
1.–Mastication in the mouth (starts)
2. Churning in the stomach: helps to reduce the size of food in stomach to 2mm or less in diameter, which is necessary for stomach contents to be able to pass through the pyloric sphincter into the small intestine during a meal.
Define Chemical Digestion?
-must occur before the intestinal epithelial cells can absorb them and involve 3 macronutrients
- Lipids: mostly consumed as triglycerides, but absorption occurs only as fatty acids and monoglycerides.
- Amino acids: consumed as proteins and large peptides but are absorbed as amino acids and small peptides.
- Carbohydrates: consumed as starches, disaccharides and monosaccharides, et only monosaccharides can be absorbed.
TRUE/FALSE: Carbohydrate digestion does not involve any enzyme that is secreted from the gastric mucosa.
TRUE: Carbohydrate digestion does not involve any enzyme that is secreted from the gastric mucosa.
Salivary Glands
(Digestive Enzyme Location)
- release enzymes to begin the chemical digestion of carbohydrates and lipids.
ENZYMES/TARGETS
Amylase/Starch
Lipase/Triglycerides
Stomach
(Digestive Enzyme Location)
ENZYMES/TARGETS
Pepsin/Proteins
Lipase/ Triglycerides
PANCREAS
(Digestive Enzyme Location)
ENZYMES/TARGETS
Amylase/Starch
LipaseColipase/Triglycerides
Phospholipase/Phospholipid
Trypsin/Peptides
Chymotrypsin/Peptides
INTESTINE
(Digestive Enzyme Location)
ENZYMES/TARGETS
Enterokinase / ACTIVATES TRYPSIN
Disaccharidases/ COMPLEX SUGARS
Dipeptidases/ PEPTIDES
IS RESPONSIBLE FOR ACTIVATING LUMINAL PANCREATIC ZYMOGENS?
TRYPSIN
TRUE/FALSE: CHYMOTRYPSIN PREFENTIALLY CLEAVES AT AMINO ACID RESIDUES WITH POSITIVELY CHARGED SIDE CHAINS.
False: This is a characteristic of trypsin. Chymotrypsin preferentially cleaves at aromatic side chains.
Breaks down phospholipids?
Phospholipase
Breaks down starch?
Amylase
Breaks down proteins?
Pepsin
Breaks down triglycerides?
Lipase
ENTEROCYTES
(wall of the colon-large intestine)
are the surface absorptive cells of the intestine.
GOBLET CELLS
(wall of the colon-large intestine)
secrete mucus and are the second most abundant epithelial cell.
ENTERIC ENDOCRINE CELL
(wall of the colon-large intestine)
secrete a variety of products, like cholecystokinin, secretin, and peptide.
ENDOCRINES
(involved during digestion)
-(Hormones)
- All GI hormones are peptides
- Released into blood ® act on distant target cell
PARACRINES
(involved during digestion)
- Some are peptides (somatostatin), some are not
(histamine) - Endocrine cells release ® diffuse to target cells
- Can act on endocrine cells (+ or –)
Neurocrines
(involved during digestion)
-(neurotransmitters)
Some are peptides (VIP), some are not (ACh, NE)
- Nerves release ® diffuse to target cells
Upper Esophageal Sphincter
Known as the high-pressure zone: this sphincter is to protect against reflux of food into the airways as well as prevent entry of air into the digestive tract
Lower Esophageal Sphincter
a ring of muscle fibers that acts as a valve to prevent stomach contents from flowing back up into the esophagus. separates the esophagus from the stomach.
Pyloric Sphincter
muscular valve that controls the flow of food from the stomach to the small intestine. (chime :small digested food)
Ileocecal. Sphincter
a muscle valve that controls the flow of digested food from the small intestine to the large intestine
Internal anal Sphincter
a ring of involuntary smooth muscle located at the end of the rectum, forming the inner part of the anal canal, and plays a crucial role in maintaining fecal continence by generating resting pressure to prevent stool leakage; essentially, it’s the muscle that keeps the anus closed without conscious effort.
External anal Sphincter
a large, circular, voluntary muscle that surrounds the anal canal and is responsible for keeping stool in the anal canal until you’re ready to defecate:
