NURS 2003H Chapter Notes - Chapter 41: Anorectic, Gastrin, Misoprostol
26 Jun 2018
School
Department
Course
Professor
1
Review of GI System Chapter 41(p.1040- 1046;1053-1062)
Structures and Functions of the GI System
-Main function: supply nutrients to body cells
oIngestion, digestion, absorption, elimination
Cool fact: 9m long (30ft) composed of mucosa, submucosa, muscle and serosa
-GI tract is innervated by the parasympathetic and sympathetic ANS
oPNS is mainly excitatory, SNS is mainly inhibitory
oPeristalsis is increased by PNS stimulation and decreased by SNS stimulation
-GI tract receives approx. 25-30% of cardiac output.
-2 types of movement of the GI tract are:
1. mixing (segmentation)
2. propulsion (peristalsis)
-Abdominal organs are almost all covered by peritoneum.
o2 layers of peritoneum are the parietal (lines abdominal cavity wall) and visceral (covers
abdominal organs)
operitoneal cavity: space between the parietal and visceral layers
o2 folds of the peritoneum are the mesentery and omentum
mesentery: attachment of SI and part of LI to the posterior abdominal wall, contains
blood and lymph vessels
Omentum: contains fat and lymph nodes, lesser omentum extends from the lesser
curvature of the stomach and upper duodenum to liver, greater omentum hangs from
the stomach over the intestines like an apron.
Ingestion & Propulsion of Food
-Appetite center is in hypothalamus
oDirectly or indirectly stimulated by hypoglycemia, empty stomach, decrease in body temp.,
input from higher brain centers.
find more resources at oneclass.com
find more resources at oneclass.com
2
oGhrelin: hormone released from stomach mucosa stimulates appetite.
oLeptin: hormone that suppresses appetite
oSight, smell, taste of food stimulates appetite
oAppetite may be inhibited by stomach distension, illness (especially with fever),
hyperglycemia, nausea and vomiting, drugs (i.e. amphetamines) and psychological factors
(i.e. stress or depression)
-Fancy name for swallowing is deglutition
-Peristalsis: coordinated, sequential contraction and relaxation of outer longitudinal and inner circular
layers of muscles.
Mouth: lips and oral cavity
oOral cavity contains 3 pairs of salivary glands the parotid, the submaxillary, and the
sublingual.
Produce saliva, which consists of water, protein, mucin, inorganic salts, and amylase.
Pharynx: musculomembranous tube that is divided into the nasopharynx, oropharynx, and laryngeal
pharynx.
oOropharynx secretes mucus, which aids in swallowing.
oEpiglottis: lid of fibrocartilage that closes over larynx during swallowing
oDuring ingestion, the oropharynx provides a route for the food to move from the mouth to
esophagus.
oWhen receptors in the oropharynx are stimulated by food or liquid, the swallowing reflex is
initiated.
Esophagus: located in thoracic cavity behind the trachea, 23-25cm long, 2cm in diameter.
oWith swallowing, the upper esophageal sphincter (cricopharyngeal muscle) relaxes, and a
peristaltic wave moves the bolus into the esophagus.
oBetween swallows, the esophagus is collapsed.
oThe muscular layers contract and propel the food to the stomach
oThe lower esophageal sphincter (LES) at the distal end of the esophagus remains contracted
except during swallowing, belching, or vomiting.
Important barrier that prevents reflux
Digestion and Absorption
find more resources at oneclass.com
find more resources at oneclass.com
3
Mouth: digestion begins in mouth, involves a mechanical process (mastification) and chemical process.
oSaliva: main function to lubricate and soften food mass to facilitate swallowing.
Contains amylase (ptyalin), which hydrolyzes starches
Stomach: Stores food, secretes digestive juices, mixes food with gastric secretions, and empties the
contents (chyme) into SI
oRugae: muscular layer of stomach that forms folds that contain many small glands that secrete
gastric juice
oChief cells: secrete pepsinogen
oParietal cells: secrete HCL acid, water, and intrinsic factor
HCL makes gastric juice acidic to protect against ingested organisms
Intrinsic factor promotes cobalamin (Vit.B12) absorption in SI
oMucus is secreted by glands in the cardiac and pyloric areas.
Small Intestine: digestion and absorption (uptake of nutrients from the gut lumen to the bloodstream)
oThe ileocecal valve, which separates the small intestine from large intestine prevents reflux of
LI contents into SI
oFolds in the mucosa slow passage of food and provide a greater SA for digestion and
absorption.
oAbsorption occurs through the villi (finger-like projections), contain goblet cells that secrete
mucus and epithelial cells that produce the intestinal digestive enzymes.
Epithelial cells on villi contain microvilli which compose the brush border.
Digestive enzymes on the brush border of microvilli chemically breakdown nutrients
so that they can be absorbed
Physiology of Digestion: the physical and chemical breakdown of food into absorbable substances.
oDigestion of proteins begins with the release of pepsinogen from chief cells.
The acidic environment of the stomach converts pepsinogen to its active form pepsin.
Pepsin begins the initial breakdown of proteins.
oAverage meals stay in stomach for 3-4 hrs.
oDigestion is completed in SI where carbs. are hydrolyzed to monosaccharides, fats to glycerol
and fatty acids, and protein to amino acids
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Main function: supply nutrients to body cells: ingestion, digestion, absorption, elimination. Cool fact: 9m long (30ft) composed of mucosa, submucosa, muscle and serosa. Gi tract is innervated by the parasympathetic and sympathetic ans: pns is mainly excitatory, sns is mainly inhibitory, peristalsis is increased by pns stimulation and decreased by sns stimulation. 2 types of movement of the gi tract are: Mesentery: attachment of si and part of li to the posterior abdominal wall, contains blood and lymph vessels. Omentum: contains fat and lymph nodes, lesser omentum extends from the lesser curvature of the stomach and upper duodenum to liver, greater omentum hangs from the stomach over the intestines like an apron. Appetite center is in hypothalamus: directly or indirectly stimulated by hypoglycemia, empty stomach, decrease in body temp. , input from higher brain centers. Peristalsis: coordinated, sequential contraction and relaxation of outer longitudinal and inner circular layers of muscles.
