Health Sciences 3300A/B Lecture Notes - Lecture 1: Diagnostic Peritoneal Lavage, Muscular Layer, Blunt Trauma
19 Sep 2016
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Lecture 1- Digestive System 10/16/2014 4:08:00 PM
**TOP HAT: aspiration of a foreign object beyond larynx ends up lodged in the right bronchus
because it is: shorter than the left primary bronchus, more vertical than the left primary bronchus,
wider than the left primary bronchus
Digestive System-Components
Alimentary Canal(GI Tract)
• mouth (head to neck)
• pharynx (thorax)
• esophagus (abdominal cavity)
• stomach (abdominal cavity)
• small intestine (abdominal cavity)
• large intestine (abdominal cavity)
• anus (pelvic cavity)
Accessory digestive organs
• teeth
• tongue
• salivary glands
• liver
• gallbladder
• pancreas
Digestive Processes
Indigestion
• taking in food
• usually through the mouth (can be taken through nasal gastric tubes)
o entry to the GI
Propulsion
• moves food through alimentary canal (forward movement generally)
• 1st stage: involves swallowing
o voluntary/involuntary
• peristalsis→ coordinated muscle contraction of walls of GI tract that move bolus of
food that we have eaten along the GI tract
o begins at esophagus
o involuntary
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o reverse peristalsis is when stomach doesn’t agree with food and brings the
food back up
o layer of GI tract of longitudinal muscle and circular muscle work to push
bolus of food along the GI tract
o segmentation: breaks up the bolus of food, segments it into smaller, digestible
bits
▪ in intestines
▪ back and forth of the muscles of the stomach or intestinal wall, bolus
stays in a central spot but is broken apart
▪ local phenomenon
Mechanical Digestion
• occurs in 2 locations
o oral cavity
o stomach
• physically prepares food
• chewing
• mixing with saliva
• churning food in stomach
o 3 layers
o allows to be mixed with digestive enzymes of the stomach
Chemical Digestion
• release of enzymes to break down food into components
• begins in mouth
• complete by small intestine
Mechanical vs. Chemical
- Mechanoreceptors
• stretch of organ wall by food
- Chemoreceptors
• osmolarity, pH
- Initiates reflexes
• enteric NS
• stimulates secretions
• mixing of luminal contents
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find more resources at oneclass.com
• movement along the GI
Reflexes: Enteric Nervous System
Submucosal nerve plexus
• in submucosa
• regulates activity of glands in gut
• activates smooth muscle of mucosa
Myenteric nerve plexus
• between longitudinal and circular muscle in muscularis externa
• major nerve supply of GI tract
• controls GI mobility → regulates peristalsis
Histology
-within mesentery
• arteries
• veins
• nerves
-GI tract made up of 4 layers
• innermost layer → mucosa
o surrounds lumen/cavity of organ
o cavity is lined with mucosa
• second layer → submucosa
o glands
o submucosa nerve plexus
• third layer → muscularis externa
o dual layer of muscle
o circular on the inside and longitudinal on the outside (myenteric nerve plexus)
• outer layer → serosa
o outer connective tissue of organ
Digestive Processes
Absorption
• in most of small intestine and large intestine
• passage from lumen of GI tract into blood
• absorption of nutrients and water that we digest
• enters mucosal cells first
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find more resources at oneclass.com
Document Summary
**top hat: aspiration of a foreign object beyond larynx ends up lodged in the right bronchus because it is: shorter than the left primary bronchus, more vertical than the left primary bronchus, wider than the left primary bronchus. Alimentary canal(gi tract: mouth (head to neck, pharynx (thorax, esophagus (abdominal cavity, stomach (abdominal cavity, small intestine (abdominal cavity) large intestine (abdominal cavity, anus (pelvic cavity) Accessory digestive organs teeth liver tongue: salivary glands, gallbladder, pancreas. Indigestion taking in food: usually through the mouth (can be taken through nasal gastric tubes, entry to the gi. Mechanical digestion: occurs in 2 locations, oral cavity, stomach, physically prepares food, chewing, mixing with saliva, churning food in stomach, 3 layers, allows to be mixed with digestive enzymes of the stomach. Chemical digestion release of enzymes to break down food into components: begins in mouth, complete by small intestine. Mechanoreceptors: stretch of organ wall by food.
