General Principles of GI Function Flashcards
Requirements of the GI System
Movement of food through the tract
Secretion of juices and digestion of food
Absorption of water, electrolytes, vitamins, and digestive products (nutrients)
Circulation of blood to carry absorbed materials
Control of these functions by local, nervous, and hormonal systems
What cell type is the esophagus composed of?
Stratified squamous epithelium
The junction connecting the esophagus to the stomach
Squamocolumnar Junction
Two types of digestion done by the stomach
Mechanically and Chemically
Thick layer of smooth muscle that regulates entry of material into the duodenum
Pyloric sphincter
The Gastric Rugae of the stomach has these two functions
Allow the stomach to expand and help with mechanical churning
Bile and pancreatic digestive enzymes are introduced here
Duodenum
This is the primary region for nutrient absorption
Jejunum
Which two parts of the small intestine are suspended in the mesentery?
Jejunum and Ileum
Which region is commonly associated with Crohn’s disease?
The illeocecal junction
Length of the Large intestine
1.5 Meters
Colons main function
Absorbs water and electrolytes from the remaining digestive material
Area between the descending colon and rectum
Sigmoid colon
The muscular band that runs longitudinally on the large intestine
Teniae Coli
What does Haustral Churning do?
Haustral churning leads to mixing, helping to expose all of the stool to mucosal surface for better absorption.
The neural sensation that suggests the need for a bowel movement is triggered by _____ of the rectum
Expansion
Fecal impactions can occur in the ____
Rectum
Accessory digestive muscles of the hepatobiliary tree
Liver
Gallbladder
Network of ducts
(Pancreas)
Two types of muscle in the muscularis layer of the GI wall
Longitudinal and circular smooth muscle
Which layer of the GI wall contains the lamina propria?
Mucosa
Which layer of the GI wall contains blood vessels, lymphatic vessels, and nerves?
Submucosa
Outermost layer of the GI Wall and what it is made of
The Serosa is a connective tissue covering that encases and protects the organ.
Three main branches of the celiac trunk
Common Hepatic Artery
Left Gastric Artery
Splenic Artery
The superior mesenteric artery supplies blood to
Most of the small intestine
The pancreas
The proximal half of the large intestine
The inferior mesenteric artery supplies blood to
The descending colon
The sigmoid colon
The rectum
Two main types of GI Blood flow modulators
Gut Activity / Metabolic Factors- Release of vasodilators
Decreased oxygen concentration
Nervous System Input- Autonomic Nervous System
The goal of the Hepatic portal system is to
drains blood from the GI tract and takes blood to the liver for further absorption and processing of material
These hormones have a vasodilatory effect on the digestive process
Cholecystokinin
Vasoactive Intestinal Peptide
Gastrin
Secretin
Two things that parasympathetic stimulation increases in GI blood flow
Increases local blood flow
Increases glandular secretions
A fight or flight response will cause
intense vasoconstriction throughout the GI tract, pushing blood out of the gastrointestinal tract and into the brain, lungs, and skeletal muscles
Where is the enteric nervous system found
lies entirely within the wall of the gut, beginning in the esophagus and ending at the anus
Two parts of the enteric nervous system
Myenteric Plexus (AKA Auerbach’s Plexus): Lies between the longitudinal and circular muscle layers, concerned mainly with controlling muscle activity along the length of the gastrointestinal tract.
Submucosal Plexus (AKA Meissner’s Plexus): Lies in the Submucosa, mainly functions to control the gastrointestinal secretions, local absorption, and local blood flow within the wall.
T/F - the Enteric Nervous System can function independently of any extrinsic neuronal input
T
Post-Ganglionic neurons from the ____ chain secrete norepinephrine on GI smooth muscle and Enterics (inhibitory action on digestion)
Sympathetic
Propolsive vs. Mixing movements
Propulsive Movements- Cause food products to move forward along the tract at an appropriate rate to accommodate digestion and absorption.
Mixing Movements- Keep the intestinal contents thoroughly mixed at all times.
GI Movement is influenced by these two things
Autonomic Input and GI Hormones
This GI Hormone increases GI motility
Motilin
Mixing movements are also mostly triggered by ____
luminal distention of the gut
Two requirements for peristalsis
Intact Myenteric Plexus of the Enteric Nervous System, as well as a fully functional Autonomic Nervous System
