1 - Gastrointestinal Physiology Overview PPT Flashcards
(Eat and Excrete)
What are the four main functions of the gastrointestinal (GI) tract?
Ingestion, Digestion, Absorption, Excretion
Acronym: “IDAE”
What is the hard palate?
The roof of the oral cavity (aka the mouth)
What role does the hard palate play in an infant’s ingestion?
Helps create a vacuum effect for suckling milk
What enzyme do infants secrete to break down milk fat?
Lingual lipase
What is the uvula’s role in digestion?
The uvula secretes saliva to moisten the throat
What are the three salivary glands?
Sublingual gland (below the tongue)
Submandibular gland (below the mandible)
Parotid gland
Mnemonic: Saliva Still Pours
What enzyme is within saliva to break down long carbs into small sugars?
Salivary amylase
What is the mass of mechanically chewed food mixed with saliva and enzymes called?
a BOLUS!!! (vine boom and airhorn)
Where on earth does that dang BOLUS go after it is swallowed through the pharynx?
Into the esophagus
What structure blocks off the airway allowing the BOLUS to move into the esophagus?
The epiglottis
Where does digestion start?
The mouth
What’s the first layer of the GI tract?
Adventitia/serosa
What is the adventitia/serosa composed of?
Thick, fibrous connective tissue and a slippery serous membrane
What’s the second layer of the GI tract?
Muscularis externa
What is the muscularis externa composed of?
Smooth muscle
What is the function of muscularis externa?
Moves BOLUS down the GI tract by constricting two muscle groups
What two muscle groups are used to move that frickin’ BOLUS down the GI tract?
Inner circular m. layer and an outer longitudinal m. layer
What is the term for a series of coordinated, wave-like muscle contractions that squeeze the BOLUS in one direction?
Peristalsis
What plexus is located between the two layers of the muscularis externa?
Myenteric plexus (aka Auerbach’s plexus)
What is the function of the Myenteric plexus (aka Auerbach’s plexus)?
Coordinates muscle contraction and relaxation
(Contraction-relaxion)
What’s the third layer of the GI tract?
Submucosa
What is contained within the submucosa?
Blood vessels
Lymphatics
Nerves
What plexus is located in the submucosa?
Submucous plexus (aka Meissner’s plexus)
What is the function of the Submucous plexus (aka Meissner’s plexus)?
Controls the size of blood vessels and the secretion of digestive juices
What’s the fourth layer of the GI tract?
Mucosa
What does the mucosa possess for a larger surface area for absorption?
Villi
What three components make up the mucosa?
Muscularis mucosa - smooth m. that contracts/breaks down food
Lamina propria - contains blood/lymph vessels
Epithelial layer - absorbs/secretes mucus and digestive enzymes
Define intrinsic innervation.
Operates via enteric nervous system to ɪɴᴅᴇᴘᴇɴᴅᴇɴᴛʟʏ control digestive activities. It is ɪɴᴅᴇᴘᴇɴᴅᴇɴᴛ!!
Define extrinsic innervation.
Operates via sympathetic nervous system to inhibit digestion, and operates via the parasympathetic nervous system to enhance digestion.
Inhibit: Fight or Flight
Enhance: Rest and Digest
Which innervation type do Meissner’s plexus and Auerbach’s plexus operate on?
Intrinsic innervation
What is a short reflex and what is it mediated by?
The process of:
- detecting food entering the GI tract via receptors
- conditioning the tract to begin peristaltic contractions to move food one direction
Its afferent and efferent components are mediated by the enteric nervous system (intrinsic innervation).
What’s a long reflex?
A long reflex is the CNS’s act of receiving afferent information and sending efferent information to the GI tract via sympathetic and parasympathetic systems (extrinsic innervation).
When is a long reflex used?
Two scenarios to observe a long reflex:
- Sympathetic is used to inhibit digestion (Fight or Flight)
- Parasympathetic is used to enhance digestion (Rest and Digest)
What are the two types of muscle contractions?
- Tonic (continuous)
- Phasic (waves, aka peristalsis)
What in tarnation do interstitial cells of Cajal do?
They act as pacemakers and control the contraction rate via rhythmic potentials of de and repolarization, pardner
Which potentials cause tonic contractions?
Slow wave potentials from enteric nervous system
Which potentials cause peristaltic contractions?
Slow wave potentials PLUS action potentials from the extrinsic nervous system
Which component of the GI tract has the lowest rate of contraction at 3 slow waves per minute?
The stomach
Which component of the GI tract has the highest rate of contraction at 12 slow waves per minute?
The duodenum
