GI Exam Lecture 2 Flashcards
Cephalic Phase:
- Activation of the GI tract in readiness for the meal
- The stimuli are cognitive and include:
- All of these can trigger responses in the GI system in the absence of food ingestion
Cephalic Phase:
- Activation of the GI tract in readiness for the meal
- The stimuli are cognitive and include:
- Idea of food
- Olfaction
- Visual stimuli
- Auditory stimuli
- All of these can trigger responses in the GI system in the absence of food ingestion
Oral Phase:
- Many of the responses are ______, only difference is _________
- Additional activation of the GI from sensory inputs from ______ and ________ in the mouth and upper pharynx
Oral Phase:
Many of the responses are the same as in the Cephalic phase, only difference is food is present in the mouth (activation of mechanoreceptor, chemical receptors)
- Additional activation of the GI from sensory inputs from taste buds (tongue) and mechanical receptors in the mouth and upper pharynx
Chewing:
- Breaking of food into small pieces - mechanical digestion
- Mixing of food with enzymes- salivary ______ and lingual _____
- Mixing of food with salivary _____ (lubrication - helps in chewing and swallowing)
- No absorption in mouth except for ___ and ____
Chewing:
- Breaking of food into small pieces - mechanical disruption
- Mixing of food with enzymes - salivary amylases and lingual lipase (modest digestion in healthy)
- Mixing of food with salivary Mucin (lubrication)
- No absorption in mouth except for alcohol and some drugs (clinically relevant)
Chewing:
- Enhancement of the GI system, tonsils sense ______ to start training the ________
In the Clinic: Explain “xerostomia or dry mouth”
Chewing:
Enhancement of the GI system, tonsils sense foreign particles to start training the immune system
In the Clinic: Xerostomia or dry mouth - impaired salivary secretion - congenital or autoimmune. The decrease in secretion reduces pH in the oral cavity- causing tooth decay, esophogeal erosions, difficulty swallowing
Salivary Secretion:
- Considerable stimulation of salivary secretion occurs during _____ and ____ phases of a meal
- There are three pairs of major salivary glands:
- Extrinsic (90%):
- Intrinsic (in the mouth) (10%)
*
Salivary Secretion:
- Considerable stimulation of salivary secretion occurs during Cephalic and Oral phases of a meal
- There are three pairs of major salivary glands:
- Extrinsic (90%)
- Parotid (serous)
- Submandibular (mixed)
- Sublingual (mucous)
- Intrinsic (in the mouth) (10%)
- Additional smaller glands are found in the oral and buccal mucosa (constant rate)
Salivary Secretion:
- There are two types of secretions:
- Mixed - _______ glands
Salivary Secretion:
- There are two types of secretions:
- Serous (water, electrolytes, enzymes): parotid glands
- Mucous (mucin glycoprotein) - sublingual glands
- Mixed - Submandibular glands
- Papillae secrete saliva _____
- Salivary glands secrete ________
- Saliva is filtered _____
- Saliva contains _______ (pain killer)
- More nerve endings than anywhere else
- Papillae secrete saliva continuously
- Salivary glands secrete when needed (neuroregulation)
- Saliva is filtered blood
- Contains opiorphin (pain killer)
- More nerve endings than everywhere else
Salivary glands are formed by two main anatomical structures:
- __________ (secretory unit)
- and a network of _______ that
Salivary glands are formed by two main anatomical structures:
- acinus (secretory unit)
- and a network of collecting ducts that empty the secretory juice into the gut
Glandular Architecture:
- The _____ is the blind end of the branching duct system, lined with ____
- The acinar cells produce _____ composed of water, ions, enzymes, mucus
- The initial saliva passes through the _____ then the ______ lined with ductal cells
- The ductal cells modify initial saliva and produce ____ by altering electrolyte concentrations
- The acinus is the blind end of the branching duct system, lined with acinar cells
- The acinar cells produce initial saliva, composed of water, ions, enzymes, mucus
- The initial saliva passes through the intercalcalated duct then the striated duct - lined with ductal cells
- The ductal cells modify initial saliva and produce final saliva by altering electrolyte concentrations
Myoepithelial cells:
- Are present in the ___ and _____
- These cells contain ____ and ____ fibers which allows them to contract
- When stimulated by neural input, the ____ to ___
Myoepithelial cells:
- Are present in the acini and intercalcalated discs
- These cells contain actin and myosin fibers, which allows them to contract
- When stimulated by neural input, they contract to expel saliva in the forward direction
Salivary Secretion:
Saliva is produced by the salivary glands at a rate of ____ per day
Functions of Saliva are:
1.
2.
3.
Salivary Secretion:
Saliva is produced by the salivary glands at the rate of 1L per day
Functions of Saliva are:
- Lubrication of ingested food with mucus to aid its movement through esophagus (also required for speech)
- Protection: diluting and buffering of ingested foods, cleans mouth
- Initial digestion of starches and lipids by salivary enzymes - not a major contribution
Minor one: painkiller
Composition of Saliva:
- Inorganic Composition is entirely dependent on the _____ and ____ of salivary flow
- -The major inorganic components are:
The major organic constituents include:
Composition of Saliva:
- Inorganic Composition is entirely dependent on the stimulus and rate of salivary flow
- major inorganic components are Na, K, Mg, Cl
- fluoride can be secreted
Major Organic Constituents Include:
- salivary a-amylase (starch digestion)
- Lingual Lipase (lipid digestion)
- Glycoprotein (mucin forms mucous when hydrated)
- Lysozyme (attacks bacterial wall)
- Opiates
Formation of Saliva:
- In humans, salivary secretion is hypertonic/hypotonic
- _____ K and HCO3- concentrations
- ______ Na and Cl concentrations
Saliva is formed in a ______ process:
- The first step is the formation of an _____ like plasma solution by acinar cells : known as _______
- The second step is a modification of this plasma-like solution by the ductal cells to produce _____
Formation of Saliva:
In humans, salivary secretion is hypotonic
- Higher K+ and HCO3- concentrations
- Lower Na and Cl concentrations
Saliva is formed in a two step process
- The first step is the formation of an isotonic plasma like solution by the acinar cells - known as primary secretion or initial saliva
- The second step is the modification of this plasma like solution by the ductal cells to produce hypotonic final saliva
Formation of Saliva:
Step 1: Initial Saliva:
- The _______ secrete initial saliva, which is ____
- Thus, in initial saliva, osmolarity, Na, K, Cl, HCO3 concentrations are _____
Formation of Saliva:
Step 1: Initial Saliva:
- The acinar cells secrete initial saliva, which is isotonic
- Thus, in initial saliva: osmolarity, Na+, K+, Cl-, HCO3- concentrations are similar to plasma
Formation of Saliva:
Step 2: Final Saliva
- The ductal cells modify initial saliva via ______
The luminal membrane contains three transporters:
1.
2.
3.
The basolateral membrane contains the ____ and ____
The combined action of all of these results in absorption of ______ and secretion of ______
More ____ is absorbed than _____ is secreted, so there is net absorption of solute
Step 2: Final Saliva:
The ductal cells modify initial saliva via complex transport mechanisms
The luminal membrane contains three transporters
- Na-H exchange
- Cl-HCO3 exchange
- H-K exchange
The basolateral membrane contains the Na-K ATPase and Cl- ion channels
The combined action of all of these results in absorption of Na and Cl- and secretion of K+ and HCo3-
More NaCl is absorbed than KHCO3 is secreted, so there is a net absorption of solute
Step 2: Final Saliva:
The ductal cells modify initial saliva via complex transport mechanisms
The combined action of all of the transporters results in absorption of ____ and secretion of _______
More ___ is absorbed than _______ is excreted, so there is a _____ of solute
Step 2: Final Saliva:
The ductal cells modify the initial saliva via complex transport mechanisms
The combined action of all of the transporters results in the absorption of Na and Cl and the secretion of K+ and HCO3-
More NaCL is reabsorpted than KHCO3 is secreted, so there is a net absorption of solute
Step 2: Final Saliva
The ductal cells are water-_______, thus
The combination of these two makes saliva ___-
Step 2: Final Saliva:
The ductal cells are water impermeable, thus water is not absorbed with the solute
The combination of these two makes final saliva hypotonic
Regulation of Salivary Stimulation:
- Control of salivary secretion is _______ (exception in the GI system- other GI secretions are both neural and hormonal)
- Salivary secretion is stimulated by __________ subdivisions of the ANS, although _____ is dominant
- There is both ____ and _____ activation of acinar and ductal cells
- Stimulation of salivary cells results in increased ____, increased ______, and contraction of _____
Regulation of Salivary Stimulation:
- Control of salivary secretion is exclusively neural
- Salivary secretion is stimulated by both parasympathetic and sympathetic subdivisions of the ANS, although parasympathetic stimulation is dominant
- There is both PSNS and SNS innervation of acinar and ductal cells
- Stimulation of salivary cells results in increased saliva production, increased HCO3- and enzyme secretions, and contraction of myoepithelial cells
Regulation of Salivary Secretion:
- Parasympathetic Innervation:
branches of _____ and _______
post ganglipnic neurons release _____ which then interacts with _____ receptors: production of ____ and increased intracellular ____ increases saliva secretion
Parasympathetic Regulation of Saliva Secretion:
Parasympathetic Innervation:
Branches of Facial (CN7) and Glossopharyngeal (CN9)
post ganglionic neurons release ACh which interacts with muscarinic receptors — production of IP3 and increased intracellular Ca++ increases saliva production
Regulation of Salivary Secretion:
Sympathetic Innervation:
originates in thoracic segments T1-T3
preganglionic nerve synpase in superior cervical ganglion
post ganglionic neurons release _____ which interacts with _____ receptors
produces ______ which increases saliva secretion
Regulation of Salivary Secretion:
Sympathetic Innervation:
originates in T1-T3, preganglionic nerves synapse in superior cervical ganglion
post-ganglionic neurons release NE which interacts with beta-adrenergic receptors
produces cAMP which increases saliva secretion
Swallowing:
- Swallowing can be initiated voluntarily, and after that it is almost entirely under ______ control
- The swallowing reflex: propels food from ___ to ____ and then to ____. It inhibits ____
- ______ of the reflex- begins when touch receptors near the opening of the pharynx are stimulated-sensory impulses transmitted to the ______ (in the medulla and lower pons)
- _______ from swallowing center travel to pharnyx and upper esophagus (via ___ nerves) and to the remaining esophagus (via _____ neurons)
Swallowing:
- Swallowing can be initiated voluntarily, and after that it is almost entirely under reflex control
- The swallowing reflex: propels food from mouth to pharnyx and then to stomach. It inhibits respiration-inhibits food entrance into trachae while swallowing
- Afferent limb of the reflex: begings when touch receptors near the opening of the pharynx are stimulated- sensory impulses transmitted to the swallowing center (in the medulla and lower pons)
- Motor impulses from swallowing center travel to the pharnyx and upper esophagus (via cranial nerves) and to the remaining esophagus (via vagal motor neurons)
Draw the flowchart describing Long Reflex Control (explaining the swallowing reflex)
Words from class:
“when the stretch receptor in the pharynx is activated, sensory signals are sent to the swallowing center (in the medulla and pons)
the swallowing center then does various things:
sends signals to cortex to stop breathing
vagal input to start nonvoluntary swallowing
Different Phases of Swallowing:
There are 3 phases in swallowing: ____, ____, _____
Explain the first two in detail
Different Phases in Swallowing:
There are three phases in swallowing: oral, pharyngeal, esophageal
Oral phase (voluntary): this is initiated with the tongue forces a bolus of food back towards the pharynx - activates stretch receptors- initiates involuntary swallowing reflex
Pharnygeal phase (involuntary < 1 sec): the soft palate is pulled upwards and the palatopharnygeal fold moves inward, creates narrow passage- prevents reflux into nose, food moves into pharnyx
- Epiglottis moves to cover larynx, larynx moves upwards against epiglottis - preventing food entry into trachae. Respiration is inhibited.
Different Phases in Swallowing:
- The ________ relaxes to receive the food bolus
- A ________ wave of contraction is initiated, which forces the bolus through the relaxes UES
- After the bolus crosses the UES (pharyngeal phase) the swallowing reflex closes the sphincter, prevents reflex into pharynx
- The upper esophageal sphincter (UES) relaxes to receive food bolus
- Pharnyx contracts, further enhancing propulsion of food into the esophagus. A peristaltic wave of contraction is initiated, which forces the bolus through the relaxed UES.
- After the bolus crosses the UES (pharnygeal phase) the swallowing reflex closes the sphincter - prevents reflux into the pharynx
Esophageal Phase of Swallowing:
- Controlled by _____ and _____
- The esophagus, the UES and the LES (lower esophageal sphincter) serve two main functions:
1.
2.
Esophageal phase of swallowing:
- The esophageal phase of swallowing is controlled by both the swallowing reflex and the enteric nervous system
- The esophagus, and its two sphincters (UES and LES) serve two main functions:
1. They propel food from the pharnyx to the stomach
2. The sphincters protect airway from swallowed material, and protect esophagus from acidic gastric reflux
Motor Activity During the Esophageal Phase:
- After the bolus crosses the UES (pharyngeal phase) the swallowing reflex closes the sphincter- prevents _____
- A __________ contraction (coordinated by the swallowing center) occurs, involves a series of coordinated sequential contractions - propels food down the esophagus
- Distension of the esophagus by the moving bolus initiates another wave called _____ (mediated by the enteric nervous system)- repitative, clears the esophagus of the bolus
After the bolus crosses the UES (pharyngeal phase) the swallowing reflex closes the sphincter - prevents reflux into pharynx
- A primary peristaltic contraction (coordinated by the swallowing center) occurs, involves a series of coordinated sequential contractions (peristaltic wave) - propels food down the esophagus
- Distension of the esophagus by the moving bolus initiates another wave called secondary peristalsis (mediated by the enteric nervous system) - repitative secondary peristalsis clears the esophagus of the bolus
Explain the difference between the primary peristaltic contraction and the secondary peristaltic contraction during the esophageal phase
- Primary peristaltic contraction is coordinated by the swallowing center, it involves a series of coordinated sequential contractions to propel food down the esophagus
- Distention of the esophagus by the moving bolus then initiates another wave called secondary peristaltis (mediated by the enteric nervous system) - repitative secondary peristalsis clears the esophagus of the bolus
Esophageal Phase:
- As the peristaltic wave and food bolus approach the LES, the sphincter opens (relaxation) : mediated by _____ fibers in the ____ that release ____
- At the same time the LES relaxes, the ____ region of the stomach also relaxes - a phenomenon called _______ ) helps in movement of bolus into the stomach
- When bolus enters the orad stomach, LES contracts, returns to its _______. At resting tone, the pressure at the sphincter is ____ than esophagus or orad stomach
Esophageal phase:
- As the peristaltic wave and food bolus approach the LES, the sphincter opens (relaxation): mediated by peptinergic fibers in the vagus nerve that release VIP
- At the same time the LES relaxes, the orad region of the stomach also relaxes - phenomenon called receptive relaxation (helps in movement of bolus into the stomach)
- When bolus reaches orad stomach, LES contracts, returns to its high resting tone. At resting tone, the pressure at the sphincter is higher than the esophagus or orad stomach
Esophageal Phase:
- Due to the anatomical position of the esophagus, the intraesophageal pressure is ____ than abdominal pressure
- This creates two problems:
Both the UES and LES are closed, except when food enters or leaves the esophagus
-Increase in ______ can lead to gastroesophageal reflux
Esophageal Phase:
-Due to the anatomical position of the esophagus, the intraesophageal pressure is lower than abdominal pressure
This creates two problems:
- keeping air out at upper end (done by UES)
- keeping gastric acidic contents out (done by LES)
Both the UES and LES are closed, except when food enters or leaves esophagus
-Increase in intra-abdominal pressure can lead to gastroesophageal reflux
The esophagus has what kind of epithelial cells?
Esophagus has squamous epithelial cells (normally aka NO absorption)
GERD:
- Conditions that lead to increased intra-abdominal pressure may cause GERD (examples?)
- This happens when LES is unable to prevent the gastric acidic contents reflux back into the distal part of the esophagus
- This region of the esophagus does not have robust protection of mucusal lining. The acid will activate pain fibers (can happen in healthy people too)
- Long term - continual reflex can damage the esophageal mucosa, which is called ____/____
- How is GERD treated?
GERD:
- Conditions that lead to increased intra-abdominal pressure may cause GERD (examples: pregnancy, obesity)
- This happens when the LES is unable to prevent the gastric acidic contents reflux back into the distal part of the esophagus
- This region of the esophagus does not have robust proteciton of mucosal lining. The acid will activate pain fibers
- Long term - continual reflux can damage the esophageal mucosa, which is called GERD/Barret’s esophagus (columnar epithelium)
- Treated with:
- H receptor agonists to reduce gastric acid secretion
- Or proton pump inhibitors (example: omeprazole)
Hiatal Hernia:
- Upper portion of the stomach protrudes into the chest cavity through an opening of the diaphragm called the _______.
- With muscle weakening and enlargement however, the opening/herniation can allow upward passage or entrapment of upper stomach into diaphragm
- ___, ___, _____ are major symptoms. LES no longer works properly
- Genetic predisposition, weight lifting, obesity, constipation are common causes
- It is estimated that ___% of the population over 60 has some degree of hiatal hernia
Hiatal Hernia:
- Upper portion of the stomach protrudes into the chest cavity through an opening of the diaphragm called the esophageal hiatus.
- With muscle weakening and enlargement, however, the opening or herniation can allow upward passage or even entrapment of the upper stomach above the diaphragm
- Pain, acid reflux are major symptoms. The LES no longer works properly.
Genetic predisposition, obesity, weight lifting and constipation are all common causes of hiatal hernia
-It is estimated that 60% of population over 60 have some degree of hiatal hernia
Achalasia: Motility Disorder
- The ________ of esophagus does not have normal peristalsis and the LES does not relax normally in response to swallowing
- ___, _____, ____ are common symptoms
- Treatment is _____. Meanwhile patients must be treated with ____, _______, and other muscle relaxants
Achalasia:
The SMOOTH MUSCLE LAYER of the esophagus does not have normal peristalsis and the LES does not relax normally in response to swallowing
- Dysphagia, regurgitation, and chest pain are common symptoms
- Treatment is surgical. Meanwhile patients must be treated with Ca++ channel blockers, BOTOX injection in the LES and other muscle relaxants
Cephalic Phase:
Sensory inputs (smell sight, idea of food) activate the _____ and _____ areas of the brain, which then transmits a signal to the ________.
The ______ neurons project to many places in the GI (such as______)
Those ___ neurons release ____ which then binds to ________
Cephalic Phase:
Sensory inputs activate the cortex and hypothalamus
Then they transmit a signal to the brainstem (lower pons/upper medula)
Then via PSNS transmits signals via the vagal nerve
PSNS stimulates places like salivary glands, gastric secretion, pancreas, gallbladder, etc.
ACh binds on muscarinic receptor
All of these prepare the GI tract to receive and digest food
