GERD Symptoms, Tests & Mechanisms: Where Are We Standing? | Part 1
SAVOR BALANCE HEALTH COORDINATES SERIES · PART 1 OF 5
The Stomach Is More Than a Container
Why GERD Symptoms, Tests, Mechanisms, and Everyday Patterns Can Describe Different Parts of the Same Reflux Experience
A systems-based guide to GERD symptoms, reflux testing, mechanisms, and AEP interpretation—and why different evidence should not be made identical.
Series Note
This series is intended for educational purposes and does not replace professional medical care.
The Stomach Is More Than a Container is a five-part Savor Balance Health Coordinates series. It explores reflux through established physiology, clinical evidence, lived experience, and AEP—AI Entity Profiler—as an interpretive framework.
AEP—AI Entity Profiler—is an original coordinate-based, non-judgmental interpretive framework proposed and developed by Yohan Choi through Savor Balance. In this health series, AEP does not diagnose gastroesophageal reflux disease (GERD), measure gastric or esophageal function, select treatment, or replace medical explanations. It asks how structure, timing, workload, sensitivity, adaptation, treatment, and everyday conditions may be viewed together without reducing the body to a single cause.
In this chapter, Position is an AEP interpretive coordinate. It is not a formal medical measurement or clinical classification. It refers to the standpoint from which a symptom, test, mechanism, treatment response, or everyday condition is being described.
Diagnosis, medication, nutrition therapy, testing, and individualized treatment decisions should always be discussed with qualified healthcare professionals.
Opening Hook — The Feeling Arrives Before the Vocabulary
Many people know reflux before they know its name.
They know a burning sensation rising behind the breastbone. They know sour or bitter material returning toward the throat. They may know pressure, unsettled fullness, a cough at night, or the uncertainty of wondering whether a familiar symptom is still safe to dismiss.
The experience arrives first. The explanations come later.
That is where the conversation begins to separate. The patient may describe what was felt. A clinician may ask whether the pattern is consistent with GERD, whether alarm features are present, and whether testing or treatment is needed. A researcher or physiologist may discuss acid exposure, reflux episodes, anti-reflux barrier function, esophageal clearance, or sensory processing. A nutrition or everyday-life observer may remember meal timing, portion size, body position, weight-related conditions, or a food that repeatedly preceded symptoms.
Each perspective may contribute something important. But they are not necessarily describing the same variable, and they do not carry the same evidentiary weight.
PART 1 CORE THESIS
Reflux cannot be understood through acid, anatomy, behavior, diet, or one gastric mechanism alone. It becomes clearer when symptoms, clinical assessment, measurements, mechanisms, treatment, and everyday conditions are placed on the same map without being made identical.
A symptom is real information, but it is not automatically a mechanism. A measurement is real information, but it does not automatically explain every symptom.
Different perspectives can describe the same person without describing the same variable.
Position clarifies what each observation can establish; it does not decide diagnosis or replace evidence.
1. One Experience, Several Starting Points
Imagine four people discussing the same episode of heartburn.
The patient begins with timing and sensation: It burned after dinner. It became worse when lying down.
The clinician begins with probability and safety: Does this sound like typical reflux? Is swallowing difficult? Is there bleeding, weight loss, recurrent vomiting, or another alarm feature? Has treatment helped?
The researcher or physiologist begins with different variables: What happened at the anti-reflux barrier? Was reflux objectively measured? How long did refluxate remain in the esophagus? How was the event perceived?
The nutrition or lifestyle perspective begins with the meal and the person: How large was the meal? When was it eaten? What was its composition? Did a particular food repeatedly precede symptoms? Is excess weight clinically relevant? Would a proposed restriction actually help, or would it make the diet unnecessarily restrictive? [1, 8]
None of these starting points is the complete map. Each selects a different coordinate.
Confusion begins when a statement from one coordinate is treated as if it settled all the others. A symptom may be real without identifying its mechanism. A test may measure acid exposure without explaining every moment of discomfort. A meal may repeatedly precede symptoms without proving that the food universally causes GERD. A medication may reduce acid-related injury without answering every question about why symptoms persist.
The first task is therefore not to decide which observer is morally or intellectually correct. It is to ask:
What is this person actually describing?
And then:
What can that description establish?
2. A Symptom Is Real — but It Is Not the Whole Mechanism
Heartburn and regurgitation are important symptoms of GERD, and typical symptom patterns can support an initial clinical approach. Yet symptoms alone do not always provide conclusive evidence of GERD or identify its precise pathophysiology, particularly when the presentation is atypical, treatment response is incomplete, or invasive therapy is being considered. Contemporary clinical frameworks distinguish symptom experience from objective evidence obtained through endoscopy and ambulatory reflux monitoring. [1, 2]
That distinction does not make the symptom less real. It makes the question more precise.
Burning describes an experience. Acid exposure time describes an objective reflux-monitoring variable measured under defined conditions. Endoscopy can identify mucosal injury and structural findings, but it may be normal in some people who have GERD. pH–impedance monitoring can characterize reflux events and their relationship to symptoms under specific testing conditions. [1, 2]
These sources of information may be related, but they are not interchangeable translations of one another.
Symptom perception may also be influenced by esophageal sensitivity and psychological factors such as stress. [3–5] In an experimental study of people with reflux symptoms, psychological stress increased perceived symptom severity without increasing the objectively measured number of reflux events. [5]
This does not mean that the symptoms were imagined, that reflux symptoms are merely “psychological,” or that objective reflux could not also be present. It shows something narrower and more useful:
Perception and measured reflux burden can change differently.
EVIDENCE BOUNDARY
A symptom is valid information about experience. A test is valid information about the variable it was designed to measure.
The two may correspond. They may also diverge.
Neither should be asked to impersonate the other.
3. GERD Is a Multifactorial Clinical Condition
GERD develops when reflux of gastric contents leads to troublesome symptoms, complications, or both. But the path from a reflux event to clinical illness is not controlled by one switch.
The anti-reflux barrier includes important contributions from the lower esophageal sphincter and the crural diaphragm. Transient lower esophageal sphincter relaxations are an important route through which reflux can occur. Hiatal hernia and other changes at the esophagogastric junction may alter barrier function in some patients.
Pressure relationships, esophageal clearance, mucosal integrity, characteristics of the refluxate, peripheral and central sensory processing, and gastric factors may also contribute. [1, 3] The importance of these mechanisms does not have to be identical in every person.
That is why familiar explanations require boundaries.
“The sphincter is weak.” This may point toward one form of barrier dysfunction, but it does not explain every patient or every reflux event.
“There is too much acid.” This can confuse gastric acid production with acid reaching the esophagus. GERD is defined by reflux and its consequences, not by proof of generalized gastric acid overproduction.
“The meal caused it.” A reproducible association may be worth observing, but sequence alone does not establish a universal food rule or a complete mechanism.
“It is only stress.” Stress may modify symptom perception in some circumstances, but this does not erase physiology or reduce a person's symptoms to psychology. [5]
A multifactorial account is not a refusal to explain. It is a refusal to claim more than the evidence can support.
The Korean source that began this series asked whether reflux might be reframed as a kind of processing failure or compensation. That question helped open a systems-based conversation, but it cannot stand as a medical conclusion.
Reflux should not be presented as the stomach deliberately compensating for delayed processing, and symptoms do not prove that gastric processing has failed. Established gastric and GERD physiology does not describe the stomach as an intentional actor that detects unfinished processing and deliberately creates reflux as compensation. [3, 7]
In this definitive English edition, terms such as Response, workload, and later capacity remain AEP interpretive terms. Established GERD mechanisms remain clinical and physiological claims that require their own evidence.
One mechanism is not GERD itself.
4. Acid Matters — but Acid Is Not the Whole Map
Acid is central to many discussions of reflux. It can contribute to symptoms and mucosal injury, and acid suppression is an established treatment for appropriate GERD indications. Proton pump inhibitors remain an important part of evidence-based GERD management, particularly for healing erosive esophagitis and controlling acid-mediated symptoms. [1]
But several statements must remain separate.
First: The stomach normally produces acid. Gastric acid has physiological roles in digestion and defense. [7]
Second: Acidic gastric contents may reflux into the esophagus.
Third: A person may experience symptoms because of acid exposure, reflux hypersensitivity, another esophageal process, or a condition that is not GERD. [1–4]
These statements overlap, but they are not synonyms. Normal gastric acid production is not itself GERD. Reflux of acidic material is not the same thing as generalized gastric acid overproduction. And the presence or intensity of a symptom does not directly measure how much acid exposure occurred.
This distinction also helps us interpret treatment. Acid suppression can change the acidity and consequences of reflux without proving that excessive gastric acid production was the original or complete cause of GERD.
Conversely, persistent symptoms during acid-suppressive treatment do not automatically mean that the medication did nothing, nor do they automatically mean that stronger acid suppression is the answer. Depending on the clinical situation, persistent symptoms may prompt review of how treatment is being taken, reconsideration or confirmation of the diagnosis, reflux monitoring under appropriate conditions, or evaluation of alternative or overlapping mechanisms. [1, 2, 4]
Persistent symptoms are information. They are not a stand-alone explanation.
The useful question is therefore not whether acid is important. It clearly can be.
The better question is:
Which part of this person's problem is acid explaining, and what evidence supports that conclusion?
EVIDENCE BOUNDARY
Acid matters. That does not mean acid explains everything.
5. Everyday Conditions Matter Without Becoming Moral Judgments
Patients often notice patterns that no single clinic visit can capture. They may notice that symptoms seem to occur after certain meals, late eating, lying down soon after eating, changes in body weight, periods of stress, or particular foods.
These observations are useful as observations. They should not automatically be converted into causal mechanisms. A repeated temporal pattern may deserve attention without proving that one food, one behavior, or one lifestyle condition universally causes GERD.
That distinction matters because everyday observations can easily become moral judgments.
They should not become a courtroom.
A person with reflux has not necessarily failed at discipline. A food that repeatedly precedes symptoms is not automatically unhealthy for everyone. A dietary identity is not refuted by one uncomfortable meal. And a recommendation to adjust timing, portion, posture, or a clinically relevant weight-related condition does not make medical treatment unnecessary.
Clinical guidance supports selected lifestyle measures according to the person's clinical pattern—for example, avoiding meals close to bedtime, addressing excess weight when relevant, elevating the head of the bed for nighttime symptoms, and avoiding foods that reliably trigger symptoms. [1]
At the same time, evidence for many food-specific dietary interventions remains heterogeneous and limited. A systematic review and meta-analysis of dietary intervention studies found possible benefits for some approaches but also emphasized the limited and inconsistent nature of the overall evidence. [8]
That is why an individualized, reproducible food association is different from a universal prohibition list.
The same caution applies to stress. Stress may intensify symptom perception or make symptoms harder to manage in some people, but it should not be used to dismiss the person experiencing the symptom or to infer that objective reflux cannot also be present. [5]
Everyday conditions may matter to exposure, perception, behavior, treatment use, and the practical sustainability of care. [1, 5, 8] But an everyday pattern is still a pattern. It is not automatically a universal cause.
And a symptom is not a verdict on character.
EVIDENCE BOUNDARY
Everyday pattern ≠ universal cause.
Symptom ≠ moral verdict.
6. Tests Answer Specific Questions
Modern reflux evaluation is strongest when the test is matched to the clinical question.
Endoscopy can assess erosive esophagitis, strictures, Barrett's esophagus, and other mucosal or structural findings. But a normal endoscopy does not, by itself, exclude GERD in every patient. [1, 2]
Ambulatory pH monitoring or pH–impedance monitoring can provide objective information about reflux-related variables under defined testing conditions, including acid exposure, reflux events, and associations between reflux events and symptoms. [1, 2]
High-resolution manometry evaluates esophageal motor function and aspects of the gastroesophageal junction. It can provide important physiological information, but it is not, by itself, a test that establishes GERD. [1, 2]
Testing strategy also depends on the clinical question. Lyon Consensus 2.0 distinguishes unproven GERD, where reflux monitoring may be used off acid-suppressive therapy to establish or refute the diagnosis, from proven GERD with persistent symptoms, where pH–impedance monitoring on optimized treatment may answer a different question. [2]
The same test therefore does not always serve the same purpose in every patient. Context matters, timing matters, treatment status matters, and the clinical question matters.
A result has meaning inside the conditions under which it was obtained. A “normal” result in one domain is not a universal declaration that every relevant digestive or esophageal function is normal. An “abnormal” result is not permission to attribute every symptom to the variable that was measured.
Personalized GERD care may therefore integrate the symptom profile, treatment response, anatomy, objective reflux evidence, motor function when relevant, and the possibility of alternative or overlapping disorders. [4]
DIAGNOSTIC PRINCIPLE
The right test does not answer every question. It answers the clinical question it was designed and timed to answer.
7. Why Position Changes the Conversation
The purpose of Position is specific: it identifies the kind of statement being made without equalizing the strength of different forms of evidence.
Evidence quality still matters. A personal observation cannot directly establish a physiological mechanism. An AEP interpretation cannot override a clinical guideline. A test result cannot legitimately be generalized beyond the variable and conditions it assessed. And a clinical decision must consider evidence, benefits, harms, alternatives, and the person receiving care.
Position therefore asks us to distinguish among several kinds of statements:
Experience: What did the person feel, notice, or fear?
Clinical Assessment: What diagnosis is plausible, what needs to be excluded, and what care or testing may be appropriate?
Measurement: What variable was measured, under what conditions, and with what limits?
Mechanism: What established physiological or pathophysiological processes could contribute?
Everyday Context: What repeated conditions may modify symptoms, exposure, treatment use, or sustainability?
AEP Interpretation: How can these different forms of information be arranged together without turning one coordinate into the whole cause?
Once the statement type becomes visible, disagreement becomes easier to examine. Two people may appear to disagree while actually answering different questions. Or they may genuinely disagree about the evidence, in which case that evidence can be examined directly instead of being hidden inside ambiguous language.
That is why the series begins with Position.
Before saying what should be suppressed, avoided, measured, changed, or endured, it first asks:
What are we actually talking about?
8. What This Series Will—and Will Not—Do
With Position established, the rest of the series can move forward without repeatedly collapsing different kinds of information into one explanation.
The Stomach Is More Than a Container is organized around five coordinates:
Position — Where is the observer standing, what is being observed, and what kind of claim is being made?
Function — How does the stomach normally accommodate, mix, grind, secrete, sense, and regulate delivery?
Response — How may gastric, esophageal, structural, and sensory systems respond when surrounding conditions change or coordination becomes more difficult?
Intervention — What do medication, testing, posture, timing, weight-related care, and selected procedural approaches actually change?
Alignment — How can meaningful choices, meal conditions, treatment, symptoms, and the body's current state be brought into a more sustainable relationship?
The series will not deny established medicine, reduce GERD to one gastric theory, describe GERD simply as a gastric processing failure, or stage a contest between medical treatment and lifestyle adjustment. It will not turn one person's experience into a universal prescription. And it will not use AEP to diagnose disease, estimate gastric capacity, select medication or testing, or claim that reflux is a purposeful compensatory strategy.
Instead, the series asks whether anatomy, physiology, symptoms, measurement, treatment, everyday conditions, lived experience, and choice can remain visible at the same time.
They can be connected without being made identical.
AEP Interpretive Coordinate — Position: Three Questions
AEP begins this series with Position because interpretation changes when the observer, variable, or purpose of observation changes.
Position can be organized through three practical questions.
1. What Is Being Observed?
Is it a symptom, a test result, an anatomical finding, a treatment response, a meal pattern, or a lived experience?
Naming the object of observation prevents a symptom from quietly becoming a laboratory result—or a laboratory result from becoming a complete description of a life.
2. From Where Is It Being Observed?
Is the observation coming from the patient's daily life, the clinician's diagnostic responsibility, the researcher's measured variable, the nutrition or lifestyle context, or the AEP/archive interpretive frame?
Different positions create different responsibilities. The patient's report is indispensable for describing experience. The clinician carries responsibility for diagnosis and care. Research measurements quantify defined variables. Lifestyle observation may reveal recurring context.
AEP arranges these forms of information. It does not make them evidentially identical.
3. What Can This Observation Establish?
Can it establish description, association, objective measurement, clinical inference, an established mechanism, or only an interpretive question that needs further evaluation?
This third question is the boundary that protects the first two.
A sensation of fullness should not automatically become proof of delayed gastric emptying. A food followed by symptoms should not automatically become universal food causation. A treatment response should not automatically become proof of the entire disease mechanism. And an AEP metaphor should not become medical physiology merely because it is useful for interpretation.
Position is therefore not an official GERD mechanism, a diagnostic score, or a treatment algorithm. Its purpose is to prevent category errors.
Used carefully, Position does not flatten perspectives. It keeps their responsibilities and evidentiary limits intact while allowing them to communicate.
Closing Reflection — Locate the View Before the Verdict
Reflux is familiar enough to invite quick explanations.
Acid. A weak sphincter. A large meal. Stress. Poor discipline. Age. The wrong food.
Each phrase may point toward something worth examining. None should become a verdict before the evidence is clear.
The patient's feeling deserves attention. The clinician's safety questions deserve priority. The researcher's measurement deserves precision. The everyday pattern deserves observation. Treatment deserves neither automatic suspicion nor automatic expansion beyond its indication. And an interpretive framework must remain honest about where interpretation ends.
This chapter does not solve reflux. That was not its task.
Its task was to establish the coordinates from which the rest of the series can ask better questions.
Before turning a symptom into a mechanism, ask what evidence connects the two. Before turning a repeated pattern into a universal rule, ask what has actually been established. Before asking one test to explain the whole body, ask what that test was designed to measure. Before deciding that two perspectives contradict one another, ask whether they are even describing the same variable.
The first act of orientation is therefore simple:
Locate the view before declaring the answer.
Next Coordinate — From Position to Function
If different observers begin from different coordinates, what physiological foundation can they share?
Part 2 begins with the stomach itself: what it is designed to do, how reservoir function becomes active function, and why accommodation, mixing, grinding, secretion, sensation, and regulated emptying must be kept in the same map. [6]
Position has clarified how we are looking.
The next question is what the stomach actually does.
References
[1] Katz PO, Dunbar KB, Schnoll-Sussman FH, Greer KB, Yadlapati R, Spechler SJ. ACG Clinical Guideline for the Diagnosis and Management of Gastroesophageal Reflux Disease. The American Journal of Gastroenterology.2022;117(1):27–56. doi:10.14309/ajg.0000000000001538. PMID: 34807007. PMCID: PMC8754510.
[2] Gyawali CP, Yadlapati R, Fass R, et al. Updates to the modern diagnosis of GERD: Lyon consensus 2.0. Gut.2024;73(2):361–371. doi:10.1136/gutjnl-2023-330616. PMID: 37734911. PMCID: PMC10846564.
[3] Bertin L, Savarino V, Marabotto E, et al. Pathophysiology of Gastroesophageal Reflux Disease. Digestion.2026;107(2):185–201. doi:10.1159/000547023. PMID: 40562014. PMCID: PMC12279320.
[4] Yadlapati R, Gyawali CP, Pandolfino JE; CGIT GERD Consensus Conference Participants. AGA Clinical Practice Update on the Personalized Approach to the Evaluation and Management of GERD: Expert Review. Clinical Gastroenterology and Hepatology. 2022;20(5):984–994.e1. doi:10.1016/j.cgh.2022.01.025. PMID: 35123084. PMCID: PMC9838103.
[5] Wright CE, Ebrecht M, Mitchell R, Anggiansah A, Weinman J. The effect of psychological stress on symptom severity and perception in patients with gastro-oesophageal reflux. Journal of Psychosomatic Research.2005;59(6):415–424. doi:10.1016/j.jpsychores.2005.05.012. PMID: 16310024.
[6] O'Grady G, Carbone F, Tack J. Gastric sensorimotor function and its clinical measurement. Neurogastroenterology & Motility. 2022;34(12). doi:10.1111/nmo.14489. PMID: 36371709. PMCID: PMC10078602.
[7] Hunt RH, Camilleri M, Crowe SE, et al. The stomach in health and disease. Gut. 2015;64(10):1650–1668. doi:10.1136/gutjnl-2014-307595. PMID: 26342014. PMCID: PMC4835810.
[8] Lakananurak N, Pitisuttithum P, Susantitaphong P, Patcharatrakul T, Gonlachanvit S. The Efficacy of Dietary Interventions in Patients with Gastroesophageal Reflux Disease: A Systematic Review and Meta-Analysis of Intervention Studies. Nutrients. 2024;16(3):464. doi:10.3390/nu16030464. PMID: 38337748. PMCID: PMC10857327.
Medical Note
This chapter discusses GERD, reflux symptoms, clinical evaluation, endoscopy, ambulatory reflux monitoring, esophageal physiology, treatment response, lifestyle conditions, dietary observations, and symptom perception. It does not diagnose GERD or determine the cause of symptoms in an individual.
Heartburn, regurgitation, throat symptoms, cough, fullness, and chest discomfort can have causes other than GERD. A normal result in one testing domain does not prove that every relevant digestive or esophageal function is normal, and an abnormal result does not automatically explain every symptom.
Do not stop or alter prescribed medication, begin an unnecessarily restrictive diet, or pursue diagnostic or procedural treatment solely on the basis of this article. Medication changes and testing decisions should be made with qualified healthcare professionals.
Persistent or worsening symptoms require appropriate medical review. Difficulty swallowing, gastrointestinal bleeding, unexplained weight loss, recurrent vomiting, anemia, or other alarm features warrant prompt evaluation. [1]
Chest pain may have cardiac or other serious causes and should not automatically be assumed to be reflux. Depending on the circumstances, urgent medical evaluation may be necessary. [1]
Health Coordinates Vocabulary
Position
An AEP interpretive coordinate describing the standpoint from which a symptom, test, mechanism, treatment response, or everyday condition is discussed. It is not a diagnostic measure or clinical classification.
Symptom
A person's experienced change, such as heartburn or regurgitation. A symptom is clinically important but does not, by itself, identify one physiological mechanism.
Objective Evidence
Information produced by a defined examination or test and interpreted according to what was measured, how it was measured, and under what conditions.
Mechanism
An established or proposed physiological or pathophysiological process that contributes to reflux events, exposure, mucosal effects, clearance, or symptom perception. Different mechanisms may coexist.
Everyday Context
Repeated conditions of daily life—such as meal timing, body position, weight-related circumstances, or reproducible personal patterns—that may interact with symptoms, treatment, or sustainability. Observation of context does not by itself establish universal causation.
AEP Interpretation
A coordinate-based way of arranging evidence, experience, treatment, and context. It does not diagnose disease, select treatment, or replace established physiology.
Category Boundary
The distinction that prevents experience, association, measurement, mechanism, clinical inference, and interpretation from being treated as the same kind of claim.
About Savor Balance
Savor Balance is a human-centered interpretive digital archive created by Yohan Choi. It connects food, health, emotion, AI, narrative, and human life through coordinate-based interpretation, while developing AEP—AI Entity Profiler—as its original interpretive framework.
Health Coordinates is a health application layer within the archive. It examines how biological systems communicate, adapt, carry workload, lose resilience, respond to care, and interact with the conditions of everyday life.
Original Source
This article is part of the series:
The Stomach Is More Than a Container
A Systems-Based Exploration of Reflux, Capacity, and Response
Written by YohanChoi
Savor Balance Health Coordinates Series
This definitive English edition was developed from the original Korean Tistory work and the earlier English draft by Yohan Choi.
This work is based on the original ideas, experiences, and records of Yohan Choi / Savor Balance. Quotation and sharing are welcome with clear attribution, a link to the source, and preservation of the connection among the author, the archive, and the framework.
Publication Provenance
Original Korean source: Tistory Korean Edition
English edition: Definitive English Edition for Savor Balance Blogger
Concept and framework: Yohan Choi / Savor Balance
Published by: Yohan Choi, publishing as YohanChoi
Series position: Part 1 of 5
Series Coordinates
SERIES MAP
Position → Function → Response → Intervention → Alignment
Part 1 · Position
Identifies what is being observed, where the observation comes from, and what kind of claim it can support.
Part 2 · Function
Explains why the stomach is both a reservoir and an active sensorimotor organ that accommodates, mixes, grinds, secretes, senses, and regulates transfer of a meal.
Part 3 · Response
Examines how gastric, esophageal, structural, and sensory systems may respond when surrounding conditions change or coordination becomes more difficult, while separating normal regulation, objective abnormality, symptom experience, and AEP interpretation.
Part 4 · Intervention
Examines what medical and everyday interventions actually change while separating treatment target, measurable biological change, symptom response, everyday condition change, and AEP interpretation.
Part 5 · Alignment
Returns the series to choice and asks how intention, meal conditions, treatment, lived experience, and the body's current state can be brought into a sustainable relationship without turning symptoms into moral judgment.
End of Part 1 of 5
The symptom was real.
The explanation depended on where we stood.
Experience, evidence, mechanism, treatment, and context were not the same coordinate.
Part 1 located the view.
Part 2 asks what the stomach actually does.
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