29.2 Introduction to the Esophagus and Stomach
2 min read•june 18, 2024
The and work together to start the digestion process. The esophagus moves food from your mouth to your stomach, while the stomach stores and breaks down food. Both have special muscles that control the flow of food and prevent backflow.
Digestion in the stomach happens in three phases. It starts when you see or smell food, continues when food enters the stomach, and finishes as food moves to the small intestine. The stomach produces acid and enzymes to break down food during these phases.
Anatomy and Physiology of the Esophagus and Stomach
Esophagus and stomach structure and function, including sphincters
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- Esophagus
- Muscular tube connects pharynx to stomach
- Transports food from mouth to stomach via peristaltic contractions
- (UES)
- Prevents air from entering esophagus during breathing
- Relaxes during swallowing allowing food passage (bolus)
- (LES)
- Prevents reflux of stomach contents back into esophagus (acid, enzymes)
- Relaxes during swallowing allowing food to enter stomach
- Stomach
- J-shaped, muscular organ in upper left abdomen
- Functions: food storage, mechanical digestion (churning), chemical digestion (enzymes, acid)
- Four main regions: (esophageal junction), (upper portion), (main central region), (lower portion connecting to duodenum)
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- Controls passage of partially digested food (chyme) from stomach to duodenum
- Regulates rate of gastric emptying into small intestine
Common esophageal and stomach disorders
- ###gastroesophageal_reflux_disease_()_0###
- Chronic condition caused by reflux of stomach contents into esophagus
- Symptoms: heartburn, regurgitation (backflow of stomach contents), dysphagia (difficulty swallowing)
- Complications: (inflammation), (precancerous changes), esophageal strictures (narrowing)
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- Inflammation of stomach lining
- Causes: H. pylori bacterial infection, (ibuprofen), alcohol, stress
- Symptoms: abdominal pain, nausea, vomiting, indigestion
- Complications: (open sores), gastric cancer
Physiology of Digestion in the Stomach
Three phases of digestion and role of gastric acid secretion
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- Initiated by sight, smell, or thought of food
- Mediated by stimulation
- Stimulates gastric acid secretion and (contractions)
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- Initiated by presence of food in stomach
- Mechanical digestion: stomach contractions mix and churn food
- Chemical digestion: secretion of gastric juice
- () denatures proteins and activates
- converted to , breaks down proteins into peptides
- secreted, facilitates vitamin absorption in ileum
- Gastric acid secretion regulated by hormones () and neural factors (vagus nerve)
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- Occurs when chyme enters duodenum
- Hormones and released, regulate pancreatic and gallbladder secretions
- Feedback mechanisms inhibit further gastric acid secretion and slow gastric emptying
Key Terms to Review (45)
Aspiration: Aspiration is the inhalation of food, liquid, or other material into the respiratory tract. It can cause serious complications such as pneumonia.
Barrett's Esophagus: Barrett's esophagus is a condition in which the normal squamous epithelium lining the esophagus is replaced by specialized columnar epithelium, typically in response to chronic gastroesophageal reflux disease (GERD). This metaplastic change is considered a precursor to esophageal adenocarcinoma, a type of cancer that can develop in the esophagus.
Body: The body refers to the physical structure and form of a living organism. It encompasses the entirety of an individual's anatomy, including all the organs, tissues, and systems that work together to sustain life. In the context of the esophagus and stomach, the body is a crucial component that houses and facilitates the functions of these vital digestive organs.
Cardia: The cardia, also known as the cardiac orifice, is the opening between the esophagus and the stomach. It is the superior portion of the stomach and serves as the connection between the digestive tract and the esophagus, allowing the passage of food and liquids from the esophagus into the stomach.
CCK: CCK, or cholecystokinin, is a peptide hormone primarily produced in the small intestine that plays a crucial role in the regulation of digestion and appetite. It is responsible for stimulating the release of digestive enzymes and bile from the pancreas and gallbladder, respectively, as well as promoting feelings of fullness and satiety.
Cephalic Phase: The cephalic phase is the initial stage of the digestive process, which begins before food even enters the mouth. It is a reflex response triggered by the sight, smell, taste, or even thought of food, preparing the body for the impending arrival of nutrients.
Chief Cells: Chief cells, also known as principal cells, are the predominant cell type found in the gastric glands of the stomach. These cells are responsible for secreting hydrochloric acid (HCl) and pepsinogen, which are essential components of the stomach's digestive juices.
Cholecystokinin: Cholecystokinin (CCK) is a peptide hormone produced by the intestinal I cells that plays a crucial role in the regulation of various digestive processes. It is primarily responsible for stimulating the release of bile from the gallbladder and the secretion of digestive enzymes from the pancreas, thereby facilitating the breakdown and absorption of fats and proteins in the small intestine.
Deglutition: Deglutition, also known as swallowing, is the complex physiological process of transferring food or liquid from the mouth to the stomach. It involves the coordinated action of various muscles and structures within the oral cavity, pharynx, and esophagus to facilitate the safe and efficient passage of ingested material.
Enteric Nervous System: The enteric nervous system is an intrinsic nervous system located within the gastrointestinal tract that controls its functions. It is often referred to as the 'second brain' due to its complex structure and ability to operate independently of the central nervous system.
Epiglottis: The epiglottis is a flap of cartilage located at the base of the tongue, which covers the trachea during swallowing to prevent food and liquid from entering the airway. It plays a crucial role in directing food to the esophagus.
Esophagitis: Esophagitis is a condition characterized by inflammation of the esophagus, the tube that connects the throat to the stomach. This inflammation can lead to various symptoms and complications, and it is an important consideration in the context of the esophagus, stomach, and certain medications.
Esophagus: The esophagus is a muscular tube that connects the throat (pharynx) to the stomach, allowing food and liquids to pass from the mouth to the digestive system. It is a crucial part of the gastrointestinal system and plays a vital role in the introduction of the esophagus and stomach.
Fundus: The fundus is the rounded, upper part of a hollow organ, such as the stomach or uterus. It is the region farthest from the opening or neck of the organ. In the context of the esophagus and stomach, the fundus refers to the dome-shaped upper portion of the stomach.
Gastric Motility: Gastric motility refers to the coordinated contractions and relaxations of the stomach muscles that facilitate the movement and mixing of food within the stomach. This process is essential for the proper digestion and emptying of the stomach contents into the small intestine.
Gastric Mucosa: The gastric mucosa is the innermost layer of the stomach wall, consisting of a protective layer of epithelial cells that secrete mucus, enzymes, and other substances to aid in the digestion and protection of the stomach contents. It plays a crucial role in the functioning of the esophagus and stomach, as well as the mechanisms of action for certain drugs used to treat gastric conditions.
Gastric Phase: The gastric phase is a stage in the digestive process that occurs after food enters the stomach. It involves the secretion of various enzymes and acids that begin the breakdown of food, preparing it for further digestion and absorption in the small intestine.
Gastrin: Gastrin is a hormone produced by G cells in the lining of the stomach and duodenum. It is primarily responsible for stimulating the secretion of gastric acid, which is essential for the digestion of food and the absorption of nutrients.
Gastritis: Gastritis is the inflammation of the stomach lining, often caused by infection, chronic use of NSAIDs, or excessive alcohol consumption. Symptoms may include stomach pain, nausea, and indigestion.
Gastroesophageal Reflux Disease: Gastroesophageal reflux disease (GERD) is a chronic condition in which the contents of the stomach, including acid and digestive enzymes, flow back (reflux) into the esophagus, causing irritation and damage to the lining of the esophagus. This condition is closely related to the topics of the esophagus, stomach, and the medications used to manage it.
Gastroesophageal reflux disease (GERD): Gastroesophageal reflux disease (GERD) is a chronic condition where stomach acid or bile flows back into the esophagus, causing irritation and symptoms like heartburn. This persistent reflux can lead to complications if left untreated.
GERD: GERD, or Gastroesophageal Reflux Disease, is a chronic condition in which stomach contents, including acid, flow back (reflux) into the esophagus, causing irritation and inflammation. This term is crucial in understanding the topics of the esophagus, stomach, and various medications used to manage reflux and related symptoms.
Helicobacter pylori: Helicobacter pylori is a spiral-shaped bacterium that colonizes the human stomach and is a major cause of peptic ulcers, gastritis, and certain types of stomach cancer. It is a significant player in the context of the esophagus and stomach, as its presence and effects can have far-reaching implications for the digestive system.
Hydrochloric (HCl) acid: Hydrochloric acid (HCl) is a strong acid secreted by the stomach lining to aid in digestion. It helps break down food and creates an acidic environment for digestive enzymes.
Hydrochloric Acid: Hydrochloric acid (HCl) is a strong, corrosive acid produced naturally in the stomach. It plays a vital role in the digestive process and in maintaining overall homeostasis within the body.
Intestinal Phase: The intestinal phase is a key part of the digestive process that occurs after food has passed through the stomach. This phase focuses on the small intestine, where the majority of nutrient absorption takes place through a complex series of chemical and mechanical processes.
Intrinsic Factor: Intrinsic factor is a glycoprotein secreted by the parietal cells in the stomach. It is essential for the absorption of vitamin B12 (cobalamin) from the diet in the small intestine.
Lower esophageal sphincter: The lower esophageal sphincter (LES) is a muscular ring at the junction between the esophagus and stomach. It prevents the backflow of stomach contents into the esophagus.
Lower Esophageal Sphincter: The lower esophageal sphincter (LES) is a ring of muscle located at the junction between the esophagus and the stomach. It acts as a valve, controlling the passage of food and liquid between the esophagus and the stomach, and plays a crucial role in the digestive process.
Nonsteroidal anti-inflammatory drugs (NSAIDs): Nonsteroidal anti-inflammatory drugs (NSAIDs) are medications that reduce inflammation, pain, and fever without the use of steroids. They inhibit cyclooxygenase enzymes (COX-1 and COX-2), which are involved in the production of prostaglandins.
NSAIDs: NSAIDs, or Non-Steroidal Anti-Inflammatory Drugs, are a class of medications that are widely used to reduce inflammation, alleviate pain, and lower fever. They work by inhibiting the production of prostaglandins, which are key mediators of the inflammatory response. NSAIDs are commonly employed in the management of various conditions, including arthritis, menstrual cramps, headaches, and post-operative pain.
Parietal Cells: Parietal cells are a type of epithelial cells located in the lining of the stomach. They are responsible for producing hydrochloric acid (HCl) and the intrinsic factor, which are essential for the digestion and absorption of nutrients, particularly vitamin B12.
Pepsin: Pepsin is a digestive enzyme produced in the stomach that plays a crucial role in the breakdown of proteins. It is an important component of the digestive system, contributing to the overall process of metabolism and nutrient absorption.
Pepsinogen: Pepsinogen is an inactive enzyme precursor secreted by the chief cells in the stomach. It is converted into the active enzyme pepsin in the acidic environment of the stomach, aiding in protein digestion.
Pepsinogen: Pepsinogen is an inactive precursor of the digestive enzyme pepsin, which is secreted by the chief cells in the stomach. Pepsinogen is a key component in the initial stages of protein digestion within the stomach.
Peptic Ulcers: Peptic ulcers are sores or lesions that develop in the lining of the esophagus, stomach, or small intestine (duodenum) due to the damaging effects of stomach acid and digestive enzymes. They are a common gastrointestinal disorder that can cause significant discomfort and potentially lead to serious complications if left untreated.
Peristalsis: Peristalsis is the coordinated, rhythmic contractions of smooth muscles that move food through the gastrointestinal tract. It ensures the progressive movement of contents from the esophagus to the rectum.
Peristalsis: Peristalsis is the rhythmic, wave-like contraction of smooth muscles that propels food and other materials through the digestive tract. This coordinated movement is essential for the proper functioning of the gastrointestinal system and is influenced by the nervous system.
Pyloric Sphincter: The pyloric sphincter is a ring-like muscle located at the junction between the stomach and the small intestine, specifically the duodenum. It acts as a valve, controlling the flow of partially digested food from the stomach into the small intestine.
Pylorus: The pylorus is the distal opening of the stomach that connects to the small intestine. It acts as a valve, controlling the flow of food from the stomach into the duodenum, the first segment of the small intestine.
Secretin: Secretin is a gastrointestinal hormone produced by the S cells in the duodenum of the small intestine. It plays a crucial role in the regulation of digestive processes, particularly in the esophagus, stomach, and small and large intestines.
Stomach: The stomach is a J-shaped, expandable organ located in the upper abdomen that is part of the digestive system. It serves as a temporary storage and processing chamber for food, initiating the breakdown of food through mechanical and chemical digestion.
Upper esophageal sphincter: The upper esophageal sphincter (UES) is a ring of skeletal muscle located at the top of the esophagus. It controls the passage of food and liquids from the pharynx into the esophagus.
Upper Esophageal Sphincter: The upper esophageal sphincter (UES) is a ring-like muscle at the top of the esophagus that acts as a valve, controlling the passage of food and air between the throat and the esophagus. It plays a crucial role in swallowing and preventing the backflow of contents from the esophagus into the throat.
Vagus Nerve: The vagus nerve, also known as the tenth cranial nerve, is a crucial component of the parasympathetic nervous system. It originates in the brainstem and extends throughout the body, playing a vital role in the regulation of various physiological processes, including those related to the topics of antitussives and the esophagus and stomach.