23.3 The Mouth, Pharynx, and Esophagus
3 min read•june 18, 2024
The mouth, pharynx, and work together to start digestion and move food to the stomach. These structures have specialized parts that break down food, form it into a , and push it along the digestive tract.
Swallowing is a complex process involving voluntary and involuntary actions. It ensures food goes down the right path, avoiding the airway. The journey from mouth to stomach involves mechanical and chemical processes, preparing food for further digestion.
Anatomy of the Mouth, Pharynx, and Esophagus
Structures and roles of mouth
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- form anterior boundary of mouth prevent food and liquid from spilling out
- form lateral boundaries of mouth assist in keeping food between teeth during chewing ()
- forms roof of mouth provides firm surface for to push food against during chewing and swallowing
- located posterior to hard palate elevates to prevent food and liquid from entering nasal cavity during swallowing ()
- muscular organ attached to floor of mouth manipulates food during chewing assists in forming food pushes food bolus into pharynx during swallowing ()
- include parotid, submandibular, and secrete saliva to moisten food and initiate chemical digestion of carbohydrates ( enzyme)
Arrangement of adult teeth
- Adult consists of 32 arranged in specific pattern
- Four types of teeth serve different functions
- anterior teeth with sharp, chisel-shaped crowns function in cutting and biting food (central and lateral )
- cone-shaped teeth lateral to incisors function in tearing and gripping food ()
- posterior to canines function in crushing and grinding food ()
- posterior to function in crushing and grinding food (first, second, and third )
- Dental formula for adult dentition: represents number of each tooth type in one-half of upper and lower jaws (quadrants)
Process of swallowing
- Oral phase (voluntary) tongue pushes food bolus against hard palate and into
- Pharyngeal phase (involuntary) involves multiple coordinated actions
- elevates to prevent food from entering ()
- covers larynx to prevent aspiration ()
- Pharyngeal constrictor muscles contract, propelling food bolus into ()
- Esophageal phase (involuntary) begins as food bolus enters esophagus
- relaxes to allow food bolus passage ()
- Peristaltic contractions of esophageal smooth muscle propel food bolus towards stomach ()
- relaxes to allow food bolus to enter stomach ()
Journey from mouth to stomach
- Mouth food is mechanically broken down by chewing () saliva moistens food and begins carbohydrate digestion tongue forms food into bolus ()
- and laryngopharynx food bolus is propelled through pharynx by swallowing reflex covers larynx to prevent aspiration ()
- Esophagus upper esophageal sphincter relaxes to allow food bolus entry peristaltic contractions propel food bolus towards stomach lower esophageal sphincter relaxes, allowing food bolus to enter stomach (gastric filling)
Digestive tract features
- : wave-like muscle contractions that move food through the digestive tract
- : circular muscles that control the passage of food between different regions of the digestive system
- : innermost layer of the digestive tract, which secretes mucus and enzymes to aid in digestion and protect the tract lining
Key Terms to Review (73)
Amylase: Amylase is an enzyme that breaks down complex carbohydrates, such as starch, into simpler sugars like maltose and glucose. It plays a crucial role in the digestive process by facilitating the breakdown and absorption of starches throughout the digestive system.
Bicuspids: Bicuspids, also known as premolars, are the teeth located between the canines and molars in the human dentition. They are characterized by having two cusps or points on the chewing surface, which is the distinguishing feature that gives them their name.
Bolus: A bolus is a small rounded mass of a substance, specifically of chewed food at the moment of swallowing. It forms as the result of the mechanical digestion and saliva mixing with food in the mouth, making it easier to swallow and digest.
Bolus: A bolus is a rounded mass of food that has been chewed and mixed with saliva, forming a cohesive lump that is ready to be swallowed. It is a crucial component in the process of deglutition, or swallowing, as it facilitates the safe and efficient transfer of food from the mouth to the esophagus and ultimately the stomach.
Buccal Mucosa: The buccal mucosa is the moist, inner lining of the cheeks and lips that lines the oral cavity. It is a specialized type of mucous membrane that plays a crucial role in various functions of the mouth, including speech, taste, and the initiation of the digestive process.
Canines: Canines are the pointed, tooth-like structures located in the dental arch that play a crucial role in the process of biting and tearing food. They are situated next to the incisors and are characterized by a single cusp that helps grip and puncture food items. This unique shape allows canines to function effectively in the digestive process, as they help break down tougher food materials before they reach the throat and esophagus.
Cementum: Cementum is a specialized calcified substance covering the root of a tooth. It plays a crucial role in anchoring the tooth to the surrounding alveolar bone by attaching to the periodontal ligament.
Cheeks: The cheeks are the fleshy, muscular areas on the sides of the face, between the eyes and the chin. They play an important role in the functions of the mouth, pharynx, and esophagus by assisting with chewing, swallowing, and speech.
Cricopharyngeus Muscle: The cricopharyngeus muscle is a ring-shaped muscle that forms the lower esophageal sphincter, acting as a valve between the pharynx and the esophagus. It plays a crucial role in the swallowing process and the prevention of reflux.
Crown: In the context of anatomy and physiology, specifically within the digestive system chapter focusing on the mouth, pharynx, and esophagus, the crown refers to the visible part of a tooth above the gum line. It is covered by enamel, which is the hardest substance in the human body and protects against decay.
Cuspids: Cuspids, also known as canines, are types of teeth located at the "corner" of the dental arch. They have a single pointed tip and are designed for tearing food.
Cuspids: Cuspids, also known as canines, are the pointed teeth located between the incisors and premolars in the human mouth. They play a crucial role in the overall functioning of the oral cavity, particularly in the context of the mouth, pharynx, and esophagus.
Deciduous teeth: Deciduous teeth, also known as baby or milk teeth, are the first set of teeth in the growth development of humans and other mammals, which are eventually replaced by permanent teeth. These 20 primary teeth are critical for initial chewing, speaking, and holding space in the jaws for future adult teeth.
Deglutition: Deglutition, commonly known as swallowing, is the complex physiological process of moving food, liquid, or saliva from the mouth through the pharynx and into the esophagus. It is a crucial function that allows the body to ingest and transport nutrients necessary for survival and sustenance.
Dentes: Dentes is the Latin term for teeth, which are hard, calcified structures found in the mouth of many animals, used primarily for biting and chewing food. In humans, they play a crucial role in the digestive system by initiating the mechanical breakdown of food.
Dentin: Dentin is the dense, bony tissue that forms the bulk of a tooth beneath the enamel. It contains microscopic tubules that can transmit sensations from the outer surface of the tooth to the nerve inside.
Dentition: Dentition encompasses the development, arrangement, and number of teeth in the mouth. It plays a crucial role in the initial phase of digestion by mechanically breaking down food.
Enamel: Enamel is the hard, protective outer layer covering the crown of a tooth. It is composed primarily of hydroxyapatite, a crystalline calcium phosphate, making it the hardest substance in the human body.
Epiglottic Tilt: The epiglottic tilt is the movement of the epiglottis, a flap-like structure at the base of the tongue, during swallowing. This tilt helps protect the airway by closing off the entrance to the larynx, preventing food and liquid from entering the trachea and lungs.
Epiglottis: The epiglottis is a leaf-shaped flap of cartilage located behind the tongue, at the top of the larynx. Its primary function is to seal off the windpipe during swallowing, to prevent food from entering the airways.
Epiglottis: The epiglottis is a small, flap-like structure located at the base of the tongue that plays a crucial role in the respiratory and digestive systems. It acts as a valve, preventing food and liquid from entering the airway during swallowing.
Esophageal Motility: Esophageal motility refers to the coordinated muscle contractions and relaxations that propel food and liquids from the throat (pharynx) through the esophagus and into the stomach. This process is essential for the proper functioning of the digestive system.
Esophagus: The esophagus is a muscular tube that connects the throat (pharynx) with the stomach, serving as the passageway for food and liquids. It plays a crucial role in the digestive system by propelling swallowed food to the stomach through a series of coordinated muscle contractions known as peristalsis.
Esophagus: The esophagus is a muscular tube that transports food and liquids from the pharynx to the stomach, playing a crucial role in the digestive system. It is responsible for the movement of food through the body and is an integral part of the processes and regulation of the digestive system.
Gastroesophageal Junction: The gastroesophageal junction is the anatomical location where the esophagus connects to the stomach. It is an important transition point in the digestive system that plays a crucial role in the movement and regulation of food and fluids between the esophagus and stomach.
Gingivae: Gingivae, commonly known as gums, are the soft tissue that lines the mouth and surrounds the teeth, providing a tight seal around each tooth. They play a crucial role in oral health by protecting the bones of the teeth from bacterial infections.
Hard Palate: The hard palate is the bony, anterior portion of the roof of the mouth that separates the oral and nasal cavities. It is a key anatomical structure involved in the functions of the mouth, pharynx, and esophagus.
Incisors: Incisors are the front teeth primarily responsible for cutting food into chewable pieces. They are located at the forefront of the mouth, typically characterized by their sharp, thin edges.
Incisors: Incisors are the front teeth located in the anterior part of the mouth. They are responsible for biting and cutting food into smaller pieces during the initial stages of the digestive process.
Labial frenulum: The labial frenulum is a small fold of tissue that secures the lips to the gums, found in both the upper and lower lips. It plays a crucial role in oral mobility and health, aiding in speech, eating, and maintaining the position of the lips.
Lingual frenulum: The lingual frenulum is a small fold of mucous membrane that extends from the floor of the mouth to the midline of the underside of the tongue. It helps in securing the tongue's position in the mouth and aids in movements such as speech and swallowing.
Lingual Frenulum: The lingual frenulum is a thin, membranous fold of tissue that connects the underside of the tongue to the floor of the mouth. It plays an important role in the functions of the mouth, pharynx, and esophagus.
Lingual lipase: Lingual lipase is an enzyme secreted by glands in the mouth that begins the digestion of fats into fatty acids and glycerol. It remains active in the acidic environment of the stomach, continuing fat digestion until it reaches the small intestine.
Lips: The lips are the fleshy, movable structures that form the outer borders of the mouth. They play a crucial role in various functions, including speech, eating, and facial expression, within the context of the mouth, pharynx, and esophagus.
Lower esophageal sphincter: The Lower Esophageal Sphincter is a ring-like muscle at the bottom of the esophagus that acts as a valve, opening to allow food and liquid to enter the stomach and closing to prevent stomach contents from refluxing back into the esophagus. It plays a crucial role in the digestive process by controlling the flow of food and protecting the esophagus from acidic gastric contents.
Mastication: Mastication is the process of chewing food to break it down into smaller, more digestible pieces via mechanical actions of the teeth and jaw muscles. This process is crucial for the initial stage of digestion, facilitating enzyme action and swallowing.
Mastication: Mastication is the process of chewing food in the mouth, involving the coordinated action of the muscles, teeth, and tongue to break down solid food into smaller particles that can be more easily swallowed and digested. This process is a crucial part of the digestive system and is closely linked to the functioning of the cranial nerves.
Molars: Molars are large, flat teeth located at the back of the mouth, primarily used for grinding food into smaller pieces to facilitate digestion. They are the most posterior teeth in the mouth, coming after the premolars.
Molars: Molars are the large, flat teeth located in the back of the mouth. They are primarily responsible for grinding and chewing food into smaller pieces, which aids in the digestive process. Molars are an essential part of the mouth, pharynx, and esophagus as they facilitate the initial stages of food breakdown and swallowing.
Mucosa: Mucosa is the innermost layer of the gastrointestinal tract, which lines the entire digestive system and is crucial for absorption and secretion. This layer consists of epithelial cells, connective tissue, and a thin layer of smooth muscle, providing both structural support and functional roles in the digestive process. The mucosa interacts with food substances, plays a key role in nutrient absorption, and acts as a barrier against pathogens.
Nasopharynx: The nasopharynx is the upper part of the pharynx, lying above the soft palate, that connects the nasal cavity to the throat and serves as an air passageway. It plays a crucial role in respiratory function by allowing the passage of air from the nose to the lower respiratory tract.
Nasopharynx: The nasopharynx is the upper part of the pharynx, located behind the nasal cavity. It is a crucial component of both the respiratory and digestive systems, serving as a passageway for air and food.
Oral cavity: The oral cavity is the beginning section of the digestive tract, encompassing the mouth area where food intake occurs, initial digestion begins, and speech and respiratory movements are facilitated. It includes structures such as the teeth, tongue, and salivary glands that play crucial roles in chewing, taste perception, and saliva secretion.
Oral cavity: The oral cavity, commonly known as the mouth, is the entry point for food and is essential for digestion and communication. It is lined with mucous membranes and contains various structures, including teeth, gums, the tongue, and salivary glands that play critical roles in breaking down food and facilitating speech.
Oral vestibule: The oral vestibule is the narrow space between the lips and cheeks on the outside, and the gums and teeth on the inside. It acts as an entryway to the oral cavity proper, facilitating the movement of food and air.
Oropharynx: The oropharynx is a part of the pharynx located between the soft palate and the upper edge of the epiglottis. It serves as a passageway for both air and food, playing a crucial role in the respiratory and digestive systems.
Oropharynx: The oropharynx is the middle part of the pharynx, located between the oral cavity and the laryngopharynx. It plays a crucial role in the respiratory and digestive systems, serving as a passageway for both air and food.
Palatoglossal arch: The palatoglossal arch is a muscular fold that extends from the lateral side of the soft palate to the side of the tongue, marking the boundary between the oral cavity and the oropharynx. It plays a role in swallowing by helping to close off the nasal passages during this process.
Palatopharyngeal arch: The palatopharyngeal arch is a muscular structure that forms part of the boundary between the oral cavity and the pharynx, playing a key role in swallowing and speech. It is located at the back of the mouth, extending from the soft palate to the side of the pharynx.
Pancreatic amylase: Pancreatic amylase is an enzyme produced by the pancreas that breaks down carbohydrates into simpler sugars during digestion. It plays a crucial role in the chemical digestion process by converting starches into maltose and dextrin in the small intestine.
Parotid glands: The parotid glands are the largest of the salivary glands, located just in front of the ears on each side of the face, responsible for producing saliva that initiates the digestion of starches. They release saliva into the mouth through ducts that open near the upper molars.
Parotid Glands: The parotid glands are a pair of salivary glands located in front of and below the ears. They are the largest of the salivary glands and play a crucial role in the production and secretion of saliva, which is essential for the mouth, pharynx, and esophagus.
Peristalsis: Peristalsis is a series of wave-like muscle contractions that moves food through the digestive tract. It involves the rhythmic contraction and relaxation of muscles in the organ walls to push contents forward.
Peristalsis: Peristalsis is the coordinated wave-like muscle contractions that propel food and other materials through the digestive tract. It is a fundamental process that enables the movement of contents through the esophagus, stomach, and intestines, ensuring the efficient digestion and elimination of waste.
Permanent teeth: Permanent teeth are the set of 32 adult teeth that replace the primary (baby) teeth and are meant to last a lifetime. They include incisors, canines, premolars, and molars, each serving specific functions in the mouth related to cutting, tearing, and grinding food.
Pharyngeal peristalsis: Pharyngeal peristalsis refers to the rhythmic, wave-like muscle contractions that occur in the pharynx to propel food from the mouth into the esophagus. This process is essential for swallowing, ensuring that food is moved smoothly and efficiently through the throat and into the digestive tract. The contractions are involuntary and involve coordinated actions of several muscle groups in the pharynx.
Premolars: Premolars are a type of tooth located between the canines and molars in the mouth. They are primarily used for chewing and grinding food before swallowing.
Premolars: Premolars, also known as bicuspids, are the teeth located between the canines and molars in the human dentition. They play a crucial role in the mouth, pharynx, and esophagus by assisting in the chewing and grinding of food during the digestive process.
Pulp cavity: The pulp cavity is the central part of a tooth that contains the tooth's nerve and blood vessels. It is essential for providing the nutrients needed for the tooth’s health and transmitting sensory signals such as pain.
Salivary glands: Salivary glands are specialized organs that produce saliva, which begins the process of digestion and helps in maintaining oral hygiene. These glands are located in the mouth and discharge saliva into the oral cavity through ducts.
Salivary Glands: Salivary glands are exocrine glands located in the oral cavity that produce and secrete saliva, a complex fluid that plays a crucial role in the digestive system, oral health, and various other physiological processes.
Salivation: Salivation is the production and release of saliva from the salivary glands in the mouth. It is a critical process that begins the digestive process by lubricating food and initiating starch digestion.
Soft palate: The soft palate is a flexible muscular flap at the back of the roof of the mouth, separating the mouth from the nasopharynx above. It plays a crucial role in swallowing and speech by moving to close off the nasal passages during these activities.
Soft Palate: The soft palate, also known as the velum, is the posterior, muscular portion of the palate that extends from the hard palate. It acts as a movable partition between the oral and nasal cavities, playing a crucial role in swallowing, speech, and breathing.
Sphincters: Sphincters are circular muscles that surround and constrict openings in the body, controlling the passage of substances through these openings. They play a crucial role in regulating bodily functions, particularly in areas such as the digestive and urinary systems, ensuring that substances move efficiently and at the right times.
Sublingual glands: Sublingual glands are one of the three major pairs of salivary glands, located beneath the tongue, responsible for secreting saliva to aid in digestion and oral lubrication. Unlike other salivary glands, most of their secretion is mucous in nature, helping to efficiently moisten and lubricate food for easier swallowing.
Submandibular glands: Submandibular glands are salivary glands located beneath the floor of the mouth, responsible for producing and secreting saliva which aids in digestion and oral hygiene. These glands contribute to around 60-70% of the total saliva produced in the mouth.
Submandibular Glands: The submandibular glands are a pair of major salivary glands located beneath the floor of the mouth, just under the jawbone. They are responsible for producing and secreting saliva, which helps with the initial stages of digestion and maintains the health of the oral cavity.
Tongue: The tongue is a muscular organ located in the mouth, essential for various functions including taste, swallowing, and speech. It is highly flexible and covered with taste buds that detect flavors.
Tongue: The tongue is a muscular organ located in the oral cavity that plays a crucial role in various functions, including taste, swallowing, and speech. It is an integral part of the mouth, pharynx, and esophagus, and its structure and functions are closely related to these anatomical regions.
Upper esophageal sphincter: The upper esophageal sphincter (UES) is a ring of muscle at the top of the esophagus that controls the passage of food from the pharynx into the esophagus. It opens during swallowing and closes to prevent backflow of food and acid.
Velopharyngeal Closure: Velopharyngeal closure is the process by which the soft palate (velum) and the posterior and lateral pharyngeal walls come together to seal off the nasal cavity from the oral cavity during certain functions, such as swallowing, speaking, and blowing. This mechanism ensures proper airflow and prevents nasal regurgitation of food or liquids.
Voluntary phase: The voluntary phase is the initial stage of swallowing where the tongue pushes the bolus (chewed food) towards the back of the mouth, initiating the swallowing process. This action is consciously controlled by the individual.