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Swallowing, sometimes called deglutition in scientific contexts, is the process in the human or animal body that allows for a substance to pass from the
mouth In animal anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science which deals with the structural organization ...

mouth
, to the
pharynx The pharynx (plural: pharynges) is the part of the throat behind the human mouth, mouth and nasal cavity, and above the esophagus and trachea – the tubes going down to the stomach and the lungs. It is found in vertebrates and invertebrates, thou ...

pharynx
, and into the
oesophagus The esophagus (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of variety (linguistics), varieties of the English language native to the United State ...

oesophagus
, while shutting the
epiglottis The epiglottis is a leaf-shaped flap in the throat In vertebrate anatomy, the throat is the front part of the neck, internally positioned in front of the vertebra, vertebrae. It contains the Human pharynx, pharynx and larynx. An important secti ...

epiglottis
. Swallowing is an important part of
eating Eating (also known as consuming) is the ingestion Ingestion is the consumption of a substance by an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are ...

eating
and
drinking Drinking is the act of ingesting water Water (chemical formula H2O) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's ...

drinking
. If the process fails and the material (such as food, drink, or medicine) goes through the
trachea The trachea, also known as the windpipe, is a cartilaginous Cartilage (cartilaginous tissue) is a resilient and smooth elastic tissue, rubber-like padding that covers and protects the ends of long bone A bone is a Stiffness, rigid tissue ...
, then
choking Choking, or foreign body#REDIRECT Foreign body A foreign body (FB) is any object originating outside the body of an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual c ...
or
pulmonary aspiration Pulmonary aspiration is the entry of material such as pharyngeal secretions, food or drink, or stomach contents from the oropharynx The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity The nasal cavit ...
can occur. In the human body the automatic temporary closing of the epiglottis is controlled by the swallowing
reflex In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanism ...

reflex
. The portion of food, drink, or other material that will move through the
neck The neck is the part of the body on many vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With ...

neck
in one swallow is called a bolus. Swallowing comes so easily to most people that the process rarely prompts much thought. However, from the viewpoints of
physiology Physiology (; ) is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence in the real world. ...
, of
speech–language pathology Speech–language pathology (or speech and language pathology) is a field of expertise practiced by a clinician known as a speech–language pathologist (SLP) or a speech and language therapist, both of whom may be known by the shortened descrip ...
, and of
health care Healthcare is the maintenance or improvement of health Health, according to the , is "a state of complete physical, and social and not merely the absence of and ".. (2006)''Constitution of the World Health Organization''– ''Basic Docume ...

health care
for people with difficulty in swallowing (dysphagia), it is an interesting topic with extensive
scientific literature : ''For a broader class of literature, see Academic publishing Academic publishing is the subfield of publishing which distributes academic research and scholarship. Most academic work is published in academic journal articles, books or thes ...
.


In humans


Coordination and control

Eating and swallowing are complex neuromuscular activities consisting essentially of three phases, an oral, pharyngeal and esophageal phase. Each phase is controlled by a different neurological mechanism. The oral phase, which is entirely voluntary, is mainly controlled by the
medial Medial may refer to: Mathematics * Medial magma, a mathematical identity in algebra Geometry * Medial axis, in geometry the set of all points having more than one closest point on an object's boundary * Medial graph, another graph that repres ...
temporal lobe The temporal lobe is one of the four major lobes of the cerebral cortex The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex m ...

temporal lobe
s and
limbic system The limbic system, also known as the paleomammalian cortex, is a set of brain A brain is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and anim ...
of the
cerebral cortex The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex mostly consists of the six-layered neocortex, with just 10% consisting of a ...
with contributions from the motor cortex and other cortical areas. The pharyngeal swallow is started by the oral phase and subsequently is coordinated by the swallowing center on the
medulla oblongata The medulla oblongata or simply medulla is a long stem-like structure which makes up the lower part of the brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain A brain is an organ Organ may refer to: ...

medulla oblongata
and
pons The pons (Latin for "bridge") is part of the brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain A brain is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (bi ...

pons
. The reflex is initiated by touch receptors in the
pharynx The pharynx (plural: pharynges) is the part of the throat behind the human mouth, mouth and nasal cavity, and above the esophagus and trachea – the tubes going down to the stomach and the lungs. It is found in vertebrates and invertebrates, thou ...

pharynx
as a bolus of food is pushed to the back of the mouth by the tongue, or by stimulation of the palate (palatal reflex). Swallowing is a complex mechanism using both skeletal muscle (
tongue The tongue is a muscular organ (anatomy), organ in the mouth of a typical tetrapod. It manipulates food for mastication and swallowing as part of the digestive system, digestive process, and is the primary organ of taste. The tongue's upper surfa ...

tongue
) and smooth muscles of the pharynx and
esophagus The esophagus (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of variety (linguistics), varieties of the English language native to the United State ...

esophagus
. The
autonomic nervous system The autonomic nervous system (ANS), formerly the vegetative nervous system, is a division of the peripheral nervous system that supplies smooth muscle and glands, and thus influences the function of viscera, internal organs. The autonomic nervous ...

autonomic nervous system
(ANS) coordinates this process in the pharyngeal and esophageal phases.


Phases


Oral phase

Prior to the following stages of the oral phase, the mandible depresses and the lips abduct to allow food or liquid to enter the oral cavity. Upon entering the oral cavity, the mandible elevates and the lips adduct to assist in oral containment of the food and liquid. The following stages describe the normal and necessary actions to form the bolus, which is defined as the state of the food in which it is ready to be swallowed. 1) Moistening Food is moistened by saliva from the
salivary glands The salivary glands in mammal Mammals (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'' ...

salivary glands
(
parasympathetic The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of t ...
). 2) Mastication Food is mechanically broken down by the action of the teeth controlled by the muscles of mastication (V3) acting on the
temporomandibular joint In anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science which deals with the structural organization of ...

temporomandibular joint
. This results in a bolus which is moved from one side of the oral cavity to the other by the tongue.
Buccinator The buccinator () is a thin quadrilateral muscle occupying the interval between the maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone A bone is a Stiffness, rigid tissue (anato ...
(VII) helps to contain the food against the occlusal surfaces of the teeth. The bolus is ready for swallowing when it is held together by saliva (largely mucus), sensed by the
lingual nerve The lingual nerve carries sensory innervation from the anterior two-thirds of the tongue. It contains fibres from both the mandibular division The mandibular nerve (V3) is the largest of the three divisions of the trigeminal nerve, the fifth crani ...
of the tongue (VII—chorda tympani and IX—lesser petrosal) (V3). Any food that is too dry to form a bolus will not be swallowed. 3) Trough formation A trough is then formed at the back of the tongue by the intrinsic muscles (XII). The trough obliterates against the hard palate from front to back, forcing the bolus to the back of the tongue. The intrinsic muscles of the tongue (XII) contract to make a trough (a longitudinal concave fold) at the back of the tongue. The tongue is then elevated to the roof of the mouth (by the mylohyoid (mylohyoid nerve—V3),
genioglossus The genioglossus is one of the paired extrinsic muscles of the tongue. The genioglossus is the major muscle responsible for protruding (or sticking out) the tongue. Structure Genioglossus is the fan-shaped extrinsic tongue muscle that forms the ma ...

genioglossus
,
styloglossus The styloglossus, the shortest and smallest of the three styloid muscles, arises from the anterior and lateral surfaces of the Temporal styloid process, styloid process near its apex, and from the stylomandibular ligament. Passing inferiorly and an ...

styloglossus
and
hyoglossus The hyoglossus, thin and quadrilateral, arises from the side of the body and from the whole length of the greater cornu The hyoid bone (lingual bone or tongue-bone) () is a horseshoe-shaped bone situated in the anterior midline of the neck between ...

hyoglossus
(the rest XII)) such that the tongue slopes downwards posteriorly. The contraction of the
genioglossus The genioglossus is one of the paired extrinsic muscles of the tongue. The genioglossus is the major muscle responsible for protruding (or sticking out) the tongue. Structure Genioglossus is the fan-shaped extrinsic tongue muscle that forms the ma ...

genioglossus
and
styloglossus The styloglossus, the shortest and smallest of the three styloid muscles, arises from the anterior and lateral surfaces of the Temporal styloid process, styloid process near its apex, and from the stylomandibular ligament. Passing inferiorly and an ...

styloglossus
(both XII) also contributes to the formation of the central trough. 4) Movement of the bolus posteriorly At the end of the oral preparatory phase, the food bolus has been formed and is ready to be propelled posteriorly into the pharynx. In order for anterior to posterior transit of the bolus to occur, orbicularis oris contracts and adducts the lips to form a tight seal of the oral cavity. Next, the superior longitudinal muscle elevates the apex of the tongue to make contact with the hard palate and the bolus is propelled to the posterior portion of the oral cavity. Once the bolus reaches the
palatoglossal arch The palatoglossal arch (glossopalatine arch, anterior pillar of fauces) on either side runs downward, Lateral (anatomy), lateral (to the side), and forward to the side of the Posterior tongue, base of the tongue, and is formed by the projection of ...
of the oropharynx, the pharyngeal phase, which is reflex and involuntary, then begins. Receptors initiating this reflex are proprioceptive (afferent limb of reflex is IX and efferent limb is the pharyngeal plexus- IX and X). They are scattered over the base of the tongue, the palatoglossal and palatopharyngeal arches, the tonsillar fossa, uvula and posterior pharyngeal wall. Stimuli from the receptors of this phase then provoke the pharyngeal phase. In fact, it has been shown that the swallowing reflex can be initiated entirely by peripheral stimulation of the internal branch of the
superior laryngeal nerve The superior laryngeal nerve is a branch of the vagus nerve The vagus nerve, historically cited as the pneumogastric nerve, is the tenth cranial nerve or CN X, and interfaces with the parasympathetic control of the heart The heart is a m ...
. This phase is ''voluntary'' and involves important
cranial nerves Cranial nerves are the nerve A nerve is an enclosed, cable-like bundle of fibers (called axon An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see American and British English spelling differences#-re, -er, ...
:
V (trigeminal)
V (trigeminal)
,
VII (facial)
VII (facial)
and XII (hypoglossal).


Pharyngeal phase

For the pharyngeal phase to work properly all other egress from the pharynx must be occluded—this includes the
nasopharynx The pharynx (plural: pharynges) is the part of the throat In vertebrate anatomy, the throat is the front part of the neck, positioned in front of the vertebra. It contains the Human pharynx, pharynx and larynx. An important section of it is th ...
and the
larynx The larynx (), commonly called the voice box, is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist ...

larynx
. When the pharyngeal phase begins, other activities such as chewing, breathing, coughing and vomiting are concomitantly inhibited. 5) Closure of the nasopharynx The soft palate is tensed by
tensor palati The tensor veli palatini muscle (tensor palati or tensor muscle of the velum palatinum) is a broad, thin, ribbon-like muscle in the head that tenses the soft palate. Structure The tensor veli palatini is found anterior-lateral to the levator veli p ...
ni (Vc), and then elevated by
levator palatiLevator muscle can refer to: * Levator scapulae muscle * Levator palpebrae superioris muscle * Levator ani * Levator labii superioris alaeque nasi muscle * Levator veli palatini * Levator muscle of thyroid gland * Levator labii superioris * Levator a ...
ni (pharyngeal plexus—IX, X) to close the nasopharynx. There is also the simultaneous approximation of the walls of the pharynx to the posterior free border of the soft palate, which is carried out by the palatopharyngeus (pharyngeal plexus—IX, X) and the upper part of the superior constrictor (pharyngeal plexus—IX, X). 6) The pharynx prepares to receive the bolus The pharynx is pulled upwards and forwards by the suprahyoid and longitudinal pharyngeal muscles –
stylopharyngeus The stylopharyngeus is a muscle in the head that stretches between the temporal styloid process The temporal styloid process is a process of bone that extends down from the temporal bone The temporal bones are situated at the sides and base of th ...
(IX),
salpingopharyngeus
salpingopharyngeus
(pharyngeal plexus—IX, X) and
palatopharyngeus The palatopharyngeus (palatopharyngeal or pharyngopalatinus) muscle is a small muscle Muscle is a soft tissue found in most animals. Muscle cells contain protein Proteins are large biomolecules or macromolecules that are comprised of one ...
(pharyngeal plexus—IX, X) to receive the bolus. The palatopharyngeal folds on each side of the pharynx are brought close together through the superior constrictor muscles, so that only a small bolus can pass. 7) Opening of the
auditory tube In anatomy, the Eustachian tube, also known as the auditory tube or pharyngotympanic tube, is a tube that links the nasopharynx to the middle ear, of which it is also a part. In adult humans, the Eustachian tube is approximately long and in d ...
The actions of the
levator palatiLevator muscle can refer to: * Levator scapulae muscle * Levator palpebrae superioris muscle * Levator ani * Levator labii superioris alaeque nasi muscle * Levator veli palatini * Levator muscle of thyroid gland * Levator labii superioris * Levator a ...
ni (pharyngeal plexus—IX, X),
tensor palati The tensor veli palatini muscle (tensor palati or tensor muscle of the velum palatinum) is a broad, thin, ribbon-like muscle in the head that tenses the soft palate. Structure The tensor veli palatini is found anterior-lateral to the levator veli p ...
ni (Vc) and
salpingopharyngeus
salpingopharyngeus
(pharyngeal plexus—IX, X) in the closure of the nasopharynx and elevation of the pharynx opens the auditory tube, which equalises the pressure between the nasopharynx and the middle ear. This does not contribute to swallowing, but happens as a consequence of it. 8) Closure of the
oropharynx The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity The nasal cavity is a large, air-filled space above and behind the nose A nose is a protuberance in vertebrate Vertebrates () comprise all speci ...
The oropharynx is kept closed by palatoglossus (pharyngeal plexus—IX, X), the intrinsic muscles of tongue (XII) and styloglossus (XII). 9) Laryngeal closure The primary laryngopharyngeal protective mechanism to prevent aspiration during swallowing is via the closure of the true vocal folds. The adduction of the vocal cords is effected by the contraction of the lateral cricoarytenoids and the oblique and transverse arytenoids (all recurrent laryngeal nerve of vagus). Since the true vocal folds adduct during the swallow, a finite period of apnea (swallowing apnea) must necessarily take place with each swallow. When relating swallowing to respiration, it has been demonstrated that swallowing occurs most often during expiration, even at full expiration a fine air jet is expired probably to clear the upper larynx from food remnants or liquid. The clinical significance of this finding is that patients with a baseline of compromised lung function will, over a period of time, develop respiratory distress as a meal progresses. Subsequently, false vocal fold adduction, adduction of the aryepiglottic folds and retroversion of the epiglottis take place. The aryepiglotticus (recurrent laryngeal nerve of vagus) contracts, causing the arytenoids to appose each other (closes the laryngeal aditus by bringing the aryepiglottic folds together), and draws the epiglottis down to bring its lower half into contact with arytenoids, thus closing the aditus. Retroversion of the epiglottis, while not the primary mechanism of protecting the airway from laryngeal penetration and aspiration, acts to anatomically direct the food bolus laterally towards the piriform fossa. Additionally, the larynx is pulled up with the pharynx under the tongue by stylopharyngeus (IX), salpingopharyngeus (pharyngeal plexus—IX, X), palatopharyngeus (pharyngeal plexus—IX, X) and inferior constrictor (pharyngeal plexus—IX, X). This phase is ''passively'' controlled reflexively and involves cranial nerves V, X (vagus), XI (accessory) and XII (hypoglossal). The respiratory center of the medulla is directly inhibited by the swallowing center for the very brief time that it takes to swallow. This means that it is briefly impossible to breathe during this phase of swallowing and the moment where breathing is prevented is known as ''deglutition
apnea Apnea (BrE British English (BrE) is the standard dialect A standard language (also standard variety, standard dialect, and standard) is a language variety that has undergone substantial codification of grammar and usage and is employed ...
''. 10)
Hyoid The hyoid bone (lingual bone or tongue-bone) () is a horseshoe A horseshoe is a fabricated product, normally made of metal A metal (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ε ...
elevation The hyoid is elevated by digastric (V & VII) and stylohyoid (VII), lifting the pharynx and larynx up even further. 11) Bolus transits pharynx The bolus moves down towards the esophagus by pharyngeal
peristalsis Peristalsis is a radially symmetrical Symmetry in biology refers to the symmetry observed in organisms, including plants, animals, fungi, and bacteria. External symmetry can be easily seen by just looking at an organism. For example, take ...

peristalsis
which takes place by sequential contraction of the superior, middle and inferior pharyngeal constrictor muscles (pharyngeal plexus—IX, X). The lower part of the inferior constrictor ( cricopharyngeus) is normally closed and only opens for the advancing bolus. Gravity plays only a small part in the upright position—in fact, it is possible to swallow solid food even when standing on one’s head. The velocity through the pharynx depends on a number of factors such as viscosity and volume of the bolus. In one study, bolus velocity in healthy adults was measured to be approximately 30–40 cm/s.


Esophageal phase

12) Esophageal peristalsis Like the pharyngeal phase of swallowing, the esophageal phase of swallowing is under involuntary neuromuscular control. However, propagation of the food bolus is significantly slower than in the pharynx. The bolus enters the esophagus and is propelled downwards first by striated muscle (recurrent laryngeal, X) then by the smooth muscle (X) at a rate of 3–5 cm/s. The upper esophageal sphincter relaxes to let food pass, after which various striated constrictor muscles of the pharynx as well as peristalsis and relaxation of the
lower esophageal sphincter The esophagus (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, American E ...

lower esophageal sphincter
sequentially push the bolus of food through the esophagus into the stomach. 13) Relaxation phase Finally the larynx and pharynx move down with the hyoid mostly by elastic recoil. Then the larynx and pharynx move down from the hyoid to their relaxed positions by elastic recoil. Swallowing therefore depends on coordinated interplay between many various muscles, and although the initial part of swallowing is under voluntary control, once the deglutition process is started, it is quite hard to stop it.


Clinical significance

Swallowing becomes a great concern for the elderly since
stroke A stroke is a medical condition A disease is a particular abnormal condition that negatively affects the structure or function (biology), function of all or part of an organism, and that is not due to any immediate external injury. Di ...

stroke
s and
Alzheimer's disease Alzheimer's disease (AD), also referred to simply as Alzheimer's, is a neurodegenerative disease A neurodegenerative disease is caused by the progressive loss of structure or function of neuron A neuron or nerve cell is an membrane p ...
can interfere with the
autonomic nervous system The autonomic nervous system (ANS), formerly the vegetative nervous system, is a division of the peripheral nervous system that supplies smooth muscle and glands, and thus influences the function of viscera, internal organs. The autonomic nervous ...

autonomic nervous system
. Speech pathologists commonly diagnose and treat this condition since the speech process uses the same neuromuscular structures as swallowing. Diagnostic procedures commonly performed by a speech pathologist to evaluate dysphagia include Fiberoptic Endoscopic Evaluation of Swallowing and Modified Barium Swallow Study. Occupational Therapists may also offer swallowing rehabilitation services as well as prescribing modified feeding techniques and utensils. Consultation with a dietician is essential, in order to ensure that the individual with dysphagia is able to consume sufficient calories and nutrients to maintain health. In terminally ill patients, a failure of the reflex to swallow leads to a build-up of mucus or saliva in the throat and airways, producing a noise known as a
death rattle Terminal respiratory secretions (or simply terminal secretions),, known colloquially as a death rattle, are sounds often produced by someone who is near death as a result of fluids such as saliva Saliva (commonly referred to as spit) is an ex ...
(not to be confused with
agonal respiration Agonal respiration, gasping respiration or agonal breathing is a distinct abnormal pattern of breath Breathing (or ventilation) is the process of moving air File:Atmosphere gas proportions.svg, Composition of Earth's atmosphere by vol ...
, which is an abnormal pattern of breathing due to cerebral ischemia or hypoxia). Abnormalities of the pharynx and/or oral cavity may lead to oropharyngeal dysphagia. Abnormalities of the esophagus may lead to esophageal dysphagia. The failure of the lower esophagus sphincter to respond properly to swallowing is called
achalasia Esophageal achalasia, often referred to simply as achalasia, is a failure of smooth muscle Smooth muscle is an involuntary non-striated muscle Striated muscle tissue is a muscle tissue Muscle tissue is a soft tissue that composes muscles i ...
.


In non-mammal animals

In many birds, the esophagus is largely a mere gravity chute, and in such events as a
seagull Gulls, or colloquially seagulls, are seabirds Seabirds (also known as marine birds) are bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , characterised by feathers, toothless beaked ...

seagull
swallowing a fish or a
stork Storks are large, long-legged, long-necked wading bird FIle:Vadare - Ystad-2021.jpg, 245px, A flock of Dunlins and Red knots Waders are birds of the order Charadriiformes commonly found along shorelines and mudflats that wikt:wade#Etymology ...

stork
swallowing a
frog A frog is any member of a diverse and largely carnivorous A carnivore , meaning "meat Meat is animal flesh that is eaten as food. Humans have hunted and killed animals for meat since prehistoric times. The advent of civilization all ...

frog
, swallowing consists largely of the bird lifting its head with its beak pointing up and guiding the prey with tongue and jaws so that the prey slides inside and down. In
fish Fish are aquatic Aquatic means relating to water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the ...

fish
, the tongue is largely bony and much less mobile and getting the food to the back of the pharynx is helped by pumping water in its mouth and out of its
gill A gill () is a respiratory organ that many aquatic Aquatic means relating to water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent ...
s. In
snake Snakes are elongated, limbless, carnivore, carnivorous reptiles of the suborder Serpentes . Like all other Squamata, squamates, snakes are ectothermic, amniote vertebrates covered in overlapping Scale (zoology), scales. Many species of snakes ...

snake
s, the work of swallowing is done by raking with the lower jaw until the prey is far enough back to be helped down by body undulations.


See also

*
Dysphagia Dysphagia is difficulty in swallowing Swallowing, sometimes called deglutition in scientific contexts, is the process in the human or animal body that allows for a substance to pass from the mouth In animal anatomy Anatomy (Greek ''anat ...
* Occlusion *
Speech and language pathology Speech is human vocal communication Communication (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around R ...


References


External links

*
Overview at nature.com

Anatomy and physiology of swallowing at dysphagia.com

Swallowing animation (flash) at hopkins-gi.org
* rticle on French WikipediaSee : " déglutition atypique" = unfunctional or pathological swallowing.
Normal Swallowing and Dysphagia: Pediatric Population
{{Authority control Reflexes Physiology Articles containing video clips