Anatomy and Physiology of Feeding and Swallowing: Normal and Abnormal

doi:10.1016/j.pmr.2008.06.001

Physical Medicine and Rehabilitation Clinics of North America

Volume 19, Issue 4, November 2008, Pages 691-707

https://doi.org/10.1016/j.pmr.2008.06.001 Get rights and content

Eating and swallowing are complex behaviors involving volitional and reflexive activities of more than 30 nerves and muscles. They have two crucial biologic features: food passage from the oral cavity to stomach and airway protection. The swallowing process is commonly divided into oral, pharyngeal, and esophageal stages, according to the location of the bolus. The movement of the food in the oral cavity and to the oropharynx differs depending on the type of food (eating solid food versus drinking liquid). Dysphagia can result from a wide variety of functional or structural deficits of the oral cavity, pharynx, larynx, or esophagus. The goal of dysphagia rehabilitation is to identify and treat abnormalities of feeding and swallowing while maintaining safe and efficient alimentation and hydration.

Section snippets

Anatomy of structures

Understanding the normal physiology and pathophysiology of eating and swallowing is fundamental to evaluating and treating disorders of eating and swallowing and to developing dysphagia rehabilitation programs. Eating and swallowing are complex behaviors that include volitional and reflexive activities involving more than 30 nerves and muscles [1].

Fig. 1 shows the anatomy of the oral cavity, pharynx, and larynx; Table 1 lists the innervation of the major muscles related to swallowing. The

Physiology

Two paradigmatic models are commonly used to describe the physiology of normal eating and swallowing: the four-stage model for drinking and swallowing liquid and the process model for eating and swallowing solid food. The normal swallow in humans was originally described using a three-stage sequential model whereby the swallowing process was divided into oral, pharyngeal, and esophageal stages according to the location of the bolus [2], [3]. The oral stage was later subdivided into the

Abnormal eating and swallowing

Dysphagia (abnormal swallowing) can result from a wide variety of diseases and disorders (Box 1) [40], [41]. Functional or structural deficits of the oral cavity, pharynx, larynx, esophagus, or esophageal sphincters can cause dysphagia. Dysphagia may lead to serious complications, including dehydration, malnutrition, pneumonia, or airway obstruction. In dysphagia rehabilitation, clinicians consider how a given abnormality affects bolus passage and airway protection.

References (52)

K.S. Dua et al.
Coordination of deglutitive glottal function and pharyngeal bolus transit during normal eating
Gastroenterology
(1997)
K.M. Hiiemae
Feeding in mammals
J.B. Palmer et al.
Tongue-jaw linkages in human feeding: a preliminary videofluorographic study
Arch Oral Biol
(1997)
L. Mioche et al.
A postero-anterior videofluorographic study of the intra-oral management of food in man
Arch Oral Biol
(2002)
J.B. Palmer
Bolus aggregation in the oropharynx does not depend on gravity
Arch Phys Med Rehabil
(1998)
R. Shaker et al.
Coordination of deglutitive glottic closure with oropharyngeal swallowing
Gastroenterology
(1990)
J. Smith et al.
Coordination of eating, drinking and breathing in adults
Chest
(1989)
A. van der Bilt et al.
The effect of missing postcanine teeth on chewing performance in man
Arch Oral Biol
(1993)
A. Eisbruch et al.
Objective assessment of swallowing dysfunction and aspiration after radiation concurrent with chemotherapy for head-and-neck cancer
Int J Radiat Oncol Biol Phys
(2002)
P. Moayyedi et al.
Gastro-oesophageal reflux disease
Lancet
(2006)

W.J. Dodds et al.

Physiology and radiology of the normal oral and pharyngeal phases of swallowing

AJR Am J Roentgenol

(1990)

J.A. Logemann

Evaluation and treatment of swallowing disorders

(1998)

J.B. Palmer et al.

Coordination of mastication and swallowing

Dysphagia

(1992)

K.M. Hiiemae et al.

Food transport and bolus formation during complete feeding sequences on foods of different initial consistency

Dysphagia

(1999)

K. Matsuo et al.

Cyclic motion of the soft palate in feeding

J Dent Res

(2005)

A. Buettner et al.

Observation of the swallowing process by application of videofluoroscopy and real-time magnetic resonance imaging—consequences for retronasal aroma stimulation

Chem Senses

(2001)

M. Hodgson et al.

Simultaneous real-time measurements of mastication, swallowing, nasal airflow, and aroma release

J Agric Food Chem

(2003)

J.B. Palmer et al.

Eating and breathing: interactions between respiration and feeding on solid food

Dysphagia

(2003)

E. Saitoh et al.

Chewing and food consistency: effects on bolus transport and swallow initiation

Dysphagia

(2007)

Y. Ohmae et al.

Timing of glottic closure during normal swallow

Head Neck

(1995)

J.A. Logemann et al.

Closure mechanisms of laryngeal vestibule during swallow

Am J Physiol

(1992)

I.J. Cook et al.

Opening mechanisms of the human upper esophageal sphincter

Am J Physiol

(1989)

C. Ertekin et al.

Electromyography of human cricopharyngeal muscle of the upper esophageal sphincter

Muscle Nerve

(2002)

D.W. Shaw et al.

Influence of normal aging on oral-pharyngeal and upper esophageal sphincter function during swallowing

Am J Physiol

(1995)

S.K. Daniels et al.

Swallowing physiology of sequential straw drinking

Dysphagia

(2001)

Cited by (480)

An analysis of the relationship between hyoid bone movement and ultrasound signal during swallowing: A proof of concept study
2024, Biomedical Signal Processing and Control
Swallowing monitoring and assessment system (SMAS) using an ultrasonic Doppler sensor array was developed to overcome the limitations of existing dysphagia evaluation methods such as videofluoroscopic swallowing study (VFSS) and fiberoptic endoscopic evaluation of swallowing (FEES). This study aimed to identify the relationship between swallowing-related hyoid bone movements measured through VFSS imaging and ultrasound signals collected using SMAS. SMAS signals and VFSS images were collected when 10 healthy participants (6 males and 4 females) performed swallowing movements under a combination of 2 viscosity (Vc) conditions (thin and thick) and 2 vol (Vl) conditions (3 ml and 9 ml). The VFSS images and ultrasound signals were divided into 10-time intervals; for each time interval the movement speeds of the hyoid bone on the anterior-posterior (AP) and superior-inferior (SI) axes and the average amplitude were analyzed. A 3-phase swallowing motion profile (posterior-superior (P-S) ascending, anterior–superior (A-S) ascending, and posterior-inferior (P-I) descending) of the hyoid bone was identified. While the composite distance (2.55 ± 0.13 cm) and time (0.72 ± 0.03 sec) of hyoid bone movement were the longest in the P-I descending phase, the composite speed of hyoid bone movement (7.25 ± 0.51 cm/s) was the fastest in the A-S ascending phase. The correlation between hyoid bone movement speed and average SMAS amplitude was highest in the AP axis (r = 0.68 ± 0.03). Further research is needed to examine if the presence of dysphagia and their severity level can be identified using SMAS.
Analysis of head motions during food intake in Japanese adults using a new motion capture system
2024, Archives of Oral Biology
A new motion capture system was developed to verify the hypothesis that “during food intake, head motion changes according to the properties of the food.”
Twenty healthy males and 20 healthy females with right-handed and normal occlusion participated in this study. The motion capture system used consisted of a Microsoft Xbox One Kinect Sensor® and a newly-developed program. Meatballs (solid), yogurt (paste), and water (fluid) were used as food samples. Head motion distance, head turning angle, and head forward angle were measured during food intake. Unpaired t-tests were used to analyze each head motion and compare the sexes. A one-way repeated measures analysis of variance was used to analyze each head motion for different food samples.
Head motion distance was significantly smaller in females for the meatball and yogurt, but not for water. There were no significant differences between the sexes for head turning angle or head forward angle. Head motion distance and head forward angle were significantly larger for water than for meatballs and yogurt. The head turning angle was significantly smaller for the meatball than for yogurt and water.
The results indicated that females tend to consume food without moving their heads when eating solid and paste foods. As the fluidity of the food increased, the head moved in a turning motion to avoid spilling the food, and the heads tilted forward. The motion capture system used in this study was also effective in analyzing head motion during eating.
Characteristics of Tongue Pressure Measured by Novel Multisite Flexible Sensors in Nasopharyngeal Carcinoma Patients With Dysphagia
2024, Archives of Physical Medicine and Rehabilitation
To explore characteristics of tongue pressure changes in nasopharyngeal carcinoma (NPC) patients with dysphagia after radiotherapy using a novel system with multisite flexible sensors.
Prospective observational study.
Inpatient rehabilitation centers and community dwellings.
Nineteen patients with dysphagia after radiotherapy for NPC and 19 healthy participants were recruited for this study (N=38).
Not applicable.
A new 9-site (3 × 3) flexible tongue pressure sensor was used to measure tongue-to-palate pressure across different parts of the tongue. The oral tongue was divided into 3 parts: anterior tongue region (TAR), central tongue region (TCR), and posterior tongue region (TPR); 3 sensors were placed on each part. The mean tongue pressure and endurance time at the 3 sites in the TAR, TCR, and TPR were analyzed. The ratios of the mean TAR, TCR, and TPR values were calculated.
Pressures of TAR, TCR, and TPR in NPC patients with dysphagia were significantly lower than those in healthy participants (P<.05). The pressure in TPR decreased most significantly, followed by that in TCR. The endurance times of TAR and TCR were longer than those of healthy participants (P<.05). The endurance time of TPR was not significantly different between the patients and healthy participants (P>.05). Ratios of pressure between TAR and TCR and TAR and TPR in patients were lower than that in healthy participants (P<.05). There was no significant difference in the TCR to TPR pressure ratio between patients and healthy participants (P>.05).
Tongue pressure significantly decreased in NPC patients with dysphagia, and the drop in pressure was most pronounced in the TPR area. The results of our study indicate that we should pay attention to the pressure training of the TPR during treatments. The endurance time of the TAR and TCR increased significantly, which may be due to bolus transport compensation. Therefore, clinical rehabilitation strategies should aim to increase the endurance time training in NPC patients after radiotherapy to help increase the effectiveness of the swallowing process in patients.
RNA-based liposomes for oral cancer: From biophysical characterization to biological evaluation
2024, International Journal of Biological Macromolecules
Oral cancer incidence and mortality are increasing over time. The most common therapies for oral cancers are surgery and radiotherapy, either used alone or combined, and immunotherapy can be also an option. Although there are several therapeutic options, none of them are completely effective, and in addition, there are numerous associated side effects. To overcome these limitations, researchers have been trying to reduce these drawbacks by using drug delivery systems that carry drugs for specific delivery to cancer cells. For that purpose, RNA-coated liposomes to selectively deliver the ligands C₈ (acridine orange derivative) and dexamethasone to oral cancer cells were produced, characterized, and biologically evaluated.
Firstly, the RNA structure and binding interaction with ligands (C₈ and dexamethasone) were evaluated by circular dichroism (CD), thermal difference spectroscopy (TDS), nuclear magnetic resonance (NMR) and fluorescence titrations. The biophysical assays evidenced the formation of an RNA hairpin and duplex structure. Moreover, steady-state and time-resolved fluorescence intensity and anisotropy experiments show that C₈ forms a complex with RNA and adopts an open conformation upon RNA binding.
Then, RNA-coated liposomes were characterized by dynamic light scattering, and diameters near 160 nm were observed. Time-resolved anisotropy measurements of C₈ loaded in RNA-functionalized liposomes indicate the co-existence of free C₈ in solution (inside the liposome) and C₈ bound to RNA at the external liposome surface. The RNA-functionalized liposomes loaded with C₈ or dexamethasone mediated a significant reduction in the cell viability of malignant UPCI-SCC-154 cells while maintaining viable non-malignant NHDF cells. Additionally, the liposomes were able to internalize the cells, with higher uptake by the malignant cell line.
Overall, the results obtained in this work can contribute to the development of new drug delivery systems based on RNA-coated liposomes.
Oropharyngeal dysphagia
2024, Dysphagia: A Clinical Guide
Swallowing is one of the key processes required for life. It is an essential everyday process and largely continues without any complications in most people, requiring the involvement of both voluntary and involuntary muscles of the upper gastrointestinal tract that contract in a fashion that allows breathing to continue without disruption. As the anatomic pathway has dual functionality, the risks of aspiration are high and may lead to complications such as pneumonia. Oropharyngeal dysphagia usually occurs when there is a problem with the anatomy, physiology, or neurophysiology of any of these structures and is most commonly related to chronic neurologic conditions, particularly Parkinson’s disease, stroke, and dementia; it is not considered part of normal aging (see sections on causation below). The options for investigation and treatment of oropharyngeal dysphagia are also discussed and remain tailored to the patients' disease and presentation.
Clinical signs to predict the severity of dysphagia in Acute Ischemic Stroke patients
2024, Clinical Neurology and Neurosurgery
In the current era, clinicians working in areas with limited and/or without facilities are only able to manage their patients based on clinical signs to detect dysphagia. This study assesses the performance of 5 simple clinical signs for predicting the severity of dysphagia.
We systematically documented 5 targeted bedside clinical signs within 24 h after admission in 737 consecutive patients with acute stroke. We examined the median onset of each sign and calculated their ratios associated with severe dysphagia. The performance and significance of these special clinical signs were evaluated by further computation.
In total, 184 of 737 AIS patients were screened positive dysphagia by the modified V-VST. The 5 targeted bedside clinical signs were differed among the patients with and without dysphagia. Patients with serious dysphagia (n = 61,33.15%) showed higher positive percentages of larynx movement disorders than those classified as moderate (73.77% [60.99%−83.50%] vs 29.27% [21.82%−38.03%], p < 0.001). Logistic regression analyses conducted in the subsets confirmed larynx movement disorders as an independent predictor of dysphagia severity.
Larynx movement disorders is correlated with a higher probability of severe dysphagia as measured by the modified V-VST in AIS patients.

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Anatomy and Physiology of Feeding and Swallowing: Normal and Abnormal

Section snippets

Anatomy of structures

Physiology

Abnormal eating and swallowing

Gastroenterology

Arch Oral Biol

Arch Oral Biol

Arch Phys Med Rehabil

Gastroenterology

Chest

Arch Oral Biol

Int J Radiat Oncol Biol Phys

Lancet

Physiology and radiology of the normal oral and pharyngeal phases of swallowing

AJR Am J Roentgenol

Evaluation and treatment of swallowing disorders

Coordination of mastication and swallowing

Dysphagia

Food transport and bolus formation during complete feeding sequences on foods of different initial consistency

Dysphagia

Cyclic motion of the soft palate in feeding

J Dent Res

Observation of the swallowing process by application of videofluoroscopy and real-time magnetic resonance imaging—consequences for retronasal aroma stimulation

Chem Senses

Simultaneous real-time measurements of mastication, swallowing, nasal airflow, and aroma release

J Agric Food Chem

Eating and breathing: interactions between respiration and feeding on solid food

Dysphagia

Chewing and food consistency: effects on bolus transport and swallow initiation

Dysphagia

Timing of glottic closure during normal swallow

Head Neck

Closure mechanisms of laryngeal vestibule during swallow

Am J Physiol

Opening mechanisms of the human upper esophageal sphincter

Am J Physiol

Electromyography of human cricopharyngeal muscle of the upper esophageal sphincter

Muscle Nerve

Influence of normal aging on oral-pharyngeal and upper esophageal sphincter function during swallowing

Am J Physiol

Swallowing physiology of sequential straw drinking

Dysphagia