Category Archives: Ear, Nose, Throat (ENT)

– Snoring and sleep apnea.
– Swallowing and dysphagia.
– Sinusitis.

Mechanism of Hearing, with Animation

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Sounds are produced by vibrating objects. The vibrations of a sound source cause the surrounding air molecules to move back and forth, creating a series of alternating regions of high and low pressures. A sound wave is basically a pressure wave – it propagates in the form of fluctuations in air pressures.
The loudness of a sound is determined by the amplitude of sound waves, which represents the strength of vibrations produced by the sound source. The stronger the vibrations, the higher the amplitude of sound waves, the louder the sound.
The pitch of a sound is related to the frequency of sound waves, which indicates how fast the sound source vibrates. The higher the frequency, the higher the pitch. Frequency is measured in hertz. A young human ear can detect sounds in the range of 20 to 20,000 hertz. Some animal species can hear frequencies well beyond this range.
Hearing is the process by which the ear transforms sound vibrations into nerve impulses that can be interpreted by the brain as sounds. The human ear has 3 distinct regions, called the outer, middle, and inner ear.
The outer ear funnels sound waves through the auditory canal to the tympanic membrane, also called eardrum, which separates the outer ear from the middle ear. The eardrum is attached to a chain of three small bones in the middle ear, called the ossicles: the malleus, incus, and stapes. Sound waves cause the tympanic membrane to vibrate, and the vibrations are transmitted through the three bones to the oval window, where the inner ear begins. Since the eardrum is much larger in area than the oval window, the sound pressure that arrives at the oval window is much greater than the original pressure received by the eardrum. This amplification is essential for the stapes to push against the higher resistance of the fluid in the inner ear.
The organ of hearing in the inner ear is the cochlea, essentially a long tube that is coiled up in a spiral to save space. The cochlea is composed of three fluid-filled chambers. The central chamber, known as the cochlear duct, is where mechanical vibrations are transformed into nerve impulses. There are four rows of hair cells within the cochlear duct, supported on the basilar membrane. The movements back and forth of the stapes push on the fluid in the cochlear duct, causing the basilar membrane, and the hair cells, to move up and down. These movements bend the cilia of hair cells, opening the mechanically-gated potassium channels on their surface. Influx of potassium depolarizes the cells, stimulating them to send nerve impulses to the cochlear nerve and on to the brain.
Our ability to differentiate sounds of different loudness and pitch depends on the ability of the cochlea to respond differently to different amplitudes and sound frequencies. Louder sounds cause more hair cells to move and generate greater nerve signals to the brain. Different frequencies stimulate different parts of the basilar membrane, which acts like a set of piano strings. The basilar membrane is narrowest and stiffest at the base, near the oval window; and widest and most flexible at the far end. High-frequency sounds with more energy can move the stiffer part of the membrane, while low-frequency sounds can only move the more flexible part. Thus, high-pitch sounds excite nerve fibers that are closer to the oval window, while low-pitch sounds send signals through the fibers at the far end.

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Deglutição, Fases e Visão Geral do Controle Neural, com Animação.

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A deglutição é o processo pelo qual os alimentos passam da boca para o esôfago, através da faringe. Pode parecer simples para as pessoas saudáveis, no entanto, a deglutição é um processo muito complexo que requer uma coordenação extremamente precisa com a respiração, já que ambos os processos compartilham a mesma entrada – a faringe. Falha nessa coordenação resultaria em asfixia ou aspiração pulmonar.
A deglutição envolve mais de vinte músculos da boca, garganta e esôfago, que são controlados por diversas áreas corticais no cérebro e pelo centro da deglutição, localizado no tronco cerebral. O encéfalo se comunica com os músculos através de vários nervos cranianos.
A deglutição consiste em três fases:
1. Fase oral ou bucal: esta é a parte voluntária da deglutição. A comida é humedecida com a saliva e mastigada, formando o bolo alimentar, que é empurrado pela língua para a parte posterior da garganta – a faringe. Este processo está sob controle neural de várias áreas do córtex cerebral, incluindo o córtex motor.
2. A Fase faríngea começa com a estimulação dos receptores tácteis na orofaringe pelo bolo alimentar. O reflexo da deglutição é iniciado e está sob controle neuromuscular involuntário. As seguintes ações ocorrem para assegurar a passagem de comida ou bebida para o esôfago:
– A língua bloqueia a cavidade oral para evitar que a comida retorne para a boca.
– O palato mole bloqueia a entrada para a cavidade nasal.
– As pregas vocais se fecham para proteger as vias aéreas.
– A laringe é puxada para cima e ocorre a inclinação da epiglote, fechando a entrada da traqueia. Este é a etapa mais importante, pois, a passagem de alimentos para os pulmões pode ser potencialmente fatal.
– O esfíncter superior do esôfago se abre para permitir a passagem para o esôfago.
3. Fase esofágica: o bolo alimentar é impulsionado para o esôfago pelos movimentos peristálticos – ondas de contração muscular que empurram o bolo alimentar pera frente. A laringe se move para baixo, retornando à posição inicial.

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Le Réflexe de Déglutition, Phases et Contrôle Neuronal, avec Animation.

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L’action d’avaler, ou la déglutition, est le processus par lequel les aliments passent de la bouche dans le pharynx puis dans l’œsophage. Aussi simple que cela puisse paraître pour les personnes en bonne santé, la déglutition est en fait une action très complexe qui nécessite une coordination extrêmement précise avec la respiration puisque ces deux processus partagent la même entrée – le pharynx. L’absence de coordination se traduirait par l’étouffement ou les fausses routes. La déglutition implique plus de vingt muscles de la bouche, de la gorge et de l’oesophage qui sont contrôlés par plusieurs aires corticales et par les centres de déglutition dans le tronc cérébral. Le cerveau communique avec les muscles à travers plusieurs nerfs crâniens.
La déglutition se compose de trois phases:
1. Phase orale ou buccale: ceci est la partie volontaire de déglutition, la nourriture est humidifiée avec de la salive et mâchée, bol alimentaire est formé et la langue le propulse à l’arrière de la gorge – le pharynx. Ce processus est sous contrôle neuronal de plusieurs aires du cortex cérébral, y compris le cortex moteur.
2. Phase pharyngée commence par la stimulation des récepteurs tactiles dans l’oropharynx par le bol alimentaire. Le réflexe de déglutition est déclenché et est sous contrôle neuromusculaire involontaire. Les mesures suivantes sont prises pour assurer le passage de la nourriture ou des boissons dans l’œsophage:
– La langue ferme la cavité buccale pour empêcher les aliments de revenir à la bouche.
– Le palais mou couvre la cavité nasale pour éviter que les aliments remontent dans le nez.
– Les cordes vocales se resserrent et bouchent les voies aériennes. L’élévation du larynx se traduit par l’abaissement de l’épiglotte et cela couvre le passage vers la trachée. Ceci est l’étape la plus importante car l’entrée de la nourriture ou des boissons dans les poumons peut être potentiellement mortelle.
– Le sphincter oesophagien supérieur s’ouvre pour permettre le passage à l’oesophage.
3. Phase oesophagienne: bol alimentaire est propulsé dans l’œsophage par péristaltisme – des ondes de contraction musculaire qui poussent le bol jusqu’à l’estomac. Le larynx descend à sa position initiale.

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Reflejo de la Deglución, Fases y Descripción General del Control Neural, con Animación.

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Tragar, o deglución, es el proceso mediante el cual la comida pasa desde la boca, a través de la faringe y hacia el esófago. Tan simple como podría parecer a las personas sanas, la deglución es en realidad una acción muy compleja que requiere de una coordinación extremadamente precisa con la respiración, ya que estos dos procesos comparten la misma entrada – la faringe. Fallas en la coordinación pueden resultar en atragantamiento o broncoaspiración. La deglución involucra más de veinte músculos de la boca, garganta y esófago que son controlados por diversas áreas corticales del cerebro y por los centros de la deglución en el tallo cerebral. El encéfalo se comunica con los músculos a través de varios nervios craneales.
La deglución consiste en tres fases:
1. La fase oral o bucal: Esta es la parte VOLUNTARIA de la deglución, la comida es humedecida con saliva y es masticada, el bolo alimenticio se forma y la lengua lo empuja hacia la parte posterior de la garganta – la faringe. Este proceso está bajo el control neural de diferentes áreas de la corteza cerebral incluyendo la corteza motora.
2. La fase faríngea empieza con la estimulación de receptores táctiles en la orofaringe por el bolo alimenticio. El reflejo de la deglución es iniciado y está bajo control neuromuscular INVOLUNTARIO. Se toman las siguientes acciones para asegurar el paso de comida o bebida hacia el esófago:
-La lengua bloquea la cavidad oral para prevenir que la comida se devuelva a la boca. -El paladar blando bloquea la entrada a la cavidad nasal. -Las cuerdas vocales se cierran para proteger la vía aérea a los pulmones. La laringe es halada hacia arriba y la epiglotis se rebate hacia atrás CUBRIENDO la entrada hacia la tráquea. Este es el paso más importante ya que la entrada de comida o bebida en los pulmones puede ser potencialmente peligrosa para la vida.
-El esfínter esofágico superior se abre para permitir el paso hacia el esófago.
3. La fase esofágica: El bolo alimenticio es impulsado en el esófago por peristalsis – una onda de contracción muscular que empuja el bolo por delante de esta. La laringe se mueve hacia abajo de nuevo a su posición original.

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TMJ and Myofascial Pain Syndrome

Below is a narrated animation of TMJ and Myofascial Pain Syndrome . Click here to license this video on Alila Medical Media website.

The temporomandibular joint

The temporomandibular joint – the TMJ – is the joint between the lower jawbone – the mandible – and the temporal bone of the skull. The TMJ is responsible for jaw movement and enables chewing, talking and yawning. Temporomandibular disorders, or TMD, refer to a group of conditions characterized by pain in the jaw area and limited movement of the mandible. TMD may be caused by problems in the joint itself or in the muscles surrounding the joint. Problems in the joint include: arthritis, inflammation and internal derangements. When the problem is in the muscles, the condition is called myofascial pain syndrome.

Myofascial pain syndrome

Myofascial pain syndrome is very common and can occur in patients with a normal temporomandibular joint. The syndrome is characterized by presence of hyperirritable spots located in skeletal muscles called trigger points. A trigger point can be felt as a nodule of muscle with harder than normal consistency. Palpation of trigger points may elicit pain in a different location. This is called referred pain.
Muscles of mastication labeled.

Fig. 1: Muscles of mastication (chewing muscles). Click on image to see it on Alila Medical Media website where the image is also available for licensing.


Paranasal sinuses, or simply “sinuses” in common language,  are air cavities in the bones of the skull. There are four pairs of sinuses (see Fig. 1, 2 and upper panel of Fig. 3):

– the maxillary sinuses are under the eyes, in the maxillary bones.
– the frontal sinuses are above the eyes, in the frontal bone.
– the ethmoid sinuses are between the nose and the eyes, in the ethmoid bone.
– the sphenoid sinuses are behind the nasal cavity, in the sphenoid bones.

Sinusitis
Fig.1: The four pairs of sinuses. Red = frontal, green =  ethmoid, blue = sphenoid, beige =  maxillary. The right panel show normal sinuses on half of the head and inflamed sinuses on the other half. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.

 

The sinuses are lined with respiratory epithelium producing mucus. The mucus drains into nasal cavity through small openings (Fig. 2 left panel, Fig. 3 upper panel). Impaired sinus drainage has been associated with inflammation of sinuses (sinusitis, see below).
Biological function of the sinuses remains unclear.

Nose anatomy labeled. .
Fig. 2: Front view of the sinuses (left panel) showing connections to the nasal cavity. Right panel shows mid-sagittal section of the head. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.

 

 

Sinusitis or rhinosinusitis is inflammation of the paranasal sinuses (Fig. 1, right panel). This can be due to:
– allergy (allergic rhinitis): allergens such as pollen, pet dander,.. trigger overreaction of the mucosa of the nose and sinuses resulting in excess mucus, nasal congestion, sneezing and itching.
– infection: usually as a complication of an earlier viral infection of the nasal mucosa, pharynx or tonsils such as during a common cold. Impaired sinus drainage due to inflammation of nasal mucosa during a cold often leads to infection of the sinus itself. Cold-like symptoms plus headache and facial pain/pressure are common complaints.
– other conditions that cause blockage of sinus drainage: structural abnormality such as deviated nasal septum (Fig. 3); formation of nasal polyps (Fig. 4). When a sinus is blocked, fluid builds up making it a favorable environment for bacteria, viruses or fungi to grow and cause infection.
Deviated nasal septum
Fig. 3: Front view of the sinuses (upper panel) showing connections to the nasal cavity, also shown the nasal septum (light blue color). Lower panel shows deviated septum blocking drainage of the right maxillary sinus (your left). Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.

 

 

 

 

Nasal polyps

Fig. 4: Nasal polyps – overgrowths of nasal mucosa – block sinus drainage. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.

 

 

 

Treatment depends on the cause of sinusitis:
– For viral infection : symptom relief medications such as nasal spray for irrigation and decongestion; other conservative treatment for common cold such as rest and drinking plenty of fluid.
– For bacterial infection: antibiotics may be prescribed.
– For allergy: intranasal corticosteroids are commonly used.
– For recurrent (chronic) sinusitis due to structural abnormalities or nasal polyps, nasal surgery may be recommended.

                                                                                                           See all Respiratory topics

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Swallowing and Dysphagia (with Animation)

Swallowing

Below is a narrated animation about swallowing reflex, phases and overview of neural control. Click here to license this video on Alila Medical Media website.

Swallowing, or deglutition, is the process by which food passes from the mouth, through the pharynx and into the esophagus. As simple as it might seem to healthy people, swallowing is actually a very complex action that requires an extremely precise coordination with breathing since both of these processes share the same entrance: the pharynx. Failure to coordinate would result in choking or pulmonary aspiration. Swallowing involves over twenty muscles of the mouth, throat and esophagus that are controlled by several cortical areas and by the swallowing centers in the brainstem. The brain communicates with the muscles through several cranial nerves.

Swallowing consists of three phases

1. Oral or buccal phase: this is the voluntary part of swallowing, the food is moistened with saliva and chewed, food bolus is formed and the tongue  pushes it to the back of the throat (pharynx). This process is under neural control of several areas of cerebral cortex including the motor cortex.
2. Pharyngeal phase starts with stimulation of tactile receptors in the oropharynx by the food bolus. The swallow reflex is initiated and is under involuntary neuromuscular control. The following actions are taken to ensure the passage of food or drink into the esophagus:
– The tongue blocks the oral cavity to prevent going back to the mouth.
– The soft palate blocks entry to the nasal cavity.
– The vocal folds close to protect the airway to the lungs.The larynx is pulled up with the epiglottis flipping over covering the entry to the trachea (the windpipe). This is the most important step since entry of food or drink into the lungs may potentially be life threatening.
– The upper esophageal sphincter (UES) opens to allow passage to the esophagus.
3. Esophageal phase: food bolus is propelled down the esophagus by peristalsis – a wave of muscular contraction that pushes the bolus ahead of it. The larynx moves down back to original position.

Click here to see an animation of the swallowing process on on Alila Medical Media website where the video is also available for licensing.
Swallowing, labeled
Fig. 1: Anatomy of swallowing. See text for details of phases. The blue arrows represent breathed air. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.

 

 

Dysphagia (swallowing disorders)


This  video is available for licensing on Alila Medical Media website. Click HERE!

Dysphagia refers to a group of conditions characterized by difficulty swallowing. There are two main classes of problems that can lead to swallowing disorders:


 1. Neuromuscular problems: 

– Muscular disorders that affect skeletal muscles, such as muscular dystrophy, myasthenia gravis…

– Diseases of the nervous system that compromise the way the brain controls the swallowing reflex, such as stroke, Parkinson’s disease, multiple sclerosis…

– Weakened muscles and/or impaired coordination as a result of aging.

This class commonly affects the first two phases of swallowing.

2. Narrowing of the throat or esophagus due to throat cancer, esophageal cancer and formation of small sacs or rings in the walls of the esophagus.  Gastroesophageal reflux disease – GERD – is also a common cause. In GERD, scars resulted from stomach acid injuries may obstruct the esophagus and cause difficulty swallowing.

This class mostly affects the third phase of swallowing.

Schatzki ring blocks esophagus
Fig. 2: Schatzki ring makes the lumen of esophagus smaller. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.

 

 

 

For people with dysphagia, eating becomes a challenge. The consequences may be serious. Someone who cannot swallow safely is at high risks of choking, pulmonary aspiration and may not be able to eat enough to stay healthy.

Treatment depends on the cause of the condition:

– Muscle strength and coordination exercises may be recommended for some.

– A change in the position of the head and neck when eating could be beneficial to others.

– Right choice of food and drink is important for most. Soft textured food and thickened drinks are recommended for safe swallowing.

– Surgery may be needed to remove narrowed parts of the esophagus.

– Finally, patients with severe dysphagia and recurrent aspiration may have to resort to tube feeding to get nutrition to the body.

                                                                                                                            See all ENT topics

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Snoring and Sleep Apnea

Below is a narrated  animation of snoring, sleep apnea and treatment with a mandibular advancement device. Click here to license this video and/or other related videos on Alila Medical Media website.


No one likes to share a bedroom with a person who snores. Snoring is definitely well established as a social/marital problem. Not many are aware, however, that snoring maybe a sign of, or might progress to, a more serious, potentially life threatening health problem: obstructive sleep apnea (OSA).
Sleep apnea is a sleep disorder characterized by instances of cessation of breathing (apnea).

Anatomy of snoring and sleep apnea

In normal breathing, air enters the nostrils and goes through the throat and the trachea (the windpipe) to the lungs (blue arrow in Fig. 1). In people who snore this airway is partially obstructed by excess tissue of the throat (large tonsils, soft palate, tongue). Another common cause of obstruction is the dropping of the tongue into the throat due to over- relaxation of tongue muscles during sleep. To get enough air the body reacts by breathing through the mouth. The two air currents from the nose and the mouth competing through narrow spaces in the throat cause the soft palate (essentially a piece of soft tissue hanging in the throat) to vibrate. This vibration is the source of the noise we hear when someone is snoring.

 

Snoring and sleep apnea

Fig. 1: Anatomy of snoring and sleep apnea. Click on image to see a larger version on  Alila Medical Media website where the image is also available for licensing.

 

 

 

 

 

Sleep apnea happens when the airway is completely obstructed, no air can go through and the person stops breathing (apnea). This cessation of breathing triggers the brain to response by waking up the person just enough to take a breath. This repeats itself again and again during the course of the night and may result in sleep deprivation.

How do I know if i have sleep apnea?

Not everyone who snores has sleep apnea. It’s hard to self diagnose when one is sleeping. The biggest tell-tale to look for is daytime drowsiness together with other signs of sleep deprivation such as loss of concentration, loss of memory, headache in the morning,…It would also help to have a bed partner observing for episodes of breathing pauses.  If you suspect that you may have sleep apnea  based on those symptoms, it’s important that you visit your doctor immediately. The doctor will examine your throat and if a sleep disorder is suspected, you will be sent to a sleep clinic where your sleep will be monitored and data about your breathing patterns will be collected.

Treatments for snoring and sleep apnea

(in order from mild to severe)

Life style changes: Snoring and mild sleep apnea may be treated with life style changes such as losing some weight, avoiding alcohol and heavy meals. In some people, sleeping on the side instead of on the back might be a solution.
Oral appliances (snoring mouthpiece) are small devices that can be worn in the mouth at night. An oral appliance prevents the tongue and other soft tissue from falling back into your throat and thus keeps the airway open. It’s best to have the device made to measure to ensure fitting to your mouth.
Continuous Positive Airway Pressure (CPAP) is the first line treatment for patients with severe OSA. In this case a small machine is used to generate a constant air flow that is delivered to the patient through a mask fitted on the nose. It looks pretty much like a snorkeling mask except that the tube is connected to a machine.
It is important to note that CPAP and oral appliances help to keep your airway open and enable you to sleep at night but they do not cure the condition. The symptoms will return as soon as you stop using them.
Surgery: Various surgical procedures are available for treatment of sleep apnea. Surgery can be performed on the soft palate, the tongue, the hyoid bone, the jaws or a combination of those. Your surgeon will advice which is best for each patient.

                                                                                                                           See all ENT topics

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