The pharynx in horses is a muscular tube that serves as a passageway for both the respiratory and digestive systems. It connects the nasal and oral cavities to the larynx and esophagus, facilitating the movement of air to the lungs and food to the stomach. The equine pharynx plays a role in breathing, swallowing, and vocalization. Anatomically, it is divided into the nasopharynx, oropharynx, and laryngopharynx, each with distinct functions. This section provides access to peer-reviewed research studies and scholarly articles that explore the anatomy, physiology, and clinical relevance of the pharynx in equine health, including its involvement in respiratory and swallowing disorders.
Lindsay FE, Clayton HM.Using histological techniques, anatomical dissection, fibre optic endoscopy and radiography, the nasopharynx and larynx of the donkey were examined and described. Compared with horses, donkeys have a much deeper pharyngeal recess extending 4.0-6.0 cm caudally from a constricted orifice, through which it communicates with the nasopharynx. Movements of the membranous lining of the recess reflect pressure changes in the upper airways. A shallow, thumb shaped depression on the rostral face of each vocal fold corresponds in position to the lateral ventricle in the horse. In the donkey, large paired...
Deegen E.With the aid of a flexible glassfibre endoscope, a 300 W cold light source and a special adapted camera, colour photographs of the upper respiratory tract of horses were taken. These pictures served to present especially the disease processes of the different areas of the upper respiratory tract which lead to a constriction of the lumen. These included proliferation in the nose, guttural pouch diseases and larynx diseases such as hemiplegia, subepiglottic cysts, epiglottic entrapment and rostral displacement of the plica palatopharyngica. Furthermore endoscopic findings of changes in the soft ...
Hoquet F, Higgins R, Lessard P, Vrins A, Marcoux M.A total of 43 horses were used for the study of the pharyngeal bacterial flora. The median value of the number of bacteria in the group of 19 normal horses was 3.8 x 10(4) cfu/g of secretions. This value was 6.4 x 10(4)cfu/g in horses with grade I pharyngitis, 1.3 x 10(5) cfu/g in horses with grade II pharyngitis and 3.5 x 10(6) cfu/g in horses affected with grades III and IV pharyngitis. Corynebacterium spp, coagulase-negative staphylococci, Nocardia spp, Moraxella spp and Enterobacter spp were the most frequently encountered bacteria in the normal animals as well as in horses affected with p...
Brock KA.A pharyngeal performation, probably associated with endotracheal intubation, occurred in a healthy 4 1/2-month-old colt. Inhalation anesthesia was carried out for elective surgery, but acute cervical cellulitis, pleuritis, and pneumonia developed after the surgery. Antibacterial and supportive therapy was ineffective.
Todhunter RJ, Brown CM, Stickle R.Five horses with retropharyngeal (RP) infections had clinical signs of dysphagia and/or dyspnea. Diagnosis was confirmed, using pharyngeal endoscopy and lateral radiography of the pharynx. One horse responded to surgical drainage of a RP abscess and was sound at light work. One horse responded to medical management after the site of infection was surgically explored. Two horses recovered after medical management; the RP abscess of 1 of these 2 horses ruptured spontaneously into the pharynx and the other horse became racing sound. The fifth horse remained dysphagic and had left laryngeal hemipl...
Sweeney CR, Sweeney RW, Raker CW, Freeman DE.A 3-year-old Thoroughbred filly had a pharyngeal abscess causing obstruction of the upper respiratory tract. Diagnosis was made by a combination of endoscopy, biopsy, cytology, and radiography. Treatment with antimicrobials and analgesics resulted in successful resolution of the abscess.
Auer DE, Wilson RG, Groenendyk S.The prevalence of pharyngeal lymphoid hyperplasia in Thoroughbred racehorses in training was investigated using a fibre optic endoscope. Of the 70 horses examined, all but 8 showed evidence of pharyngeal lymphoid hyperplasia and the severity of the pharyngeal changes decreased with age. Two-year old horses had greater pharyngeal lymphoid hyperplasia (p less than 0.05) when compared to all other age groups. More horses (p less than 0.05) with Grade 3 or Grade 4 pharyngeal lymphoid hyperplasia experienced recent mild respiratory disease than did horses with Grade 2 or less pharyngeal lymphoid hy...
Bayly WM, Grant BD, Breeze RG.Arterial blood gas and acid-base values during maximal exercise over a 1.2 km distance were recorded in four Thoroughbred horses before and after the chemical induction of pharyngeal lymphoid hyperplasia (PLH). Samples were collected after galloping 0.8 km and 1.2 km, immediately upon stopping and 5 mins after exercising. In only one horse was any difference noted in the pre and post PLH induction results. The horse was more hypercapnoeic at the 1.2 km mark and also took much longer to complete the gallop when it had PLH. However, it also had signs of lower respiratory disease. In the other ho...
Orr JA, Fraser DB, Shirer HW, Wagerle LC, DeSoignie RC.Carbon dioxide concentrations were increased during expiration in the upper one-half of the trachea, pharynx, and nasal sinuses to determine if elevation of upper airway CO2 would alter breathing or arterial blood gases in the awake pony. Carbon dioxide (100%) was injected into the midcervical trachea via a chronically implanted transcutaneous cannula during the first part of the animal's expiration. This maneuver elevated upper airway expiratory CO2 concentrations but prevented any exogenous CO2 from entering the lung and being absorbed into the arterial blood. Twelve experiments were perform...
Grabner A.Using a fibreoptic endoscope ("small gastroscope" with outside diameter of 9.3 mm) a simple and sparing inspection of the guttural pouch is performed. The flap-type tube cover is opened by means of medial leverage with a guidance probe shifted through the work duct of the endoscope. The same procedure is used in diagnostic specimen collection and therapeutical measures such as irrigations. Guttural pouch topography and pathological disorders are illustrated by endoscopic photography. The different diseases such as follicular hyperplasia, ascending pharyngeal catarrh, perforating abscesses of t...
Blythe LL, Cardinet GH, Meagher DM, Brown MP, Wheat JD.The histologic and histochemical features of palatine muscles from 53 horses were studied; 25 of the horses were racehorses that had upper airway obstruction associated with dorsal displacement of the soft palate and 28 of the horses did not have any respiratory disorders and served as controls. Pathologic features observed included myonecrosis, phagocytosis, mononuclear cell infiltration of perimysial connective tissue, alkaline phosphatase-positive myofibers, and myofibers with cytoarchitectural changes that included irregular staining of the intermyofibrillar sarcoplasm and sarcoplasmic mas...
Linford RL, O'Brien TR, Wheat JD, Meagher DM.A lateral radiograph of the pharyngeal region provides a technique for identifying pharyngeal disorders, including entrapment of the epiglottic cartilage and dorsal displacement of the soft palate. Epiglottic cartilage length, predicted from radiographs by measurement from the body of the thyroid cartilage to the tip of the epiglottis (thyroepiglottic length), was well correlated to actual length at postmortem examination (r2 = 0.98). Thyroepiglottic length, corrected for magnification, was 8.76 +/- 0.44 cm in 24 healthy Thoroughbreds. Nine Thoroughbreds with entrapment of the epiglottic carti...
Speirs VC, van Veenendaal JC, Harrison IW, Smyth GB, Anderson GA, Wilson DV, Gilbo B.Endoscopic examinations of the upper respiratory tract were done on 92 of 314 Standardbred horses that raced one or more times at 4 consecutive, weekly race meetings. Although participation was voluntary, the characteristics of the population of horses examined were not statistically different from those of all horses that raced. No horse showed epistaxis, but 34 (32.4%) examinations of the trachea revealed blood that ranged from a trace in the tracheal mucus to large amounts scattered over the tracheal walls. Forty-four horses exhibited minor degrees of pharyngeal lymphoid hyperplasia, 2 had ...
Malan FS, Reinecke RK, Scialdo RC.The tongue, pharynx, oesophagus and gums are examined for larvae of gasterophilus spp., and the nose and sinuses for oestrid larvae. The gastro-intestinal tract is divided into separate specimens-stomach, small intestine, caecum, ventral colon, dorsal colon, descending colon and rectum- and each is examined separately. Aliquots of ingesta of 1/4 by mass of the stomach and 1/10 by mass of the small intestine, caecum, ventral colon and dorsal colon are collected for microscopic examination. Each part of the wall of the caecum, ventral and dorsal colon is washed and specimens are collected for su...
Bisgard GE, Forster HV, Klein JP.Resting ventilation (PaCO2) and ventilatory responses to acute hypoxia and to intravenous NaCN were assessed over a 4-yr period following cutting of the carotid sinus nerves and stripping the adventitia of the aortic arch. The data indicated essentially complete loss of peripheral chemoreceptor function immediately after surgery and hypoventilation during normoxia (delta PaCO2 = +8.7 Torr). There was a time-dependent, partial recovery of peripheral chemoreceptor function between 2 and 22 mo after surgery. Approximately 10% of the ventilatory response to iv NaCN returned, and 30-40% of the norm...
Greet TR, Baker GJ, Lee R.Using fluoroscopic techniques and videotape recordings, a study of normal deglutition was made in 2 ponies. Paryngeal function was studied at intervals after laryngoplasty on 1 animal and after a sham technique on the other. Two clinical cases of laryngeal paralysis, which had been treated by laryngoplasty, were also examined. In the 2 experimental ponies, liquid food passed into the lower respiratory tract post-operatively. One of the clinical cases appeared to swallow solid food normally, but some food material entered the larynx of the other horse. It is suggested that pharyngeal dysfunctio...
Heffron CJ, Baker GJ, Lee R.Videofluoroscopy was used to study the deglutition reflexin 2 horses believed, on the basis of endoscopic and clinical examination, to have normal pharyngeal and laryngeal function. The reflex was found to be the same as that described in man and in the rabbit. A feature of deglutition in the horse was the temporary increase in size of the auditory tube diverticuli (gluttural pouches) as a result of contraction of the pharyngeal muscles.
Heffron CJ, Baker GJ.Cine-endoscopy was used to study the deglutition reflex in 2 apparently normal horses. Closure of the nasopharyngeal sphincter was brought about by a lowering of the pharyngeal roof and an elevation of the soft palate caudal to the pharyngeal ostia of the auditory tubes. The medial cartilages of the ostia were not directly involved in bringing about closure of the sphincter. It is postulated that the opening of the ostia of the auditory tubes is brought about during deglutition by the combined action of the palatopharyngeus, pterygopharyngeus and tensor veli palatini muscles.
Heffron CJ, Baker GJ.Fibreoptic endoscopy was used to study the movements of the larynx and pharynx during nasal occlusion in 10 horses, which showed signs consistent with functional pharyngeal obstruction (FPO) on exercise. Cine-endoscopic films were made on 3 such horses. Consideration of the anatomy of the region indicates that FPO may best be regarded as a subluxation of the nasopharyngeal and larygneal airways and it was found that a constant component of the movements which brought about this subluxation was a marked caudal retraction of the larynx. It is suggested that this caudal retraction of the larynx o...
Rawlinson RJ, Jones RT.The history and clinical findings of 1 horses with guttural pouch mycosis referred to us are described. The salient features of the history and clinical signs common to both cases were profuse spontaneous nasal haemorrhage, partial pharyngeal paralysis; subsequently bilateral nasal discharge containing food material, inability to drink and parotid pain became evident. One case made a gradual recovery with conservative medical treatment while the second case was destroyed and submitted for post-mortem, histopathological and microbiological examination. This examination failed to establish the i...
Knight AP.Dysphagia developed in a 2-year-old Quarter Horse filly following an incident in which it fell over backward while exercising on a mechanical horse walker. Hyperextension of the neck at this time apparently caused unilateral rupture of the longus capitis (rectus capitis ventralis major) and the rectus capitis ventralis minor muscles at their insertion. An existing mycotic lesion involving the dorsomedial wall of the left guttural pouch may have weakened the area of insertion of the involved muscles. Tearing of the tendinous insertion of these muscles caused damage to the IX, X, and XI cranial ...
Heffron CJ, Baker GJ, Lee R.Videofluoroscopy was used to study the deglutition reflexin 2 horses believed, on the basis of endoscopic and clinical examination, to have normal pharyngeal and laryngeal function. The reflex was found to be the same as that described in man and in the rabbit. A feature of deglutition in the horse was the temporary increase in size of the auditory tube diverticuli (gluttural pouches) as a result of contraction of the pharyngeal muscles.
McGivney CL, Sweeney J, Gough KF, Hill EW, Katz LM.Endoscopic tip placement in the pharynx and water flushing interval (FI) may affect exercising upper respiratory tract (URT) endoscopic results. Objective: To determine associations between the endoscopic tip position in the pharynx and automated FI with overground endoscopic (OGE) results. Methods: Randomised balanced 2X5 factorial design. Methods: A total of n = 200 horses undergoing OGE were randomly assigned into 10 groups (n = 20/group) of different automated endoscopic FIs (no flushing, 60, 120, 180, 240 s) with the endoscope tip positioned either rostrally (position A) or caudally ...
O'Brien RT, Biller DS.This article addresses the current status and clinical opportunities for portable radiography and ultrasonography. Radiology is indicated for imaging the nasal cavity, larynx, pharynx and thin portions of the neck. In young foals, adequate radiographs of the entire respiratory tract may be possible. Ultrasonography is indicated in superficial parts of the head and neck, the pleural space and diseased parts of the lungfields.
Embertson RM.Upper respiratory tract conditions of the older horse that are not necessarily associated with athletic exercise intolerance are discussed. Some of the diseases described include ethmoid hematoma, sinus disease, guttural pouch empyema and mycosis, retropharyngeal abscess, nasopharyngeal cicatrix, arytenoid chondropathy, and neoplasia.
Adams R, Calderwood-Mays MB, Peyton LC.Three horses were examined for ulcerative pharyngitis, which had been unresponsive to treatment. Biopsy specimens of the pharyngeal lesions were characterized histologically by a mixed population of lymphocytes and histiocytes, suggesting chronic inflammation. Only when biopsy specimens of regional lymph nodes revealed this cell population disrupting the lymph node architecture was the diagnosis of malignant lymphoma made.
Grabner A.Using a fibreoptic endoscope ("small gastroscope" with outside diameter of 9.3 mm) a simple and sparing inspection of the guttural pouch is performed. The flap-type tube cover is opened by means of medial leverage with a guidance probe shifted through the work duct of the endoscope. The same procedure is used in diagnostic specimen collection and therapeutical measures such as irrigations. Guttural pouch topography and pathological disorders are illustrated by endoscopic photography. The different diseases such as follicular hyperplasia, ascending pharyngeal catarrh, perforating abscesses of t...
Hardy J.Upper airway obstruction may result from nasal, pharyngeal, or tracheal diseases. In the young horse, a relatively severe obstruction usually is present before clinical signs are evident. This article reviews the clinical manifestations, diagnostic features, treatment, and outcome of commonly encountered conditions of the nasal passages, pharynx, larynx, and trachea in young horses.
Sullins KE.Common equine upper respiratory conditions are diagnosed via endoscopy. Endoscopic surgery facilitates correction of many conditions without general anesthesia or laryngotomy, reducing the morbidity and cost of the procedures. Modalities of endoscopic surgery include the Nd-YAG laser or electrosurgery, which may be complementary. The least expensive method is electrosurgery, and instruments are available that can be passed through the biopsy channel of the endoscope. Conditions amenable to such procedures include entrapped epiglottis, rostral displacement of the palatopharyngeal arch, pharynge...
Proudman CJ, Knottenbelt DC, May SA, Edwards GB.Several imaging techniques were used to diagnose hypoplasia of the soft palate in a horse. The absence of the caudal soft palate, hypertrophied lymphoid tissue and the formation of a pseudouvula were observed endoscopically. Plain and contrast radiography were used to demonstrate a soft palate remnant and to identify structures rostral to the epiglottis. Retrograde endoscopy of the pharynx via a tracheotomy incision is described.
Guglick MA, MacAllister CG, Breazile JE.An 18-month-old Quarter Horse gelding was examined because of weight loss and dysphagia of 1 month's duration. Clinical signs included lethargy, dehydration, ptyalism, and probable aspiration pneumonia. Severe dyspnea and cyanosis were evident after mild exercise. Endoscopy revealed laryngospasm and pharyngospasm. Because clinical signs and endoscopic findings were suggestive of hyperkalemic periodic paralysis (HPP), acetazolamide treatment was instituted. Marked improvement was observed within 48 hours. The horse was determined to be homozygous for HPP. It is likely that this horse's dysphagi...
Sullivan EK, Parente EJ.Pharyngeal disorders are complex and difficult to treat. Disorders that lead to anatomic derangement, such as trauma and neoplasia, can significantly affect the function of this organ. Pharyngeal dysfunction can manifest as dysphagia, persistent palatal displacement, or exercise intolerance. Secondary complications are serious and life threatening and include aspiration pneumonia, weight loss, and death. Pharyngeal disorders that are only recognizable during strenuous exercise are difficult to diagnose and are treated with limited success, even though they are responsible for significant econo...
Cornelisse CJ, Holcombe SJ, Derksen FJ, Berney C, Jackson CA.To determine the effect of a tongue-tie on upper airway mechanics in exercising horses. Methods: 5 Standardbreds. Methods: Peak inspiratory and expiratory tracheal and pharyngeal pressures and airflow were measured while horses exercised on a treadmill with and without a tongue-tie. Respiratory rate was also measured. Horses ran at speeds that corresponded to 50 (HR50), 75, 90 (HR90), and 100% of maximal heart rate. The tongue-tie was applied by pulling the tongue forward out of the mouth as far as possible and tying it at the level of the base of the frenulum to the mandible with an elastic g...
Blikslager AT, Tate LP.There are clearly a number of applications for which flexible endoscopic laser surgery has become the state of the art in equine surgery, and the Nd:YAG laser seems to be the most versatile instrument for this type of surgery. Nevertheless, it is critical to understand the advantages and disadvantages of each laser technique. For example, the Nd:YAG laser used in a noncontact fashion seems to be superior when ablation of tissue is required such as treatment of upper airway masses. Conversely, contact Nd:YAG laser techniques have proven themselves to be superior when more precise cutting is adv...
Moorman VJ, Marshall JF, Jann HW.A 7-year-old sexually intact male Thoroughbred racehorse was evaluated because of exercise intolerance, respiratory tract noise, and coughing when eating. Results: A persistent dorsal displacement of the soft palate was identified during endoscopic examination of the upper portions of the respiratory tract. Radiography of the pharyngeal and laryngeal regions revealed a hypoplastic epiglottis that was ventral to, and not in contact with, the soft palate. The horse was anesthetized, and an oral endoscopic examination revealed a subepiglottic frenulum that had resulted in the dorsal displacement ...
Roethlisberger-Holm K, Roepstorff L, Obel N.After giving an account of the principles of pressure measurement in flowing air and a review of the literature on tracheal catheters, the authors describe the construction, the introduction and the function of their own transtracheal catheter. This is a teflon catheter with several side-ports which is introduced into the cervical trachea by a guide technique. After introduction, the catheter is stiffened by the insertion of 2 steel wires. The catheter was studied in model experiments concerning: a) the ability to measure the static pressure in flowing air, and b) the dynamic accuracy of a rec...
Blikslager AT, Tate LP, Tudor R.To document the use and clinical outcome of transendoscopic laser techniques for treatment of rostral displacement of the palatopharyngeal arch (RDPA) in horses. Background: Rostral displacement of the palatopharyngeal arch is a rare cause of upper respiratory noise and exercise intolerance in horses, and may be associated with abnormal laryngeal anatomy. There are few reports of successful treatment of this condition, and no reports of the treatment of RDPA using laser techniques. Methods: The diagnosis of RDPA was based on the presence of palatal tissue covering the dorsal aspect of the aryt...
Baptiste K.The pharyngeal orifice of the equine auditory tube has not been adequately described. Its larger size and position, further rostral within the nasopharynx compared with other species, cannot be easily explained, but could be important for the proposed brain-cooling function of the guttural pouches; however, unlike other species, it may not be the sole regulator of auditory tube aeration. A 'second orifice' (representing the final entrance to the auditory tube diverticulum) deserves recognition in performing a role in air exchange between the auditory tube, diverticulum and middle ear. The resu...
Yarbrough TB, Voss E, Herrgesell EJ, Shaw M.To report the clinical signs and management of 4 foals with persistent frenulum of the epiglottis. Methods: Case report. Methods: Four newborn foals. Methods: Foals were admitted with a complaint of oronasal reflux after nursing. Variable systemic signs of aspiration pneumonia were evident. Nasal endoscopy confirmed persistent dorsal displacement of the soft palate. Persistent frenulum of the epiglottis, confirmed by oral endoscopic examination, was transected. Results: After surgery, all foals had the epiglottis positioned normally, dorsal to the soft palate. Clinical signs of oronasal reflux...
Colbath AC, Valdés-Martínez A, Leise BS, Hackett ES.OBJECTIVE To determine the pharyngeal and laryngeal distribution of radiopaque contrast medium administered orally or via nasopharyngeal catheter to standing horses. ANIMALS 5 healthy adult horses. PROCEDURES A crossover study was conducted. Radiopaque contrast medium (12 mL) was administered orally and via nasopharyngeal catheter to each horse. Pharyngeal and laryngeal distribution of contrast medium was determined by examination of radiographs obtained immediately after administration of contrast medium, compared with those obtained before administration. Regional distribution of contrast me...
Schumacher J, Hanselka DV.Nasopharyngeal cicatrices were observed endoscopically in 47 horses examined because of abnormal respiratory noises and/or exercise intolerance. A review of these cases revealed a correlation between cicatrization and age, sex, and the presence of other upper airway abnormalities. The age of affected horses ranged from 6 to 21 years, with a mean age of 12.7 +/- 7.8 (+/- 2 SD) years. Females were affected 2.7 times more frequently than males. Abnormalities commonly observed with a nasopharyngeal cicatrix included chondritis of the arytenoid cartilage, epiglottic deformity, and deformity of the ...
Lumsden JM, Stick JA, Caron JP, Nickels FA.Medical records of 51 horses with epiglottic entrapment were reviewed, and the outcome after surgical treatment was evaluated by use of results from a survey of owners and from race records. Horses with epiglottic entrapment and no additional problem (uncomplicated) of the nares, nasal passages, pharynx, or larynx (upper airway) that were treated by transoral axial division (group 1) or resection via laryngotomy (group 2), and horses with epiglottic entrapment complicated by an additional upper airway abnormality (group 3) were compared. The cost of treatment, duration of hospitalization, time...
Offord S, Tulloch LK, Franklin SH, Tremaine WH, Woodford NS, Allen KJ.The laryngeal tie-forward (LTF) procedure has been shown to move the larynx rostrally and dorsally whilst repositioning the basihyoid bone caudally and dorsally. Other studies have shown that the position of the hyoid bones influences the size of the nasopharynx. The effect of the LTF procedure on the size of the nasopharynx is unknown. It was hypothesised that the LTF procedure would result in a decrease in dorsoventral nasopharyngeal diameter. Twenty-five thoroughbred horses which underwent LTF with or without soft palate cautery (LTF±SPC) for treatment of dorsal displacement of the soft pa...
