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•~~~A~2ol0 08I J oýPC°''° AD-A270 208 NP AGE K1ý- 0 CA6I(to r),. 1. AGEN... . tvtr ojani)# 2 REPORT DATE 3. REPORT TYPE ANC DATES COVERED 1993 THFSIS/MSS NU 4. TITLE AND SUBTITLE S S . 'F"UNDING NUMBERS Movement of the Epiglottis in Fammals 6, AUTHOR(S) James E. Larson 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBEr AFIT Student Attes,,zing: Univ of Washington AFIT/CI/CIA- 93-133 9SS PONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10 SPONSORING MONITOR NG DEPARTMENT OF THE AIR FORCE AGENCY REPORT NUMBEIR AFIT/CI 2950 P STREET WRIGHT-PATTERSON AFB OH 45433-7765 11. SUPPLEMENTARY NOTES 12a. DISTRIBUTION! AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE Approved for Public Release IAW 190-1 D;stribution Unlimited MICHAEL M. BRICKER, SMSgt, USAF Chief Administration 13. ABSTRACT (Maximum 2C0 words) DTIC fl ELECTE OCT06 1993 93-23216 j 0 4 D 4 8 IIIl}illml IIIIlI o WP 14. SUBJECT TERMS 15. NUMBE3R Of PAGES 16 PRICE CODE 17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACT OF REPORT OF THIS PAGE OF ABSTRACT NSN 7540-011-280-5500 S0o~v f V ' ,- O MOVEMENT OF THE EPIGLOTTIS IN MAMMALS by James E. Larson D.D.S. Ac7WO For i A thesis submitted in partial fulfillment ,, N 7 of the requirements for the degree of MASTER OF SCIENCE IN DENTISTRY .-y UNIVERSITY OF WASHINGTON , I (cid:127)V;2 UCt 1993 ~TQ~J A~I~ ... PT(cid:127)CTID a4 by Approved (Chairperson of Research Committee) Department School of Dentistry (Departmental Faculty sponsoring candidate) Date Master's Thesis In presenting this thesis in partial fulfillment of the requirements for an advanced degree at the University of Washington, I agree that the Library shall make it freely available for inspection. I further agree that permission for extensive copying of this thesis is allowable only for scholarly purposes, consistent with "fair use" as prescribed in the U.S. Copyright Law. Any other reproduction for any purposes or by any means shall not be allowed without written permission. Signature Date TABLE OF CONTENTS List of Figures ii List of Tables iii Introduction 1 The Problem 1 Position of the Epiglottis 1 Role of the Epiglottis During Swallowing 3 A. The Adult Human 3 B. The Human Infant 4 C. Other Mammals 6 Purpose 7 Materials and Methods 8 Results 11 Anatomy 11 Fluoroscopy - Technical Considerations 11 Movements 12 Timing 13 Bolus 15 Discussion 16 Bibliography 31 LIST OF FIGURES Number 1A . Adult human at rest 20 1B . Adult human swallowing 21 1C . Human infant at rest 22 2. Schematic showing pig skull and view of 23 structures as seen during videofluoroscopy 3. Relationship of the ferret epiglottis to 24 other cranial structures 4. Series of sketches of pig barium liquid 25 swallow 5. Digitized frames of pig swallowing hard 26 chow 6. Series of digitized frames of ferret 27 swallowing hard chow 7. Photo of food streaming past epiglottis 28 prior to swallow; Pig, swallowing barium liquid, 1 frame prior to initiation of epiglottic depression fi LIST OF TABLES Number Pg 1. Duration and frequency of swallows for 29 the pig and ferret for various types of food 2. Time intervals for epiglottic movement 30 III,. ACKNOWLEDGMENTS I would like to particularly thank the chairperson of my research committee, Dr. Sue Herring for her extensive advice, guidance and encouragement. Her dedication to her work will always be an inspiration to me. My thanks also are extended to the other members of my committee, Dr. Peter Shapiro, Dr. Doug Ramsay ana Dr Lars Hollender. Dr. Raymond Fink was an unofficial member of my committee. I appreciated his advice and wisdom. Trish Emry put in many hours in helping around the lab, especially in pig training and for that I am very grateful. Thanks are also extended to David Wright for his computer help and aid with statistics. Jim Clark helped with my illustrations and photography for which I am very appreciative. Frank "Rusty" Starr performed all of the cinefluoroscopy which was at the heart of this study. I am thankful also to the alumni who funded this study ana whose dedication and guidance will be with me always. My classmates offered much valuable advice and encouraged me every step of the way along our journey. It was an honor and a total pleasure to be associated with them. To my wife, Mary, and to my sons Tim, Jon, Jeff, Ethan, Ben and Eric goes all of my love forever. I do everything thinking of you. INTRODUCTION The Problem The spatial positioning of the human larynx and epiglottis relative to the pharynx is uniquely different from that found in other mammals. However, it has not been clearly established whether these anatomical differences reflect functional differences. The epiglottis of the adult human moves downward during swallowing movements (Mosher, 1927; Welin, 1939; Johnstone, 1942; Saunders et al., 1951; Rushmer and Henderson, 1951; Fink, 1956; Ardran and Kemp, 1967), presumably to protect the airway (Fig. la,b), but such an action has been disputed in human infants and other mammals. Position of the Epiglottis From as early as 21 weeks in utero (Magriples and Laitman, 1986) to approximately 4 to 6 months of age (Sasaki et al., 1977) or 6 years of age (Crelin, 1987) the epiglottis of human infants makes contact with the soft palate because of the superior location of the entire hyolaryngeal apparatus (Fig. 1c). Thus, until at least six months of age and perhaps up to six years, humans are obligate nasal breathers. The age disparity between the cited studies is large and suggests that preserved specimens may not always reflect in vivo morphology. Nevertheless, in the adult human the epiglottis never touches the soft palate and mature humans are quite capable of nasal and/or oral breathing. The contrast between infant and adult epiglottic position has been viewed within the context of human evolution by Lieberman and colleagues (1972) and Laitman (1982), who argued from cranial base 1 anatomy that Neanderthals had contact of the epiglottis and soft palate. Thus, they speculated that early men were obligate nasal breathers, like infants, and had a heightened sense of smell. While not universally accepted (DuBrul, 1976), these findings have had broad currency in linguistic and anthropological circles (e.g., Bickerton, 1990; Ross, 1991). Negus (1949), who did the classic, descriptive work on the larynx, noted that some reptiles and birds have an epiglottis but the relative size is small compared to mammals. In mammals a prominent epiglottis is the rule. Negus extrapolated from his dissections to live animals and concluded that, except in mature humans, the epiglottis touches or overlaps the posterior or the anterior surface of the soft palate during breathing. According to Negus, this would serve to enforce nasal breathing and thus heighten the sense of smell, the same advantages that Laitman ascribed to Neanderthals. Among land mammals, the ungulates represent an extreme condition in which a large epiglottis extends well into the nasopharynx on the posterior side of the soft palate. Negus noted that this arrangement would promote uninterrupted olfaction and breathing even during feeding, an advantage for these prey animals which must spend large amounts of time consuming their non- nutritious diets. Although Negus' comprehensive anatomical studies have been influential in the anthropological community, his physiological deductions have not proved reliable. For example, Negus postulated that in dogs the anterior-lying epiglottis acts as a two-way valve to direct air through the nose during inhalation and through the mouth 2 during exhalation, facilitating temperature regulation. However, Biewener and associates found that the in vivo_ position of the epiglottis in dogs varies and that it actually lies posterior to the soft palate during many activities (1985). This study points out the limitations of making conjectures based on anatomic study alone and raises doubts about other commonly accepted tenets of laryngeal function. Role of Epiglottis During Swallowing A.The Adult Human While epiglottic anatomy has rarely been debated, this has not been the case for epiglottic movement during swallowing. Magendie (1816, cited by Negus, 1949) exemplified the prevailing view of his time, which was that the epiglottis folded down, lid-like, over the laryngeal inlet during swallowing. In 1892 Stuart, in making observations on a patient with a lateral pharyngostomy, reported that the epiglottis remained upright during swallowing movements (cited by Negus, 1949). (In retrospect, this could have been a case of paralysis such as those reported by Ekberg [1983]). This incident, along with the anatomical data, was used as support by Negus (1949) for his contention that the epiglottis of man and other mammals remained upright and respiration continued during the swallowing of liquid or semi-solid food. The bulk of evidence, however, contradicts the theory that the human epiglottis remains upright during swallowing. Using radiography, Mosher (1927) reported that the epiglottis "does act as a cover for the larynx in swallowing." His results have been 3