Development and Behavior: The Very Young Child

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The Development of Normal Feeding and Swallowing Richard D. Stevenson, MD,* and Janet H. Allaire, MAt

The physical act of feeding is a complex physiologic process. This process depends on two factors that are closely interrelated: structure and function. In infants and young children, this entire process is dynamic because of ongoing growth and development. Anatomic structures, which are essential to competent feeding skills, undergo growth that changes their physical relationship to one another and consequently affects their function. Functional feeding skills, which depend on the integrity of anatomic structures, undergo change based on neurologic maturation and experiential learning. Two important elements implicit to normal feeding and swallowing are the acquisition of adequate nutrition for growth and protection of the airway. When feeding problems arise, malnutrition and respiratory symptoms often result. The basic physiologic complexity of feeding is further compounded by interpersonal and cultural influences. Feeding in children occurs in the context of a parent-child relationship within a larger family unit within a still larger culture. Not only are children influenced by their parents, family, and society, but they exert their own quite significant influence on parents and family. Thus, the feeding of infants and children impacts not only the child, but others as well. Feeding and the development of feeding abilities are very important to children and families. This article focuses on the development of feeding skills and the multiple interacting factors that affect this development. The major goal of this article is to describe the complex development of feeding skills and thereby provide a framework for understanding feeding problems in infants and young children.

STRUCTURE An understanding of the anatomy of the pharynx is essential to a thorough understanding of the feeding process (Fig. 1). Anatomically, the *Assistant Professor, Department of Pediatrics, Kluge Children's Rehabilitation Center, University of Virginia School of Medicine, Charlottesville, Virginia tAssistant Professor, Department of Pediatrics, Kluge Children's Rehabilitation Center, University of Virginia Health Sciences Center, Charlottesville, Virginia

Pediatric Clinics of North America-Vol. 38, No.6, December 1991

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RICHARD

D.

STEVENSON AND JANET

H.

ALLAIRE

nasal conchae hard palate pharyngeal tonsil ~J..2~-f~_---~7(adenOidS)

of tube maxilla ~:¢i~~~~~~~}f::=1FI---i~z::--:----f_opening _ eustachian tongue

nasopharynx

mandible~

soft p.alate (velum) vallecula

I~F=BE=====:t===ePiglottis pharyngeal wall

~"""~~"e?,-:f;fJJl hyoid bone

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thyroid _ _ cartilage

·:11fi=t1ri=======false vocal fOld) larynx 11 true vocal fold -cricoid cartilage esophagus trachea

Figure 1. The mouth and pharynx of the adult. (From Morris SE: The Normal Acquisition of Oral Feeding Skills: Implications for Assessment and Treatment. New York, Therapeutic Media Inc., 1982, p 31; with permission.)

pharynx is made up of three compartments: the nasopharynx, the oropharynx, and the hypopharynx. 8 The nasopharynx extends from the base of the skull to the roof of the soft palate. The oropharynx extends from the palate above to the base of the tongue below and includes the valleculae. The oral cavity is in continuity with the oropharynx. The hypophyarynx extends from the valleculae to the cricopharyngeus. The larynx opens into the hypopharynx anteriorly through the laryngeal aditus. 8 Whereas the nasopharynx is not a part of the alimentary tract, the oropharynx and the hypopharynx are part of both the alimentary and respiratory tracts. These anatomic compartments are involved in three categories of motor function: stabilization and maintenance of structural position and form, alimentation, and respiration. 3 Although these categories of functions share common anatomic structures and motor units, each has its own network of neural control mechanisms and its own calendar of development. 3 A total of 31 pairs of striated muscles are involved during the various phases of swallowing. 7 These muscles are important both as structural and functional elements. The muscles of the face and mandible play an important role during the oral-preparatory phase. These muscles are innervated by

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THE DEVELOPMENT OF NORMAL FEEDING AND SWALLOWING

the facial nerve (VII) and the mandibular branch (V3 ) of the trigeminal nerve, respectively. The tongue, which is important in both the oralpreparatory and the pharyngeal phases of swallowing, is affected by four intrinsic and four extrinsic muscles. The intrinsic muscles are innervated by the hypoglossal nerve (XII), and the extrinsic muscles-with the exception of the palatoglossus (X)-are innervated by the ansa cervicalis (C C C 2). Suprahyoid and infrahyoid muscle groups, responsible for hyoid and laryngeal movement, are innervated by V3 , VII, and the ansa cervicalis (CcC 2 ). The muscles of the palate, pharynx, and larynx, with few exceptions, are innervated by the vagus (X). Although the basic arrangement of the mouth, pharynx, and larynx in the infant is similar to that of the adult, some differences are noteworthy (Fig. 2). The tongue, the soft palate, and the arytenoid mass (arytenoid cartilage, false vocal cords, and true vocal cords) are larger relative to their surrounding chambers when compared with the adult. 3 In the infant, the tongue lies entirely within the oral cavity, resulting in a small oropharynx. 3, 22 In addition, the lateral walls of the oral cavity are stabilized by a sucking pad, composed of densely compacted fatty tissue that further reduces the size of the oral cavity.2 The larynx lies high in the infant, and the tip of the

nasal conchae

opening of eustachian tube

hard palate

pharyngeal tonsil (adenoids)

maxilla

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