2022 Lect 4 Y1 INTERNAL Orofac Struc Palateue RV

Development and Growth of Internal Orofacial Structures

Introduction

  • Focus on the development of oro-facial structures in human embryos.

  • Processes include formation of the palate, nasal cavity, septum, and tongue.

Palate Development

  • Primary Palate Formation:

    • Emerges from the intermaxillary segment formed by merging medial nasal processes during the 5th week.

    • Forms the anterior part of the hard palate.

  • Secondary Palate Formation:

    • Involves the growth of palatine shelves from maxillary processes at about 7 weeks.

    • Shelves grow medially and fuse with the primary palate and nasal septum.

  • Completion of Palate:

    • Fusion of primary and secondary palates occurs by the end of the 12th week, forming definitive hard and soft palates.

Nasal Cavity and Septum Development

  • Origin:

    • Nasal cavity originates from nasal placodes that invaginate to form nasal pits in the 6th week.

  • Growth:

    • The nasal septum develops from the medial nasal processes and grows downward during the 9th week, fusing with palates.

Tongue Development

  • Body of Tongue Formation:

    • Developed from lateral lingual swellings, merging with the median tongue bud (tuberculum impar) in the 4th to 8th weeks.

  • Base of Tongue Formation:

    • Formed from the copula overgrowing the second branchial arch, around the 6th to 8th weeks.

  • Completion of Tongue Formation:

    • By the 8th week, the merges complete forming the anatomical division noted by the sulcus terminalis.

Developmental Disturbances of Palate & Tongue

  • Cleft Palate:

    • Failure of fusion between palatine shelves, leading to a split in the roof of the mouth.

  • Ankyloglossia:

    • Short or tight lingual frenulum limiting tongue mobility.

  • Macroglossia:

    • Unusual enlargement of the tongue causing functional and aesthetic issues.

  • Bifid Tongue:

    • An anterior lengthwise cleft of the tongue, may result from genetic factors or trauma.

Anatomical Planes Related to Orofacial Development

  • Sagittal Plane:

    • Divides the body into left and right.

  • Coronal Plane:

    • Divides the body into anterior and posterior.

Growth of Nasal & Oral Cavities

  • Nasal Cavity Communication:

    • Oronasal membrane ruptures during the 7th week, establishing communication between nasal and oral cavities.

Structural Components of Tongue Development

  • Muscle Origins:

    • Derived from occipital somites, innervated by the hypoglossal nerve (CN XII).

  • Functionality and Mobility:

    • Develops functional muscle coordination, essential for speaking, eating, and swallowing.

Cleft Lip and Palate Issues

  • Cleft Lip:

    • Resulting from incomplete fusion between maxillary and medial nasal processes.

  • Cleft Palate:

    • Results from the failure of palatine shelves to fuse.

Genetic and Environmental Factors Influencing Developmental Issues

  • Multifactorial Causes:

    • Include genetic factors, maternal medication use (e.g., anticonvulsants), nutritional deficiencies, or infections during pregnancy.

Lingual Frenulum Development

  • Anatomy of Lingual Frenulum:

    • Connects the tongue’s ventral surface to the floor of the mouth; plays a role in tongue mobility.

  • Ankyloglossia Mechanism:

    • Failure of frenulum tissue to regress leads to tongue tie.

Summary of Major Findings

  • Orofacial development involves complex interactions of various structures and processes occurring in a defined time frame.

  • Major disturbances in these processes result in common congenital anomalies that require clinical attention.