DHYG 103: Chapter 4-Embryonic Face and Neck Development

Vocabulary flashcards covering embryonic face, neck, brachial arch, and oral structure development based on the lecture notes.

Oropharyngeal membrane

A membrane formed in the third week of prenatal development by the invagination of ectoderm at the cephalic end, which disintegrates during the fourth week to create the primitive oropharynx.

Stomoidium

The primitive oral cavity that develops in the midline between the brain and heart as the embryonic brain expands.

Frontal nasal process

The embryonic swelling located above the stomoidium formed by the developing brain that gives rise to the forehead and nose.

First brachial arch

Also known as the mandibular arch, this is the first part of the face to form and divides into two maxillary processes and two mandibular processes.

Maxillary process

Formed by buds on the supralateral border of the first brachial arch, forming the upper cheek, upper lip, and most of the palate.

Mandibular process

The remaining portion of the first brachial arch that forms the lower cheek, lower lip, lower jaw, and part of the tongue.

Mandibular symphysis

The site of fusion between the right and left halves of the mandibular bone; a lack of fusion at this site results in a cleft chin.

Hyoid arch

The second brachial arch, which contains Reichert's cartilage and forms the facial muscles, middle ear muscles, suprahyoid muscles, blood vessels, and hyoid bone.

Reichert's cartilage

Specialized cartilage within the second brachial (hyoid) arch that forms the middle ear bone, the process of the temporal bone, the hyoid bone, and hyoid ligaments.

Meckel's cartilage

Cartilage belonging to the first brachial (mandibular) arch that forms first and gives rise to the mandible via intramembranous ossification.

Nasal placodes

Bilateral thickened areas of specialized ectoderm on the surface of the frontal nasal process containing olfactory cells for smell, which form nasal pits that become nostrils.

Lateral nasal processes

Structures derived from the nasal placodes that form the outer sides of the nose.

Median nasal processes

Structures derived from the nasal placodes that form the bridge of the nose and join with the maxillary processes to form the philtrum and primary palate.

Philtrum

The vertical depression located above the upper lip and below the nose, created by the fusion of the median nasal processes with the maxillary processes.

First pharyngeal pouch

An endoderm-lined pouch that develops into the external auditory canal, tympanic membrane, middle ear, and auditory (eustachian) tube.

Second pharyngeal pouch

An endoderm-lined pouch responsible for the development of the palatine tonsils.

Third and fourth pharyngeal pouches

Endoderm-lined pharyngeal pouches that give rise to the parathyroid gland and thymus gland.

Four dice spots

Also known as four dice granules, these are trapped sebaceous glands in the adult oral mucosa resulting from entrapment during closure of the maxillary and mandibular processes, present in about 50% of patients.

Cleft lip

A developmental disturbance caused by the failure of the median nasal process to fuse with the maxillary process and mesenchyme to grow beneath ectoderm, which is more common and severe in boys.

Teratogans

Environmental factors—specifically drugs, chemicals, infections, and radiation—that can cause facial and brachial arch defects prior to the fifth week of prenatal development.