**Terminology index**

**Atresia:** The absence or closure of the external auditory canal

**Auricular hillocks:** Six (three-paired) mesenchymal condensations around the first pharyngeal cleft

**Branchial arch:** Paired structures associated with the pharynx that contribute greatly to the formation of the head and neck

**Branchial cleft:** The slit-like openings in the gills of fish between the branchial arches

**Ectoderm:** One of the three primary germ layers in the early embryo

**Goldenhar syndrome:** A complex congenital anomaly characterized by abnormal development of the eye, ear, and spine

**Hemifacial microsomia:** A congenital condition in which one or more parts of the face are underdeveloped

**Pharyngeal pouch:** Saclike diverticula that formed on the endodermal side between the pharyngeal arches

**Primordium:** An organ or part in the earliest recognizable stage of development

**Mesenchyme:** A type of undifferentiated connective tissue comprised of loose cells embedded in the extracellular matrix

**Microtia:** A congenital malformation of variable severity of the ear

**Otic capsule:** The cartilage that surrounds the developing otic vesicle and develops into the bony labyrinth of the internal ear
