A section through the angle of the mouth, tongue tip and beginning of the esophagus.
Observe:
1. The frenulum of the tongue lateral to which is the orifice of the submandibular duct.
2. The lower facial muscles beneath the developing skin.
3. The strap muscles of the neck ventral to the thyroid cartilage.
4. The rostral parathyroid gland (pouch 4) dorsal to the thyroid gland.
5. The cricoid cartilage surrounding the infraglottic cavity of the larynx.
Keywords: C-3 / C-4 interganglion region, C-3 neural arch, angle of mouth (rima oris), anterior digastric muscle, common carotid artery, cricoid cartilage, depressor anguli oris muscle, esophagus, frenulum of tongue, genioglossus muscle, geniohyoid muscle, infraglottic cavity, infrahyoid muscles (strap muscles of neck), jugular lymph sac, lower lip, mandible, mylohyoid muscle, notochord, orbicularis oris muscle, pharyngeal arch 1 cartilage (Meckel), platysma, rostral parathyroid gland (pouch 4), sternocleidomastoid muscle, submandibular duct, thyroid cartilage, thyroid gland, tongue (near tip), upper lip, vagus nerve (CN X), vertebral artery
Source: Atlas of Human Embryos.