The early development of the thyroid gland in Amia calva

✍ Scribed by Benjamin Harvey Hill

• Publisher: John Wiley and Sons
• Year: 1935
• Tongue: English
• Weight: 763 KB
• Volume: 57
• Category: Article
• ISSN: 0362-2525
• DOI: 10.1002/jmor.1050570209

✦ Synopsis

Abstract

The thyroid primordium is a solid median outgrowth from the pharynx which is attached to the truncus arteriosus at its bifuracation. The thyroid is soon detached from the pharynx and migrates to its definitive position ventral to the aorta between the bases of the third visceral pouches. After detachment the primary follicle appears in the lower part of the primordium; during migration and early growth it is divided apparently by stress and pressure to form secondary follicles. Independent follicles are formed also by secretion of colloid between solid masses of thyroid cells. Other secondary follicles are formed by pinching off evaginations from large follicles. Colloid appears soon after the primary follicle is divided. The adult thyroid is a group of follicles scatterd in a venous plexus in the ventral pharyngeal region, around the aorta.