Chapter 27.2, Problem 5MI

Summary Introduction

To analyze:

The importance of an endostyle.

Introduction:

Invertebrate chordates are the animals that have a notochord at some point during their development, but vertebral column or backbone is absent. these animals are placed in the subphyla Tunicata and Cephalochordata of the phylum Chordata.

Explanation of Solution

In the pharynx of invertebrate chordates, a ventral groove with glandular walls is located called endostyle. It is thought to be homologous with the follicular thyroid of vertebrates.

In the pharyngeal organ of invertebrate chordate such as Amphioxus, endostyle is present. The function of endostyle secretes mucus to catch food. It captures iodine and produces thyroid hormones.

Conclusion

An endostyle represents an early form of the thyroid gland.