Workbook > Unit 8
Unit 8 - The Endocrine System
THE ENDOCRINE GLANDS IN DETAIL
Thyroid and Parathyroid Glands
Located in the anterior part of the neck are the thyroid gland and parathyroid glands. The thyroid gland is a butterfly-shaped endocrine organ that wraps around the larynx (laryng/o). The thyroid gland consists of a right and left lobe, connected by a narrow bridge. The parathyroid glands are four pea-sized organs embedded within the posterior side of the much larger thyroid gland.
The thyroid secretes a mixture of hormones, mainly thyroxine (T4) and triiodothyronine (T3). Because thyroid hormones contain iodine, laboratories can measure these hormones and study thyroid gland activity by following iodine levels.
The parathyroid glands affect calcium metabolism; parathyroid hormone (PTH) increases the blood level of calcium. It works in concert with the thyroid hormone calcitonin, which lowers blood calcium, in order to maintain proper calcium levels.
