Lesson 1.2.4

1.2.4 page 2

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Anatomy of the Thyroid Gland

 

The structure of the thyroid gland is different from other endocrine glands. Thyroid tissue contains many spherical follicles consisting of a single layer of secretory cells surrounding a storage space. The secretory cells produce a precursor of thyroxine which is stored in the storage space. Stimulation by thyroid stimulating hormone, produced by the anterior pituitary, causes the follicles to change the precursor and release it as thyroxine into the many blood capillaries between the follicles. Look at the micrograph of thyroid tissue. Notice that between the follicles there are some large cells (C cells or parafollicular cells). These cells secrete calcitonin, another important thyroid hormone which will be addressed later in this lesson.

 

Read pp. 446 – 447 on the structure of the thyroid gland; study Figure 13.16 on p. 448, and then complete Try This #1.

 

follicle: as it relates to the thyroid gland, is a microscopic structure consisting of a circle of cells called follicle cells surrounding a central cavity; thyroid gland consists of many follicles

 

central cavity: also called the lumen, is surrounded by follicle cells and stores the precursor for thyroxine formation


follicle cells: as they relate to the thyroid gland, they are the cells that surround the central cavity and are responsible for storing iodine and synthesizing thyroxine from the precursor

 

C cells: also called parafollicular cells, they are located between the follicles of the thyroid gland and are responsible for synthesizing calcitonin

 

calcitonin: hormone produced by the C cells (parafollicular cells) in the thyroid gland that decreases blood calcium levels by increasing uptake of calcium into the skeleton and inhibiting decomposition of bone when the blood levels of calcium are too high

 

thyroxine: hormone produced by the follicle cells of the thyroid gland; mainly controls the rate at which the body metabolizes carbohydrates, fats, and proteins for energy and stimulates the proper development of the nervous system

 

precursor: an inactive form of a molecule that can easily be changed into the active form; the precursor thyroglobin can easily be changed into the active thyroxine by the addition of iodine atoms



Try This

 

TR 1.

 

On the Thyroid Tissue Handout, label the follicle, storage space, C cells and the blood capillaries (vessels). Annotate the diagram by indicating the function of each structure in brackets after the name label. Once you have finished, check your diagram and annotations and place it in your course folder.

 

 

Check your work.
Self-Check Answers

 

TR 1.

 

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