Thyroid gland (edited v.)
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Thyroid gland (edited v.)
- 2. THYROID GLAND Located in the anterior neck region adjacent to the larynx and trachea Consists of two lateral lobes united by an isthmus Develops from the endodermal lining of the floor of the primitive pharynx Composed of connective tissue septa and follicles
- 4. Tri – iodothyronine (T3)
- 7. STROMA A low-power micrograph of thyroid gland shows the thin capsule (C), from which septa (S) with the larger blood vessels, lymphatics, and nerves enter the gland
- 8. FOLLICULAR EPITHELIUM Surrounds each follicle Composed of reticular fibers and network of capillaries Can be simple squamous, cuboidal, or low columnar epithelium
- 10. Roughly spherical cyst-like compartment
- 11. Wall formed by follicular epithelium
- 12. Central cavity contains a gelatinous substance called colloid
- 15. FOLLICULAR CELLS Principal cells Most numerous cell type Cuboidal in shape with spherical nucleus Periods of increased activity – cells are more columnar and colloid is less abundant
- 17. Synthesize, release, and store their product outside their cytoplasm
- 19. PARAFOLLICULAR CELLS C (clear) cells Larger than follicular cells Contain secretory granules Can occur either alone or in clumps Synthesize and secrete calcitonin
- 20. PARAFOLLICULAR CELLS RED– Follicle with colloid BLUE – Parafollicular cells PINK – Retracted or distorted colloid
- 21. FOLLICULAR AND C CELLS C cells may be part of the follicular epithelium or present singly or in groups outside of follicles. Follicular cells (F) can usually be distinguished from C cells (C) by the smaller size and darker staining properties. Unlike follicular cells, C cells seldom vary in their size or pale staining characteristics.
- 22. FOLLICULAR AND C CELLS
- 23. FOLLICULAR AND C CELLS
- 24. ULTRASTRUCTURE (Follicular and C cells)
- 25. ULTRASTRUCTURE (Follicular and C cells)
- 27. Tri – iodothyronine (T3)
- 29. CALCITONIN Lower blood calcium levels through inhibition of bone resorption Secretion is triggered by elevation of blood calcium concentration
- 30. HORMONES
Notas del editor
- TEM of the follicular epithelium shows pseudopodia and microvilli extending from the follicular cells (F) into the colloid of the lumen (L). The cells have apical junctional complexes, much RER, well-developed Golgi complexes, and many lysosomes. Inside the basement membrane (BM) of the follicle, but often not contacting the colloid in the lumen, are occasional C or parafollicular cells (C). To the left and right of the two C cells seen here are capillaries intimately associated with the follicular cells, but outside the basement membrane
- A TEM of a C cell, with its large Golgi apparatus (G), extensive RER, and cytoplasm filled with small secretory granules containing calcitonin.