Thyroid gland tumors Prepared by Dr Ghada Ahmed
Thyroid gland tumors Prepared by Dr. Ghada Ahmed Askar Assistant lecturer of pathology
Thyroid gland Development At 3– 4 weeks gestational age it appears as an epithelial proliferation at the base of the tongue. The thyroid then descends through the thyroglossal duct, passing in front of the hyoid bone. At the end of the fifth week the thyroglossal duct degenerates and the detached thyroid continues on to its final position over the following two weeks. A lingual thyroid results from failure of the normal caudal migration of the thyroid from foramen caecum down to its normal location anterior to the larynx and upper trachea. Thyroid tissue may be found anywhere along the course of the thyroglossal duct, however, complete arrest with thyroid tissue located at the base of the tongue is most common and represents 90% of all cases of ectopic thyroid
IT Is an butterfly-shaped endocrine gland, consisting of two lobes connected by an isthmus. It is found at the front of the neck, below the Adam's apple. Four parathyroid glands, two on each side, lie on each side between the two layers of the capsule, at the back of the thyroid lobes Function The thyroid gland secretes thyroid hormones, which primarily influence the metabolic rate and protein synthesis. The hormones also have many other effects including those on development. The thyroid hormones triiodothyronine (T 3) and thyroxine (T 4) are created from iodine and tyrosine. The thyroid also produces the hormone calcitonin, which plays a role in calcium homeostasis. Hormonal output from the thyroid is regulated by thyroid-stimulating hormone (TSH) secreted from the anterior pituitary gland, which itself is regulated the hypothalamus. by thyrotropin-releasing hormone (TRH) produced by
In the thyroid gland hormones are stored in the follicles. To secrete the hormone, the hormone is re-absorbed from the cavity, and then released into the surrounding interstitial spaces. The stored hormone is bound to a glycoprotein, and this stored hormone is called 'colloid'. This gland secretes iodine containing hormones called Tri-iodo thyronine (T 3) and thyroxine (T 4) of which T 3 is more active. Colloid is an inactive precursor of T 3 and T 4. It is made up of a glycoprotein called thyroglobulin, made by the epithelial cells, which is bound to iodine. The iodine binds to the tyrosine residues of thyroglobulin.
Structure Divided into lobules of 20 - 40 round to oval follicles, each 50 - 500 microns, with a single layer of cuboidal to low columnar epithelium. Lumen contains colloid and stroma contains C cells, formerly called parafollicular cells , derived from neural crest scattered among follicular cells and in spaces between the spherical follicles which secrete calcitonin. [
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