from where do thyroid arises?

Answer 1

We all know what the tyroid is it for, where it is, how big it is and bladibladibal, right?

I might be wrong, but I think the question referres to the "embryonic" origin of the gland thyroid
The thyroid is formed by the fusion of two structures of separate embryonic origin: the thyroid diverticulum, derived from the endoepithelium in the floor of the pharynx; and the ultimobranchial bodies, formed as evaginations of the 4th pouches. For each of these endodermal evaginations, there is a corresponding ectodermal invagination or pharyngeal cleft. The ectodermal and endodermal epithelia, placed back to back, form the pharyngeal membrane. During their descent in the neck, these pharyngeal organs are surrounded by mesenchyme derived from the cranial neural crest.

Hope this was the correct interpretation of your question.
Have alook at this website for more details
http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=endocrin.box.331

Answer 2

The thyroid is situated on the front side of the neck, starting at the oblique line on the thyroid cartilage (just below the laryngeal prominence or Adam's apple), and extending to the 6th Tracheal ring (C-shaped cartilagenous ring of the trachea). Vertebral levels are inappropriate to demarcate the gland's upper and lower border with vertebral levels as it moves position in relation to these during swallowing. It lies over the trachea and is covered by layers of pretracheal fascia (allowing it to move), muscle and skin.

The thyroid is one of the larger endocrine glands - 10-20 grams in adults and butterfly-shaped. The wings correspond to the lobes and the body to the isthmus of the thyroid. It may enlarge substantially during pregnancy and when affected by a variety of diseases.

Answer 3

The thyroid (from the Greek word for "shield", after its shape) is one of the larger endocrine glands in the body. It is a double-lobed structure located in the neck and produces hormones, principally thyroxine (T4) and triiodothyronine (T3), that regulate the rate of metabolism and affect the growth and rate of function of many other systems in the body. The hormone calcitonin is also produced and controls calcium blood levels. Iodine is necessary for the production of both hormones. Hyperthyroidism (overactive thyroid) and hypothyroidism (underactive thyroid) are the most common problems of the thyroid gland. Specialists are called Thyroidologists.
1) Hormone Production. To produce thyroxine (T4) requires manganese, iodine, tyrosine, cyclic AMP, vitamin C and B-complex, and other micronutrients. Radiation toxicity, excessive oxidant stress or toxic chemicals can block hormone synthesis. Mercury and copper toxicity stimulate hormone synthesis.

2) Hormone Release. Secretion of thyroid hormones requires sympathetic nervous stimulation. Many people have exhausted adrenals or other autonomic imbalances that may affect the sympathetic nervous system.

3) Absorption into the Cells. Once released into the blood, T4 must be absorbed into the body cells. For this to occur, the cell membranes must function properly. Accumulation of biounavailable calcium and magnesium excessively stabilize cell membranes and reduce cell permeability. Deficient calcium and magnesium cause excessive cell permeability. Oxidant stress or impaired fatty acid metabolism or other damage to cell membranes can also block absorption of thyroxine.
Copper affects absorption by altering calcium and potassium levels. Cadmium or nickel toxicity affect hormone absorption by affecting the levels of calcium, sodium and other critical minerals.

4) Utilization in the Mitochondria. Once inside the cells, thyroxine must be converted to to T3 and utilized in the mitochondria. Potassium plays a role in sensitizing the mitochondria to thyroid hormone. Fluorides in drinking water and chlorides found in bleaches used to make white flour are powerful inhibitors of thyroid hormone utilization. They interfere with iodine metabolism. Substances in soy and in raw cabbage, cauliflower and broccoli also inhibit thyroid hormone utilization. The worst foods for one's thyroid are soy products and foods made with white flour. Many packaged foods processed with water contain high levels of fluorides that have found their way into water supplies.
Cells must also be able to respond to thyroid hormone stimulation. A range of vitamins and minerals are required for energy production in the glycolysis and carboxylic acid cycles in the mitochondria. If these co-factors are missing or toxins block steps in the pathway, thyroid hormone will be ineffective in increasing energy production
:P