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29 Cards in this Set

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How many lobes make up the thyroid gland? Where are they?
2; on each side of the trachea in the anterior neck
What makes up the folicle?
cuboidal epithelial cells
what shape is the folicle?
circular
what is the functional unit?
the folicle
Where is the thyroid hormone contained
In the glycoprotein thyroglobin, in the colloid
What happens to the epithelial cells when the gland is stimulated?
they get a columnar shape
What does the thyroid secret?
Throxine (t4), triiodothyronine (t3)
reverse t3
What is secreted the most?
t4
Which is the more biologically active form?
T3, therefore t4 is converted into this form
What is colloid?
protein rich fluid that synthesizes/stores T3 and T4
Name 3 places iodide is actively concentrated?
thryroid, salivary, and gastroinstetrinal
How many grams of iodide does the thyroid trap per day?
70-80 micrograms
What is Na+I- cotransport's fxn? where is it located?
it traps iodide. in the basal lamina of the thyroid cells
What is Na+I- cotransport's fxn? where is it located?
it traps iodide. in the basal lamina of the thyroid cells
Describe Iodide trapping and turn over?
1. Iodide is trapped by Na+ I- cotransport
2. It moves across the apical cell and into the follecular lumen
3. It is oxidized to Iodine
4.It's incorportated to the tyrosine residuals in the thyrogobulin
synthesis of thyrogobulin ?
synthesized in the ER of the follicle and packed by the golgi
What does the Thryroglobulin do after it is synthesized?
1.Thyroglobulin moves into the lumen
2. residual tyrosines are iodonized to MIT and DIT
3. The MITs and DITs couple to make t3 and t4
How many months of hormones does thyroid store in the colloid of the follicle?
2-3 months
How many months of hormones does thyroid store in the colloid of the follicle?
2-3 months
Describe the secretion of the thyroid hormone
1. Thyrogobulin is endocytosed into the thyroid cells
2. Lysosomal protease releases the thyroid hormone into circulations
What is the major binding protein of t3 and t4? Where is it synthesized?
Thyroxine-binding globulin (t3 & t4). The liver.
what are the fxns of th thyroxine-binding globulin?
1. keeps a large circulating resivoir of t4
2. keeps it from being secreted in the urine
What happens to the iodinated tyrosine residues that were not incorporated into thyroid hormone?
the thyroid gland recycles them
What effects does TSH have on thyroid gland activity?
1. growth proliferation of follicle cells
2.Iodide trapping
3.Proteolysis of the thyroglobin
4.Secretion of the thyroid hormone
5. Iodination of tyrosine to form thyroid hormone
6. Endocytosis of colloid
7. Synthesis of thyroglobulin
What regulates secretion of TRH/TSH
1. Iodide availability
2. Calories
3. Exposure to cold
4. Drugs
5. Anxiety/stress
6. Negative feedback
What are the major effects of thyroid hormone
fetal/child brain development
basal metabolic rate
What is an indication of hyperthyrodism?
an elevated heart rate
What happens to thy thyroid homrone once inside?
1. Free t3 and T4 inter by energy requiring carrying processes
2. most of t4 converted to t3 by deionating enzymes
3. T3 binds to receptors on target cells
4. Proteins are made
What protiens do the thyroid hormone stimulate the synthesis of?
Na+/K+ ATPase
Mitochondrial enzymes
Enzyme that effect the BMR