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Controls many body functions - exerts control by releasing special chemical substances into the blood called hormones - Hormones affect other endocrine glands or body systems Consists of several glands located in various parts of the body. 1.Pituitary gland
- lies in the anterior neck just below the larynyx.
- Two lobes, located on either side of the trachea, connected by a narrow band of tissue called the isthmus .
- Sacs inside the gland contain colloid
thyroxine ( T4 )
triiodothyronine ( T3 )
“ C” cells within the thyroid produce the hormone calcitonin .
Calcitonin , when released, lowers the amount of calcium in the blood.
hypothyroidism, or Myxedema.
hyperthyroidism, commonly called Graves’ disease.
Long term hyperthyroidism:
bulging of the eyeballs
In severe cases - a medical emergency called t hyrotoxicosis can result.
3. Parathyroid Glands
small, pea-shaped glands, located in the neck near the thyroid
usually 4 - number can vary
regulate the level of calcium in the body
produce parathyroid hormone - level of calcium in blood
Hypocalcemia can result if parathyroids are removed or destroyed.
Islets of Langerhans
specialized tissues in which the endocrine functions of the pancreas occurs
include 3 types of cells:
alpha ( )
beta ( )
delta ( )
each secretes an important hormone .
Alpha ( ) cells release glucagon , essential for controlling blood glucose levels. When blood glucose levels fall, cells the amount of glucagon in the blood. Beta Cells ( ) release insulin (antagonistic to glucagon). Insulin the rate at which various body cells take up glucose. Thus, insulin lowers the blood glucose level. Delta Cells ( ) produce somatostatin , which inhibits both glucagon and insulin.
5. Adrenal Glands
2 small glands that sit atop both kidneys.
Each has 2 divisions, each with different functions.
Stimuli which cause growth hormone release Fasting Hypoglycaemia Exercise Stress Gh secretion is ↓ by ↑ in plasma free fatty acids High dose of glucocorticoids β adrenergic agonist Gh secretion is ↑ by 5HT agonist α adrenergic agonist