Anatomy and Physiology of the Endocrine System

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The Endocrine System
Controls many body functions
~exerts control by releasing special chemical substances into the blood called hormones ~Hormones affect other endocrine glands or body systems
Derives its name from the fact that various glands release hormones directly into the blood, which in turn transports the hormones to target tissues via ducts.

Exocrine glands-transport their hormones to target tissues via ducts. Endocrine glands- secrete hormones into the bloodstream
The Endocrine System

Consists of several glands located in various parts of the body ~Pituitary gland- a small gland located on a stalk hanging from the base of the brain- AKA ~"The Master Gland"
-Primary function is to control other glands
-Produces many hormones
-Secretion is controlled by the hypothalamus in the base of the brain

The Pituitary Gland is divided into 2 areas, which differ
~structurally and functionally
~each area has separate types of hormone production

The 2 segments are:
~Posterior Pituitary
-produces oxytocin and antidiuretic hormone (ADH)
~Anterior Pituitary
-produces thyroid-stimulating hormone (TSH)
-growth hormone (GH)
-adrenocorticotropin (ACTH)
-follicle-stimulating hormone (FSH)
~luteinizing hormone (LH)

detailed info over pituitary gland
~Posterior Pituitary
-Oxytocin (the natural form of pitocin)
*stimulates gravid uterus
*causes "let down" of milk from the breast
-ADH (vasopressin) causes the kidney to retain water
The Endocrine System
Anterior Pituitary
~Primarily regulates other endocrine glands
~TSH stimulates the thyroid gland to release its hormones, thus increasing the metabolic rate ~Growth hormone (GH)
-lower glucose usage
-higher consumption of fats as an energy source
~ACTH stimulates the adrenal cortex to release its hormone
~FSH and LH stimulates maturation & release of eggs from ovary

The Thyroid Gland
~lies in the anterior neck just below the larynx
~Two lobes, located on either side of the trachea, connected by a narror band of tissue called the isthmus. ~Sacs inside the gland contain colloid
~Within the colloid are the thyroid hormones:
-Thyroxine (T4)
-Triiodothyronine (T3)
*When stimulated (by TSH or by cold), these are released into the circulatory system and increase the metabolic rate The Endocrine System
Calcitonin is also produced by the thyroid
-Inhibits the action of osteoclasts
-Accelerates calcium and phosphate absorption into bone extracellular matrix thus lowering the amount of blood calcium phosphates.

Parathyroid Glands
-small, pea-shaped glands, located in the neck near the thyroid -usually 4- number can vary though
-regulate the level of calcium in the body
-produce parathyroid hormone- increases level of calcium in blood

-a key gland located in the folds of the duodenum
-has both endocrine and exocrine functions
-secretes several key digestive enzymes

Islets of Langerhans
-specialized tissues in which the endocrine functions of the pancreas occurs -inclue 3 types of cells:
-each secretes an important hormone

Alpha cells release glucagon, essential for controlling blood glucose levels When blood glucose levels fall, alpha cells increase the amount of glucagon in the blood The surge of glucagon stimulates the liver to release glucose stores (from glycogen and additional storage sites). Also, glucagon stimulates the liver to manufacture glucose-


Beta Cells release insulin (antagonistic to glucagon)
Insulin increases the rate at which various body cells take up glucose. Thus, insulin lowers the blood glucose level. Insulin is rapidly broken down by the liver and must be secreted constantly. Delta cells produce somatostatin, which inhibits both glucagon and insulin

Adrenal glands
-2 small glands that sit atop both kidneys
-2 regions: adrenal cortex (80-90%) and the adrenal medulla
The Adrenal Cortex secretes 3 classes of hormones, all steroid...
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