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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.

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Presentation Transcript
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.

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Exocrine glands - transport their hormones to target tissues via ducts.

Endocrine Emergencies:

from common:

Diabetes

to the unusual:

Thyrotoxicosis

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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.

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The Pituitary Gland is divided into 2 areas, which differ

structurally and functionally

each area has separate types of hormone production.

The two 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)

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And even more…

luteinizing hormone (LH)

prolactin

Let’s go over these one at a time...

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.

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Anterior Pituitary

Primarily regulates other endocrine glands

rarely a factor in endocrinological emergencies

TSH stimulates the thyroid gland to release its hormones, thus  metabolic rate

Anterior Pituitary…

Growth hormone (GH)

 glucose usage

 consumption of fats as an energy source

ACTH stimulates the adrenal cortex to release its hormones

FSH & LH stimulates maturation & release of eggs from ovary.

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The Thyroid 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

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  the metabolic rate.

“C” cells within the thyroid produce the hormone calcitonin.

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Calcitonin, when released, lowers the amount of calcium in the blood.

Inadequate levels of thyroid hormones = hypothyroidism, or Myxedema.

Myxedema symptoms:

Facial bloating

weakness

cold intolerance

lethargy

altered mental status

oily skin and hair

TX: replacement of thyroid hormone.

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Increased thyroid hormone release causes hyperthyroidism, commonly called Graves’ disease.

Signs and symptoms:

insomnia, fatigue

tachycardia

hypertension

heat intolerance

weight loss

Long term hyperthyroidism:

Exopthalmos

bulging of the eyeballs (picture Barbara Bush)

In severe cases - a medical emergency called thyrotoxicosis can result.

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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.

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Pancreas

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

include 3 types of cells:

alpha ( )

beta ()

delta ()

each secretes an important hormone.

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Alpha () cells release glucagon, essential for controlling blood glucose levels.

When blood glucose levels fall,  cells  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 -

gluconeogenesis.

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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.

Insulin is rapidly broken down by the liver and must be secreted constantly.

Delta Cells () produce somatostatin, which inhibits both glucagon and insulin.

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Adrenal Glands

2 small glands that sit atop both kidneys.

Each has 2 divisions, each with different functions.

the Adrenal Medulla secretes the catecholamine hormones norepinephrine and epinephrine (closely related to the sympathetic component of the autonomic nervous system).

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The Adrenal Cortex secretes 3 classes of hormones, all steroid hormones:

gluticocorticoids mineralocorticoids

androgenic hormones

One at a time…

gluticocorticoids:

accounts for 95% of adrenal cortex hormone production

 the level of glucose in the blood

Released in response to stress, injury, or serious infection - like the hormones from the adrenal medulla.

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Mineralocorticoids:

work to regulate the concentration of potassium and sodium in the body.

Prolonged  in adrenal cortex hormone results in Cushing’s Disease.

Signs & Symptoms of Cushing’s Disease:

 in blood sugar levels

unusual body fat distribution

rapid mood swings

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And - if there is an  in mineralocorticoids as well

A serious electolyte imbalance will occur due to the  potassium excretion by the kidney, which results in hypokalemia.

Sodium can also be retained by the kidney, resulting in hyponatremia.

Causes:

dysrhythmias

coma

death

usually results from a tumor - TX? Removal of tumor.

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Gonads and Ovaries:

the endocrine glands associated with human reproduction.

Female ovaries produce eggs

Male gonads produce sperm

both have endocrine functions.

Ovaries:

located in the abdominal cavity adjacent to the uterus.

Under the control of LH and FSH from the anterior pituitary they manufacture

estrogen

protesterone

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Estrogen and Progesterone have several functions, including sexual development and preparation of the uterus for implantation of the egg.

Testes:

located in the scrotum

produce sperm for reproduction

manufacture testosterone -

promotes male growth and masculinization

Controlled by anterior pituitary hormones FSH and LH.

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Endocrine Emergencies:

Diabetes Mellitus

one of the most common diseases in North America.

 insulin secretion by the Beta () cells of the islets of Langerhans in the pancreas.

Complications of Diabetes:

contributes to heart disease

stroke

kidney disease

blindness

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Pathophysiology of Diabetes:

Glucose Metabolism

Glucose (dextrose) is a simple sugar required by the body to produce energy.

Sugars, or carbohydrates, are 1 of 3 major food sources used by the body.

The other 2 major food sources are

proteins

fats

Most sugars in the human diet are complex and must be broken down into simple sugars: glucose, galactose and fructose - before use.

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Breakdown of sugars is carried out by enzymes in the gastro intestinal system.

As simple sugars, these are absorbed from the GE system into the body.

More than 95% enter the body as glucose.

To be converted into energy, glucose must first be transmitted through the cell membrane. BUT - the glucose molecule is large and doesn’t readily diffuse through the cell membrane.

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Glucose must pass into the cell by binding to a special carrier protein on the cell’s surface.

Facilitated diffusion - doesn’t use energy. The carrier protein binds with the glucose and carries it into the cell.

The rate at which glucose can enter the cell is dependent upon insulin levels.

Insulin serves as the messenger - travels via blood to target tissues.

Combines with specific insulin receptors on the surface of the cell membrane.

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