Download pdf - The Endocrine System - Union High Schooluhs.twpunionschools.org/subsites/spiotrowski/documents/7...The Endocrine System 11 •Pancreas –a key gland located in the folds of the duodenum

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The Endocrine System 1

• 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

Emergencies:

– from common:

• Diabetes

• to the unusual:

– Thyrotoxicosis

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Overview of 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.

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Hypothalamus/pituitary gland


• 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) -

Neurosecretory

– Anterior Pituitary:

• produces thyroid-

stimulating hormone

(TSH)

• growth hormone (GH)

• adrenocorticotropin

(ACTH)

• follicle-stimulating

hormone (FSH)

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Posterior pituitary

Summary of pituitary activity

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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.


• 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.

The thyroid gland

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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.


• Increased thyroid

hormone release

causes

hyperthyroidism,

commonly called

Graves’ disease.

– Signs and

symptoms:

• insomnia, fatigue

• tachycardia

• hypertension

• heat intolerance

• weight loss

– Long term

hyperthyroidism:

• Exophthalmos

– bulging of the

eyeballs

– In severe cases -

a medical

emergency called

thyrotoxicosis

can result.

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Thyroid hormone affects metabolic

rate

Disorders are common

The Endocrine System 10 • 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.

Pancreas is an endocrine and exocrine

gland

99% of tissue

A cells- glucagon

B cells- insulin

D cells- somatostatin

F cells- pancreatic

polypeptide

Responds to eating or fasting

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The Endocrine System-12 alpha

• 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.

The Endocrine System- 12 Beta/Delta

• 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).

Location, blood supply, histology of

adrenal glands

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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.


• 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.


• 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.


• 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.


• Breakdown of sugars

is carried out by

enzymes in the gastro

intestinal system.

– As simple sugars, these

are absorbed from the

GI 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

membrane.

Summary

• Endocrine organs are distributed over the body

• Some are regulated by hypothalamus and

pituitary, some by negative feedback

• Exert effects by releasing hormones that

activate specific cells

• Abnormal levels of hormone secretion or

activity can cause complex disorders