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Endocrine System
What does the endocrine system consist of?
All the organs of the body that are endocrine glands
What do endocrine glands do?
An endocrine gland secretes endocrine hormones.
What are endocrine hormones?
Endocrine hormones are hormones that are secreted
into the blood.
What are hormones?
Hormones are substances that are secreted by one group
of cells that affects the physiology of another group of
cells (organs).
What is the endocrine system controlled by?
The endocrine system is controlled by the pituitary
gland and the hypothalamus.
Compared to most other organs in the body, is
the endocrine well vascularized?
Yes, endocrine organs are well vascularized.
What does the endocrine system do?
 A system of ductless glands, they secrete
messenger molecules called HORMONES.
 Interacts closely with the nervous system.
What is ENDOCRINOLOGY?
The study of hormones and endocrine glands.
Major Endocrine Glands:
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Hypothalamus
Pituitary Gland
Thyroid Gland
Parathyroid Glands
Thymus Gland
Adrenal Glands
Pancreas
Ovaries
Testes
Pineal Gland
Where are the Endocrine Organs?
They are scattered throughout the body
Richly Vasculurized
What are the pure endocrine organs?
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Pituitary
Pineal
Thyroid
Parathyroid
Adrenal Glands
What organs contain endocrine cells?
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Pancreas
Thymus
Gonads
Hypothalamus
What is the endocrine system controlled by?
The pituitary gland and the hypothalamus.
Always controlled by feedback loops
What happens if blood concentration
declines below a minimum?
More hormone is secreted.
What happens if blood concentration
exceeds maximum?
Hormone production is halted
Where is hypothalamus located and part of
what system?
The hypothalamus is located in the base of the brain.
It is part of the limbic system.
What does the limbic system control?
The limbic system controls the autonomic nervous
system and the endocrine systems.
How does the hypothalamus control the
endocrine system?
By controlling the pituitary gland.
 Secretes releasing factors to release hormones.
 Secretes inhibiting hormones to turn off
secretion of hormones.
Where is the PITUITARY GLAND located?
In the sella tursica (totally encased in bone), VERY
important gland.
What is the PITUITARY GLAND a major
source of?
The PITUITARY GLAND is a major source of
steroid hormones in the body.
What can trauma to the PITUITARY
GLAND cause?
Diabetes
What can a tumor of the PITUITARY
GLAND lead to?
It can lead to blindness because it is so close to the
optic chiasma.
How many major hormones does the
PITUITARY GLAND secrete?
Secretes nine major hormones.
How does the PITUITARY GLAND attach to
the hypothalamus?
Attached to the hypothalamus by the infundibulum.
What are the two parts of the PITUITARY
GLAND?
1. ADENOHYPOPHYSIS is the anterior pituitary.
2. NEUROHYPOPHYSIS is the posterior pituitary.
The ADENOHYPOPHYSIS (Anterior Pituitary) secretes hormones
which affect what glands?
* Growth hormone (GH) : causes body to grow
* Prolactin (PRL): Stimulates lactation in females
Unknown effects in males
* Thyroid Stimulating Hormone (TSH):
Causes the thyroid gland to release thyroid hormone.
*Adrenocorticotropic hormone (ACTH): Acts on adrenal cortex to
stimulate the release of cortisol.
Helps people cope with stress.
* Melanocyte-stimulating hormone (MSH): Darkens skin pigmentation
* Follicle-stimulating hormone (FSH): present in males & females, affects
both. Stimulates maturation of sex cells.
*Luteinizing hormone (LH): Induces ovulation
What does the NEUROHYPOPHYSIS
(posterior pituitary) do?
It is a continuation of the brain; cell bodies of special
neurons in the hypothalamus have axons which go to
the neurohypophysis and synapse on the capillaries.
What do Nerohypophysis release instead of
neurotransmitters?
They release hormones
*Oxytocin
-Childbirth contractions
*Antidiuretic hormone (ADH)
-Signals kidneys to increase water reabsorption.
What controls the pituitary gland?
The HYPOTHALAMUS (the master gland)
What are some disorders of the pituitary gland?
Gigantism and Acromegaly
-Hypersecretion oh GH in children
-Giantism is overall growth
-Acromegaly is enlarged hand and feet.
Pituitary dwarfism
-Hyposecretion of GH
Diabetes insipidus
-Not enough ADH (anti-diuretic hormone)
What hormones does the Hypothalamus produce?
*Thyroid Stimulating Hormone Release Hormone-(TSH-RH)
This affects the adenohypophysis to secrete Thyroid Stimulating Hormone
TSH affects the thyroid gland to secrete Thyroid hormone (TH)
The hypothalamus can also secrete inhibiting hormones:
TSH – Inhibiting Hormone prevents the adenohypophysis from secreting
TSH.
The hypothalamus affects the adenohypophysis & that’s about it.
Where is the THYROID GLAND located?
It is located in the anterior neck, inferior to thyroid
cartilage.
What does THYROID GLAND do?
*Largest pure endocrine gland
*Produces two hormones
* Thyroid hormone (TH)
-Acts on most cells of the body
-Increases metabolic rate
-Controlled by humeral (blood) elements
-Iodine is needed to make TH
*Calcitonin
-Lowers blood calcium levels in children
-Slows osteoclasts to allow for bone deposition
(Vitamin D is synthesized and secreted by bone cells)
What is the major stimulus for the release of
thyroid hormone?
It is humeral
(Blood elements tell the body it needs more thyroid
hormone)
What is thyroid hormone partly made of?
It is partly made of Iodine.
Iodine is essential for the formation of thyroxin.
If you do not eat enough iodine, they cannot make
thyroid hormone.
How does hypothalamus respond?
The hypothalamus responds by putting out more
TSH-RH
How does pituitary respond?
The pituitary will respond by releasing TSH.
What is GOITER?
If not enough iodine to make hormone (TH) the size of
the follicle grows >gland grows>GOITER.
What is Hyperthyroidism (Grave’s Disease)?
*Caused by autoimmune disorder.
*Leads to nervousness, weight loss, sweating and rapid
heart rate.
What is HYPOTHYROIDISM?
 Decreases metabolism, causes obesity.
What is adult hypothyroidism?
MYXEDEMA
 antibodies attack & destroy thyroid tissue
 Low metabolic rate & weight gain are common
symptoms.
What is hypothyroidism in children called?
CRETINISM
*Short, disproportionate body, thick tongue &
mental retardation
What are PARATHYROID GLANDS?
These are 4 glands embedded in the thyroid gland.
*Parathyroid hormone (PTH)
*Increases blood concentration of Ca2+
*Tells osteoclasts to release calcium from bone
*Tells kidneys to decrease secretion of calcium
*Activates vitamin D which increases calcium
uptake by intestines
DOES NOT METABOLIZE CALCIUM
What DOES NOT metabolize calcium?
PARATHYROID GLANDS
What does the THYMUS GLAND do?
Hormones produced by this organ stimulate the
production of T cells.
Adrenal Glands – they are 2 glands in 1:
What are they?
Adrenal Cortex & Adrenal Medulla
What does ADRENAL CORTEX do?
Bulk of the adrenal gland
Secretes Steroids:
1. CORTISONE: reduces inflammation
2. CORTISOL: helps body deal w/stressful situations like fasting,
anxiety, trauma and infection. When the perceives a stressful situation,
the hypothalamus tells the pituitary gland to secrete (ACTH), which
travels to the adrenal gland & signals it to release cortisol to most of
the cells in the body.
3. ALDOSTERONE: increases blood volume during hemorrhage or
drop in blood pressure, causing kidneys to reabsorb more sodium,
water follows with it, so blood volume increases.
4. SEX HORMONES: for opposite sex
Males produce estrogen here, & females produce testosterone.
What is the ADRENAL MEDULLA?
What does the ADRENAL MEDULLA
secrete?
The adrenal medulla is a knot of nervous tissue within the gland.
It secretes adrenalin neurotransmitter for the sympathetic nervous
system.
The adrenal medulla also has sympathetic neurons which synapse on
it, so when you are spooked, the neurons fire and also stimulates the
adrenal medulla to release more epinephrine to increase the effects of
the sympathetic nervous system.
What Adrenal Gland Disorders are there?
 CUSHING’S SYNDROME
-Hypersecretion of cortisol
-Round “moon” face and “buffalo bump”
 ADDISON”S DISEASE
-Hyposecretion of cortisol
-Low Blood pressure results
What is the PINEAL GLAND?
Shaped like a pinecone
Pinealocytes secrete melatonin
- A hormone that regulates circadian rhythms (sense of
day & night; it regulates sleep cycle).
“Pineal Sand” is radiopaque
-mineral deposits within pineal gland
-Used as a landmark to identify brain structures in XRays
What is the PANCREAS?
This is an endocrine & an exocrine gland
Exocrine glands secrete into a duct
The pancreas has channels that end in exocrine
glands.
What are interspersed among the pancreas channels
that end in exocrine glands?
PANCREATIC ISLETS, which are endocrine
Exocrine Cells-acinar cells-secrete digestive enzymes
Endocrine cells-pancreatic islets (islets of Langerhans)
*About one million islets-scattered in thru pancreas
*Secrete Insulin
*Secretes Glucagon
What does GLUCAGON do?
*Signals liver to release glucose from glycogen
*Raises blood sugar
What does INSULIN do?
*Signals most body cells to take up glucose from the
blood
*Promotes storage of glucose as glycogen in liver
*Lowers blood sugar
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What are 2 different kinds of
DIABETES?
1. DIABETES INSIPIDUS
2. DIABETES MELLITUS
What is DIABETES INSPIDUS?
When the pituitary gland does not secrete antidiuretic hormone
or the kidney does not respond to the hormone.
What causes DIABETES INSIPIDUS?
It can be caused by damage to the pituitary or kidney damage.
What is DIABETES MELLITUS?
Tends to be hereditary, caused by lack of insulin
secretion in the pancreas, or resistance to insulin in the
body’s cell.
Two different types:
Type I & Type II
What is TYPE I DIABETES?
Insulin dependent, develops in children
It is caused by the destruction of pancreatic islets by
autoimmune disorders.
They must have insulin injections daily throughout life.
What is TYPE II DIABETES?
Much more common
Usually appears after 40
It is a consequence of obesity
They produce insulin, but their cells are less sensitive to the
effects of insulin.
Steps of treatment:
1. Diet & exercise
2. Oral medicine or injected insulin
What do the OVARIES do?
Secrete progesterone: prepares uterus for pregnancy
Secrete estrogen:
* Female characteristics
* Stores enough for several months
What is the primary sex organ in males?
*Testes are primary sex organ, NOT the penis!
*Promotes formation of sperm
*Maintains secondary sex characteristics.
Endocrine gland:
What does the Heart do?
Pumps blood & produces hormones
The heart is an organ that is an endocrine gland
What does the GI Tract do?
Digest food & produces hormones
The GI TRACT is an organ that is an endocrine gland
What does the Liver do?
Makes enzymes & produces hormones
(Calcium metabolism)
The liver is an organ that is an endocrine gland
What do the kidneys do?
Calcium metabolism
RBC Production
The kidneys are organs that is an endocrine gland
Function of DERMIS?
Calcium Metabolism
Vitamin D
*Epithelial glands that have ducts are NOT endocrine
glands!
The dermis is an organ that is an endocrine gland
What is the function of the LUNGS?
Oxygenates & produces hormones
The lungs are organs that is an endocrine gland
The function of BONES?
Synthesize & secrete Vitamin D
Bones are organs that is an endocrine gland
The function of the PLACENTA?
Oxygenates & produces hormones
The placenta is an organ that is an endocrine gland
What does NOT make hormones?
Epithelial Glands
The only thing that does NOT make hormones is epithelial
glands that have ducts.
(Hormone glands are by definition without ducts)
Hormone: ADH
Where Made: Posterior Pituitary
Target Organ: Kidney
Effect: Increases water absorption
Hormone: Parathyroid
Where Made: Parathyroid Gland
Target Organ: Bone, Kidney & Intestines
Effect: Increases blood volume
Hormone: Thyroid
Where Made: Thyroid Gland
Target Organ: Most Cells
Effect: Increases Metabolic Rate
Hormone: ACTH
Where Made: Anterior Pituitary
Target Organ: Adrenal Cortex
Effect: Stimulates release of cortisol
Hormone: Cortisol
Where Made: Adrenal Cortex
Target Organ: Most Cells
Effect: Affects glucose & protein blood
levels & metabolic rates
Are steroids dangerous?
Yes, because:
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Synthetic testosterone is taken in doses 100X larger than a prescription.
Increase rage & aggression
Cause kidney & liver disease
Cause impotency & sterility
Baldness
Decrease the size of testicles
Cause low sperm count
Give women hair on face & chest
Enlarge breast on males
Decrease female breasts
Cancer
Severe Acne
High blood pressure & high cholesterol
Can stunt bone growth in those that have not yet finished growing
Shorten life span by several decades
Which gland sits on top of each kidney?
adrenal